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help / color / mirror / Atom feedFrom: Kyotaro Horiguchi <[email protected]>
Subject: [PATCH 4/4] Documentation for slot-limit feature
Date: Thu, 11 Jan 2018 15:00:32 +0900
---
doc/src/sgml/catalogs.sgml | 28 ++++++++++++++++++++++++++++
doc/src/sgml/config.sgml | 23 +++++++++++++++++++++++
doc/src/sgml/high-availability.sgml | 8 +++++---
3 files changed, 56 insertions(+), 3 deletions(-)
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 0179deea2e..84a937e1fe 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -9879,6 +9879,34 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
</entry>
</row>
+ <row>
+ <entry><structfield>wal_status</structfield></entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+
+ <entry>Availability of WAL records claimed by the
+ slot. <literal>streaming</literal>, <literal>keeping</literal>,
+ <literal>lost</literal>
+ or <literal>unknown</literal>. <literal>streaming</literal> means that
+ the claimed records are available. <literal>keeping</literal> means that
+ some of them are to be removed by the next checkpoint.
+ <literal>lost</literal> means that some of them are no longer
+ available. The last two states are seen only when
+ <xref linkend="guc-max-slot-wal-keep-size"/> is non-negative. If the
+ slot doesn't have valid restart_lsn, this field
+ is <literal>unknown</literal>.
+ </entry>
+ </row>
+
+ <row>
+ <entry><structfield>remain</structfield></entry>
+ <entry><type>bigint</type></entry>
+ <entry></entry>
+ <entry>The amount in bytes that WAL location (LSN) can advance until the
+ slot may lose required WAL records.
+ </entry>
+ </row>
+
</tbody>
</tgroup>
</table>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index bee4afbe4e..edd5419ec6 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3116,6 +3116,29 @@ include_dir 'conf.d'
</listitem>
</varlistentry>
+ <varlistentry id="guc-max-slot-wal-keep-size" xreflabel="max_slot_wal_keep_size">
+ <term><varname>max_slot_wal_keep_size</varname> (<type>integer</type>)
+ <indexterm>
+ <primary><varname>max_slot_wal_keep_size</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Specify the maximum size of WAL files
+ that <link linkend="streaming-replication-slots">replication
+ slots</link> are allowed to retain in the <filename>pg_wal</filename>
+ directory at checkpoint time.
+ If <varname>max_slot_wal_keep_size</varname> is -1 (the default),
+ replication slots retain unlimited size of WAL files. If restart_lsn
+ of a replication slot gets behind more than that bytes from the
+ current LSN, the standby using the slot may no longer be able to
+ reconnect due to removal of required WAL records. You can see the WAL
+ availability of replication slots
+ in <link linkend="view-pg-replication-slots">pg_replication_slots</link>.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry id="guc-wal-sender-timeout" xreflabel="wal_sender_timeout">
<term><varname>wal_sender_timeout</varname> (<type>integer</type>)
<indexterm>
diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index 8cb77f85ec..04cdccb10d 100644
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -927,9 +927,11 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass'
<xref linkend="guc-archive-command"/>.
However, these methods often result in retaining more WAL segments than
required, whereas replication slots retain only the number of segments
- known to be needed. An advantage of these methods is that they bound
- the space requirement for <literal>pg_wal</literal>; there is currently no way
- to do this using replication slots.
+ known to be needed. On the other hand, replication slots can retain so
+ many WAL segments that they fill up the space allotted
+ for <literal>pg_wal</literal>;
+ <xref linkend="guc-max-slot-wal-keep-size"/> limits the size of WAL files
+ retained by replication slots.
</para>
<para>
Similarly, <xref linkend="guc-hot-standby-feedback"/>
--
2.16.3
----Next_Part(Thu_Sep_13_18_29_31_2018_032)----
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