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Streaming replication and WAL archive interactions 31+ messages / 9 participants [nested] [flat]
* Streaming replication and WAL archive interactions @ 2014-12-12 13:46 Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2014-12-12 13:46 UTC (permalink / raw) To: pgsql-hackers There have been a few threads on the behavior of WAL archiving, after a standby server is promoted [1] [2]. In short, it doesn't work as you might expect. The standby will start archiving after it's promoted, but it will not archive files that were replicated from the old master via streaming replication. If those files were not already archived in the master before the promotion, they are not archived at all. That's not good if you wanted to restore from a base backup + the WAL archive later. The basic setup is a master server, a standby, a WAL archive that's shared by both, and streaming replication between the master and standby. This should be a very common setup in the field, so how are people doing it in practice? Just live with the wisk that you might miss some files in the archive if you promote? Don't even realize there's a problem? Something else? And how would we like it to work? There was some discussion in August on enabling WAL archiving in the standby, always [3]. That's a related idea, but it assumes that you have a separate archive in the master and the standby. The problem at promotion happens when you have a shared archive between the master and standby. [1] http://www.postgresql.org/message-id/[email protected].... [2] http://www.postgresql.org/message-id/20140904175036.310c6466@erg [3] http://www.postgresql.org/message-id/[email protected]..... - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2014-12-16 08:24 Borodin Vladimir <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Borodin Vladimir @ 2014-12-16 08:24 UTC (permalink / raw) To: Heikki Linnakangas <[email protected]>; +Cc: pgsql-hackers 12 дек. 2014 г., в 16:46, Heikki Linnakangas <[email protected]> написал(а): > There have been a few threads on the behavior of WAL archiving, after a standby server is promoted [1] [2]. In short, it doesn't work as you might expect. The standby will start archiving after it's promoted, but it will not archive files that were replicated from the old master via streaming replication. If those files were not already archived in the master before the promotion, they are not archived at all. That's not good if you wanted to restore from a base backup + the WAL archive later. > > The basic setup is a master server, a standby, a WAL archive that's shared by both, and streaming replication between the master and standby. This should be a very common setup in the field, so how are people doing it in practice? Just live with the wisk that you might miss some files in the archive if you promote? Don't even realize there's a problem? Something else? Yes, I do live like that (with streaming replication and shared archive between master and replicas) and don’t even realize there’s a problem :( And I think I’m not the only one. Maybe at least a note should be added to the documentation? > > And how would we like it to work? > > There was some discussion in August on enabling WAL archiving in the standby, always [3]. That's a related idea, but it assumes that you have a separate archive in the master and the standby. The problem at promotion happens when you have a shared archive between the master and standby. AFAIK most people use the scheme with shared archive. > > [1] http://www.postgresql.org/message-id/[email protected].... > > [2] http://www.postgresql.org/message-id/20140904175036.310c6466@erg > > [3] http://www.postgresql.org/message-id/[email protected]..... > > - Heikki > > > -- > Sent via pgsql-hackers mailing list ([email protected]) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers -- Vladimir ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2014-12-16 19:11 Heikki Linnakangas <[email protected]> parent: Borodin Vladimir <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2014-12-16 19:11 UTC (permalink / raw) To: Borodin Vladimir <[email protected]>; +Cc: pgsql-hackers On 12/16/2014 10:24 AM, Borodin Vladimir wrote: > 12 дек. 2014 г., в 16:46, Heikki Linnakangas > <[email protected]> написал(а): > >> There have been a few threads on the behavior of WAL archiving, >> after a standby server is promoted [1] [2]. In short, it doesn't >> work as you might expect. The standby will start archiving after >> it's promoted, but it will not archive files that were replicated >> from the old master via streaming replication. If those files were >> not already archived in the master before the promotion, they are >> not archived at all. That's not good if you wanted to restore from >> a base backup + the WAL archive later. >> >> The basic setup is a master server, a standby, a WAL archive that's >> shared by both, and streaming replication between the master and >> standby. This should be a very common setup in the field, so how >> are people doing it in practice? Just live with the wisk that you >> might miss some files in the archive if you promote? Don't even >> realize there's a problem? Something else? > > Yes, I do live like that (with streaming replication and shared > archive between master and replicas) and don’t even realize there’s a > problem :( And I think I’m not the only one. Maybe at least a note > should be added to the documentation? Let's try to figure out a way to fix this in master, but yeah, a note in the documentation is in order. >> And how would we like it to work? Here's a plan: Have a mechanism in the standby, to track how far the master has archived its WAL, and don't throw away WAL in the standby that hasn't been archived in the master yet. This is similar to the physical replication slots, which prevent the master from recycling WAL that a standby hasn't received yet, but in reverse. I think we can use the .done and .ready files for this. Whenever a file is streamed (completely) from the master, create a .ready file for it. When we get an acknowledgement from the master that it has archived it, create a .done file for it. To get the information from the master, add the "last archived WAL segment" e.g. in the streaming replication keep-alive message, or invent a new message type for it. At promotion, archive all the WAL from the old timeline that the master hadn't already archived. While doing this, the archive_command can be called for files that have in fact already been archived in the master, so the command needs to return success if it's asked to archive a file and an identical file already exists in the archive. That's a bit difficult to write into a one-liner, but hopefully we can still provide an example of this. Or have another command, e.g. "promotion_archive_command", which can just assume that everything is OK if the file already exists. To enable this new mode, let's add a third option to archive_mode, besides on/off. Or just make this the default; I'm not sure if anyone would want the old behavior. >> There was some discussion in August on enabling WAL archiving in >> the standby, always [3]. That's a related idea, but it assumes that >> you have a separate archive in the master and the standby. The >> problem at promotion happens when you have a shared archive between >> the master and standby. > > AFAIK most people use the scheme with shared archive. Yeah. Anyway, we can support both scenarios. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2014-12-18 10:32 Fujii Masao <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Fujii Masao @ 2014-12-18 10:32 UTC (permalink / raw) To: Heikki Linnakangas <[email protected]>; +Cc: Borodin Vladimir <[email protected]>; pgsql-hackers On Wed, Dec 17, 2014 at 4:11 AM, Heikki Linnakangas <[email protected]> wrote: > On 12/16/2014 10:24 AM, Borodin Vladimir wrote: >> >> 12 дек. 2014 г., в 16:46, Heikki Linnakangas >> <[email protected]> написал(а): >> >>> There have been a few threads on the behavior of WAL archiving, >>> after a standby server is promoted [1] [2]. In short, it doesn't >>> work as you might expect. The standby will start archiving after >>> it's promoted, but it will not archive files that were replicated >>> from the old master via streaming replication. If those files were >>> not already archived in the master before the promotion, they are >>> not archived at all. That's not good if you wanted to restore from >>> a base backup + the WAL archive later. >>> >>> The basic setup is a master server, a standby, a WAL archive that's >>> shared by both, and streaming replication between the master and >>> standby. This should be a very common setup in the field, so how >>> are people doing it in practice? Just live with the wisk that you >>> might miss some files in the archive if you promote? Don't even >>> realize there's a problem? Something else? >> >> >> Yes, I do live like that (with streaming replication and shared >> archive between master and replicas) and don’t even realize there’s a >> problem :( And I think I’m not the only one. Maybe at least a note >> should be added to the documentation? > > > Let's try to figure out a way to fix this in master, but yeah, a note in the > documentation is in order. +1 >>> And how would we like it to work? > > > Here's a plan: > > Have a mechanism in the standby, to track how far the master has archived > its WAL, and don't throw away WAL in the standby that hasn't been archived > in the master yet. This is similar to the physical replication slots, which > prevent the master from recycling WAL that a standby hasn't received yet, > but in reverse. I think we can use the .done and .ready files for this. > Whenever a file is streamed (completely) from the master, create a .ready > file for it. When we get an acknowledgement from the master that it has > archived it, create a .done file for it. To get the information from the > master, add the "last archived WAL segment" e.g. in the streaming > replication keep-alive message, or invent a new message type for it. Sounds OK to me. How does this work in cascade replication case? The cascading walsender just relays the archive location to the downstream standby? What happens when WAL streaming is terminated and the startup process starts to read the WAL file from the archive? After reading the WAL file from the archive, probably we would need to change .ready files of every older WAL files to .done. Regards, -- Fujii Masao -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2014-12-19 20:56 Heikki Linnakangas <[email protected]> parent: Fujii Masao <[email protected]> 0 siblings, 2 replies; 31+ messages in thread From: Heikki Linnakangas @ 2014-12-19 20:56 UTC (permalink / raw) To: Fujii Masao <[email protected]>; +Cc: Borodin Vladimir <[email protected]>; pgsql-hackers On 12/18/2014 12:32 PM, Fujii Masao wrote: > On Wed, Dec 17, 2014 at 4:11 AM, Heikki Linnakangas > <[email protected]> wrote: >> On 12/16/2014 10:24 AM, Borodin Vladimir wrote: >>> >>> 12 дек. 2014 г., в 16:46, Heikki Linnakangas >>> <[email protected]> написал(а): >>> >>>> There have been a few threads on the behavior of WAL archiving, >>>> after a standby server is promoted [1] [2]. In short, it doesn't >>>> work as you might expect. The standby will start archiving after >>>> it's promoted, but it will not archive files that were replicated >>>> from the old master via streaming replication. If those files were >>>> not already archived in the master before the promotion, they are >>>> not archived at all. That's not good if you wanted to restore from >>>> a base backup + the WAL archive later. >>>> >>>> The basic setup is a master server, a standby, a WAL archive that's >>>> shared by both, and streaming replication between the master and >>>> standby. This should be a very common setup in the field, so how >>>> are people doing it in practice? Just live with the wisk that you >>>> might miss some files in the archive if you promote? Don't even >>>> realize there's a problem? Something else? >>> >>> >>> Yes, I do live like that (with streaming replication and shared >>> archive between master and replicas) and don’t even realize there’s a >>> problem :( And I think I’m not the only one. Maybe at least a note >>> should be added to the documentation? >> >> >> Let's try to figure out a way to fix this in master, but yeah, a note in the >> documentation is in order. > > +1 > >>>> And how would we like it to work? >> >> >> Here's a plan: >> >> Have a mechanism in the standby, to track how far the master has archived >> its WAL, and don't throw away WAL in the standby that hasn't been archived >> in the master yet. This is similar to the physical replication slots, which >> prevent the master from recycling WAL that a standby hasn't received yet, >> but in reverse. I think we can use the .done and .ready files for this. >> Whenever a file is streamed (completely) from the master, create a .ready >> file for it. When we get an acknowledgement from the master that it has >> archived it, create a .done file for it. To get the information from the >> master, add the "last archived WAL segment" e.g. in the streaming >> replication keep-alive message, or invent a new message type for it. > > Sounds OK to me. > > How does this work in cascade replication case? The cascading walsender > just relays the archive location to the downstream standby? Hmm. Yeah, I guess so. > What happens when WAL streaming is terminated and the startup process starts to > read the WAL file from the archive? After reading the WAL file from the archive, > probably we would need to change .ready files of every older WAL files to .done. I suppose. Although there's no big harm in leaving them in .ready state. As soon as you reconnect, the primary will tell if they were archived. If the server is promoted before reconnecting, it will try to archive the files and archive_command will see that they are already in the archive. It has to be prepared for that situation anyway, so that's OK too. Here's a first cut at this. It includes the changes from your standby_wal_archiving_v1.patch, so you get that behaviour if you set archive_mode='always', and the new behaviour I wanted with archive_mode='shared'. I wrote it on top of the other patch I posted recently to not archive bogus recycled WAL segments after promotion (http://www.postgresql.org/message-id/[email protected]), but it seems to apply without it too. I suggest reading the documentation changes first, it hopefully explains pretty well how to use this. The code should work too, and comments on that are welcome too, but I haven't tested it much. I'll do more testing next week. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers Attachments: [text/x-diff] 0001-Make-WAL-archival-behave-more-sensibly-in-standby-mo.patch (24.2K, 2-0001-Make-WAL-archival-behave-more-sensibly-in-standby-mo.patch) download | inline diff: From 03dced40178c0a0b7c28ff630a15cf664995525d Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas <[email protected]> Date: Tue, 16 Dec 2014 23:09:03 +0200 Subject: [PATCH 1/1] Make WAL archival behave more sensibly in standby mode. This add two new archive_modes, 'shared' and 'always', to indicate whether the WAL archive is shared between the primary and standby, or not. In shared mode, the standby tracks which files have been archived by the primary. The standby refrains from recycling files that the primary has not yet archived, and at failover, the standby archives all those files too from the old timeline. In 'always' mode, the standby's WAL archive is taken to be separate from the primary's, and the standby independently archives all files it receives from the primary. Fujii Masao and me. --- doc/src/sgml/config.sgml | 12 +- doc/src/sgml/high-availability.sgml | 48 +++++++ doc/src/sgml/protocol.sgml | 31 +++++ src/backend/access/transam/xlog.c | 29 ++++- src/backend/postmaster/postmaster.c | 37 ++++-- src/backend/replication/walreceiver.c | 172 ++++++++++++++++++++------ src/backend/replication/walsender.c | 47 +++++++ src/backend/utils/misc/guc.c | 21 ++-- src/backend/utils/misc/postgresql.conf.sample | 2 +- src/include/access/xlog.h | 14 ++- 10 files changed, 351 insertions(+), 62 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 48ae3e4..986d6eb 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -2475,7 +2475,7 @@ include_dir 'conf.d' <variablelist> <varlistentry id="guc-archive-mode" xreflabel="archive_mode"> - <term><varname>archive_mode</varname> (<type>boolean</type>) + <term><varname>archive_mode</varname> (<type>enum</type>) <indexterm> <primary><varname>archive_mode</> configuration parameter</primary> </indexterm> @@ -2484,7 +2484,15 @@ include_dir 'conf.d' <para> When <varname>archive_mode</> is enabled, completed WAL segments are sent to archive storage by setting - <xref linkend="guc-archive-command">. + <xref linkend="guc-archive-command">. In addition to <literal>off</>, + to disable, there are three modes: <literal>on</>, <literal>shared</>, + and <literal>always</>. During normal operation, there is no + difference between the three modes, but in archive recovery or + standby mode, it indicates whether the WAL archive is shared between + the primary and the standby server or not. See + <xref linkend="continuous-archiving-in-standby"> for details. + </para> + <para> <varname>archive_mode</> and <varname>archive_command</> are separate variables so that <varname>archive_command</> can be changed without leaving archiving mode. diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml index d249959..c22b15a 100644 --- a/doc/src/sgml/high-availability.sgml +++ b/doc/src/sgml/high-availability.sgml @@ -1220,6 +1220,54 @@ primary_slot_name = 'node_a_slot' </sect3> </sect2> + + <sect2 id="continuous-archiving-in-standby"> + <title>Continuous archiving in standby</title> + + <indexterm> + <primary>continuous archiving</primary> + <secondary>in standby</secondary> + </indexterm> + + <para> + When continuous WAL archiving is used in a standby, there are two + different scenarios: the WAL archive can be shared between the primary + and the standby, or the standby can have its own WAL archive. In the + shared archive scenario, <varname>archive_mode</varname> must be set to + <literal>shared</literal>, and in the separate archive scenario, to + <literal>always</literal>. Setting it to <literal>on</literal> in a + standby server, or when performing point-in-time recovery, is not + allowed and an error will be raised. When a server is not in recovery + mode, there is no difference between <literal>on</literal>, + <literal>shared</literal>, and <literal>always</literal> modes. + </para> + + <para> + In <literal>shared</literal> archive mode, the standby server tries to + ensure that the archive is complete, even if the primary crashes and + failover happens. The standby server will not archive any WAL segments + as long as it is in standby mode; it is the primary server's + responsibility to do so. It will, however, keep track of which files + have already been archived by the primary, and if failover happens, it + takes over and attempts to archive any files that the primary had not + yet archived. + </para> + + <para> + In <literal>always</literal> archive mode, the standby server will + archive all WAL it receives, whether it's through streaming replication + or by restoring from the primary's archive using + <varname>restore_command</varname>. + </para> + + <para> + In cascading replication, the first standby server and the cascaded + standby servers can use <varname>archive_mode</varname> settings. In + each standby, it should be set to <literal>shared</literal> or + <literal>always</literal>, depending on whether that standby shares the + archive with the primary or standby it is connected to. + </para> + </sect2> </sect1> <sect1 id="warm-standby-failover"> diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml index efe75ea..60235fe 100644 --- a/doc/src/sgml/protocol.sgml +++ b/doc/src/sgml/protocol.sgml @@ -1646,6 +1646,37 @@ The commands accepted in walsender mode are: </para> </listitem> </varlistentry> + <varlistentry> + <term> + WAL archival report message (B) + </term> + <listitem> + <para> + <variablelist> + <varlistentry> + <term> + Byte1('a') + </term> + <listitem> + <para> + Tells the receiver the last archived WAL segment. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + Byte<replaceable>n</replaceable> + </term> + <listitem> + <para> + Filename of the latest archived file. