public inbox for [email protected]
help / color / mirror / Atom feedFrom: [email protected] <[email protected]>
To: Amit Kapila <[email protected]>
To: Masahiko Sawada <[email protected]>
Cc: Euler Taveira <[email protected]>
Cc: [email protected] <[email protected]>
Cc: Peter Smith <[email protected]>
Cc: Fabrice Chapuis <[email protected]>
Cc: Simon Riggs <[email protected]>
Cc: Petr Jelinek <[email protected]>
Cc: [email protected] <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: Ajin Cherian <[email protected]>
Subject: RE: Logical replication timeout problem
Date: Thu, 21 Apr 2022 09:50:57 +0000
Message-ID: <OS3PR01MB62754DF6581A3904A78A37CB9EF49@OS3PR01MB6275.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <OS3PR01MB6275BBCFA72DE68FA863CD0A9EF49@OS3PR01MB6275.jpnprd01.prod.outlook.com>
References: <CAA4eK1K6rHbMrKHuqGGULg_31bZmgndd+BL=nT0y3KfMUG6pHw@mail.gmail.com>
<CAA4eK1+KssQYCjKdMd7VfZqd3uPL+yVsS-qX-ocPnGuba3zSGQ@mail.gmail.com>
<OS3PR01MB6275BBCFA72DE68FA863CD0A9EF49@OS3PR01MB6275.jpnprd01.prod.outlook.com>
On Wed, Apr 21, 2022 at 10:15 AM I wrote:
> The comments by Sawada-San sound reasonable to me.
> After doing check, I found that padding in HEAD is the same as in REL14.
> So I change the approach of patch for HEAD just like the patch for REL14.
Also attach the back-branch patches for REL10~REL13.
(REL12 and REL11 patch are the same, so only post one patch for these two
branches.)
The patch for HEAD:
HEAD_v18-0001-Fix-the-logical-replication-timeout-during-large.patch
The patch for REL14:
REL14_v2-0001-Fix-the-logical-replication-timeout-during-large-.patch
The patch for REL13:
REL13_v1-0001-Fix-the-logical-replication-timeout-during-large-.patch
The patch for REL12 and REL11:
REL12-REL11_v1-0001-Fix-the-logical-replication-timeout-during-large-.patch
The patch for REL10:
REL10_v1-0001-Fix-the-logical-replication-timeout-during-large-.patch
BTW, after doing check, I found that padding in REL11~REL13 are similar as HEAD
and REL14 (7 bytes padding after fast_forward). But in REL10, the padding is
different. There are three parts padding behind the following member variables:
- 4 bytes after options
- 6 bytes after prepared_write
- 4 bytes after write_xid
So, in the patches for branches REL11~HEAD, I add the new variable after
fast_forward. In the patch for branch REL10, I add the new variable after
prepared_write.
For each version, the size of the structure does not change after applying the
patch.
Regards,
Wang wei
Attachments:
[application/octet-stream] HEAD_v18-0001-Fix-the-logical-replication-timeout-during-large.patch (13.1K, ../OS3PR01MB62754DF6581A3904A78A37CB9EF49@OS3PR01MB6275.jpnprd01.prod.outlook.com/2-HEAD_v18-0001-Fix-the-logical-replication-timeout-during-large.patch)
download | inline diff:
From 3421adeb9a89c54c4733ae1862b7ba18e129b797 Mon Sep 17 00:00:00 2001
From: wangw <[email protected]>
Date: Thu, 21 Apr 2022 09:27:20 +0800
Subject: [PATCH v18] Fix the logical replication timeout during large
transactions.
The problem is that we don't send keep-alive messages for a long time
while processing large transactions during logical replication where we
don't send any data of such transactions. This can happen when the table
modified in the transaction is not published or because all the changes
got filtered. We do try to send the keep_alive if necessary at the end of
the transaction (via WalSndWriteData()) but by that time the
subscriber-side can timeout and exit.
To fix this we try to send the keepalive message if required after
processing certain threshold of changes.
---
src/backend/replication/logical/logical.c | 93 ++++++++++++++++++++-
src/backend/replication/pgoutput/pgoutput.c | 6 ++
src/backend/replication/walsender.c | 27 +++++-
src/include/replication/logical.h | 5 ++
4 files changed, 125 insertions(+), 6 deletions(-)
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 788769dd73..3eb7d77582 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -669,17 +669,41 @@ OutputPluginWrite(struct LogicalDecodingContext *ctx, bool last_write)
}
/*
- * Update progress tracking (if supported).
+ * Update progress tracking and try to send a keepalive message (if supported).
+ *
+ * For a large transaction, if we don't send any change to the downstream for a
+ * long time (exceeds the wal_receiver_timeout of standby) then it can timeout.
+ * This can happen when all or most of the changes are either not published or
+ * got filtered out.
*/
void
OutputPluginUpdateProgress(struct LogicalDecodingContext *ctx,
bool skipped_xact)
{
+ static int changes_count = 0;
+
if (!ctx->update_progress)
return;
- ctx->update_progress(ctx, ctx->write_location, ctx->write_xid,
- skipped_xact);
+ /*
+ * We don't want to try sending a keepalive message after processing each
+ * change as that can have overhead. Tests revealed that there is no
+ * noticeable overhead in doing it after continuously processing 100 or so
+ * changes.
+ */
+#define CHANGES_THRESHOLD 100
+
+ /*
+ * If we are at the end of transaction LSN, update progress tracking.
+ * Otherwise, after continuously processing CHANGES_THRESHOLD changes, we
+ * try to send a keepalive message if required.
+ */
+ if (ctx->end_xact || ++changes_count >= CHANGES_THRESHOLD)
+ {
+ ctx->update_progress(ctx, ctx->write_location, ctx->write_xid,
+ skipped_xact);
+ changes_count = 0;
+ }
}
/*
@@ -747,6 +771,9 @@ startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool i
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.startup_cb(ctx, opt, is_init);
@@ -774,6 +801,9 @@ shutdown_cb_wrapper(LogicalDecodingContext *ctx)
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.shutdown_cb(ctx);
@@ -809,6 +839,9 @@ begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn)
ctx->write_xid = txn->xid;
ctx->write_location = txn->first_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.begin_cb(ctx, txn);
@@ -840,6 +873,9 @@ commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn; /* points to the end of the record */
+ /* set lsn state */
+ ctx->end_xact = true;
+
/* do the actual work: call callback */
ctx->callbacks.commit_cb(ctx, txn, commit_lsn);
@@ -880,6 +916,9 @@ begin_prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn)
ctx->write_xid = txn->xid;
ctx->write_location = txn->first_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/*
* If the plugin supports two-phase commits then begin prepare callback is
* mandatory
@@ -924,6 +963,9 @@ prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn; /* points to the end of the record */
+ /* set lsn state */
+ ctx->end_xact = true;
+
/*
* If the plugin supports two-phase commits then prepare callback is
* mandatory
@@ -968,6 +1010,9 @@ commit_prepared_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn; /* points to the end of the record */
+ /* set lsn state */
+ ctx->end_xact = true;
+
/*
* If the plugin support two-phase commits then commit prepared callback
* is mandatory
@@ -1013,6 +1058,9 @@ rollback_prepared_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn; /* points to the end of the record */
+ /* set lsn state */
+ ctx->end_xact = true;
+
/*
* If the plugin support two-phase commits then rollback prepared callback
* is mandatory
@@ -1062,6 +1110,9 @@ change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
ctx->callbacks.change_cb(ctx, txn, relation, change);
/* Pop the error context stack */
@@ -1102,6 +1153,9 @@ truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
ctx->callbacks.truncate_cb(ctx, txn, nrelations, relations, change);
/* Pop the error context stack */
@@ -1130,6 +1184,9 @@ filter_prepare_cb_wrapper(LogicalDecodingContext *ctx, TransactionId xid,
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ret = ctx->callbacks.filter_prepare_cb(ctx, xid, gid);
@@ -1160,6 +1217,9 @@ filter_by_origin_cb_wrapper(LogicalDecodingContext *ctx, RepOriginId origin_id)