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + </listitem> + </varlistentry> </variablelist> </para> diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index e267ca1..9d0c672 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -83,7 +83,7 @@ int CheckPointSegments = 3; int wal_keep_segments = 0; int XLOGbuffers = -1; int XLogArchiveTimeout = 0; -bool XLogArchiveMode = false; +int XLogArchiveMode = ARCHIVE_MODE_OFF; char *XLogArchiveCommand = NULL; bool EnableHotStandby = false; bool fullPageWrites = true; @@ -139,6 +139,25 @@ const struct config_enum_entry sync_method_options[] = { {NULL, 0, false} }; + +/* + * Although only "on", "off", and "always" are documented, + * we accept all the likely variants of "on" and "off". + */ +const struct config_enum_entry archive_mode_options[] = { + {"shared", ARCHIVE_MODE_SHARED, false}, + {"always", ARCHIVE_MODE_ALWAYS, false}, + {"on", ARCHIVE_MODE_ON, false}, + {"off", ARCHIVE_MODE_OFF, false}, + {"true", ARCHIVE_MODE_ON, true}, + {"false", ARCHIVE_MODE_OFF, true}, + {"yes", ARCHIVE_MODE_ON, true}, + {"no", ARCHIVE_MODE_OFF, true}, + {"1", ARCHIVE_MODE_ON, true}, + {"0", ARCHIVE_MODE_OFF, true}, + {NULL, 0, false} +}; + /* * Statistics for current checkpoint are collected in this global struct. * Because only the checkpointer or a stand-alone backend can perform @@ -757,7 +776,7 @@ static MemoryContext walDebugCxt = NULL; #endif static void readRecoveryCommandFile(void); -static void exitArchiveRecovery(TimeLineID endTLI, XLogSegNo endLogSegNo); +static void exitArchiveRecovery(TimeLineID endTLI, XLogRecPtr endOfLog); static bool recoveryStopsBefore(XLogReaderState *record); static bool recoveryStopsAfter(XLogReaderState *record); static void recoveryPausesHere(void); @@ -5825,6 +5844,12 @@ StartupXLOG(void) if (ArchiveRecoveryRequested) { + /* archive_mode=on is not allowed during archive recovery. */ + if (XLogArchiveMode == ARCHIVE_MODE_ON) + ereport(ERROR, + (errmsg("archive_mode='on' cannot be used in archive recovery"), + (errhint("Use 'shared' or 'always' mode instead.")))); + if (StandbyModeRequested) ereport(LOG, (errmsg("entering standby mode"))); diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index 5106f52..b41e34d 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -824,9 +824,9 @@ PostmasterMain(int argc, char *argv[]) write_stderr("%s: max_wal_senders must be less than max_connections\n", progname); ExitPostmaster(1); } - if (XLogArchiveMode && wal_level == WAL_LEVEL_MINIMAL) + if (XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level == WAL_LEVEL_MINIMAL) ereport(ERROR, - (errmsg("WAL archival (archive_mode=on) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); + (errmsg("WAL archival (archive_mode=on/always/shared) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); if (max_wal_senders > 0 && wal_level == WAL_LEVEL_MINIMAL) ereport(ERROR, (errmsg("WAL streaming (max_wal_senders > 0) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); @@ -1624,13 +1624,21 @@ ServerLoop(void) start_autovac_launcher = false; /* signal processed */ } - /* If we have lost the archiver, try to start a new one */ - if (XLogArchivingActive() && PgArchPID == 0 && pmState == PM_RUN) - PgArchPID = pgarch_start(); - - /* If we have lost the stats collector, try to start a new one */ - if (PgStatPID == 0 && pmState == PM_RUN) - PgStatPID = pgstat_start(); + /* + * If we have lost the archiver, try to start a new one. + * + * If WAL archiving is enabled always, we try to start a new archiver + * even during recovery. + */ + if (PgArchPID == 0 && wal_level >= WAL_LEVEL_ARCHIVE) + { + if ((pmState == PM_RUN && XLogArchiveMode > ARCHIVE_MODE_OFF) || + ((pmState == PM_RECOVERY || pmState == PM_HOT_STANDBY) && + XLogArchiveMode == ARCHIVE_MODE_ALWAYS)) + { + PgArchPID = pgarch_start(); + } + } /* If we need to signal the autovacuum launcher, do so now */ if (avlauncher_needs_signal) @@ -4796,6 +4804,17 @@ sigusr1_handler(SIGNAL_ARGS) Assert(BgWriterPID == 0); BgWriterPID = StartBackgroundWriter(); + /* + * Start the archiver if we're responsible for (re-)archiving received + * files. + */ + Assert(PgArchPID == 0); + if (wal_level >= WAL_LEVEL_ARCHIVE && + XLogArchiveMode == ARCHIVE_MODE_ALWAYS) + { + PgArchPID = pgarch_start(); + } + pmState = PM_RECOVERY; } if (CheckPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY) && diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c index c2d4ed3..b178d4f 100644 --- a/src/backend/replication/walreceiver.c +++ b/src/backend/replication/walreceiver.c @@ -52,8 +52,11 @@ #include "libpq/pqformat.h" #include "libpq/pqsignal.h" #include "miscadmin.h" +#include "pgstat.h" +#include "postmaster/pgarch.h" #include "replication/walreceiver.h" #include "replication/walsender.h" +#include "storage/fd.h" #include "storage/ipc.h" #include "storage/pmsignal.h" #include "storage/procarray.h" @@ -107,6 +110,9 @@ static struct XLogRecPtr Flush; /* last byte + 1 flushed in the standby */ } LogstreamResult; +/* */ +static char primary_last_archived[MAX_XFN_CHARS + 1]; + static StringInfoData reply_message; static StringInfoData incoming_message; @@ -141,6 +147,7 @@ static void XLogWalRcvFlush(bool dying); static void XLogWalRcvSendReply(bool force, bool requestReply); static void XLogWalRcvSendHSFeedback(bool immed); static void ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime); +static void ProcessArchivalReport(void); /* Signal handlers */ static void WalRcvSigHupHandler(SIGNAL_ARGS); @@ -537,21 +544,12 @@ WalReceiverMain(void) */ if (recvFile >= 0) { - char xlogfname[MAXFNAMELEN]; - XLogWalRcvFlush(false); if (close(recvFile) != 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not close log segment %s: %m", XLogFileNameP(recvFileTLI, recvSegNo)))); - - /* - * Create .done file forcibly to prevent the streamed segment from - * being archived later. - */ - XLogFileName(xlogfname, recvFileTLI, recvSegNo); - XLogArchiveForceDone(xlogfname); } recvFile = -1; @@ -857,6 +855,26 @@ XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len) XLogWalRcvSendReply(true, false); break; } + case 'a': /* Archival report */ + { + /* the content of the message is a filename */ + if (len >= sizeof(primary_last_archived)) + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg_internal("invalid archival report message with length %d", + (int) len))); + memcpy(primary_last_archived, buf, len); + primary_last_archived[len] = '\0'; + if (strspn(buf, VALID_XFN_CHARS) != len) + { + primary_last_archived[0] = '\0'; + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg_internal("unexpected character in primary's last archived filename"))); + } + ProcessArchivalReport(); + break; + } default: ereport(ERROR, (errcode(ERRCODE_PROTOCOL_VIOLATION), @@ -878,39 +896,18 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr) { int segbytes; - if (recvFile < 0 || !XLByteInSeg(recptr, recvSegNo)) + if (!XLByteInSeg(recptr, recvSegNo)) { bool use_existent; /* - * fsync() and close current file before we switch to next one. We - * would otherwise have to reopen this file to fsync it later + * We take care to always close the current file, after writing + * the last byte to it. So this shouldn't happen. */ if (recvFile >= 0) - { - char xlogfname[MAXFNAMELEN]; - - XLogWalRcvFlush(false); - - /* - * XLOG segment files will be re-read by recovery in startup - * process soon, so we don't advise the OS to release cache - * pages associated with the file like XLogFileClose() does. - */ - if (close(recvFile) != 0) - ereport(PANIC, - (errcode_for_file_access(), - errmsg("could not close log segment %s: %m", - XLogFileNameP(recvFileTLI, recvSegNo)))); - - /* - * Create .done file forcibly to prevent the streamed segment - * from being archived later. - */ - XLogFileName(xlogfname, recvFileTLI, recvSegNo); - XLogArchiveForceDone(xlogfname); - } - recvFile = -1; + ereport(ERROR, + (errmsg("unexpected WAL receive location %s", + XLogFileNameP(recvFileTLI, recvSegNo)))); /* Create/use new log file */ XLByteToSeg(recptr, recvSegNo); @@ -965,6 +962,51 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr) buf += byteswritten; LogstreamResult.Write = recptr; + + /* + * If we just wrote the last byte to this segment, fsync() and close + * current file before we switch to next one. We would otherwise have + * to reopen this file to fsync it later. + */ + if (recvOff == XLOG_SEG_SIZE) + { + char xlogfname[MAXFNAMELEN]; + + XLogWalRcvFlush(false); + + /* + * XLOG segment files will be re-read by recovery in startup + * process soon, so we don't advise the OS to release cache + * pages associated with the file like XLogFileClose() does. + */ + if (close(recvFile) != 0) + ereport(PANIC, + (errcode_for_file_access(), + errmsg("could not close log segment %s: %m", + XLogFileNameP(recvFileTLI, recvSegNo)))); + recvFile = -1; + + /* + * Now that this segment is complete, do we need to archive it? + * + * In 'always' mode, we clearly need to archive this. + * + * In 'shared' mode, we might need to, if we get promoted before + * the master has archived this file, so create a .ready file. It + * will be replaced with .done later, if we get acknowledgemet + * from the primary that this has already been archived. + * + * In 'on' mode, we're only responsible for WAL we've generated + * ourselves. + */ + if (XLogArchiveMode == ARCHIVE_MODE_ALWAYS || + XLogArchiveMode == ARCHIVE_MODE_SHARED) + { + XLogFileName(xlogfname, recvFileTLI, recvSegNo); + + XLogArchiveCheckDone(xlogfname); + } + } } } @@ -1215,3 +1257,61 @@ ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime) pfree(receipttime); } } + +/* + * Create .done and .ready files, based on the master's last archival report. + */ +static void +ProcessArchivalReport(void) +{ + DIR *xldir; + struct dirent *xlde; + + elog(DEBUG2, "received archival report from master: %s", + primary_last_archived); + + if (XLogArchiveMode != ARCHIVE_MODE_SHARED) + return; + + /* Check that the filename the primary reported looks valid */ + if (strlen(primary_last_archived) < 24 || + strspn(primary_last_archived, "0123456789ABCDEF") != 24) + return; + + xldir = AllocateDir(XLOGDIR); + if (xldir == NULL) + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not open transaction log directory \"%s\": %m", + XLOGDIR))); + + while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) + { + /* + * We ignore the timeline part of the XLOG segment identifiers in + * deciding whether a segment is still needed. This ensures that we + * won't prematurely remove a segment from a parent timeline. We could + * probably be a little more proactive about removing segments of + * non-parent timelines, but that would be a whole lot more + * complicated. + * + * We use the alphanumeric sorting property of the filenames to decide + * which ones are earlier than the lastoff segment. + */ + if (strlen(xlde->d_name) == 24 && + strspn(xlde->d_name, "0123456789ABCDEF") == 24 && + strcmp(xlde->d_name + 8, primary_last_archived + 8) <= 0) + { + XLogArchiveForceDone(xlde->d_name); + } + } + + FreeDir(xldir); + + /* + * Remember this location in pgstat as well. This makes it visible in + * pg_stat_archiver, and allows the location to be relayed to cascaded + * standbys. + */ + pgstat_send_archiver(primary_last_archived, false); +} diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c index 019ae6a..b51bd80 100644 --- a/src/backend/replication/walsender.c +++ b/src/backend/replication/walsender.c @@ -55,6 +55,7 @@ #include "libpq/pqformat.h" #include "miscadmin.h" #include "nodes/replnodes.h" +#include "pgstat.h" #include "replication/basebackup.h" #include "replication/decode.h" #include "replication/logical.h" @@ -153,6 +154,7 @@ static StringInfoData tmpbuf; * wal_sender_timeout doesn't need to be active. */ static TimestampTz last_reply_timestamp = 0; +static char last_archival_report[MAX_XFN_CHARS + 1] = ""; /* Have we sent a heartbeat message asking for reply, since last reply? */ static bool waiting_for_ping_response = false; @@ -210,6 +212,8 @@ static void ProcessStandbyHSFeedbackMessage(void); static void ProcessRepliesIfAny(void); static void WalSndKeepalive(bool requestReply); static void WalSndKeepaliveIfNecessary(TimestampTz now); +static void WalSndArchivalReport(void); +static void WalSndArchivalReportIfNecessary(void); static void WalSndCheckTimeOut(TimestampTz now); static long WalSndComputeSleeptime(TimestampTz now); static void WalSndPrepareWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid, bool last_write); @@ -2889,6 +2893,11 @@ WalSndKeepaliveIfNecessary(TimestampTz now) TimestampTz ping_time; /* + * Send an archival status message, if necessary. + */ + WalSndArchivalReportIfNecessary(); + + /* * Don't send keepalive messages if timeouts are globally disabled or * we're doing something not partaking in timeouts. */ @@ -2917,6 +2926,44 @@ WalSndKeepaliveIfNecessary(TimestampTz now) } /* + * This function is used to send archival report message to standby. + */ +static void +WalSndArchivalReport(void) +{ + elog(LOG, "sending archival report: %s", last_archival_report); + + /* construct the message... */ + resetStringInfo(&output_message); + pq_sendbyte(&output_message, 'a'); + pq_sendbytes(&output_message, last_archival_report, strlen(last_archival_report)); + + /* ... and send it wrapped in CopyData */ + pq_putmessage_noblock('d', output_message.data, output_message.len); +} + +static void +WalSndArchivalReportIfNecessary(void) +{ + PgStat_ArchiverStats *archiver_stats; + + archiver_stats = pgstat_fetch_stat_archiver(); + + if (strcmp(last_archival_report, archiver_stats->last_archived_wal) == 0) + { + pgstat_clear_snapshot(); + return; + } + + strlcpy(last_archival_report, archiver_stats->last_archived_wal, + sizeof(last_archival_report)); + + pgstat_clear_snapshot(); + + WalSndArchivalReport(); +} + +/* * This isn't currently used for anything. Monitoring tools might be * interested in the future, and we'll need something like this in the * future for synchronous replication. diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index b1bff7f..6f5b284 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -424,6 +424,7 @@ static const struct config_enum_entry row_security_options[] = { * Options for enum values stored in other modules */ extern const struct config_enum_entry wal_level_options[]; +extern const struct config_enum_entry archive_mode_options[]; extern const struct config_enum_entry sync_method_options[]; extern const struct config_enum_entry dynamic_shared_memory_options[]; @@ -1458,16 +1459,6 @@ static struct config_bool ConfigureNamesBool[] = }, { - {"archive_mode", PGC_POSTMASTER, WAL_ARCHIVING, - gettext_noop("Allows archiving of WAL files using archive_command."), - NULL - }, - &XLogArchiveMode, - false, - NULL, NULL, NULL - }, - - { {"hot_standby", PGC_POSTMASTER, REPLICATION_STANDBY, gettext_noop("Allows connections and queries during recovery."), NULL @@ -3446,6 +3437,16 @@ static struct config_enum ConfigureNamesEnum[] = }, { + {"archive_mode", PGC_POSTMASTER, WAL_ARCHIVING, + gettext_noop("Allows archiving of WAL files using archive_command."), + NULL + }, + &XLogArchiveMode, + ARCHIVE_MODE_OFF, archive_mode_options, + NULL, NULL, NULL + }, + + { {"trace_recovery_messages", PGC_SIGHUP, DEVELOPER_OPTIONS, gettext_noop("Enables logging of recovery-related debugging information."), gettext_noop("Each level includes all the levels that follow it. The later" diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index b053659..fff5de0 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -204,7 +204,7 @@ # - Archiving - -#archive_mode = off # allows archiving to be done +#archive_mode = off # allows archiving to be done; off, on, shared, or always # (change requires restart) #archive_command = '' # command to use to archive a logfile segment # placeholders: %p = path of file to archive diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h index d06fbc0..c9448c7 100644 --- a/src/include/access/xlog.h +++ b/src/include/access/xlog.h @@ -93,13 +93,22 @@ extern int CheckPointSegments; extern int wal_keep_segments; extern int XLOGbuffers; extern int XLogArchiveTimeout; -extern bool XLogArchiveMode; extern char *XLogArchiveCommand; extern bool EnableHotStandby; extern bool fullPageWrites; extern bool wal_log_hints; extern bool log_checkpoints; +/* Archive modes */ +typedef enum ArchiveMode +{ + ARCHIVE_MODE_OFF = 0, /* disabled */ + ARCHIVE_MODE_ON, /* enabled while server is running normally */ + ARCHIVE_MODE_SHARED, /* archive is shared with master */ + ARCHIVE_MODE_ALWAYS /* enabled always (even during recovery) */ +} ArchiveMode; +extern int XLogArchiveMode; + /* WAL levels */ typedef enum WalLevel { @@ -110,7 +119,8 @@ typedef enum WalLevel } WalLevel; extern int wal_level; -#define XLogArchivingActive() (XLogArchiveMode && wal_level >= WAL_LEVEL_ARCHIVE) +#define XLogArchivingActive() \ + (XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level >= WAL_LEVEL_ARCHIVE) #define XLogArchiveCommandSet() (XLogArchiveCommand[0] != '\0') /* -- 2.1.3 ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-01-31 13:07 Andres Freund <[email protected]> parent: Heikki Linnakangas <[email protected]> 1 sibling, 1 reply; 31+ messages in thread From: Andres Freund @ 2015-01-31 13:07 UTC (permalink / raw) To: Heikki Linnakangas <[email protected]>; +Cc: Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers Hi, On 2014-12-19 22:56:40 +0200, Heikki Linnakangas wrote: > This add two new archive_modes, 'shared' and 'always', to indicate whether > the WAL archive is shared between the primary and standby, or not. In > shared mode, the standby tracks which files have been archived by the > primary. The standby refrains from recycling files that the primary has > not yet archived, and at failover, the standby archives all those files too > from the old timeline. In 'always' mode, the standby's WAL archive is > taken to be separate from the primary's, and the standby independently > archives all files it receives from the primary. I don't really like this approach. Sharing a archive is rather dangerous in my experience - if your old master comes up again (and writes in the last wal file) or similar, you can get into really bad situations. What I was thinking about was instead trying to detect the point up to which files were safely archived by running restore command to check for the presence of archived files. Then archive anything that has valid content and isn't yet archived. That doesn't sound particularly complicated to me. Greetings, Andres Freund -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: [HACKERS] Streaming replication and WAL archive interactions @ 2015-02-12 00:15 Миша Тюрин <[email protected]> parent: Andres Freund <[email protected]> 0 siblings, 0 replies; 31+ messages in thread From: Миша Тюрин @ 2015-02-12 00:15 UTC (permalink / raw) To: Andres Freund <[email protected]>; Heikki Linnakangas <[email protected]>; +Cc: pgsql-hackers; Sergey Burladyan <[email protected]> > This should be a very common setup in the field, so how are people doing it in practice? One of possible workaround with archive and streaming was to use pg_receivexlog from standby to copy/save WALs to archive. but with pg_receivexlog was also issue with fsync. [ master ] -- streaming --> [ standby ] -- pg_receivexlog --> [ /archive ] In that case archive is always in pre standby state and it could be better than had archive broken on promote. -- Misha ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-02-28 22:36 Venkata Balaji N <[email protected]> parent: Heikki Linnakangas <[email protected]> 1 sibling, 1 reply; 31+ messages in thread From: Venkata Balaji N @ 2015-02-28 22:36 UTC (permalink / raw) To: Heikki Linnakangas <[email protected]>; +Cc: Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers > > > Here's a first cut at this. It includes the changes from your > standby_wal_archiving_v1.patch, so you get that behaviour if you set > archive_mode='always', and the new behaviour I wanted with > archive_mode='shared'. I wrote it on top of the other patch I posted > recently to not archive bogus recycled WAL segments after promotion ( > http://www.postgresql.org/message-id/[email protected]), but it > seems to apply without it too. > > I suggest reading the documentation changes first, it hopefully explains > pretty well how to use this. The code should work too, and comments on that > are welcome too, but I haven't tested it much. I'll do more testing next > week. Patch did get applied successfully to the latest master. Can you please rebase. Regards, Venkata Balaji N ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-16 11:57 Heikki Linnakangas <[email protected]> parent: Venkata Balaji N <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2015-04-16 11:57 UTC (permalink / raw) To: Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; +Cc: Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 03/01/2015 12:36 AM, Venkata Balaji N wrote: > Patch did get applied successfully to the latest master. Can you please > rebase. Here you go. On 01/31/2015 03:07 PM, Andres Freund wrote: > On 2014-12-19 22:56:40 +0200, Heikki Linnakangas wrote: >> This add two new archive_modes, 'shared' and 'always', to indicate whether >> the WAL archive is shared between the primary and standby, or not. In >> shared mode, the standby tracks which files have been archived by the >> primary. The standby refrains from recycling files that the primary has >> not yet archived, and at failover, the standby archives all those files too >> from the old timeline. In 'always' mode, the standby's WAL archive is >> taken to be separate from the primary's, and the standby independently >> archives all files it receives from the primary. > > I don't really like this approach. Sharing a archive is rather dangerous > in my experience - if your old master comes up again (and writes in the > last wal file) or similar, you can get into really bad situations. It doesn't have to actually be shared. The master and standby could archive to different locations, but the responsibility of archiving is shared, so that on promotion, the standby ensures that every WAL file gets archived. If the master didn't do it, then the standby will. Yes, if the master comes up again, it might try to archive a file that the standby already archived. But that's not so bad. Both copies of the file will be identical. You could put logic in archive_command to check, if the file already exists in the archive, whether the contents are identical, and return success without doing anything if they are. Oh, hang on, that's not necessarily true. On promotion, the standby archives the last, partial WAL segment from the old timeline. That's just wrong (http://www.postgresql.org/message-id/[email protected]), and in fact I somehow thought I changed that already, but apparently not. So let's stop doing that. > What I was thinking about was instead trying to detect the point up to > which files were safely archived by running restore command to check for > the presence of archived files. Then archive anything that has valid > content and isn't yet archived. That doesn't sound particularly > complicated to me. Hmm. That assumes that the standby has a valid restore_command, and can access the WAL archive. Not a too unreasonable requirement I guess, but with the scheme I proposed, it's not necessary. Seems a bit silly to copy a whole segment from the archive just to check if it exists, though. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers Attachments: [application/x-patch] v2-0001-Make-WAL-archival-behave-more-sensibly-in-standby.patch (24.3K, 2-v2-0001-Make-WAL-archival-behave-more-sensibly-in-standby.patch) download | inline diff: From db5c4311baf4e3a2ae3308c4d0d9975ee3692a18 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas <[email protected]> Date: Thu, 16 Apr 2015 14:40:24 +0300 Subject: [PATCH v2 1/1] Make WAL archival behave more sensibly in standby mode. This adds two new archive_modes, 'shared' and 'always', to indicate whether the WAL archive is shared between the primary and standby, or not. In shared mode, the standby tracks which files have been archived by the primary. The standby refrains from recycling files that the primary has not yet archived, and at failover, the standby archives all those files too from the old timeline. In 'always' mode, the standby's WAL archive is taken to be separate from the primary's, and the standby independently archives all files it receives from the primary. Fujii Masao and me. --- doc/src/sgml/config.sgml | 12 +- doc/src/sgml/high-availability.sgml | 48 +++++++ doc/src/sgml/protocol.sgml | 31 +++++ src/backend/access/transam/xlog.c | 29 ++++- src/backend/postmaster/postmaster.c | 37 ++++-- src/backend/replication/walreceiver.c | 172 ++++++++++++++++++++------ src/backend/replication/walsender.c | 47 +++++++ src/backend/utils/misc/guc.c | 21 ++-- src/backend/utils/misc/postgresql.conf.sample | 2 +- src/include/access/xlog.h | 14 ++- 10 files changed, 351 insertions(+), 62 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index b30c68d..e352b8e 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -2521,7 +2521,7 @@ include_dir 'conf.d' <variablelist> <varlistentry id="guc-archive-mode" xreflabel="archive_mode"> - <term><varname>archive_mode</varname> (<type>boolean</type>) + <term><varname>archive_mode</varname> (<type>enum</type>) <indexterm> <primary><varname>archive_mode</> configuration parameter</primary> </indexterm> @@ -2530,7 +2530,15 @@ include_dir 'conf.d' <para> When <varname>archive_mode</> is enabled, completed WAL segments are sent to archive storage by setting - <xref linkend="guc-archive-command">. + <xref linkend="guc-archive-command">. In addition to <literal>off</>, + to disable, there are three modes: <literal>on</>, <literal>shared</>, + and <literal>always</>. During normal operation, there is no + difference between the three modes, but in archive recovery or + standby mode, it indicates whether the WAL archive is shared between + the primary and the standby server or not. See + <xref linkend="continuous-archiving-in-standby"> for details. + </para> + <para> <varname>archive_mode</> and <varname>archive_command</> are separate variables so that <varname>archive_command</> can be changed without leaving archiving mode. diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml index a17f555..62f7c75 100644 --- a/doc/src/sgml/high-availability.sgml +++ b/doc/src/sgml/high-availability.sgml @@ -1220,6 +1220,54 @@ primary_slot_name = 'node_a_slot' </sect3> </sect2> + + <sect2 id="continuous-archiving-in-standby"> + <title>Continuous archiving in standby</title> + + <indexterm> + <primary>continuous archiving</primary> + <secondary>in standby</secondary> + </indexterm> + + <para> + When continuous WAL archiving is used in a standby, there are two + different scenarios: the WAL archive can be shared between the primary + and the standby, or the standby can have its own WAL archive. In the + shared archive scenario, <varname>archive_mode</varname> must be set to + <literal>shared</literal>, and in the separate archive scenario, to + <literal>always</literal>. Setting it to <literal>on</literal> in a + standby server, or when performing point-in-time recovery, is not + allowed and an error will be raised. When a server is not in recovery + mode, there is no difference between <literal>on</literal>, + <literal>shared</literal>, and <literal>always</literal> modes. + </para> + + <para> + In <literal>shared</literal> archive mode, the standby server tries to + ensure that the archive is complete, even if the primary crashes and + failover happens. The standby server will not archive any WAL segments + as long as it is in standby mode; it is the primary server's + responsibility to do so. It will, however, keep track of which files + have already been archived by the primary, and if failover happens, it + takes over and attempts to archive any files that the primary had not + yet archived. + </para> + + <para> + In <literal>always</literal> archive mode, the standby server will + archive all WAL it receives, whether it's through streaming replication + or by restoring from the primary's archive using + <varname>restore_command</varname>. + </para> + + <para> + In cascading replication, the first standby server and the cascaded + standby servers can use <varname>archive_mode</varname> settings. In + each standby, it should be set to <literal>shared</literal> or + <literal>always</literal>, depending on whether that standby shares the + archive with the primary or standby it is connected to. + </para> + </sect2> </sect1> <sect1 id="warm-standby-failover"> diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml index 3a753a0..a42344e 100644 --- a/doc/src/sgml/protocol.sgml +++ b/doc/src/sgml/protocol.sgml @@ -1646,6 +1646,37 @@ The commands accepted in walsender mode are: </para> </listitem> </varlistentry> + <varlistentry> + <term> + WAL archival report message (B) + </term> + <listitem> + <para> + <variablelist> + <varlistentry> + <term> + Byte1('a') + </term> + <listitem> + <para> + Tells the receiver the last archived WAL segment. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + Byte<replaceable>n</replaceable> + </term> + <listitem> + <para> + Filename of the latest archived file. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + </listitem> + </varlistentry> </variablelist> </para> diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2580996..22b5dda 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -84,7 +84,7 @@ int min_wal_size = 5; /* 80 MB */ int wal_keep_segments = 0; int XLOGbuffers = -1; int XLogArchiveTimeout = 0; -bool XLogArchiveMode = false; +int XLogArchiveMode = ARCHIVE_MODE_OFF; char *XLogArchiveCommand = NULL; bool EnableHotStandby = false; bool fullPageWrites = true; @@ -138,6 +138,25 @@ const struct config_enum_entry sync_method_options[] = { {NULL, 0, false} }; + +/* + * Although only "on", "off", and "always" are documented, + * we accept all the likely variants of "on" and "off". + */ +const struct config_enum_entry archive_mode_options[] = { + {"shared", ARCHIVE_MODE_SHARED, false}, + {"always", ARCHIVE_MODE_ALWAYS, false}, + {"on", ARCHIVE_MODE_ON, false}, + {"off", ARCHIVE_MODE_OFF, false}, + {"true", ARCHIVE_MODE_ON, true}, + {"false", ARCHIVE_MODE_OFF, true}, + {"yes", ARCHIVE_MODE_ON, true}, + {"no", ARCHIVE_MODE_OFF, true}, + {"1", ARCHIVE_MODE_ON, true}, + {"0", ARCHIVE_MODE_OFF, true}, + {NULL, 0, false} +}; + /* * Statistics for current checkpoint are collected in this global struct. * Because only the checkpointer or a stand-alone backend can perform @@ -756,7 +775,7 @@ static MemoryContext walDebugCxt = NULL; #endif static void readRecoveryCommandFile(void); -static void exitArchiveRecovery(TimeLineID endTLI, XLogSegNo endLogSegNo); +static void exitArchiveRecovery(TimeLineID endTLI, XLogRecPtr endOfLog); static bool recoveryStopsBefore(XLogReaderState *record); static bool recoveryStopsAfter(XLogReaderState *record); static void recoveryPausesHere(void); @@ -5949,6 +5968,12 @@ StartupXLOG(void) if (ArchiveRecoveryRequested) { + /* archive_mode=on is not allowed during archive recovery. */ + if (XLogArchiveMode == ARCHIVE_MODE_ON) + ereport(ERROR, + (errmsg("archive_mode='on' cannot be used in archive recovery"), + (errhint("Use 'shared' or 'always' mode instead.")))); + if (StandbyModeRequested) ereport(LOG, (errmsg("entering standby mode"))); diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index a9f20ac..72fe4fd 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -828,9 +828,9 @@ PostmasterMain(int argc, char *argv[]) write_stderr("%s: max_wal_senders must be less than max_connections\n", progname); ExitPostmaster(1); } - if (XLogArchiveMode && wal_level == WAL_LEVEL_MINIMAL) + if (XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level == WAL_LEVEL_MINIMAL) ereport(ERROR, - (errmsg("WAL archival (archive_mode=on) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); + (errmsg("WAL archival (archive_mode=on/always/shared) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); if (max_wal_senders > 0 && wal_level == WAL_LEVEL_MINIMAL) ereport(ERROR, (errmsg("WAL streaming (max_wal_senders > 0) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); @@ -1645,13 +1645,21 @@ ServerLoop(void) start_autovac_launcher = false; /* signal processed */ } - /* If we have lost the archiver, try to start a new one */ - if (XLogArchivingActive() && PgArchPID == 0 && pmState == PM_RUN) - PgArchPID = pgarch_start(); - - /* If we have lost the stats collector, try to start a new one */ - if (PgStatPID == 0 && pmState == PM_RUN) - PgStatPID = pgstat_start(); + /* + * If we have lost the archiver, try to start a new one. + * + * If WAL archiving is enabled always, we try to start a new archiver + * even during recovery. + */ + if (PgArchPID == 0 && wal_level >= WAL_LEVEL_ARCHIVE) + { + if ((pmState == PM_RUN && XLogArchiveMode > ARCHIVE_MODE_OFF) || + ((pmState == PM_RECOVERY || pmState == PM_HOT_STANDBY) && + XLogArchiveMode == ARCHIVE_MODE_ALWAYS)) + { + PgArchPID = pgarch_start(); + } + } /* If we need to signal the autovacuum launcher, do so now */ if (avlauncher_needs_signal) @@ -4807,6 +4815,17 @@ sigusr1_handler(SIGNAL_ARGS) Assert(BgWriterPID == 0); BgWriterPID = StartBackgroundWriter(); + /* + * Start the archiver if we're responsible for (re-)archiving received + * files. + */ + Assert(PgArchPID == 0); + if (wal_level >= WAL_LEVEL_ARCHIVE && + XLogArchiveMode == ARCHIVE_MODE_ALWAYS) + { + PgArchPID = pgarch_start(); + } + pmState = PM_RECOVERY; } if (CheckPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY) && diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c index 9c7710f..e53ffeb 100644 --- a/src/backend/replication/walreceiver.c +++ b/src/backend/replication/walreceiver.c @@ -52,8 +52,11 @@ #include "libpq/pqformat.h" #include "libpq/pqsignal.h" #include "miscadmin.h" +#include "pgstat.h" +#include "postmaster/pgarch.h" #include "replication/walreceiver.h" #include "replication/walsender.h" +#include "storage/fd.h" #include "storage/ipc.h" #include "storage/pmsignal.h" #include "storage/procarray.h" @@ -107,6 +110,9 @@ static struct XLogRecPtr Flush; /* last byte + 1 flushed in the standby */ } LogstreamResult; +/* */ +static char primary_last_archived[MAX_XFN_CHARS + 1]; + static StringInfoData reply_message; static StringInfoData incoming_message; @@ -141,6 +147,7 @@ static void XLogWalRcvFlush(bool dying); static void XLogWalRcvSendReply(bool force, bool requestReply); static void XLogWalRcvSendHSFeedback(bool immed); static void ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime); +static void ProcessArchivalReport(void); /* Signal handlers */ static void WalRcvSigHupHandler(SIGNAL_ARGS); @@ -526,21 +533,12 @@ WalReceiverMain(void) */ if (recvFile >= 0) { - char xlogfname[MAXFNAMELEN]; - XLogWalRcvFlush(false); if (close(recvFile) != 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not close log segment %s: %m", XLogFileNameP(recvFileTLI, recvSegNo)))); - - /* - * Create .done file forcibly to prevent the streamed segment from - * being archived later. - */ - XLogFileName(xlogfname, recvFileTLI, recvSegNo); - XLogArchiveForceDone(xlogfname); } recvFile = -1; @@ -846,6 +844,26 @@ XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len) XLogWalRcvSendReply(true, false); break; } + case 'a': /* Archival report */ + { + /* the content of the message is a filename */ + if (len >= sizeof(primary_last_archived)) + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg_internal("invalid archival report message with length %d", + (int) len))); + memcpy(primary_last_archived, buf, len); + primary_last_archived[len] = '\0'; + if (strspn(buf, VALID_XFN_CHARS) != len) + { + primary_last_archived[0] = '\0'; + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg_internal("unexpected character in primary's last archived filename"))); + } + ProcessArchivalReport(); + break; + } default: ereport(ERROR, (errcode(ERRCODE_PROTOCOL_VIOLATION), @@ -867,39 +885,18 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr) { int segbytes; - if (recvFile < 0 || !XLByteInSeg(recptr, recvSegNo)) + if (!XLByteInSeg(recptr, recvSegNo)) { bool use_existent; /* - * fsync() and close current file before we switch to next one. We - * would otherwise have to reopen this file to fsync it later + * We take care to always close the current file, after writing + * the last byte to it. So this shouldn't happen. */ if (recvFile >= 0) - { - char xlogfname[MAXFNAMELEN]; - - XLogWalRcvFlush(false); - - /* - * XLOG segment files will be re-read by recovery in startup - * process soon, so we don't advise the OS to release cache - * pages associated with the file like XLogFileClose() does. - */ - if (close(recvFile) != 0) - ereport(PANIC, - (errcode_for_file_access(), - errmsg("could not close log segment %s: %m", - XLogFileNameP(recvFileTLI, recvSegNo)))); - - /* - * Create .done file forcibly to prevent the streamed segment - * from being archived later. - */ - XLogFileName(xlogfname, recvFileTLI, recvSegNo); - XLogArchiveForceDone(xlogfname); - } - recvFile = -1; + ereport(ERROR, + (errmsg("unexpected WAL receive location %s", + XLogFileNameP(recvFileTLI, recvSegNo)))); /* Create/use new log file */ XLByteToSeg(recptr, recvSegNo); @@ -954,6 +951,51 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr) buf += byteswritten; LogstreamResult.Write = recptr; + + /* + * If we just wrote the last byte to this segment, fsync() and close + * current file before we switch to next one. We would otherwise have + * to reopen this file to fsync it later. + */ + if (recvOff == XLOG_SEG_SIZE) + { + char xlogfname[MAXFNAMELEN]; + + XLogWalRcvFlush(false); + + /* + * XLOG segment files will be re-read by recovery in startup + * process soon, so we don't advise the OS to release cache + * pages associated with the file like XLogFileClose() does. + */ + if (close(recvFile) != 0) + ereport(PANIC, + (errcode_for_file_access(), + errmsg("could not close log segment %s: %m", + XLogFileNameP(recvFileTLI, recvSegNo)))); + recvFile = -1; + + /* + * Now that this segment is complete, do we need to archive it? + * + * In 'always' mode, we clearly need to archive this. + * + * In 'shared' mode, we might need to, if we get promoted before + * the master has archived this file, so create a .ready file. It + * will be replaced with .done later, if we get acknowledgemet + * from the primary that this has already been archived. + * + * In 'on' mode, we're only responsible for WAL we've generated + * ourselves. + */ + if (XLogArchiveMode == ARCHIVE_MODE_ALWAYS || + XLogArchiveMode == ARCHIVE_MODE_SHARED) + { + XLogFileName(xlogfname, recvFileTLI, recvSegNo); + + XLogArchiveCheckDone(xlogfname); + } + } } } @@ -1215,3 +1257,61 @@ ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime) pfree(receipttime); } } + +/* + * Create .done and .ready files, based on the master's last archival report. + */ +static void +ProcessArchivalReport(void) +{ + DIR *xldir; + struct dirent *xlde; + + elog(DEBUG2, "received archival report from master: %s", + primary_last_archived); + + if (XLogArchiveMode != ARCHIVE_MODE_SHARED) + return; + + /* Check that the filename the primary reported looks valid */ + if (strlen(primary_last_archived) < 24 || + strspn(primary_last_archived, "0123456789ABCDEF") != 24) + return; + + xldir = AllocateDir(XLOGDIR); + if (xldir == NULL) + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not open transaction log directory \"%s\": %m", + XLOGDIR))); + + while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) + { + /* + * We ignore the timeline part of the XLOG segment identifiers in + * deciding whether a segment is still needed. This ensures that we + * won't prematurely remove a segment from a parent timeline. We could + * probably be a little more proactive about removing segments of + * non-parent timelines, but that would be a whole lot more + * complicated. + * + * We use the alphanumeric sorting property of the filenames to decide + * which ones are earlier than the lastoff segment. + */ + if (strlen(xlde->d_name) == 24 && + strspn(xlde->d_name, "0123456789ABCDEF") == 24 && + strcmp(xlde->d_name + 8, primary_last_archived + 8) <= 0) + { + XLogArchiveForceDone(xlde->d_name); + } + } + + FreeDir(xldir); + + /* + * Remember this location in pgstat as well. This makes it visible in + * pg_stat_archiver, and allows the location to be relayed to cascaded + * standbys. + */ + pgstat_send_archiver(primary_last_archived, false); +} diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c index 4a20569..74bdeff 100644 --- a/src/backend/replication/walsender.c +++ b/src/backend/replication/walsender.c @@ -55,6 +55,7 @@ #include "libpq/pqformat.h" #include "miscadmin.h" #include "nodes/replnodes.h" +#include "pgstat.h" #include "replication/basebackup.h" #include "replication/decode.h" #include "replication/logical.h" @@ -152,6 +153,7 @@ static StringInfoData tmpbuf; * wal_sender_timeout doesn't need to be active. */ static TimestampTz last_reply_timestamp = 0; +static char last_archival_report[MAX_XFN_CHARS + 1] = ""; /* Have we sent a heartbeat message asking for reply, since last reply? */ static bool waiting_for_ping_response = false; @@ -209,6 +211,8 @@ static void ProcessStandbyHSFeedbackMessage(void); static void ProcessRepliesIfAny(void); static void WalSndKeepalive(bool requestReply); static void WalSndKeepaliveIfNecessary(TimestampTz now); +static void WalSndArchivalReport(void); +static void WalSndArchivalReportIfNecessary(void); static void WalSndCheckTimeOut(TimestampTz now); static long WalSndComputeSleeptime(TimestampTz now); static void WalSndPrepareWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid, bool last_write); @@ -2879,6 +2883,11 @@ WalSndKeepaliveIfNecessary(TimestampTz now) TimestampTz ping_time; /* + * Send an archival status message, if necessary. + */ + WalSndArchivalReportIfNecessary(); + + /* * Don't send keepalive messages if timeouts are globally disabled or * we're doing something not partaking in timeouts. */ @@ -2907,6 +2916,44 @@ WalSndKeepaliveIfNecessary(TimestampTz now) } /* + * This function is used to send archival report message to standby. + */ +static void +WalSndArchivalReport(void) +{ + elog(LOG, "sending archival report: %s", last_archival_report); + + /* construct the message... */ + resetStringInfo(&output_message); + pq_sendbyte(&output_message, 'a'); + pq_sendbytes(&output_message, last_archival_report, strlen(last_archival_report)); + + /* ... and send it wrapped in CopyData */ + pq_putmessage_noblock('d', output_message.data, output_message.len); +} + +static void +WalSndArchivalReportIfNecessary(void) +{ + PgStat_ArchiverStats *archiver_stats; + + archiver_stats = pgstat_fetch_stat_archiver(); + + if (strcmp(last_archival_report, archiver_stats->last_archived_wal) == 0) + { + pgstat_clear_snapshot(); + return; + } + + strlcpy(last_archival_report, archiver_stats->last_archived_wal, + sizeof(last_archival_report)); + + pgstat_clear_snapshot(); + + WalSndArchivalReport(); +} + +/* * This isn't currently used for anything. Monitoring tools might be * interested in the future, and we'll need something like this in the * future for synchronous replication. diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index f43aff2..7115bcc 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -396,6 +396,7 @@ static const struct config_enum_entry row_security_options[] = { * Options for enum values stored in other modules */ extern const struct config_enum_entry wal_level_options[]; +extern const struct config_enum_entry archive_mode_options[]; extern const struct config_enum_entry sync_method_options[]; extern const struct config_enum_entry dynamic_shared_memory_options[]; @@ -1530,16 +1531,6 @@ static struct config_bool ConfigureNamesBool[] = }, { - {"archive_mode", PGC_POSTMASTER, WAL_ARCHIVING, - gettext_noop("Allows archiving of WAL files using archive_command."), - NULL - }, - &XLogArchiveMode, - false, - NULL, NULL, NULL - }, - - { {"hot_standby", PGC_POSTMASTER, REPLICATION_STANDBY, gettext_noop("Allows connections and queries during recovery."), NULL @@ -3552,6 +3543,16 @@ static struct config_enum ConfigureNamesEnum[] = }, { + {"archive_mode", PGC_POSTMASTER, WAL_ARCHIVING, + gettext_noop("Allows archiving of WAL files using archive_command."), + NULL + }, + &XLogArchiveMode, + ARCHIVE_MODE_OFF, archive_mode_options, + NULL, NULL, NULL + }, + + { {"trace_recovery_messages", PGC_SIGHUP, DEVELOPER_OPTIONS, gettext_noop("Enables logging of recovery-related debugging information."), gettext_noop("Each level includes all the levels that follow it. The later" diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 110983f..90371d7 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -206,7 +206,7 @@ # - Archiving - -#archive_mode = off # allows archiving to be done +#archive_mode = off # allows archiving to be done; off, on, shared, or always # (change requires restart) #archive_command = '' # command to use to archive a logfile segment # placeholders: %p = path of file to archive diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h index 2b1f423..3a49702 100644 --- a/src/include/access/xlog.h +++ b/src/include/access/xlog.h @@ -95,7 +95,6 @@ extern int wal_keep_segments; extern int XLOGbuffers; extern int XLogArchiveTimeout; extern int wal_retrieve_retry_interval; -extern bool XLogArchiveMode; extern char *XLogArchiveCommand; extern bool EnableHotStandby; extern bool fullPageWrites; @@ -105,6 +104,16 @@ extern bool log_checkpoints; extern int CheckPointSegments; +/* Archive modes */ +typedef enum ArchiveMode +{ + ARCHIVE_MODE_OFF = 0, /* disabled */ + ARCHIVE_MODE_ON, /* enabled while server is