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ret = ctx->callbacks.filter_by_origin_cb(ctx, origin_id);
@@ -1197,6 +1257,9 @@ message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
ctx->write_location = message_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.message_cb(ctx, txn, message_lsn, transactional, prefix,
message_size, message);
@@ -1239,6 +1302,9 @@ stream_start_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = first_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* in streaming mode, stream_start_cb is required */
if (ctx->callbacks.stream_start_cb == NULL)
ereport(ERROR,
@@ -1286,6 +1352,9 @@ stream_stop_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = last_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* in streaming mode, stream_stop_cb is required */
if (ctx->callbacks.stream_stop_cb == NULL)
ereport(ERROR,
@@ -1326,6 +1395,9 @@ stream_abort_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = abort_lsn;
+ /* set lsn state */
+ ctx->end_xact = true;
+
/* in streaming mode, stream_abort_cb is required */
if (ctx->callbacks.stream_abort_cb == NULL)
ereport(ERROR,
@@ -1370,6 +1442,9 @@ stream_prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn;
+ /* set lsn state */
+ ctx->end_xact = true;
+
/* in streaming mode with two-phase commits, stream_prepare_cb is required */
if (ctx->callbacks.stream_prepare_cb == NULL)
ereport(ERROR,
@@ -1410,6 +1485,9 @@ stream_commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn;
+ /* set lsn state */
+ ctx->end_xact = true;
+
/* in streaming mode, stream_commit_cb is required */
if (ctx->callbacks.stream_commit_cb == NULL)
ereport(ERROR,
@@ -1457,6 +1535,9 @@ stream_change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* in streaming mode, stream_change_cb is required */
if (ctx->callbacks.stream_change_cb == NULL)
ereport(ERROR,
@@ -1502,6 +1583,9 @@ stream_message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
ctx->write_location = message_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.stream_message_cb(ctx, txn, message_lsn, transactional, prefix,
message_size, message);
@@ -1549,6 +1633,9 @@ stream_truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
ctx->callbacks.stream_truncate_cb(ctx, txn, nrelations, relations, change);
/* Pop the error context stack */
diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index b197bfd565..4e2531601f 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -1360,6 +1360,8 @@ pgoutput_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
TupleTableSlot *old_slot = NULL;
TupleTableSlot *new_slot = NULL;
+ OutputPluginUpdateProgress(ctx, false);
+
if (!is_publishable_relation(relation))
return;
@@ -1592,6 +1594,8 @@ pgoutput_truncate(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
Oid *relids;
TransactionId xid = InvalidTransactionId;
+ OutputPluginUpdateProgress(ctx, false);
+
/* Remember the xid for the change in streaming mode. See pgoutput_change. */
if (in_streaming)
xid = change->txn->xid;
@@ -1655,6 +1659,8 @@ pgoutput_message(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
PGOutputData *data = (PGOutputData *) ctx->output_plugin_private;
TransactionId xid = InvalidTransactionId;
+ OutputPluginUpdateProgress(ctx, false);
+
if (!data->messages)
return;
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 63a818140b..d9068ab591 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -1475,6 +1475,9 @@ ProcessPendingWrites(void)
* Write the current position to the lag tracker (see XLogSendPhysical).
*
* When skipping empty transactions, send a keepalive message if necessary.
+ *
+ * In logical replication, if too many changes are processed then try to send a
+ * keepalive message. It might avoid a timeout in the subscriber.
*/
static void
WalSndUpdateProgress(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
@@ -1482,14 +1485,20 @@ WalSndUpdateProgress(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId
{
static TimestampTz sendTime = 0;
TimestampTz now = GetCurrentTimestamp();
+ bool pending_writes = false,
+ end_xact = ctx->end_xact;
/*
* Track lag no more than once per WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS to
* avoid flooding the lag tracker when we commit frequently.
+ *
+ * We don't have a mechanism to get the ack for any LSN other than end xact
+ * LSN from the downstream. So, we track lag only for end of transaction
+ * LSN.
*/
#define WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS 1000
- if (TimestampDifferenceExceeds(sendTime, now,
- WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS))
+ if (end_xact && TimestampDifferenceExceeds(sendTime, now,
+ WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS))
{
LagTrackerWrite(lsn, now);
sendTime = now;
@@ -1515,8 +1524,20 @@ WalSndUpdateProgress(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId
/* If we have pending write here, make sure it's actually flushed */
if (pq_is_send_pending())
- ProcessPendingWrites();
+ pending_writes = true;
}
+
+ /*
+ * Process pending writes if any or try to send a keepalive if required. We
+ * don't need to try sending keep alive messages at the transaction end as
+ * that will be done at a later point in time. This is required only for
+ * large transactions where we don't send any changes to the downstream and
+ * the receiver can timeout due to that.
+ */
+ if (pending_writes || (!end_xact &&
+ now >= TimestampTzPlusMilliseconds(last_reply_timestamp,
+ wal_sender_timeout / 2)))
+ ProcessPendingWrites();
}
/*
diff --git a/src/include/replication/logical.h b/src/include/replication/logical.h
index a6ef16ad5b..0a2fdf498f 100644
--- a/src/include/replication/logical.h
+++ b/src/include/replication/logical.h
@@ -50,6 +50,11 @@ typedef struct LogicalDecodingContext
*/
bool fast_forward;
+ /*
+ * Is the end of transaction LSN?
+ */
+ bool end_xact;
+
OutputPluginCallbacks callbacks;
OutputPluginOptions options;
--
2.23.0.windows.1
[application/octet-stream] REL14_v2-0001-Fix-the-logical-replication-timeout-during-large-.patch (13.3K, ../OS3PR01MB62754DF6581A3904A78A37CB9EF49@OS3PR01MB6275.jpnprd01.prod.outlook.com/3-REL14_v2-0001-Fix-the-logical-replication-timeout-during-large-.patch)
download | inline diff:
From 919b99d8ae45fe6646d4e3447922aca7f01e838c Mon Sep 17 00:00:00 2001
From: wangw <[email protected]>
Date: Thu, 21 Apr 2022 09:20:52 +0800
Subject: [PATCH v2] Fix the logical replication timeout during large
transactions.
The problem is that we don't send keep-alive messages for a long time
while processing large transactions during logical replication where we
don't send any data of such transactions. This can happen when the table
modified in the transaction is not published. We do try to send the keep_alive
if necessary at the end of the transaction (via WalSndWriteData()) but
by that time the subscriber-side can timeout and exit.
To fix this we try to send the keepalive message if required after
processing certain threshold of changes.
---
src/backend/replication/logical/logical.c | 90 ++++++++++++++++++++-
src/backend/replication/pgoutput/pgoutput.c | 6 ++
src/backend/replication/walsender.c | 39 ++++++++-
src/include/replication/logical.h | 5 ++
4 files changed, 134 insertions(+), 6 deletions(-)
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index d536a5f3ba..514e04a088 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -649,15 +649,38 @@ OutputPluginWrite(struct LogicalDecodingContext *ctx, bool last_write)
}
/*
- * Update progress tracking (if supported).
+ * Update progress tracking and try to send a keepalive message (if supported).
+ *
+ * For a large transaction, if we don't send any change to the downstream for a
+ * long time (exceeds the wal_receiver_timeout of standby) then it can timeout.
+ * This can happen when all or most of the changes are not published.
*/
void
OutputPluginUpdateProgress(struct LogicalDecodingContext *ctx)
{
+ static int changes_count = 0;
+
if (!ctx->update_progress)
return;
- ctx->update_progress(ctx, ctx->write_location, ctx->write_xid);
+ /*
+ * We don't want to try sending a keepalive message after processing each
+ * change as that can have overhead. Tests revealed that there is no
+ * noticeable overhead in doing it after continuously processing 100 or so
+ * changes.