running normally */ + ARCHIVE_MODE_SHARED, /* archive is shared with master */ + ARCHIVE_MODE_ALWAYS /* enabled always (even during recovery) */ +} ArchiveMode; +extern int XLogArchiveMode; + /* WAL levels */ typedef enum WalLevel { @@ -115,7 +124,8 @@ typedef enum WalLevel } WalLevel; extern int wal_level; -#define XLogArchivingActive() (XLogArchiveMode && wal_level >= WAL_LEVEL_ARCHIVE) +#define XLogArchivingActive() \ + (XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level >= WAL_LEVEL_ARCHIVE) #define XLogArchiveCommandSet() (XLogArchiveCommand[0] != '\0') /* -- 2.1.4 ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-21 06:53 Michael Paquier <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Michael Paquier @ 2015-04-21 06:53 UTC (permalink / raw) To: [email protected]; +Cc: Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On Thu, Apr 16, 2015 at 8:57 PM, Heikki Linnakangas wrote: > Oh, hang on, that's not necessarily true. On promotion, the standby archives > the last, partial WAL segment from the old timeline. That's just wrong > (http://www.postgresql.org/message-id/[email protected]), and in > fact I somehow thought I changed that already, but apparently not. So let's > stop doing that. Er. Are you planning to prevent the standby from archiving the last partial segment from the old timeline at promotion? I thought from previous discussions that we should do it as master (be it crashed, burned, burried or dead) may not have the occasion to do it. By preventing its archiving you close the door to the case where master did not have the occasion to archive it. +/* */ +static char primary_last_archived[MAX_XFN_CHARS + 1]; This is visibly missing a comment. As primary_last_archived is used only by ProcessArchivalReport(), wouldn't it be better to pass it as argument to this function? + /* Check that the filename the primary reported looks valid */ + if (strlen(primary_last_archived) < 24 || + strspn(primary_last_archived, "0123456789ABCDEF") != 24) + return; Not related to this patch, but we had better have a macro doing this job I think... It keeps spreading around. People may be surprised that a base backup taken from a node that has archive_mode = on set (that's the case in a very large number of cases) will not be able to work as-is as node startup will fail as follows: FATAL: archive_mode='on' cannot be used in archive recovery HINT: Use 'shared' or 'always' mode instead. One idea would be to simply ignore the fact that archive_mode = on on nodes in recovery instead of dropping an error. Note that I like the fact that it drops an error as that's clear, I just point the fact that people may be surprised that base backups are not working anymore now in this case. Are both WalSndArchivalReport() and WalSndArchivalReportIfNecessary() really necessary? I think that for simplicity you could merge them and use last_archival_report as a local variable. Creating a dependency between the pgstat machinery and the WAL sender looks weak to me. For example with this patch a master cannot stop, as it waits indefinitely: LOG: using stale statistics instead of current ones because stats collector is not responding LOG: sending archival report: You could scan archive_status/ but that would be costly if there are many entries to scan and I think that walsender should be highly responsive. Or you could directly store the name of the lastly archived WAL segment marked as .done in let's say archive_status/last_archived. An entry for that in the control file does not seem the right place as a node may not have archive_mode enabled that's why I am not mentioning it. Regards, -- Michael ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-21 07:38 Heikki Linnakangas <[email protected]> parent: Michael Paquier <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2015-04-21 07:38 UTC (permalink / raw) To: Michael Paquier <[email protected]>; +Cc: Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 04/21/2015 09:53 AM, Michael Paquier wrote: > On Thu, Apr 16, 2015 at 8:57 PM, Heikki Linnakangas wrote: >> Oh, hang on, that's not necessarily true. On promotion, the standby > archives >> the last, partial WAL segment from the old timeline. That's just wrong >> (http://www.postgresql.org/message-id/[email protected]), and in >> fact I somehow thought I changed that already, but apparently not. So > let's >> stop doing that. > > Er. Are you planning to prevent the standby from archiving the last partial > segment from the old timeline at promotion? Yes. > I thought from previous discussions that we should do it as master > (be it crashed, burned, burried or dead) may not have the occasion to > do it. By preventing its archiving you close the door to the case > where master did not have the occasion to archive it. The current situation is a mess: 1. Even though we archive the last segment in the standby, there is no guarantee that the master had archived all the previous segments already. 2. If the master is not totally dead, it might try to archive the same file with more WAL in it, at the same time or just afterwards, or even just before the standby has completed promotion. Which copy do you keep in the archive? Having to deal with that makes the archive_command more complicated. Note that even though we don't archive the partial last segment on the previous timeline, the same WAL is copied to the first segment on the new timeline. So the WAL isn't lost. > People may be surprised that a base backup taken from a node that has > archive_mode = on set (that's the case in a very large number of cases) > will not be able to work as-is as node startup will fail as follows: > FATAL: archive_mode='on' cannot be used in archive recovery > HINT: Use 'shared' or 'always' mode instead. Hmm, good point. > One idea would be to simply ignore the fact that archive_mode = on on nodes > in recovery instead of dropping an error. Note that I like the fact that it > drops an error as that's clear, I just point the fact that people may be > surprised that base backups are not working anymore now in this case. By "ignore", what behaviour do you mean? Would "on" be equivalent to "shared", "always", or something else? Or we could keep the current behaviour with archive_mode=on (except for the last segment thing, which is just wrong), where the standby only archives the new timeline, and nothing from the previous timelines. Are the use cases where you'd want that, rather than the new "shared" mode? I wanted to keep the 'on' mode for backwards-compatibility, but if that causes more problems, it might be better to just remove it and force the admin to choose what kind of a setup he has, with "shared" or "always". > Creating a dependency between the pgstat machinery and the WAL sender looks > weak to me. For example with this patch a master cannot stop, as it waits > indefinitely: > LOG: using stale statistics instead of current ones because stats > collector is not responding > LOG: sending archival report: Hmm, yeah, having walsender to wait for the stats file to appear is not good. > You could scan archive_status/ but that would be costly if there are many > entries to scan and I think that walsender should be highly responsive. Or > you could directly store the name of the lastly archived WAL segment marked > as .done in let's say archive_status/last_archived. An entry for that in > the control file does not seem the right place as a node may not have > archive_mode enabled that's why I am not mentioning it. The ways that the archiver process can communicate with the rest of the system are limited, for the sake of robustness. Writing to the control file is definitely not OK. I think using the stats collector is OK for this, but we'll have to arrange it so that the walsender doesn't block on it, and should probably not force new stat file so often. A 5-10 seconds old stats file would be perfectly fine for this purpose. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-21 09:04 Michael Paquier <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Michael Paquier @ 2015-04-21 09:04 UTC (permalink / raw) To: [email protected]; +Cc: Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On Tue, Apr 21, 2015 at 4:38 PM, Heikki Linnakangas <[email protected]> wrote: > On 04/21/2015 09:53 AM, Michael Paquier wrote: > >> On Thu, Apr 16, 2015 at 8:57 PM, Heikki Linnakangas wrote: >> >>> Oh, hang on, that's not necessarily true. On promotion, the standby >>> >> archives >> >>> the last, partial WAL segment from the old timeline. That's just wrong >>> (http://www.postgresql.org/message-id/[email protected]), and >>> in >>> fact I somehow thought I changed that already, but apparently not. So >>> >> let's >> >>> stop doing that. >>> >> >> Er. Are you planning to prevent the standby from archiving the last >> partial >> segment from the old timeline at promotion? >> > > Yes. > > I thought from previous discussions that we should do it as master >> (be it crashed, burned, burried or dead) may not have the occasion to >> do it. By preventing its archiving you close the door to the case >> where master did not have the occasion to archive it. >> > > The current situation is a mess: > > 1. Even though we archive the last segment in the standby, there is no > guarantee that the master had archived all the previous segments already. > 2. If the master is not totally dead, it might try to archive the same file > with more WAL in it, at the same time or just afterwards, or even just > before the standby has completed promotion. Which copy do you keep in the > archive? Having to deal with that makes the archive_command more > complicated. > > Note that even though we don't archive the partial last segment on the > previous timeline, the same WAL is copied to the first segment on the new > timeline. So the WAL isn't lost. > But if the failed master has archived those segments safely, we may need them, no? I am not sure we can ignore a user who would want to do a PITR with recovery_target_timeline pointing to the one of the failed master. > > People may be surprised that a base backup taken from a node that has >> archive_mode = on set (that's the case in a very large number of cases) >> will not be able to work as-is as node startup will fail as follows: >> FATAL: archive_mode='on' cannot be used in archive recovery >> HINT: Use 'shared' or 'always' mode instead. >> > > Hmm, good point. > > One idea would be to simply ignore the fact that archive_mode = on on >> nodes >> in recovery instead of dropping an error. Note that I like the fact that >> it >> drops an error as that's clear, I just point the fact that people may be >> surprised that base backups are not working anymore now in this case. >> > > By "ignore", what behaviour do you mean? Would "on" be equivalent to > "shared", "always", or something else? > I meant something backward-compatible, with files marked as .done when they are finished replaying... But now my words *are* weird as on != off ;) Or we could keep the current behaviour with archive_mode=on (except for the > last segment thing, which is just wrong), where the standby only archives > the new timeline, and nothing from the previous timelines. > I guess this would solve the issue here then, which is not a bad thing in itself: http://www.postgresql.org/message-id/20140918180734.361021e1@erg We would need to check if the situation improves with the 'always' mode btw. > Are the use cases where you'd want that, rather than the new "shared" > mode? I wanted to keep the 'on' mode for backwards-compatibility, but if > that causes more problems, it might be better to just remove it and force > the admin to choose what kind of a setup he has, with "shared" or "always". > The 'on' mode is still useful IMO to get a behavior a maximum close to what previous releases did. Regards, -- Michael ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-21 10:55 Heikki Linnakangas <[email protected]> parent: Michael Paquier <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2015-04-21 10:55 UTC (permalink / raw) To: Michael Paquier <[email protected]>; +Cc: Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 04/21/2015 12:04 PM, Michael Paquier wrote: > On Tue, Apr 21, 2015 at 4:38 PM, Heikki Linnakangas <[email protected]> wrote: > >> Note that even though we don't archive the partial last segment on the >> previous timeline, the same WAL is copied to the first segment on the new >> timeline. So the WAL isn't lost. > > But if the failed master has archived those segments safely, we may need > them, no? I am not sure we can ignore a user who would want to do a PITR > with recovery_target_timeline pointing to the one of the failed master. I think it would be acceptable. If you want to maintain an up-to-the-second archive, you can use pg_receivexlog. Mind you, if the standby wasn't promoted, the partial segment would not be present in the archive anyway. And you can copy the WAL segment manually from 0000000200000000000000XX to pg_xlog/0000000100000000000000XX before starting PITR. Another thought is that we could archive the partial file, but with a different name to avoid confusing it with the full segment. For example, we could archive a partial 000000010000000000000012 segment as "000000020000000000000012.00000128.partial", where 00000128 indicates how far that file is valid (this naming is similar to how the backup history files are named). Recovery wouldn't automatically pick up those files, but the DBA could easily copy the partial file into pg_xlog with the full segment's name, if he wants to do PITR to that piece of WAL. >> Are the use cases where you'd want that, rather than the new "shared" >> mode? I wanted to keep the 'on' mode for backwards-compatibility, but if >> that causes more problems, it might be better to just remove it and force >> the admin to choose what kind of a setup he has, with "shared" or "always". > > The 'on' mode is still useful IMO to get a behavior a maximum close to what > previous releases did. But would you ever want the old behaviour, rather than the new shared or always behaviour? - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-21 21:42 Robert Haas <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 2 replies; 31+ messages in thread From: Robert Haas @ 2015-04-21 21:42 UTC (permalink / raw) To: hlinnaka <[email protected]>; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On Tue, Apr 21, 2015 at 6:55 AM, Heikki Linnakangas <[email protected]> wrote: > On 04/21/2015 12:04 PM, Michael Paquier wrote: >> On Tue, Apr 21, 2015 at 4:38 PM, Heikki Linnakangas <[email protected]> >> wrote: >>> Note that even though we don't archive the partial last segment on the >>> previous timeline, the same WAL is copied to the first segment on the new >>> timeline. So the WAL isn't lost. >> >> But if the failed master has archived those segments safely, we may need >> them, no? I am not sure we can ignore a user who would want to do a PITR >> with recovery_target_timeline pointing to the one of the failed master. > > I think it would be acceptable. If you want to maintain an up-to-the-second > archive, you can use pg_receivexlog. Mind you, if the standby wasn't > promoted, the partial segment would not be present in the archive anyway. > And you can copy the WAL segment manually from 0000000200000000000000XX to > pg_xlog/0000000100000000000000XX before starting PITR. > > Another thought is that we could archive the partial file, but with a > different name to avoid confusing it with the full segment. For example, we > could archive a partial 000000010000000000000012 segment as > "000000020000000000000012.00000128.partial", where 00000128 indicates how > far that file is valid (this naming is similar to how the backup history > files are named). Recovery wouldn't automatically pick up those files, but > the DBA could easily copy the partial file into pg_xlog with the full > segment's name, if he wants to do PITR to that piece of WAL. So, suppose you A replicating to B (via an archive) replicating to C (via a separate archive); A dies, B is promoted. It sounds to me like today this will work and with your proposed change it will require manual intervention. I don't think that's OK. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-22 00:30 Michael Paquier <[email protected]> parent: Robert Haas <[email protected]> 1 sibling, 2 replies; 31+ messages in thread From: Michael Paquier @ 2015-04-22 00:30 UTC (permalink / raw) To: Robert Haas <[email protected]>; +Cc: hlinnaka <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On Wed, Apr 22, 2015 at 6:42 AM, Robert Haas <[email protected]> wrote: > > On Tue, Apr 21, 2015 at 6:55 AM, Heikki Linnakangas <[email protected]> wrote: > > On 04/21/2015 12:04 PM, Michael Paquier wrote: > >> On Tue, Apr 21, 2015 at 4:38 PM, Heikki Linnakangas <[email protected]> > >> wrote: > >>> Note that even though we don't archive the partial last segment on the > >>> previous timeline, the same WAL is copied to the first segment on the new > >>> timeline. So the WAL isn't lost. > >> > >> But if the failed master has archived those segments safely, we may need > >> them, no? I am not sure we can ignore a user who would want to do a PITR > >> with recovery_target_timeline pointing to the one of the failed master. > > > > I think it would be acceptable. If you want to maintain an up-to-the-second > > archive, you can use pg_receivexlog. Mind you, if the standby wasn't > > promoted, the partial segment would not be present in the archive anyway. > > And you can copy the WAL segment manually from 0000000200000000000000XX to > > pg_xlog/0000000100000000000000XX before starting PITR. > > > > Another thought is that we could archive the partial file, but with a > > different name to avoid confusing it with the full segment. For example, we > > could archive a partial 000000010000000000000012 segment as > > "000000020000000000000012.00000128.partial", where 00000128 indicates how > > far that file is valid (this naming is similar to how the backup history > > files are named). Recovery wouldn't automatically pick up those files, but > > the DBA could easily copy the partial file into pg_xlog with the full > > segment's name, if he wants to do PITR to that piece of WAL. > > So, suppose you A replicating to B (via an archive) replicating to C > (via a separate archive); A dies, B is promoted. It sounds to me like > today this will work and with your proposed change it will require > manual intervention. I don't think that's OK. This is going to change a behavior that people are used to for a couple of releases. I would not mind having this patch do "archive_mode = on during recovery" => archive only segments generated by this node + the last partial segment on the old timeline at promotion, without renaming to preserve backward compatible behavior. If master and standby point to separate archive locations, this way the operator can sort out later the one he would want to use. If they point to the same location, archive_command scripts already do internally such renaming, at least that's what I suspect an experienced user would do, now it is true that not many people are experienced in this area I see mistakes regarding such things on a weekly basis... This .partial segment renaming is something that we should let the archive_command manage with its internal logic. Regards, -- Michael -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-22 06:17 Heikki Linnakangas <[email protected]> parent: Robert Haas <[email protected]> 1 sibling, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2015-04-22 06:17 UTC (permalink / raw) To: Robert Haas <[email protected]>; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 04/22/2015 12:42 AM, Robert Haas wrote: > On Tue, Apr 21, 2015 at 6:55 AM, Heikki Linnakangas <[email protected]> wrote: >> On 04/21/2015 12:04 PM, Michael Paquier wrote: >>> On Tue, Apr 21, 2015 at 4:38 PM, Heikki Linnakangas <[email protected]> >>> wrote: >>>> Note that even though we don't archive the partial last segment on the >>>> previous timeline, the same WAL is copied to the first segment on the new >>>> timeline. So the WAL isn't lost. >>> >>> But if the failed master has archived those segments safely, we may need >>> them, no? I am not sure we can ignore a user who would want to do a PITR >>> with recovery_target_timeline pointing to the one of the failed master. >> >> I think it would be acceptable. If you want to maintain an up-to-the-second >> archive, you can use pg_receivexlog. Mind you, if the standby wasn't >> promoted, the partial segment would not be present in the archive anyway. >> And you can copy the WAL segment manually from 0000000200000000000000XX to >> pg_xlog/0000000100000000000000XX before starting PITR. >> >> Another thought is that we could archive the partial file, but with a >> different name to avoid confusing it with the full segment. For example, we >> could archive a partial 000000010000000000000012 segment as >> "000000020000000000000012.00000128.partial", where 00000128 indicates how >> far that file is valid (this naming is similar to how the backup history >> files are named). Recovery wouldn't automatically pick up those files, but >> the DBA could easily copy the partial file into pg_xlog with the full >> segment's name, if he wants to do PITR to that piece of WAL. > > So, suppose you A replicating to B (via an archive) replicating to C > (via a separate archive); A dies, B is promoted. It sounds to me like > today this will work and with your proposed change it will require > manual intervention. No. If there is no streaming replication involved, no partial files will be archived, with or without this patch. There is no change to that scenario. Note that it's a bit complicated to set up that scenario today. Archiving is never enabled in recovery mode, so you'll need to use a custom cron job or something to maintain the archive that C uses. The files will not automatically flow from B to the second archive. With the patch we're discussing, however, it would be easy: just set archive_mode='always' in B. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-22 06:38 Heikki Linnakangas <[email protected]> parent: Michael Paquier <[email protected]> 1 sibling, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2015-04-22 06:38 UTC (permalink / raw) To: Michael Paquier <[email protected]>; Robert Haas <[email protected]>; +Cc: Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 04/22/2015 03:30 AM, Michael Paquier wrote: > This is going to change a behavior that people are used to for a > couple of releases. I would not mind having this patch do > "archive_mode = on during recovery" => archive only segments generated > by this node + the last partial segment on the old timeline at > promotion, without renaming to preserve backward compatible behavior. > If master and standby point to separate archive locations, this way > the operator can sort out later the one he would want to use. If they > point to the same location, archive_command scripts already do > internally such renaming, at least that's what I suspect an > experienced user would do, now it is true that not many people are > experienced in this area I see mistakes regarding such things on a > weekly basis... This .partial segment renaming is something that we > should let the archive_command manage with its internal logic. Currently, the archive command doesn't know if the segment it's archiving is partial or not, so you can't put any logic there to manage it. But if we archive it with the .partial suffix, then you can put logic in the restore_command to check for .partial files, if you really want to. I feel that the best approach is to archive the last, partial segment, but with the .partial suffix. I don't see any plausible real-world setup where the current behaviour would be better. I don't really see much need to archive the partial segment at all, but there's also no harm in doing it, as long as it's clearly marked with the .partial suffix. BTW, pg_receivexlog also uses a ".partial" file, while it's streaming WAL from the server. The .partial suffix is removed when the segment is complete. So there's some precedence to this. pg_receivexlog adds just ".partial" to the filename, it doesn't add any information of what portion of the file is valid like I suggested here, though. Perhaps we should follow pg_receivexlog's example at promotion too, for consistency. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-22 07:07 Michael Paquier <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Michael Paquier @ 2015-04-22 07:07 UTC (permalink / raw) To: [email protected]; +Cc: Robert Haas <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On Wed, Apr 22, 2015 at 3:38 PM, Heikki Linnakangas <[email protected]> wrote: > On 04/22/2015 03:30 AM, Michael Paquier wrote: >> >> This is going to change a behavior that people are used to for a >> couple of releases. I would not mind having this patch do >> "archive_mode = on during recovery" => archive only segments generated >> by this node + the last partial segment on the old timeline at >> promotion, without renaming to preserve backward compatible behavior. >> If master and standby point to separate archive locations, this way >> the operator can sort out later the one he would want to use. If they >> point to the same location, archive_command scripts already do >> internally such renaming, at least that's what I suspect an >> experienced user would do, now it is true that not many people are >> experienced in this area I see mistakes regarding such things on a >> weekly basis... This .partial segment renaming is something that we >> should let the archive_command manage with its internal logic. > > > Currently, the archive command doesn't know if the segment it's archiving is > partial or not, so you can't put any logic there to manage it. But if we > archive it with the .partial suffix, then you can put logic in the > restore_command to check for .partial files, if you really want to. Well, now you can check as well if there is a file with the same name already archived and append a suffix to the new file copied, keep the two files, and then let restore_command sort things up as it wants with the two segment files it finds. > I feel that the best approach is to archive the last, partial segment, but > with the .partial suffix. I don't see any plausible real-world setup where > the current behavior would be better. I don't really see much need to > archive the partial segment at all, but there's also no harm in doing it, as > long as it's clearly marked with the .partial suffix. Well, as long as it is clearly archived at promotion, even with a suffix, I guess that I am fine... This will need some tweaking on restore_command for existing applications, but as long as it is clearly documented I am fine. Shouldn't this be a different patch though? > BTW, pg_receivexlog also uses a ".partial" file, while it's streaming WAL > from the server. The .partial suffix is removed when the segment is > complete. So there's some precedence to this. pg_receivexlog adds just > ".partial" to the filename, it doesn't add any information of what portion > of the file is valid like I suggested here, though. Perhaps we should follow > pg_receivexlog's example at promotion too, for consistency. Consistency here sounds good to me. -- Michael -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-22 18:30 Robert Haas <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Robert Haas @ 2015-04-22 18:30 UTC (permalink / raw) To: hlinnaka <[email protected]>; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On Wed, Apr 22, 2015 at 2:17 AM, Heikki Linnakangas <[email protected]> wrote: > Note that it's a bit complicated to set up that scenario today. Archiving is > never enabled in recovery mode, so you'll need to use a custom cron job or > something to maintain the archive that C uses. The files will not > automatically flow from B to the second archive. With the patch we're > discussing, however, it would be easy: just set archive_mode='always' in B. Hmm, I see. But if C never replays the last, partial segment from the old timeline, how does it follow the timeline switch? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-22 18:58 Robert Haas <[email protected]> parent: Michael Paquier <[email protected]> 1 sibling, 0 replies; 31+ messages in thread From: Robert Haas @ 2015-04-22 18:58 UTC (permalink / raw) To: Michael Paquier <[email protected]>; +Cc: hlinnaka <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On Tue, Apr 21, 2015 at 8:30 PM, Michael Paquier <[email protected]> wrote: > This .partial segment renaming is something that we > should let the archive_command manage with its internal logic. This strikes me as equivalent to saying "we don't know how to make this work right, but maybe our users will know". That never works out. As things stand, we have a situation where the archive_command examples in our documentation are known to be flawed. They don't fsync the file, and they'll write a partial file and then, when rerun, fail to copy the full file because there's already something there. Efforts have been made to fix these problems (see the pg_copy thread), but they haven't been completed yet, nor have we even documented the issues with the commands recommended by the documentation. Let's please not throw anything else on the pile of things we're expecting users to somehow "get right". -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-22 19:01 Heikki Linnakangas <[email protected]> parent: Robert Haas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2015-04-22 19:01 UTC (permalink / raw) To: Robert Haas <[email protected]>; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 04/22/2015 09:30 PM, Robert Haas wrote: > On Wed, Apr 22, 2015 at 2:17 AM, Heikki Linnakangas <[email protected]> wrote: >> Note that it's a bit complicated to set up that scenario today. Archiving is >> never enabled in recovery mode, so you'll need to use a custom cron job or >> something to maintain the archive that C uses. The files will not >> automatically flow from B to the second archive. With the patch we're >> discussing, however, it would be easy: just set archive_mode='always' in B. > > Hmm, I see. But if C never replays the last, partial segment from the > old timeline, how does it follow the timeline switch? At timeline switch, we copy the old segment to the new timeline, and start writing where we left off. So the WAL from the old timeline is found in the segment nominally belonging to the new timeline. For example, imagine that perform point-in-time recovery to WAL position 0/1237E568, on timeline 1. That falls within segment 000000010000000000000012. Then we end recovery, and switch to timeline 2. After the switch, and some more WAL-logged actions, we'll have these files in pg_xlog: 000000010000000000000011 000000010000000000000012 000000020000000000000012 000000020000000000000013 000000020000000000000014 Note that there are two segments ending in "12". They both have the same point up to offset 0x37E568, corresponding to the switch point 0/1237E568. After that, the contents diverge: the segment on the new timeline contains a checkpoint/end-of-recovery record at that point, followed by new WAL belonging to the new timeline. Recovery knows about that, so that if you set recovery target to timeline 2, and it needs the WAL at the beginning of segment 12 (still belonging to timeline 1), it will try to restoring both "000000010000000000000012" and "000000020000000000000012". - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-22 19:21 Robert Haas <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Robert Haas @ 2015-04-22 19:21 UTC (permalink / raw) To: hlinnaka <[email protected]>; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On Wed, Apr 22, 2015 at 3:01 PM, Heikki Linnakangas <[email protected]> wrote: > On 04/22/2015 09:30 PM, Robert Haas wrote: >> On Wed, Apr 22, 2015 at 2:17 AM, Heikki Linnakangas <[email protected]> >> wrote: >>> >>> Note that it's a bit complicated to set up that scenario today. Archiving >>> is >>> never enabled in recovery mode, so you'll need to use a custom cron job >>> or >>> something to maintain the archive that C uses. The files will not >>> automatically flow from B to the second archive. With the patch we're >>> discussing, however, it would be easy: just set archive_mode='always' in >>> B. >> >> >> Hmm, I see. But if C never replays the last, partial segment from the >> old timeline, how does it follow the timeline switch? > > At timeline switch, we copy the old segment to the new timeline, and start > writing where we left off. So the WAL from the old timeline is found in the > segment nominally belonging to the new timeline. Check. > For example, imagine that perform point-in-time recovery to WAL position > 0/1237E568, on timeline 1. That falls within segment > 000000010000000000000012. Then we end recovery, and switch to timeline 2. > After the switch, and some more WAL-logged actions, we'll have these files > in pg_xlog: > > 000000010000000000000011 > 000000010000000000000012 > 000000020000000000000012 > 000000020000000000000013 > 000000020000000000000014 Is the 000000010000000000000012 file a "partial" segment of the sort you're proposing to no longer achive? > Note that there are two segments ending in "12". They both have the same > point up to offset 0x37E568, corresponding to the switch point 0/1237E568. > After that, the contents diverge: the segment on the new timeline contains a > checkpoint/end-of-recovery record at that point, followed by new WAL > belonging to the new timeline. Check. > Recovery knows about that, so that if you set recovery target to timeline 2, > and it needs the WAL at the beginning of segment 12 (still belonging to > timeline 1), it will try to restoring both "000000010000000000000012" and > "000000020000000000000012". What if you set the recovery target to timeline 3? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-22 19:34 Heikki Linnakangas <[email protected]> parent: Robert Haas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2015-04-22 19:34 UTC (permalink / raw) To: Robert Haas <[email protected]>; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 04/22/2015 10:21 PM, Robert Haas wrote: > On Wed, Apr 22, 2015 at 3:01 PM, Heikki Linnakangas <[email protected]> wrote: >> For example, imagine that perform point-in-time recovery to WAL position >> 0/1237E568, on timeline 1. That falls within segment >> 000000010000000000000012. Then we end recovery, and switch to timeline 2. >> After the switch, and some more WAL-logged actions, we'll have these files >> in pg_xlog: >> >> 000000010000000000000011 >> 000000010000000000000012 >> 000000020000000000000012 >> 000000020000000000000013 >> 000000020000000000000014 > > Is the 000000010000000000000012 file a "partial" segment of the sort > you're proposing to no longer achive? If you did pure archive recovery, with no streaming replication involved, then no. If it was created by streaming replication, and the replication had not filled the whole segment yet, then yes, it would be a partial segment. >> Note that there are two segments ending in "12". They both have the same >> point up to offset 0x37E568, corresponding to the switch point 0/1237E568. >> After that, the contents diverge: the segment on the new timeline contains a >> checkpoint/end-of-recovery record at that point, followed by new WAL >> belonging to the new timeline. > > Check. > >> Recovery knows about that, so that if you set recovery target to timeline 2, >> and it needs the WAL at the beginning of segment 12 (still belonging to >> timeline 1), it will try to restoring both "000000010000000000000012" and >> "000000020000000000000012". > > What if you set the recovery target to timeline 3? It depends how timeline 3 was created. If timeline 3 was forked off from timeline 2, then recovery would find it. If it was forked off directly from timeline 1, then no. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-22 20:58 Robert Haas <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Robert Haas @ 2015-04-22 20:58 UTC (permalink / raw) To: hlinnaka <[email protected]>; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On Wed, Apr 22, 2015 at 3:34 PM, Heikki Linnakangas <[email protected]> wrote: > On 04/22/2015 10:21 PM, Robert Haas wrote: >> On Wed, Apr 22, 2015 at 3:01 PM, Heikki Linnakangas <[email protected]> >> wrote: >>> For example, imagine that perform point-in-time recovery to WAL position >>> 0/1237E568, on timeline 1. That falls within segment >>> 000000010000000000000012. Then we end recovery, and switch to timeline 2. >>> After the switch, and some more WAL-logged actions, we'll have these >>> files >>> in pg_xlog: >>> >>> 000000010000000000000011 >>> 000000010000000000000012 >>> 000000020000000000000012 >>> 000000020000000000000013 >>> 000000020000000000000014 >> >> >> Is the 000000010000000000000012 file a "partial" segment of the sort >> you're proposing to no longer achive? > > If you did pure archive recovery, with no streaming replication involved, > then no. If it was created by streaming replication, and the replication had > not filled the whole segment yet, then yes, it would be a partial segment. Why the difference? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-04-23 08:11 Heikki Linnakangas <[email protected]> parent: Robert Haas <[email protected]> 0 siblings, 0 replies; 31+ messages in thread From: Heikki Linnakangas @ 2015-04-23 08:11 UTC (permalink / raw) To: Robert Haas <[email protected]>; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 04/22/2015 11:58 PM, Robert Haas wrote: > On Wed, Apr 22, 2015 at 3:34 PM, Heikki Linnakangas <[email protected]> wrote: >> On 04/22/2015 10:21 PM, Robert Haas wrote: >>> On Wed, Apr 22, 2015 at 3:01 PM, Heikki Linnakangas <[email protected]> >>> wrote: >>>> For example, imagine that perform point-in-time recovery to WAL position >>>> 0/1237E568, on timeline 1. That falls within segment >>>> 000000010000000000000012. Then we end recovery, and switch to timeline 2. >>>> After the switch, and some more WAL-logged actions, we'll have these >>>> files >>>> in pg_xlog: >>>> >>>> 000000010000000000000011 >>>> 000000010000000000000012 >>>> 000000020000000000000012 >>>> 000000020000000000000013 >>>> 000000020000000000000014 >>> >>> >>> Is the 000000010000000000000012 file a "partial" segment of the sort >>> you're proposing to no longer achive? >> >> If you did pure archive recovery, with no streaming replication involved, >> then no. If it was created by streaming replication, and the replication had >> not filled the whole segment yet, then yes, it would be a partial segment. > > Why the difference? Because we don't archive partial segments, except for the last one at a timeline switch, and there was no timeline switch to timeline 1 within that segment. It doesn't really matter, though. The behaviour at the switch from timeline 1 to 2 works the same, whether the 000000010000000000000012 segment is complete or not. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-05-08 13:21 Heikki Linnakangas <[email protected]> parent: Michael Paquier <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2015-05-08 13:21 UTC (permalink / raw) To: Michael Paquier <[email protected]>; +Cc: Robert Haas <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 04/22/2015 10:07 AM, Michael Paquier wrote: > On Wed, Apr 22, 2015 at 3:38 PM, Heikki Linnakangas <[email protected]> wrote: >> I feel that the best approach is to archive the last, partial segment, but >> with the .partial suffix. I don't see any plausible real-wold setup where >> the current behavior would be better. I don't really see much need to >> archive the partial segment at all, but there's also no harm in doing it, as >> long as it's clearly marked with the .partial suffix. > > Well, as long as it is clearly archived at promotion, even with a > suffix, I guess that I am fine... This will need some tweaking on > restore_command for existing applications, but as long as it is > clearly documented I am fine. Shouldn't this be a different patch > though? Ok, I came up with the attached, which adds the .partial suffix to the partial WAL segment that's archived after promotion. I couldn't find any natural place to talk about it in the docs, though. I think after the docs changes from the main patch are applied, it would be natural to mention this in the "Continuous archiving in standby", so I think I'll add that later. Barring objections, I'll push this later tonight. Now that we got this last-partial-segment problem out of the way, I'm going to try fixing the problem you (Michael) pointed out about relying on pgstat file. Meanwhile, I'd love to get more feedback on the rest of the patch, and the documentation. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers Attachments: [application/x-patch] 0001-Add-macros-to-check-if-a-filename-is-a-WAL-segment-o.patch (6.4K, 2-0001-Add-macros-to-check-if-a-filename-is-a-WAL-segment-o.patch) download | inline diff: From 15c123141d1eef0d6b05a384d1c5c202ffa04a84 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas <[email protected]> Date: Fri, 8 May 2015 12:04:46 +0300 Subject: [PATCH 1/2] Add macros to check if a filename is a WAL segment or other such file. We had many instances of the strlen + strspn combination to check for that. This makes the code a bit easier to read. --- src/backend/access/transam/xlog.c | 11 +++-------- src/backend/replication/basebackup.c | 7 ++----- src/bin/pg_basebackup/pg_receivexlog.c | 16 ++-------------- src/bin/pg_resetxlog/pg_resetxlog.c | 8 ++++++-- src/include/access/xlog_internal.h | 18 ++++++++++++++++++ 5 files changed, 31 insertions(+), 29 deletions(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 92822a1..5097173 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -3577,8 +3577,7 @@ RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr) while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { /* Ignore files that are not XLOG segments */ - if (strlen(xlde->d_name) != 24 || - strspn(xlde->d_name, "0123456789ABCDEF") != 24) + if (!IsXLogFileName(xlde->d_name)) continue; /* @@ -3650,8 +3649,7 @@ RemoveNonParentXlogFiles(XLogRecPtr switchpoint, TimeLineID newTLI) while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { /* Ignore files that are not XLOG segments */ - if (strlen(xlde->d_name) != 24 || - strspn(xlde->d_name, "0123456789ABCDEF") != 24) + if (!IsXLogFileName(xlde->d_name)) continue; /* @@ -3839,10 +3837,7 @@ CleanupBackupHistory(void) while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { - if (strlen(xlde->d_name) > 24 && - strspn(xlde->d_name, "0123456789ABCDEF") == 24 && - strcmp(xlde->d_name + strlen(xlde->d_name) - strlen(".backup"), - ".backup") == 0) + if (IsBackupHistoryFileName(xlde->d_name)) { if (XLogArchiveCheckDone(xlde->d_name)) { diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c index 3563fd9..de103c6 100644 --- a/src/backend/replication/basebackup.c +++ b/src/backend/replication/basebackup.c @@ -350,17 +350,14 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir) while ((de = ReadDir(dir, "pg_xlog")) != NULL) { /* Does it look like a WAL segment, and is it in the range? */ - if (strlen(de->d_name) == 24 && - strspn(de->d_name, "0123456789ABCDEF") == 24 && + if (IsXLogFileName(de->d_name) && strcmp(de->d_name + 8, firstoff + 8) >= 0 && strcmp(de->d_name + 8, lastoff + 8) <= 0) { walFileList = lappend(walFileList, pstrdup(de->d_name)); } /* Does it look like a timeline history file? */ - else if (strlen(de->d_name) == 8 + strlen(".history") && - strspn(de->d_name, "0123456789ABCDEF") == 8 && - strcmp(de->d_name + 8, ".history") == 0) + else if (IsTLHistoryFileName(de->d_name)) { historyFileList = lappend(historyFileList, pstrdup(de->d_name)); } diff --git a/src/bin/pg_basebackup/pg_receivexlog.c b/src/bin/pg_basebackup/pg_receivexlog.c index e77d2b6..53802af 100644 --- a/src/bin/pg_basebackup/pg_receivexlog.c +++ b/src/bin/pg_basebackup/pg_receivexlog.c @@ -188,23 +188,11 @@ FindStreamingStart(uint32 *tli) /* * Check if the filename looks like an xlog file, or a .partial file. - * Xlog files are always 24 characters, and .partial files are 32 - * characters. */ - if (strlen(dirent->d_name) == 24) - { - if (strspn(dirent->d_name, "0123456789ABCDEF") != 24) - continue; + if (IsXLogFileName(dirent->d_name)) ispartial = false; - } - else if (strlen(dirent->d_name) == 32) - { - if (strspn(dirent->d_name, "0123456789ABCDEF") != 24) - continue; - if (strcmp(&dirent->d_name[24], ".partial") != 0) - continue; + else if (IsPartialXLogFileName(dirent->d_name)) ispartial = true; - } else continue; diff --git a/src/bin/pg_resetxlog/pg_resetxlog.c b/src/bin/pg_resetxlog/pg_resetxlog.c index 4a22575..393d580 100644 --- a/src/bin/pg_resetxlog/pg_resetxlog.c +++ b/src/bin/pg_resetxlog/pg_resetxlog.c @@ -906,14 +906,18 @@ FindEndOfXLOG(void) while (errno = 0, (xlde = readdir(xldir)) != NULL) { - if (strlen(xlde->d_name) == 24 && - strspn(xlde->d_name, "0123456789ABCDEF") == 24) + if (IsXLogFileName(xlde->d_name)) { unsigned int tli, log, seg; XLogSegNo segno; + /* + * Note: We don't use XLogFromFileName here, because we want + * to use the segment size from the control file, not the size + * the pg_resetxlog binary was compiled with + */ sscanf(xlde->d_name, "%08X%08X%08X", &tli, &log, &seg); segno = ((uint64) log) * segs_per_xlogid + seg; diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 75cf435..714850c 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -142,6 +142,14 @@ typedef XLogLongPageHeaderData *XLogLongPageHeader; (uint32) ((logSegNo) / XLogSegmentsPerXLogId), \ (uint32) ((logSegNo) % XLogSegmentsPerXLogId)) +#define IsXLogFileName(fname) \ + (strlen(fname) == 24 && strspn(fname, "0123456789ABCDEF") == 24) + +#define IsPartialXLogFileName(fname) \ + (strlen(fname) == 24 + strlen(".partial") && \ + strspn(fname, "0123456789ABCDEF") == 24 && \ + strcmp((fname) + 24, ".partial") == 0) + #define XLogFromFileName(fname, tli, logSegNo) \ do { \ uint32 log; \ @@ -158,6 +166,11 @@ typedef XLogLongPageHeaderData *XLogLongPageHeader; #define TLHistoryFileName(fname, tli) \ snprintf(fname, MAXFNAMELEN, "%08X.history", tli) +#define IsTLHistoryFileName(fname) \ + (strlen(fname) == 8 + strlen(".history") && \ + strspn(fname, "0123456789ABCDEF") == 8 && \ + strcmp((fname) + 8, ".history") == 0) + #define TLHistoryFilePath(path, tli) \ snprintf(path, MAXPGPATH, XLOGDIR "/%08X.history", tli) @@ -169,6 +182,11 @@ typedef XLogLongPageHeaderData *XLogLongPageHeader; (uint32) ((logSegNo) / XLogSegmentsPerXLogId), \ (uint32) ((logSegNo) % XLogSegmentsPerXLogId), offset) +#define IsBackupHistoryFileName(fname) \ + (strlen(fname) > 24 && \ + strspn(fname, "0123456789ABCDEF") == 24 && \ + strcmp((fname) + strlen(fname) - strlen(".backup"), ".backup") == 0) + #define BackupHistoryFilePath(path, tli, logSegNo, offset) \ snprintf(path, MAXPGPATH, XLOGDIR "/%08X%08X%08X.