+ */
+#define CHANGES_THRESHOLD 100
+
+ /*
+ * If we are at the end of transaction LSN, update progress tracking.
+ * Otherwise, after continuously processing CHANGES_THRESHOLD changes, we
+ * try to send a keepalive message if required.
+ */
+ if (ctx->end_xact || ++changes_count >= CHANGES_THRESHOLD)
+ {
+ ctx->update_progress(ctx, ctx->write_location, ctx->write_xid);
+ changes_count = 0;
+ }
}
/*
@@ -725,6 +748,9 @@ startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool i
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.startup_cb(ctx, opt, is_init);
@@ -752,6 +778,9 @@ shutdown_cb_wrapper(LogicalDecodingContext *ctx)
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.shutdown_cb(ctx);
@@ -787,6 +816,9 @@ begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn)
ctx->write_xid = txn->xid;
ctx->write_location = txn->first_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.begin_cb(ctx, txn);
@@ -818,6 +850,9 @@ commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn; /* points to the end of the record */
+ /* set lsn state */
+ ctx->end_xact = true;
+
/* do the actual work: call callback */
ctx->callbacks.commit_cb(ctx, txn, commit_lsn);
@@ -858,6 +893,9 @@ begin_prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn)
ctx->write_xid = txn->xid;
ctx->write_location = txn->first_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/*
* If the plugin supports two-phase commits then begin prepare callback is
* mandatory
@@ -902,6 +940,9 @@ prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn; /* points to the end of the record */
+ /* set lsn state */
+ ctx->end_xact = true;
+
/*
* If the plugin supports two-phase commits then prepare callback is
* mandatory
@@ -946,6 +987,9 @@ commit_prepared_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn; /* points to the end of the record */
+ /* set lsn state */
+ ctx->end_xact = true;
+
/*
* If the plugin support two-phase commits then commit prepared callback
* is mandatory
@@ -991,6 +1035,9 @@ rollback_prepared_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn; /* points to the end of the record */
+ /* set lsn state */
+ ctx->end_xact = true;
+
/*
* If the plugin support two-phase commits then rollback prepared callback
* is mandatory
@@ -1040,6 +1087,9 @@ change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
ctx->callbacks.change_cb(ctx, txn, relation, change);
/* Pop the error context stack */
@@ -1080,6 +1130,9 @@ truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
ctx->callbacks.truncate_cb(ctx, txn, nrelations, relations, change);
/* Pop the error context stack */
@@ -1108,6 +1161,9 @@ filter_prepare_cb_wrapper(LogicalDecodingContext *ctx, TransactionId xid,
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ret = ctx->callbacks.filter_prepare_cb(ctx, xid, gid);
@@ -1138,6 +1194,9 @@ filter_by_origin_cb_wrapper(LogicalDecodingContext *ctx, RepOriginId origin_id)
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ret = ctx->callbacks.filter_by_origin_cb(ctx, origin_id);
@@ -1175,6 +1234,9 @@ message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
ctx->write_location = message_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.message_cb(ctx, txn, message_lsn, transactional, prefix,
message_size, message);
@@ -1217,6 +1279,9 @@ stream_start_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = first_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* in streaming mode, stream_start_cb is required */
if (ctx->callbacks.stream_start_cb == NULL)
ereport(ERROR,
@@ -1264,6 +1329,9 @@ stream_stop_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = last_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* in streaming mode, stream_stop_cb is required */
if (ctx->callbacks.stream_stop_cb == NULL)
ereport(ERROR,
@@ -1304,6 +1372,9 @@ stream_abort_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = abort_lsn;
+ /* set lsn state */
+ ctx->end_xact = true;
+
/* in streaming mode, stream_abort_cb is required */
if (ctx->callbacks.stream_abort_cb == NULL)
ereport(ERROR,
@@ -1348,6 +1419,9 @@ stream_prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn;
+ /* set lsn state */
+ ctx->end_xact = true;
+
/* in streaming mode with two-phase commits, stream_prepare_cb is required */
if (ctx->callbacks.stream_prepare_cb == NULL)
ereport(ERROR,
@@ -1388,6 +1462,9 @@ stream_commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn;
+ /* set lsn state */
+ ctx->end_xact = true;
+
/* in streaming mode, stream_commit_cb is required */
if (ctx->callbacks.stream_commit_cb == NULL)
ereport(ERROR,
@@ -1435,6 +1512,9 @@ stream_change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* in streaming mode, stream_change_cb is required */
if (ctx->callbacks.stream_change_cb == NULL)
ereport(ERROR,
@@ -1480,6 +1560,9 @@ stream_message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
ctx->write_location = message_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.stream_message_cb(ctx, txn, message_lsn, transactional, prefix,
message_size, message);
@@ -1527,6 +1610,9 @@ stream_truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
ctx->callbacks.stream_truncate_cb(ctx, txn, nrelations, relations, change);
/* Pop the error context stack */
diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index 2ea540ce4d..31b585a6fa 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -535,6 +535,8 @@ pgoutput_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
TransactionId xid = InvalidTransactionId;
Relation ancestor = NULL;
+ OutputPluginUpdateProgress(ctx);
+
if (!is_publishable_relation(relation))
return;
@@ -677,6 +679,8 @@ pgoutput_truncate(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
Oid *relids;
TransactionId xid = InvalidTransactionId;
+ OutputPluginUpdateProgress(ctx);
+
/* Remember the xid for the change in streaming mode. See pgoutput_change. */
if (in_streaming)
xid = change->txn->xid;
@@ -735,6 +739,8 @@ pgoutput_message(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
PGOutputData *data = (PGOutputData *) ctx->output_plugin_private;
TransactionId xid = InvalidTransactionId;
+ OutputPluginUpdateProgress(ctx);
+
if (!data->messages)
return;
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 3b245c619f..12d5347b30 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -240,6 +240,7 @@ static void ProcessStandbyMessage(void);
static void ProcessStandbyReplyMessage(void);
static void ProcessStandbyHSFeedbackMessage(void);
static void ProcessRepliesIfAny(void);
+static void ProcessPendingWrites(void);
static void WalSndKeepalive(bool requestReply);
static void WalSndKeepaliveIfNecessary(void);
static void WalSndCheckTimeOut(void);
@@ -1288,6 +1289,16 @@ WalSndWriteData(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
}
/* If we have pending write here, go to slow path */
+ ProcessPendingWrites();
+}
+
+/*
+ * Wait until there is no pending write. Also process replies from the other
+ * side and check timeouts during that.
+ */
+static void
+ProcessPendingWrites(void)
+{
for (;;)
{
long sleeptime;
@@ -1336,24 +1347,44 @@ WalSndWriteData(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
* LogicalDecodingContext 'update_progress' callback.
*
* Write the current position to the lag tracker (see XLogSendPhysical).
+ *
+ * In logical replication, if too many changes are processed then try to send a
+ * keepalive message. It might avoid a timeout in the subscriber.
*/
static void
WalSndUpdateProgress(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid)
{
static TimestampTz sendTime = 0;
TimestampTz now = GetCurrentTimestamp();
+ bool end_xact = ctx->end_xact;
/*
* Track lag no more than once per WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS to
* avoid flooding the lag tracker when we commit frequently.
+ *
+ * We don't have a mechanism to get the ack for any LSN other than end xact
+ * LSN from the downstream. So, we track lag only for end of transaction
+ * LSN.