%08X.backup", tli, \ (uint32) ((logSegNo) / XLogSegmentsPerXLogId), \ -- 2.1.4 [application/x-patch] 0002-At-promotion-archive-last-segment-from-old-timeline-.patch (10.3K, 3-0002-At-promotion-archive-last-segment-from-old-timeline-.patch) download | inline diff: From 1a78bffda7034cb6d37348527cc1269a09fffe1a Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas <[email protected]> Date: Fri, 8 May 2015 16:08:26 +0300 Subject: [PATCH 2/2] At promotion, archive last segment from old timeline with .partial suffix. Previously, we would archive the possible-incomplete WAL segment with its normal filename, but that causes trouble if the server owning that timeline is still running, and tries to archive the same segment later. It's not nice for the standby to trip up the master's archival like that. And it's pretty confusing, anyway, to have an incomplete segment in the archive that's indistinguishable from a normal, complete segment. To avoid such confusion, add a .partial suffix to the file. Or to be more precise, make a copy of the old segment under the .partial suffix, and archive that instead of the original file. pg_receivexlog also uses the .partial suffix for the same purpose, to tell apart incompletely streamed files from complete ones. There is no automatic mechanism to use the .partial files at recovery, so they will go unused, unless the administrator manually copies to them to the pg_xlog directory (and removes the .partial suffix). Recovery won't normally need the WAL - when recovering to the new timeline, it will find the same WAL on the first segment on the new timeline instead - but it nevertheless feels better to archive the file with the .partial suffix, for debugging purposes if nothing else. --- src/backend/access/transam/xlog.c | 133 ++++++++++++++++++++++++++++--------- src/include/access/xlog_internal.h | 5 ++ src/include/postmaster/pgarch.h | 2 +- 3 files changed, 107 insertions(+), 33 deletions(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 5097173..6f7e3bd 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -3020,24 +3020,22 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock) } /* - * Create a new XLOG file segment by copying a pre-existing one. + * Copy a WAL segment file in pg_xlog directory. * - * destsegno: identify segment to be created. + * dstfname destination filename + * srcfname source filename + * upto how much of the source file to copy? (the rest is filled with + * zeros) * - * srcTLI, srclog, srcseg: identify segment to be copied (could be from - * a different timeline) + * If dstfname is not given, the file is created with a temporary filename, + * which is returned. Both filenames are relative to the pg_xlog directory. * - * upto: how much of the source file to copy? (the rest is filled with zeros) - * - * Currently this is only used during recovery, and so there are no locking - * considerations. But we should be just as tense as XLogFileInit to avoid - * emplacing a bogus file. + * NB: Any existing file with the same name will be overwritten! */ -static void -XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno, - int upto) +static char * +XLogFileCopy(char *dstfname, char *srcfname, int upto) { - char path[MAXPGPATH]; + char srcpath[MAXPGPATH]; char tmppath[MAXPGPATH]; char buffer[XLOG_BLCKSZ]; int srcfd; @@ -3047,12 +3045,12 @@ XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno, /* * Open the source file */ - XLogFilePath(path, srcTLI, srcsegno); - srcfd = OpenTransientFile(path, O_RDONLY | PG_BINARY, 0); + snprintf(srcpath, MAXPGPATH, XLOGDIR "/%s", srcfname); + srcfd = OpenTransientFile(srcpath, O_RDONLY | PG_BINARY, 0); if (srcfd < 0) ereport(ERROR, (errcode_for_file_access(), - errmsg("could not open file \"%s\": %m", path))); + errmsg("could not open file \"%s\": %m", srcpath))); /* * Copy into a temp file name. @@ -3094,10 +3092,12 @@ XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno, if (errno != 0) ereport(ERROR, (errcode_for_file_access(), - errmsg("could not read file \"%s\": %m", path))); + errmsg("could not read file \"%s\": %m", + srcpath))); else ereport(ERROR, - (errmsg("not enough data in file \"%s\"", path))); + (errmsg("not enough data in file \"%s\"", + srcpath))); } } errno = 0; @@ -3131,10 +3131,24 @@ XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno, CloseTransientFile(srcfd); /* - * Now move the segment into place with its final name. + * Now move the segment into place with its final name. (Or just return + * the path to the file we created, if the caller wants to handle the + * rest on its own.) */ - if (!InstallXLogFileSegment(&destsegno, tmppath, false, 0, false)) - elog(ERROR, "InstallXLogFileSegment should not have failed"); + if (dstfname) + { + char dstpath[MAXPGPATH]; + + snprintf(dstpath, MAXPGPATH, XLOGDIR "/%s", dstfname); + if (rename(tmppath, dstpath) < 0) + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not rename file \"%s\" to \"%s\": %m", + tmppath, dstpath))); + return NULL; + } + else + return pstrdup(tmppath); } /* @@ -3577,7 +3591,8 @@ RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr) while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { /* Ignore files that are not XLOG segments */ - if (!IsXLogFileName(xlde->d_name)) + if (!IsXLogFileName(xlde->d_name) && + !IsPartialXLogFileName(xlde->d_name)) continue; /* @@ -5189,25 +5204,79 @@ exitArchiveRecovery(TimeLineID endTLI, XLogRecPtr endOfLog) * of the old timeline up to the switch point, to the starting WAL segment * on the new timeline. * - * Notify the archiver that the last WAL segment of the old timeline is - * ready to copy to archival storage if its .done file doesn't exist - * (e.g., if it's the restored WAL file, it's expected to have .done file). - * Otherwise, it is not archived for a while. + * What to do with the partial segment on the old timeline? If we don't + * archive it, and the server that created the WAL never archives it + * either (e.g. because it was hit by a meteor), it will never make it to + * the archive. That's OK from our point of view, because the new segment + * that we created with the new TLI contains all the WAL from the old + * timeline up to the switch point. But if you later try to do PITR to the + * "missing" WAL on the old timeline, recovery won't find it in the + * archive. It's physically present in the new file with new TLI, but + * recovery won't look there when it's recovering to the older timeline. + * On the other hand, if we archive the partial segment, and the original + * server on that timeline is still running and archives the completed + * version of the same segment later, it will fail. (We used to do that in + * 9.4 and below, and it caused such problems). + * + * As a compromise, we archive the last segment with the .partial suffix. + * Archive recovery will never try to read .partial segments, so they will + * normally go unused. But in the odd PITR case, the administrator can + * copy them manually to the pg_xlog directory (removing the suffix). They + * can be useful in debugging, too. + * + * If a .done file already exists for the old timeline, however, there is + * already a complete copy of the file in the archive, and there is no + * need to archive the partial one. (In particular, if it was restored + * from the archive to begin with, it's expected to have .done file). */ if (endLogSegNo == startLogSegNo) { - XLogFileCopy(startLogSegNo, endTLI, endLogSegNo, - endOfLog % XLOG_SEG_SIZE); + char *tmpfname; + + XLogFileName(xlogfname, endTLI, endLogSegNo); + + /* + * Make a copy of the file on the new timeline. + * + * Writing WAL isn't allowed yet, so there are no locking + * considerations. But we should be just as tense as XLogFileInit to + * avoid emplacing a bogus file. + */ + tmpfname = XLogFileCopy(NULL, xlogfname, endOfLog % XLOG_SEG_SIZE); + if (!InstallXLogFileSegment(&endLogSegNo, tmpfname, false, 0, false)) + elog(ERROR, "InstallXLogFileSegment should not have failed"); - /* Create .ready file only when neither .ready nor .done files exist */ - if (XLogArchivingActive()) + /* + * Make a .partial copy for the archive (unless the original file was + * already archived) + */ + if (XLogArchivingActive() && XLogArchiveIsBusy(xlogfname)) { - XLogFileName(xlogfname, endTLI, endLogSegNo); - XLogArchiveCheckDone(xlogfname); + char partialfname[MAXFNAMELEN]; + + snprintf(partialfname, MAXFNAMELEN, "%s.partial", xlogfname); + + /* Make sure there's no .done or .ready file for it. */ + XLogArchiveCleanup(partialfname); + + /* + * We copy the whole segment, not just upto the switch point. + * The portion after the switch point might be garbage, but it + * might also be valid WAL, if we stopped recovery at user's + * request before reaching the end. Better to preserve the + * file as it is, garbage and all, than lose the evidence if + * something goes wrong. + */ + (void) XLogFileCopy(partialfname, xlogfname, XLOG_SEG_SIZE); + XLogArchiveNotify(partialfname); } } else { + /* + * The switch happened at a segment boundary, so just create the next + * segment on the new timeline. + */ bool use_existent = true; int fd; diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 714850c..e50d0f3 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -145,6 +145,11 @@ typedef XLogLongPageHeaderData *XLogLongPageHeader; #define IsXLogFileName(fname) \ (strlen(fname) == 24 && strspn(fname, "0123456789ABCDEF") == 24) +/* + * XLOG segment with .partial suffix. Used by pg_receivexlog and at end of + * archive recovery, when we want to archive a WAL segment but it might not + * be complete yet. + */ #define IsPartialXLogFileName(fname) \ (strlen(fname) == 24 + strlen(".partial") && \ strspn(fname, "0123456789ABCDEF") == 24 && \ diff --git a/src/include/postmaster/pgarch.h b/src/include/postmaster/pgarch.h index 9f692eb..425e2ab 100644 --- a/src/include/postmaster/pgarch.h +++ b/src/include/postmaster/pgarch.h @@ -24,7 +24,7 @@ */ #define MIN_XFN_CHARS 16 #define MAX_XFN_CHARS 40 -#define VALID_XFN_CHARS "0123456789ABCDEF.history.backup" +#define VALID_XFN_CHARS "0123456789ABCDEF.history.backup.partial" /* ---------- * Functions called from postmaster -- 2.1.4 ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-05-11 16:00 Heikki Linnakangas <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2015-05-11 16:00 UTC (permalink / raw) To: Michael Paquier <[email protected]>; +Cc: Robert Haas <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 05/08/2015 04:21 PM, Heikki Linnakangas wrote: > On 04/22/2015 10:07 AM, Michael Paquier wrote: >> On Wed, Apr 22, 2015 at 3:38 PM, Heikki Linnakangas <[email protected]> wrote: >>> I feel that the best approach is to archive the last, partial segment, but >>> with the .partial suffix. I don't see any plausible real-wold setup where >>> the current behavior would be better. I don't really see much need to >>> archive the partial segment at all, but there's also no harm in doing it, as >>> long as it's clearly marked with the .partial suffix. >> >> Well, as long as it is clearly archived at promotion, even with a >> suffix, I guess that I am fine... This will need some tweaking on >> restore_command for existing applications, but as long as it is >> clearly documented I am fine. Shouldn't this be a different patch >> though? > > Ok, I came up with the attached, which adds the .partial suffix to the > partial WAL segment that's archived after promotion. I couldn't find any > natural place to talk about it in the docs, though. I think after the > docs changes from the main patch are applied, it would be natural to > mention this in the "Continuous archiving in standby", so I think I'll > add that later. > > Barring objections, I'll push this later tonight. Applied that part. > Now that we got this last-partial-segment problem out of the way, I'm > going to try fixing the problem you (Michael) pointed out about relying > on pgstat file. Meanwhile, I'd love to get more feedback on the rest of > the patch, and the documentation. And here is a new version of the patch. I kept the approach of using pgstat, but it now only polls pgstat every 10 seconds, and doesn't block to wait for updated stats. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers Attachments: [application/x-patch] v3-0001-Make-WAL-archival-behave-more-sensibly-in-standby.patch (31.8K, 2-v3-0001-Make-WAL-archival-behave-more-sensibly-in-standby.patch) download | inline diff: From 08ca3cc7b9824503b793e149247ea9c6d3a7f323 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas <[email protected]> Date: Thu, 16 Apr 2015 14:40:24 +0300 Subject: [PATCH v3 1/1] Make WAL archival behave more sensibly in standby mode. This adds two new archive_modes, 'shared' and 'always', to indicate whether the WAL archive is shared between the primary and standby, or not. In shared mode, the standby tracks which files have been archived by the primary. The standby refrains from recycling files that the primary has not yet archived, and at failover, the standby archives all those files too from the old timeline. In 'always' mode, the standby's WAL archive is taken to be separate from the primary's, and the standby independently archives all files it receives from the primary. This adds a new "archival status" message to the protocol. WAL sender sends one automatically, when the last archived WAL file, as reported in pgstat, changes. (Or rather, some time after it changes. We're not in a hurry, the standby doesn't need an up-to-the-second status) Fujii Masao and me. --- doc/src/sgml/config.sgml | 12 +- doc/src/sgml/high-availability.sgml | 48 +++++++ doc/src/sgml/protocol.sgml | 31 +++++ src/backend/access/transam/xlog.c | 29 +++- src/backend/postmaster/pgstat.c | 44 ++++++ src/backend/postmaster/postmaster.c | 37 +++-- src/backend/replication/walreceiver.c | 172 +++++++++++++++++++----- src/backend/replication/walsender.c | 186 ++++++++++++++++++++++---- src/backend/utils/misc/guc.c | 21 +-- src/backend/utils/misc/postgresql.conf.sample | 2 +- src/include/access/xlog.h | 14 +- src/include/pgstat.h | 2 + 12 files changed, 513 insertions(+), 85 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 0d8624a..ac845e0 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -2521,7 +2521,7 @@ include_dir 'conf.d' <variablelist> <varlistentry id="guc-archive-mode" xreflabel="archive_mode"> - <term><varname>archive_mode</varname> (<type>boolean</type>) + <term><varname>archive_mode</varname> (<type>enum</type>) <indexterm> <primary><varname>archive_mode</> configuration parameter</primary> </indexterm> @@ -2530,7 +2530,15 @@ include_dir 'conf.d' <para> When <varname>archive_mode</> is enabled, completed WAL segments are sent to archive storage by setting - <xref linkend="guc-archive-command">. + <xref linkend="guc-archive-command">. In addition to <literal>off</>, + to disable, there are three modes: <literal>on</>, <literal>shared</>, + and <literal>always</>. During normal operation, there is no + difference between the three modes, but in archive recovery or + standby mode, it indicates whether the WAL archive is shared between + the primary and the standby server or not. See + <xref linkend="continuous-archiving-in-standby"> for details. + </para> + <para> <varname>archive_mode</> and <varname>archive_command</> are separate variables so that <varname>archive_command</> can be changed without leaving archiving mode. diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml index a17f555..62f7c75 100644 --- a/doc/src/sgml/high-availability.sgml +++ b/doc/src/sgml/high-availability.sgml @@ -1220,6 +1220,54 @@ primary_slot_name = 'node_a_slot' </sect3> </sect2> + + <sect2 id="continuous-archiving-in-standby"> + <title>Continuous archiving in standby</title> + + <indexterm> + <primary>continuous archiving</primary> + <secondary>in standby</secondary> + </indexterm> + + <para> + When continuous WAL archiving is used in a standby, there are two + different scenarios: the WAL archive can be shared between the primary + and the standby, or the standby can have its own WAL archive. In the + shared archive scenario, <varname>archive_mode</varname> must be set to + <literal>shared</literal>, and in the separate archive scenario, to + <literal>always</literal>. Setting it to <literal>on</literal> in a + standby server, or when performing point-in-time recovery, is not + allowed and an error will be raised. When a server is not in recovery + mode, there is no difference between <literal>on</literal>, + <literal>shared</literal>, and <literal>always</literal> modes. + </para> + + <para> + In <literal>shared</literal> archive mode, the standby server tries to + ensure that the archive is complete, even if the primary crashes and + failover happens. The standby server will not archive any WAL segments + as long as it is in standby mode; it is the primary server's + responsibility to do so. It will, however, keep track of which files + have already been archived by the primary, and if failover happens, it + takes over and attempts to archive any files that the primary had not + yet archived. + </para> + + <para> + In <literal>always</literal> archive mode, the standby server will + archive all WAL it receives, whether it's through streaming replication + or by restoring from the primary's archive using + <varname>restore_command</varname>. + </para> + + <para> + In cascading replication, the first standby server and the cascaded + standby servers can use <varname>archive_mode</varname> settings. In + each standby, it should be set to <literal>shared</literal> or + <literal>always</literal>, depending on whether that standby shares the + archive with the primary or standby it is connected to. + </para> + </sect2> </sect1> <sect1 id="warm-standby-failover"> diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml index ac13d32..bd2dd3f 100644 --- a/doc/src/sgml/protocol.sgml +++ b/doc/src/sgml/protocol.sgml @@ -1646,6 +1646,37 @@ The commands accepted in walsender mode are: </para> </listitem> </varlistentry> + <varlistentry> + <term> + WAL archival report message (B) + </term> + <listitem> + <para> + <variablelist> + <varlistentry> + <term> + Byte1('a') + </term> + <listitem> + <para> + Tells the receiver the last archived WAL segment. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + Byte<replaceable>n</replaceable> + </term> + <listitem> + <para> + Filename of the latest archived file. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + </listitem> + </varlistentry> </variablelist> </para> diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 6f7e3bd9..ee5a4a1 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -85,7 +85,7 @@ int min_wal_size = 5; /* 80 MB */ int wal_keep_segments = 0; int XLOGbuffers = -1; int XLogArchiveTimeout = 0; -bool XLogArchiveMode = false; +int XLogArchiveMode = ARCHIVE_MODE_OFF; char *XLogArchiveCommand = NULL; bool EnableHotStandby = false; bool fullPageWrites = true; @@ -139,6 +139,25 @@ const struct config_enum_entry sync_method_options[] = { {NULL, 0, false} }; + +/* + * Although only "on", "off", and "always" are documented, + * we accept all the likely variants of "on" and "off". + */ +const struct config_enum_entry archive_mode_options[] = { + {"shared", ARCHIVE_MODE_SHARED, false}, + {"always", ARCHIVE_MODE_ALWAYS, false}, + {"on", ARCHIVE_MODE_ON, false}, + {"off", ARCHIVE_MODE_OFF, false}, + {"true", ARCHIVE_MODE_ON, true}, + {"false", ARCHIVE_MODE_OFF, true}, + {"yes", ARCHIVE_MODE_ON, true}, + {"no", ARCHIVE_MODE_OFF, true}, + {"1", ARCHIVE_MODE_ON, true}, + {"0", ARCHIVE_MODE_OFF, true}, + {NULL, 0, false} +}; + /* * Statistics for current checkpoint are collected in this global struct. * Because only the checkpointer or a stand-alone backend can perform @@ -766,7 +785,7 @@ static MemoryContext walDebugCxt = NULL; #endif static void readRecoveryCommandFile(void); -static void exitArchiveRecovery(TimeLineID endTLI, XLogSegNo endLogSegNo); +static void exitArchiveRecovery(TimeLineID endTLI, XLogRecPtr endOfLog); static bool recoveryStopsBefore(XLogReaderState *record); static bool recoveryStopsAfter(XLogReaderState *record); static void recoveryPausesHere(void); @@ -6037,6 +6056,12 @@ StartupXLOG(void) if (ArchiveRecoveryRequested) { + /* archive_mode=on is not allowed during archive recovery. */ + if (XLogArchiveMode == ARCHIVE_MODE_ON) + ereport(ERROR, + (errmsg("archive_mode='on' cannot be used in archive recovery"), + (errhint("Use 'shared' or 'always' mode instead.")))); + if (StandbyModeRequested) ereport(LOG, (errmsg("entering standby mode"))); diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c index 1e6073a..13bee0c 100644 --- a/src/backend/postmaster/pgstat.c +++ b/src/backend/postmaster/pgstat.c @@ -2471,6 +2471,50 @@ pgstat_fetch_global(void) } +/* + * --------- + * pgstat_use_stale_snapshot() - + * + * Take a "snapshot" of the current stats into backend-private memory. + * pgstat_fetch_*() functions can then be used to interrogate the stats. + * + * The first call pgstat_fetch_*() in a transaction will take a snapshot + * implicitly, so this is normally not required. But this can be used if + * you don't want to wait for fresh stats, like pgstat_fetch_*() functions + * will + * --------- + */ +void +pgstat_use_stale_snapshot(void) +{ + pgstat_clear_snapshot(); + + /* + * For all the current callers, shallow stats are enough. + * + * XXX: There is no way to request global stats only; we'll get stats + * for all databases. + */ + pgStatDBHash = pgstat_read_statsfiles(InvalidOid, false, false); +} + +/* + * --------- + * pgstat_request_update() - + * + * Ask the stats collector to refresh the stats file. Normally, + * pgstat_fetch_*() will do this automatically, but this can be used together + * with pgstat_take_snapshot() to wait for poll for updated stats + * asynchronously. + * --------- + */ +void +pgstat_request_update(TimestampTz cur_ts, TimestampTz min_ts) +{ + pgstat_send_inquiry(cur_ts, min_ts, InvalidOid); +} + + /* ------------------------------------------------------------ * Functions for management of the shared-memory PgBackendStatus array * ------------------------------------------------------------ diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index a9f20ac..72fe4fd 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -828,9 +828,9 @@ PostmasterMain(int argc, char *argv[]) write_stderr("%s: max_wal_senders must be less than max_connections\n", progname); ExitPostmaster(1); } - if (XLogArchiveMode && wal_level == WAL_LEVEL_MINIMAL) + if (XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level == WAL_LEVEL_MINIMAL) ereport(ERROR, - (errmsg("WAL archival (archive_mode=on) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); + (errmsg("WAL archival (archive_mode=on/always/shared) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); if (max_wal_senders > 0 && wal_level == WAL_LEVEL_MINIMAL) ereport(ERROR, (errmsg("WAL streaming (max_wal_senders > 0) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); @@ -1645,13 +1645,21 @@ ServerLoop(void) start_autovac_launcher = false; /* signal processed */ } - /* If we have lost the archiver, try to start a new one */ - if (XLogArchivingActive() && PgArchPID == 0 && pmState == PM_RUN) - PgArchPID = pgarch_start(); - - /* If we have lost the stats collector, try to start a new one */ - if (PgStatPID == 0 && pmState == PM_RUN) - PgStatPID = pgstat_start(); + /* + * If we have lost the archiver, try to start a new one. + * + * If WAL archiving is enabled always, we try to start a new archiver + * even during recovery. + */ + if (PgArchPID == 0 && wal_level >= WAL_LEVEL_ARCHIVE) + { + if ((pmState == PM_RUN && XLogArchiveMode > ARCHIVE_MODE_OFF) || + ((pmState == PM_RECOVERY || pmState == PM_HOT_STANDBY) && + XLogArchiveMode == ARCHIVE_MODE_ALWAYS)) + { + PgArchPID = pgarch_start(); + } + } /* If we need to signal the autovacuum launcher, do so now */ if (avlauncher_needs_signal) @@ -4807,6 +4815,17 @@ sigusr1_handler(SIGNAL_ARGS) Assert(BgWriterPID == 0); BgWriterPID = StartBackgroundWriter(); + /* + * Start the archiver if we're responsible for (re-)archiving received + * files. + */ + Assert(PgArchPID == 0); + if (wal_level >= WAL_LEVEL_ARCHIVE && + XLogArchiveMode == ARCHIVE_MODE_ALWAYS) + { + PgArchPID = pgarch_start(); + } + pmState = PM_RECOVERY; } if (CheckPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY) && diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c index 9c7710f..e53ffeb 100644 --- a/src/backend/replication/walreceiver.c +++ b/src/backend/replication/walreceiver.c @@ -52,8 +52,11 @@ #include "libpq/pqformat.h" #include "libpq/pqsignal.h" #include "miscadmin.h" +#include "pgstat.h" +#include "postmaster/pgarch.h" #include "replication/walreceiver.h" #include "replication/walsender.h" +#include "storage/fd.h" #include "storage/ipc.h" #include "storage/pmsignal.h" #include "storage/procarray.h" @@ -107,6 +110,9 @@ static struct XLogRecPtr Flush; /* last byte + 1 flushed in the standby */ } LogstreamResult; +/* */ +static char primary_last_archived[MAX_XFN_CHARS + 1]; + static StringInfoData reply_message; static StringInfoData incoming_message; @@ -141,6 +147,7 @@ static void XLogWalRcvFlush(bool dying); static void XLogWalRcvSendReply(bool force, bool requestReply); static void XLogWalRcvSendHSFeedback(bool immed); static void ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime); +static void ProcessArchivalReport(void); /* Signal handlers */ static void WalRcvSigHupHandler(SIGNAL_ARGS); @@ -526,21 +533,12 @@ WalReceiverMain(void) */ if (recvFile >= 0) { - char xlogfname[MAXFNAMELEN]; - XLogWalRcvFlush(false); if (close(recvFile) != 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not close log segment %s: %m", XLogFileNameP(recvFileTLI, recvSegNo)))); - - /* - * Create .done file forcibly to prevent the streamed segment from - * being archived later. - */ - XLogFileName(xlogfname, recvFileTLI, recvSegNo); - XLogArchiveForceDone(xlogfname); } recvFile = -1; @@ -846,6 +844,26 @@ XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len) XLogWalRcvSendReply(true, false); break; } + case 'a': /* Archival report */ + { + /* the content of the message is a filename */ + if (len >= sizeof(primary_last_archived)) + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg_internal("invalid archival report message with length %d", + (int) len))); + memcpy(primary_last_archived, buf, len); + primary_last_archived[len] = '\0'; + if (strspn(buf, VALID_XFN_CHARS) != len) + { + primary_last_archived[0] = '\0'; + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg_internal("unexpected character in primary's last archived filename"))); + } + ProcessArchivalReport(); + break; + } default: ereport(ERROR, (errcode(ERRCODE_PROTOCOL_VIOLATION), @@ -867,39 +885,18 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr) { int segbytes; - if (recvFile < 0 || !XLByteInSeg(recptr, recvSegNo)) + if (!XLByteInSeg(recptr, recvSegNo)) { bool use_existent; /* - * fsync() and close current file before we switch to next one. We - * would otherwise have to reopen this file to fsync it later + * We take care to always close the current file, after writing + * the last byte to it. So this shouldn't happen. */ if (recvFile >= 0) - { - char xlogfname[MAXFNAMELEN]; - - XLogWalRcvFlush(false); - - /* - * XLOG segment files will be re-read by recovery in startup - * process soon, so we don't advise the OS to release cache - * pages associated with the file like XLogFileClose() does. - */ - if (close(recvFile) != 0) - ereport(PANIC, - (errcode_for_file_access(), - errmsg("could not close log segment %s: %m", - XLogFileNameP(recvFileTLI, recvSegNo)))); - - /* - * Create .done file forcibly to prevent the streamed segment - * from being archived later. - */ - XLogFileName(xlogfname, recvFileTLI, recvSegNo); - XLogArchiveForceDone(xlogfname); - } - recvFile = -1; + ereport(ERROR, + (errmsg("unexpected WAL receive location %s", + XLogFileNameP(recvFileTLI, recvSegNo)))); /* Create/use new log file */ XLByteToSeg(recptr, recvSegNo); @@ -954,6 +951,51 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr) buf += byteswritten; LogstreamResult.Write = recptr; + + /* + * If we just wrote the last byte to this segment, fsync() and close + * current file before we switch to next one. We would otherwise have + * to reopen this file to fsync it later. + */ + if (recvOff == XLOG_SEG_SIZE) + { + char xlogfname[MAXFNAMELEN]; + + XLogWalRcvFlush(false); + + /* + * XLOG segment files will be re-read by recovery in startup + * process soon, so we don't advise the OS to release cache + * pages associated with the file like XLogFileClose() does. + */ + if (close(recvFile) != 0) + ereport(PANIC, + (errcode_for_file_access(), + errmsg("could not close log segment %s: %m", + XLogFileNameP(recvFileTLI, recvSegNo)))); + recvFile = -1; + + /* + * Now that this segment is complete, do we need to archive it? + * + * In 'always' mode, we clearly need to archive this. + * + * In 'shared' mode, we might need to, if we get promoted before + * the master has archived this file, so create a .ready file. It + * will be replaced with .done later, if we get acknowledgemet + * from the primary that this has already been archived. + * + * In 'on' mode, we're only responsible for WAL we've generated + * ourselves. + */ + if (XLogArchiveMode == ARCHIVE_MODE_ALWAYS || + XLogArchiveMode == ARCHIVE_MODE_SHARED) + { + XLogFileName(xlogfname, recvFileTLI, recvSegNo); + + XLogArchiveCheckDone(xlogfname); + } + } } } @@ -1215,3 +1257,61 @@ ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime) pfree(receipttime); } } + +/* + * Create .done and .ready files, based on the master's last archival report. + */ +static void +ProcessArchivalReport(void) +{ + DIR *xldir; + struct dirent *xlde; + + elog(DEBUG2, "received archival report from master: %s", + primary_last_archived); + + if (XLogArchiveMode != ARCHIVE_MODE_SHARED) + return; + + /* Check that the filename the primary reported looks valid */ + if (strlen(primary_last_archived) < 24 || + strspn(primary_last_archived, "0123456789ABCDEF") != 24) + return; + + xldir = AllocateDir(XLOGDIR); + if (xldir == NULL) + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not open transaction log directory \"%s\": %m", + XLOGDIR))); + + while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) + { + /* + * We ignore the timeline part of the XLOG segment identifiers in + * deciding whether a segment is still needed. This ensures that we + * won't prematurely remove a segment from a parent timeline. We could + * probably be a little more proactive about removing segments of + * non-parent timelines, but that would be a whole lot more + * complicated. + * + * We use the alphanumeric sorting property of the filenames to decide + * which ones are earlier than the lastoff segment. + */ + if (strlen(xlde->d_name) == 24 && + strspn(xlde->d_name, "0123456789ABCDEF") == 24 && + strcmp(xlde->d_name + 8, primary_last_archived + 8) <= 0) + { + XLogArchiveForceDone(xlde->d_name); + } + } + + FreeDir(xldir); + + /* + * Remember this location in pgstat as well. This makes it visible in + * pg_stat_archiver, and allows the location to be relayed to cascaded + * standbys. + */ + pgstat_send_archiver(primary_last_archived, false); +} diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c index 4a20569..b4d4a90 100644 --- a/src/backend/replication/walsender.c +++ b/src/backend/replication/walsender.c @@ -55,6 +55,7 @@ #include "libpq/pqformat.h" #include "miscadmin.h" #include "nodes/replnodes.h" +#include "pgstat.h" #include "replication/basebackup.h" #include "replication/decode.h" #include "replication/logical.h" @@ -91,6 +92,21 @@ */ #define MAX_SEND_SIZE (XLOG_BLCKSZ * 16) +/* + * How often to report the last archived WAL file to the client? + */ +#define ARCHIVAL_REPORT_INTERVAL 10000 +/* + * After requesting the stats collector for fresh stats, how often to poll + * for the result? + * + * This is similar to PGSTAT_RETRY_DELAY and PGSTAT_INQ_INTERVAL, but we're + * much more relaxed in WAL sender, as we're not in any rush to get the latest + * status to the client. We also just use a single value, and send a new + * request after each poll. + */ +#define ARCHIVAL_REQUEST_INTERVAL 1000 + /* Array of WalSnds in shared memory */ WalSndCtlData *WalSndCtl = NULL; @@ -153,6 +169,19 @@ static StringInfoData tmpbuf; */ static TimestampTz last_reply_timestamp = 0; +/* + * Last file archived. This is updated from pgstats, last update was at + * last_archival_report_timestamp. + */ +static char last_archived_file[MAX_XFN_CHARS + 1] = ""; +static TimestampTz last_archival_report_timestamp = 0; + +/* + * Have we requested fresh stats from the stats collector? And when? + */ +static bool archival_status_requested = false; +static TimestampTz last_archival_request_timestamp = 0; + /* Have we sent a heartbeat message asking for reply, since last reply? */ static bool waiting_for_ping_response = false; @@ -209,6 +238,8 @@ static void ProcessStandbyHSFeedbackMessage(void); static void ProcessRepliesIfAny(void); static void WalSndKeepalive(bool requestReply); static void WalSndKeepaliveIfNecessary(TimestampTz now); +static void WalSndArchivalReport(void); +static void WalSndArchivalReportIfNecessary(TimestampTz now); static void WalSndCheckTimeOut(TimestampTz now); static long WalSndComputeSleeptime(TimestampTz now); static void WalSndPrepareWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid, bool last_write); @@ -1693,46 +1724,72 @@ ProcessStandbyHSFeedbackMessage(void) /* * Compute how long send/receive loops should sleep. - * - * If wal_sender_timeout is enabled we want to wake up in time to send - * keepalives and to abort the connection if wal_sender_timeout has been - * reached. */ static long WalSndComputeSleeptime(TimestampTz now) { - long sleeptime = 10000; /* 10 s */ + TimestampTz wakeup_time; + long sleeptime; + long sec_to_timeout; + int microsec_to_timeout; + TimestampTz w; + /* + * If we have no other reason to wake up, wake up every 10 seconds, + * just in case we miss something. + */ + wakeup_time = TimestampTzPlusMilliseconds(now, 10000); + + /* + * If wal_sender_timeout is enabled we want to wake up in time to send + * keepalives and to abort the connection if wal_sender_timeout has been + * reached. + */ if (wal_sender_timeout > 0 && last_reply_timestamp > 0) { - TimestampTz wakeup_time; - long sec_to_timeout; - int microsec_to_timeout; - /* * At the latest stop sleeping once wal_sender_timeout has been * reached. - */ - wakeup_time = TimestampTzPlusMilliseconds(last_reply_timestamp, - wal_sender_timeout); - - /* + * * If no ping has been sent yet, wakeup when it's time to do so. * WalSndKeepaliveIfNecessary() wants to send a keepalive once half of * the timeout passed without a response. */ - if (!waiting_for_ping_response) - wakeup_time = TimestampTzPlusMilliseconds(last_reply_timestamp, - wal_sender_timeout / 2); - - /* Compute relative time until wakeup. */ - TimestampDifference(now, wakeup_time, - &sec_to_timeout, µsec_to_timeout); + if (waiting_for_ping_response) + w = TimestampTzPlusMilliseconds(last_reply_timestamp, + wal_sender_timeout); + else + w = TimestampTzPlusMilliseconds(last_reply_timestamp, + wal_sender_timeout / 2); + if (w < wakeup_time) + wakeup_time = w; + } - sleeptime = sec_to_timeout * 1000 + - microsec_to_timeout / 1000; + /* If archiving is enabled, send a status report to the client */ + if (XLogArchivingActive()) + { + /* + * If we requested an update from pgstat, poll every + * ARCHIVE_REQUEST_INTERVAL for the result. Otherwise wait until it's + * time to send a new report. + */ + if (archival_status_requested) + w = TimestampTzPlusMilliseconds(last_archival_request_timestamp, + ARCHIVAL_REQUEST_INTERVAL); + else + w = TimestampTzPlusMilliseconds(last_archival_report_timestamp, + ARCHIVAL_REPORT_INTERVAL); + if (w < wakeup_time) + wakeup_time = w; } + /* Compute relative time until wakeup. */ + TimestampDifference(now, wakeup_time, + &sec_to_timeout, µsec_to_timeout); + + sleeptime = sec_to_timeout * 1000 + + microsec_to_timeout / 1000; + return sleeptime; } @@ -2879,6 +2936,11 @@ WalSndKeepaliveIfNecessary(TimestampTz now) TimestampTz ping_time; /* + * Send an archival status message, if necessary. + */ + WalSndArchivalReportIfNecessary(now); + + /* * Don't send keepalive messages if timeouts are globally disabled or * we're doing something not partaking in timeouts. */ @@ -2907,6 +2969,84 @@ WalSndKeepaliveIfNecessary(TimestampTz now) } /* + * This function is used to send archival report message to standby. + */ +static void +WalSndArchivalReport(void) +{ + elog(LOG, "sending archival report: %s", last_archived_file); + + /* construct the message... */ + resetStringInfo(&output_message); + pq_sendbyte(&output_message, 'a'); + pq_sendbytes(&output_message, last_archived_file, strlen(last_archived_file)); + + /* ... and send it wrapped in CopyData */ + pq_putmessage_noblock('d', output_message.data, output_message.len); +} + +static void +WalSndArchivalReportIfNecessary(TimestampTz now) +{ + TimestampTz report_time; + + /* + * If we had already asked pgstat for an update, wait until it's had + * some time to update the stats file before we retry. + */ + if (archival_status_requested) + { + TimestampTz next_retry; + + next_retry = + TimestampTzPlusMilliseconds(last_archival_request_timestamp, + ARCHIVAL_REQUEST_INTERVAL); + if (now < next_retry) + return; + } + + /* + * If more than ARCHIVAL_REPORT_INTERVAL has elapsed since we got the + * archival status from pgstat, poll. + */ + report_time = TimestampTzPlusMilliseconds(last_archival_report_timestamp, + ARCHIVAL_REPORT_INTERVAL); + if (now >= report_time) + { + PgStat_ArchiverStats *archiver_stats; + PgStat_GlobalStats *global_stats; + TimestampTz min_ts; + + pgstat_use_stale_snapshot(); + archiver_stats = pgstat_fetch_stat_archiver(); + global_stats = pgstat_fetch_global(); + + last_archival_report_timestamp = global_stats->stats_timestamp; + + if (strcmp(last_archived_file, archiver_stats->last_archived_wal) != 0) + { + strlcpy(last_archived_file, archiver_stats->last_archived_wal, + sizeof(last_archived_file)); + WalSndArchivalReport(); + } + + /* If this wasn't fresh enough, request an update */ + min_ts = TimestampTzPlusMilliseconds(now, -ARCHIVAL_REPORT_INTERVAL); + if (last_archival_report_timestamp > min_ts) + archival_status_requested = false; + else + { + /* Not fresh enough. Request an update */ + pgstat_request_update(now, min_ts); + last_archival_request_timestamp = now; + archival_status_requested = true; + } + + pgstat_clear_snapshot(); + } +} + +/* * This isn't currently used for anything. Monitoring tools might be * interested in the future, and we'll need something like this in the * future for synchronous replication. diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 5f71ded..97aca46 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -396,6 +396,7 @@ static const struct config_enum_entry row_security_options[] = { * Options for enum values stored in other modules */ extern const struct config_enum_entry wal_level_options[]; +extern const struct config_enum_entry archive_mode_options[]; extern const struct config_enum_entry sync_method_options[]; extern const struct config_enum_entry dynamic_shared_memory_options[]; @@ -1530,16 +1531,6 @@ static struct config_bool ConfigureNamesBool[] = }, { - {"archive_mode", PGC_POSTMASTER, WAL_ARCHIVING, - gettext_noop("Allows archiving of WAL files using archive_command."), - NULL - }, - &XLogArchiveMode, - false, - NULL, NULL, NULL - }, - - { {"hot_standby", PGC_POSTMASTER, REPLICATION_STANDBY, gettext_noop("Allows connections and queries during recovery."), NULL @@ -3552,6 +3543,16 @@ static struct config_enum ConfigureNamesEnum[] = }, { + {"archive_mode", PGC_POSTMASTER, WAL_ARCHIVING, + gettext_noop("Allows archiving of WAL files using archive_command."), + NULL + }, + &XLogArchiveMode, + ARCHIVE_MODE_OFF, archive_mode_options, + NULL, NULL, NULL + }, + + { {"trace_recovery_messages", PGC_SIGHUP, DEVELOPER_OPTIONS, gettext_noop("Enables logging of recovery-related debugging information."), gettext_noop("Each level includes all the levels that follow it. The later" diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 110983f..90371d7 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -206,7 +206,7 @@ # - Archiving - -#archive_mode = off # allows archiving to be done +#archive_mode = off # allows archiving to be done; off, on, shared, or always # (change requires restart) #archive_command = '' # command to use to archive a logfile segment # placeholders: %p = path of file to archive diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h index f08b676..8556bb8 100644 --- a/src/include/access/xlog.h +++ b/src/include/access/xlog.h @@ -96,7 +96,6 @@ extern int wal_keep_segments; extern int XLOGbuffers; extern int XLogArchiveTimeout; extern int wal_retrieve_retry_interval; -extern bool XLogArchiveMode; extern char *XLogArchiveCommand; extern bool EnableHotStandby; extern bool fullPageWrites; @@ -106,6 +105,16 @@ extern bool log_checkpoints; extern int CheckPointSegments; +/* Archive modes */ +typedef enum ArchiveMode +{ + ARCHIVE_MODE_OFF = 0, /* disabled */ + ARCHIVE_MODE_ON, /* enabled while server is running normally */ + ARCHIVE_MODE_SHARED, /* archive is shared with master */ + ARCHIVE_MODE_ALWAYS /* enabled always (even during recovery) */ +} ArchiveMode; +extern int XLogArchiveMode; + /* WAL levels */ typedef enum WalLevel { @@ -116,7 +125,8 @@ typedef enum WalLevel } WalLevel; extern int wal_level; -#define XLogArchivingActive() (XLogArchiveMode && wal_level >= WAL_LEVEL_ARCHIVE) +#define XLogArchivingActive() \ + (XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level >= WAL_LEVEL_ARCHIVE) #define XLogArchiveCommandSet() (XLogArchiveCommand[0] != '\0') /* diff --git a/src/include/pgstat.h b/src/include/pgstat.h index e3fe06e..b95a701 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -910,6 +910,8 @@ extern void pgstat_report_stat(bool force); extern void pgstat_vacuum_stat(void); extern void pgstat_drop_database(Oid databaseid); +extern void pgstat_request_update(TimestampTz cur_ts, TimestampTz min_ts); +extern void pgstat_use_stale_snapshot(void); extern void pgstat_clear_snapshot(void); extern void pgstat_reset_counters(void); extern void pgstat_reset_shared_counters(const char *); -- 2.1.4 ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-05-13 12:36 Robert Haas <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Robert Haas @ 2015-05-13 12:36 UTC (permalink / raw) To: hlinnaka <[email protected]>; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On Mon, May 11, 2015 at 12:00 PM, Heikki Linnakangas <[email protected]> wrote: > And here is a new version of the patch. I kept the approach of using pgstat, > but it now only polls pgstat every 10 seconds, and doesn't block to wait for > updated stats. It's not entirely a new problem, but this error message has gotten pretty crazy: + (errmsg("WAL archival (archive_mode=on/always/shared) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); Maybe: WAL archival cannot be enabled when wal_level is "minimal" I think the documentation should be explicit about what happens if the primary archives a file and dies before the standby gets notified that the archiving happened. The standby, running in shared mode, is then promoted. My first guess would be that the standby will end up with files that thinks it needs to archive but, being unable to do so because they're already there, they'll live forever in pg_xlog. I hope that's not the case. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-05-13 12:53 Heikki Linnakangas <[email protected]> parent: Robert Haas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Heikki Linnakangas @ 2015-05-13 12:53 UTC (permalink / raw) To: Robert Haas <[email protected]>; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 05/13/2015 03:36 PM, Robert Haas wrote: > On Mon, May 11, 2015 at 12:00 PM, Heikki Linnakangas <[email protected]> wrote: >> And here is a new version of the patch. I kept the approach of using pgstat, >> but it now only polls pgstat every 10 seconds, and doesn't block to wait for >> updated stats. > > It's not entirely a new problem, but this error message has gotten pretty crazy: > > + (errmsg("WAL archival > (archive_mode=on/always/shared) requires wal_level \"archive\", > \"hot_standby\", or \"logical\""))); > > Maybe: WAL archival cannot be enabled when wal_level is "minimal" > > I think the documentation should be explicit about what happens if the > primary archives a file and dies before the standby gets notified that > the archiving happened. Yes, good point. > The standby, running in shared mode, is then > promoted. My first guess would be that the standby will end up with > files that thinks it needs to archive but, being unable to do so > because they're already there, they'll live forever in pg_xlog. I > hope that's not the case. Hmm. That is exactly what happens. The standby will attempt to archive them, which will fail, so the archiver will get stuck retrying. That's not actually a new problem though. Even with a single server doing archiving, it's possible that you crash just after archive_command has archived a file, but before it has created the .done file. After restart, the server will try to archive the file again, which will fail. But yeah, with this patch, that's much more likely to happen after a promotion. Our manual says that archive_command should refuse to overwrite an existing file. But to work-around the double-archival problem, where the same file is archived twice, it would be even better if it would simply return success if the file exists, *and has identical contents*. I don't know how to code that logic in a simple one-liner though. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-05-13 13:29 Robert Haas <[email protected]> parent: Heikki Linnakangas <[email protected]> 0 siblings, 1 reply; 31+ messages in thread From: Robert Haas @ 2015-05-13 13:29 UTC (permalink / raw) To: hlinnaka <[email protected]>; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On Wed, May 13, 2015 at 8:53 AM, Heikki Linnakangas <[email protected]> wrote: > Our manual says that archive_command should refuse to overwrite an existing > file. But to work-around the double-archival problem, where the same file is > archived twice, it would be even better if it would simply return success if > the file exists, *and has identical contents*. I don't know how to code that > logic in a simple one-liner though. This is why we really, really need that pg_copy command that was proposed a while back. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers ^ permalink raw reply [nested|flat] 31+ messages in thread
* Re: Streaming replication and WAL archive interactions @ 2015-05-13 17:23 Heikki Linnakangas <[email protected]> parent: Robert Haas <[email protected]> 0 siblings, 0 replies; 31+ messages in thread From: Heikki Linnakangas @ 2015-05-13 17:23 UTC (permalink / raw) To: ; +Cc: Michael Paquier <[email protected]>; Venkata Balaji N <[email protected]>; Andres Freund <[email protected]>; Fujii Masao <[email protected]>; Borodin Vladimir <[email protected]>; pgsql-hackers On 05/13/2015 04:29 PM, Robert Haas wrote: > On Wed, May 13, 2015 at 8:53 AM, Heikki Linnakangas <[email protected]> wrote: >> Our manual says that archive_command should refuse to overwrite an existing >> file. But to work-around the double-archival problem, where the same file is >> archived twice, it would be even better if it would simply return success if >> the file exists, *and has identical contents*. I don't know how to code that >> logic in a simple one-liner though. > > This is why we really, really need that pg_copy command that was > proposed a while back. Yeah.. I took a step back and looked at the big picture again: If we just implement the "always" mode, and you have a pg_copy command or similar that handles duplicates correctly, you don't necessarily need the "shared" mode at all. You can just set archive_command='always', and have the master and standby archive to the same location. As long as the archive_command works correctly and is race-free, that should work. I cut back the patch to implement just the "always" mode. The "shared" mode might still make sense as a future patch, as I think it's easier to understand and has less strict requirements for the archive_command, but let's take one step at a time. So attached is a patch that just adds the "always" mode. This is pretty close to what Fujii submitted long ago. - Heikki -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers Attachments: [application/x-patch] 0001-Add-archive_mode-always-option.patch (13.6K, 2-0001-Add-archive_mode-always-option.patch) download | inline diff: From 71332900247a8c68a61fcf60782cb35cf662b756 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas <[email protected]> Date: Thu, 16 Apr 2015 14:40:24 +0300 Subject: [PATCH 1/1] Add archive_mode='always' option. In 'always' mode, the standby's WAL archive is taken to be separate from the primary's, and the standby independently archives all files it receives from the primary. Fujii Masao and me. --- doc/src/sgml/config.sgml | 13 +++++++-- doc/src/sgml/high-availability.sgml | 39 +++++++++++++++++++++++++++ src/backend/access/transam/xlog.c | 22 +++++++++++++-- src/backend/access/transam/xlogarchive.c | 5 +++- src/backend/postmaster/postmaster.c | 37 ++++++++++++++++++------- src/backend/replication/walreceiver.c | 10 +++++-- src/backend/utils/misc/guc.c | 21 ++++++++------- src/backend/utils/misc/postgresql.conf.sample | 2 +- src/include/access/xlog.h | 13 +++++++-- 9 files changed, 133 insertions(+), 29 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 0d8624a..5549b7d 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -2521,7 +2521,7 @@ include_dir 'conf.d' <variablelist> <varlistentry id="guc-archive-mode" xreflabel="archive_mode"> - <term><varname>archive_mode</varname> (<type>boolean</type>) + <term><varname>archive_mode</varname> (<type>enum</type>) <indexterm> <primary><varname>archive_mode</> configuration parameter</primary> </indexterm> @@ -2530,7 +2530,16 @@ include_dir 'conf.d' <para> When <varname>archive_mode</> is enabled, completed WAL segments are sent to archive storage by setting - <xref linkend="guc-archive-command">. + <xref linkend="guc-archive-command">. In addition to <literal>off</>, + to disable, there are two modes: <literal>on</>, and + <literal>always</>. During normal operation, there is no + difference between the two modes, but when set to <literal>always</> + the WAL archiver is enabled also during archive recovery or standby + mode. In <literal>always</> mode, all files restored from the archive + or streamed with streaming replication will be archived (again). See + <xref linkend="continuous-archiving-in-standby"> for details. + </para> + <para> <varname>archive_mode</> and <varname>archive_command</> are separate variables so that <varname>archive_command</> can be changed without leaving archiving mode. diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml index a17f555..e93b711 100644 --- a/doc/src/sgml/high-availability.sgml +++ b/doc/src/sgml/high-availability.sgml @@ -1220,6 +1220,45 @@ primary_slot_name = 'node_a_slot' </sect3> </sect2> + + <sect2 id="continuous-archiving-in-standby"> + <title>Continuous archiving in standby</title> + + <indexterm> + <primary>continuous archiving</primary> + <secondary>in standby</secondary> + </indexterm> + + <para> + When continuous WAL archiving is used in a standby, there are two + different scenarios: the WAL archive can be shared between the primary + and the standby, or the standby can have its own WAL archive. When + the standby has its own WAL archive, set <varname>archive_mode</varname> + to <literal>always</literal>, and the standby will call the archive + command for every WAL segment it receives, whether it's by restoring + from the archive or by streaming replication. The shared archive can + be handled similarly, but the archive_command should test if the file + being archived exists already, and if the existing file has identical + contents. This requires more care in the archive_command, as it must + be careful to not overwrite an existing file with different contents, + but return success if the exactly same file is archived twice. And + all that must be done free of race conditions, if two servers attempt + to archive the same file at the same time. + </para> + + </para> + If <varname>archive_mode</varname> is set to <literal>on</>, the + archiver is not enabled during recovery or standby mode. If the standby + server is promoted, it will start archiving after the promotion, but + will not archive any WAL it did not generate itself. To get a complete + series of WAL files in the archive, you must ensure that all WAL is + archived, before it reaches the standby. This is inherently true with + file-based log shipping, as the standby can only restore files that + are found in the archive, but not if streaming replication is enabled. + When a server is not in recovery mode, there is no difference between + <literal>on</literal> and <literal>always</literal> modes. + </para> + </sect2> </sect1> <sect1 id="warm-standby-failover"> diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 5f0551a..0485bb5 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -86,7 +86,7 @@ int min_wal_size = 5; /* 80 MB */ int wal_keep_segments = 0; int XLOGbuffers = -1; int XLogArchiveTimeout = 0; -bool XLogArchiveMode = false; +int XLogArchiveMode = ARCHIVE_MODE_OFF; char *XLogArchiveCommand = NULL; bool EnableHotStandby = false; bool fullPageWrites = true; @@ -140,6 +140,24 @@ const struct config_enum_entry sync_method_options[] = { {NULL, 0, false} }; + +/* + * Although only "on", "off", and "always" are documented, + * we accept all the likely variants of "on" and "off". + */ +const struct config_enum_entry archive_mode_options[] = { + {"always", ARCHIVE_MODE_ALWAYS, false}, + {"on", ARCHIVE_MODE_ON, false}, + {"off", ARCHIVE_MODE_OFF, false}, + {"true", ARCHIVE_MODE_ON, true}, + {"false", ARCHIVE_MODE_OFF, true}, + {"yes", ARCHIVE_MODE_ON, true}, + {"no", ARCHIVE_MODE_OFF, true}, + {"1", ARCHIVE_MODE_ON, true}, + {"0", ARCHIVE_MODE_OFF, true}, + {NULL, 0, false} +}; + /* * Statistics for current checkpoint are collected in this global struct. * Because only the checkpointer or a stand-alone backend can perform @@ -767,7 +785,7 @@ static MemoryContext walDebugCxt = NULL; #endif static void readRecoveryCommandFile(void); -static void exitArchiveRecovery(TimeLineID endTLI, XLogSegNo endLogSegNo); +static void exitArchiveRecovery(TimeLineID endTLI, XLogRecPtr endOfLog); static bool recoveryStopsBefore(XLogReaderState *record); static bool recoveryStopsAfter(XLogReaderState *record); static void recoveryPausesHere(void); diff --git a/src/backend/access/transam/xlogarchive.c b/src/backend/access/transam/xlogarchive.c index f435f65..4c69b73 100644 --- a/src/backend/access/transam/xlogarchive.c +++ b/src/backend/access/transam/xlogarchive.c @@ -480,7 +480,10 @@ KeepFileRestoredFromArchive(char *path, char *xlogfname) * Create .done file forcibly to prevent the restored segment from being * archived again later. */ - XLogArchiveForceDone(xlogfname); + if (XLogArchiveMode != ARCHIVE_MODE_ALWAYS) + XLogArchiveForceDone(xlogfname); + else + XLogArchiveNotify(xlogfname); /* * If the existing file was replaced, since walsenders might have it open, diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index a9f20ac..36440cb 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -828,9 +828,9 @@ PostmasterMain(int argc, char *argv[]) write_stderr("%s: max_wal_senders must be less than max_connections\n", progname); ExitPostmaster(1); } - if (XLogArchiveMode && wal_level == WAL_LEVEL_MINIMAL) + if (XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level == WAL_LEVEL_MINIMAL) ereport(ERROR, - (errmsg("WAL archival (archive_mode=on) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); + (errmsg("WAL archival cannot be enabled when wal_level is \"minimal\""))); if (max_wal_senders > 0 && wal_level == WAL_LEVEL_MINIMAL) ereport(ERROR, (errmsg("WAL streaming (max_wal_senders > 0) requires wal_level \"archive\", \"hot_standby\", or \"logical\""))); @@ -1645,13 +1645,21 @@ ServerLoop(void) start_autovac_launcher = false; /* signal processed */ } - /* If we have lost the archiver, try to start a new one */ - if (XLogArchivingActive() && PgArchPID == 0 && pmState == PM_RUN) - PgArchPID = pgarch_start(); - - /* If we have lost the stats collector, try to start a new one */ - if (PgStatPID == 0 && pmState == PM_RUN) - PgStatPID = pgstat_start(); + /* + * If we have lost the archiver, try to start a new one. + * + * If WAL archiving is enabled always, we try to start a new archiver + * even during recovery. + */ + if (PgArchPID == 0 && wal_level >= WAL_LEVEL_ARCHIVE) + { + if ((pmState == PM_RUN && XLogArchiveMode > ARCHIVE_MODE_OFF) || + ((pmState == PM_RECOVERY || pmState == PM_HOT_STANDBY) && + XLogArchiveMode == ARCHIVE_MODE_ALWAYS)) + { + PgArchPID = pgarch_start(); + } + } /* If we need to signal the autovacuum launcher, do so now */ if (avlauncher_needs_signal) @@ -4807,6 +4815,17 @@ sigusr1_handler(SIGNAL_ARGS) Assert(BgWriterPID == 0); BgWriterPID = StartBackgroundWriter(); + /* + * Start the archiver if we're responsible for (re-)archiving received + * files. + */ + Assert(PgArchPID == 0); + if (wal_level >= WAL_LEVEL_ARCHIVE && + XLogArchiveMode == ARCHIVE_MODE_ALWAYS) + { + PgArchPID = pgarch_start(); + } + pmState = PM_RECOVERY; } if (CheckPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY) && diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c index 9c7710f..41e57f2 100644 --- a/src/backend/replication/walreceiver.c +++ b/src/backend/replication/walreceiver.c @@ -540,7 +540,10 @@ WalReceiverMain(void) * being archived later. */ XLogFileName(xlogfname, recvFileTLI, recvSegNo); - XLogArchiveForceDone(xlogfname); + if (XLogArchiveMode != ARCHIVE_MODE_ALWAYS) + XLogArchiveForceDone(xlogfname); + else + XLogArchiveNotify(xlogfname); } recvFile = -1; @@ -897,7 +900,10 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr) * from being archived later. */ XLogFileName(xlogfname, recvFileTLI, recvSegNo); - XLogArchiveForceDone(xlogfname); + if (XLogArchiveMode != ARCHIVE_MODE_ALWAYS) + XLogArchiveForceDone(xlogfname); + else + XLogArchiveNotify(xlogfname); } recvFile = -1; diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 5f71ded..97aca46 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -396,6 +396,7 @@ static const struct config_enum_entry row_security_options[] = { * Options for enum values stored in other modules */ extern const struct config_enum_entry wal_level_options[]; +extern const struct config_enum_entry archive_mode_options[]; extern const struct config_enum_entry sync_method_options[]; extern const struct config_enum_entry dynamic_shared_memory_options[]; @@ -1530,16 +1531,6 @@ static struct config_bool ConfigureNamesBool[] = }, { - {"archive_mode", PGC_POSTMASTER, WAL_ARCHIVING, - gettext_noop("Allows archiving of WAL files using archive_command."), - NULL - }, - &XLogArchiveMode, - false, - NULL, NULL, NULL - }, - - { {"hot_standby", PGC_POSTMASTER, REPLICATION_STANDBY, gettext_noop("Allows connections and queries during recovery."), NULL @@ -3552,6 +3543,16 @@ static struct config_enum ConfigureNamesEnum[] = }, { + {"archive_mode", PGC_POSTMASTER, WAL_ARCHIVING, + gettext_noop("Allows archiving of WAL files using archive_command."), + NULL + }, + &XLogArchiveMode, + ARCHIVE_MODE_OFF, archive_mode_options, + NULL, NULL, NULL + }, + + { {"trace_recovery_messages", PGC_SIGHUP, DEVELOPER_OPTIONS, gettext_noop("Enables logging of recovery-related debugging information."), gettext_noop("Each level includes all the levels that follow it. The later" diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 110983f..7bea68a 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -206,7 +206,7 @@ # - Archiving - -#archive_mode = off # allows archiving to be done +#archive_mode = off # allows archiving to be done; off, on, or always # (change requires restart) #archive_command = '' # command to use to archive a logfile segment # placeholders: %p = path of file to archive diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h index 961e050..9567379 100644 --- a/src/include/access/xlog.h +++ b/src/include/access/xlog.h @@ -98,7 +98,6 @@ extern int wal_keep_segments; extern int XLOGbuffers; extern int XLogArchiveTimeout; extern int wal_retrieve_retry_interval; -extern bool XLogArchiveMode; extern char *XLogArchiveCommand; extern bool EnableHotStandby; extern bool fullPageWrites; @@ -108,6 +107,15 @@ extern bool log_checkpoints; extern int CheckPointSegments; +/* Archive modes */ +typedef enum ArchiveMode +{ + ARCHIVE_MODE_OFF = 0, /* disabled */ + ARCHIVE_MODE_ON, /* enabled while server is running normally */ + ARCHIVE_MODE_ALWAYS /* enabled always (even during recovery) */ +} ArchiveMode; +extern int XLogArchiveMode; + /* WAL levels */ typedef enum WalLevel { @@ -118,7 +126,8 @@ typedef enum WalLevel } WalLevel; extern int wal_level; -#define XLogArchivingActive() (XLogArchiveMode && wal_level >= WAL_LEVEL_ARCHIVE) +#define XLogArchivingActive() \ + (XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level >= WAL_LEVEL_ARCHIVE) #define XLogArchiveCommandSet() (XLogArchiveCommand[0] != '\0') /* -- 2.1.4 ^ permalink raw reply [nested|flat] 31+ messages in thread
end of thread, other threads:[~2015-05-13 17:23 UTC | newest] Thread overview: 31+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2014-12-12 13:46 Streaming replication and WAL archive interactions Heikki Linnakangas <[email protected]> 2014-12-16 08:24 ` Borodin Vladimir <[email protected]> 2014-12-16 19:11 ` Heikki Linnakangas <[email protected]> 2014-12-18 10:32 ` Fujii Masao <[email protected]> 2014-12-19 20:56 ` Heikki Linnakangas <[email protected]> 2015-01-31 13:07 ` Andres Freund <[email protected]> 2015-02-12 00:15 ` Миша Тюрин <[email protected]> 2015-02-28 22:36 ` Venkata Balaji N <[email protected]> 2015-04-16 11:57 ` Heikki Linnakangas <[email protected]> 2015-04-21 06:53 ` Michael Paquier <[email protected]> 2015-04-21 07:38 ` Heikki Linnakangas <[email protected]> 2015-04-21 09:04 ` Michael Paquier <[email protected]> 2015-04-21 10:55 ` Heikki Linnakangas <[email protected]> 2015-04-21 21:42 ` Robert Haas <[email protected]> 2015-04-22 00:30 ` Michael Paquier <[email protected]> 2015-04-22 06:38 ` Heikki Linnakangas <[email protected]> 2015-04-22 07:07 ` Michael Paquier <[email protected]> 2015-05-08 13:21 ` Heikki Linnakangas <[email protected]> 2015-05-11 16:00 ` Heikki Linnakangas <[email protected]> 2015-05-13 12:36 ` Robert Haas <[email protected]> 2015-05-13 12:53 ` Heikki Linnakangas <[email protected]> 2015-05-13 13:29 ` Robert Haas <[email protected]> 2015-05-13 17:23 ` Heikki Linnakangas <[email protected]> 2015-04-22 18:58 ` Robert Haas <[email protected]> 2015-04-22 06:17 ` Heikki Linnakangas <[email protected]> 2015-04-22 18:30 ` Robert Haas <[email protected]> 2015-04-22 19:01 ` Heikki Linnakangas <[email protected]> 2015-04-22 19:21 ` Robert Haas <[email protected]> 2015-04-22 19:34 ` Heikki Linnakangas <[email protected]> 2015-04-22 20:58 ` Robert Haas <[email protected]> 2015-04-23 08:11 ` Heikki Linnakangas <[email protected]>
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