*/
#define WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS 1000
- if (!TimestampDifferenceExceeds(sendTime, now,
+ if (end_xact && TimestampDifferenceExceeds(sendTime, now,
WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS))
- return;
+ {
+ LagTrackerWrite(lsn, now);
+ sendTime = now;
+ }
- LagTrackerWrite(lsn, now);
- sendTime = now;
+ /*
+ * Try to send a keepalive if required. We don't need to try sending keep
+ * alive messages at the transaction end as that will be done at a later
+ * point in time. This is required only for large transactions where we
+ * don't send any changes to the downstream and the receiver can timeout
+ * due to that.
+ */
+ if (!end_xact &&
+ now >= TimestampTzPlusMilliseconds(last_reply_timestamp,
+ wal_sender_timeout / 2))
+ ProcessPendingWrites();
}
/*
diff --git a/src/include/replication/logical.h b/src/include/replication/logical.h
index af551d6f4e..8f8ff92ec5 100644
--- a/src/include/replication/logical.h
+++ b/src/include/replication/logical.h
@@ -49,6 +49,11 @@ typedef struct LogicalDecodingContext
*/
bool fast_forward;
+ /*
+ * Is the end of transaction LSN?
+ */
+ bool end_xact;
+
OutputPluginCallbacks callbacks;
OutputPluginOptions options;
--
2.23.0.windows.1
[application/octet-stream] REL13_v1-0001-Fix-the-logical-replication-timeout-during-large-.patch (8.8K, ../OS3PR01MB62754DF6581A3904A78A37CB9EF49@OS3PR01MB6275.jpnprd01.prod.outlook.com/4-REL13_v1-0001-Fix-the-logical-replication-timeout-during-large-.patch)
download | inline diff:
From 2a428c76d58bfaed024660238d62c0e0a77e9fca Mon Sep 17 00:00:00 2001
From: wangw <[email protected]>
Date: Thu, 21 Apr 2022 15:01:02 +0800
Subject: [PATCH v1] Fix the logical replication timeout during large
transactions.
The problem is that we don't send keep-alive messages for a long time
while processing large transactions during logical replication where we
don't send any data of such transactions. This can happen when the table
modified in the transaction is not published. We do try to send the keep_alive
if necessary at the end of the transaction (via WalSndWriteData()) but
by that time the subscriber-side can timeout and exit.
To fix this we try to send the keepalive message if required after
processing certain threshold of changes.
---
src/backend/replication/logical/logical.c | 51 ++++++++++++++++++++-
src/backend/replication/pgoutput/pgoutput.c | 4 ++
src/backend/replication/walsender.c | 39 ++++++++++++++--
src/include/replication/logical.h | 5 ++
4 files changed, 93 insertions(+), 6 deletions(-)
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 61902be3b0..91283f1de7 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -546,15 +546,38 @@ OutputPluginWrite(struct LogicalDecodingContext *ctx, bool last_write)
}
/*
- * Update progress tracking (if supported).
+ * Update progress tracking and try to send a keepalive message (if supported).
+ *
+ * For a large transaction, if we don't send any change to the downstream for a
+ * long time (exceeds the wal_receiver_timeout of standby) then it can timeout.
+ * This can happen when all or most of the changes are not published.
*/
void
OutputPluginUpdateProgress(struct LogicalDecodingContext *ctx)
{
+ static int changes_count = 0;
+
if (!ctx->update_progress)
return;
- ctx->update_progress(ctx, ctx->write_location, ctx->write_xid);
+ /*
+ * We don't want to try sending a keepalive message after processing each
+ * change as that can have overhead. Tests revealed that there is no
+ * noticeable overhead in doing it after continuously processing 100 or so
+ * changes.
+ */
+#define CHANGES_THRESHOLD 100
+
+ /*
+ * If we are at the end of transaction LSN, update progress tracking.
+ * Otherwise, after continuously processing CHANGES_THRESHOLD changes, we
+ * try to send a keepalive message if required.
+ */
+ if (ctx->end_xact || ++changes_count >= CHANGES_THRESHOLD)
+ {
+ ctx->update_progress(ctx, ctx->write_location, ctx->write_xid);
+ changes_count = 0;
+ }
}
/*
@@ -623,6 +646,9 @@ startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool i
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.startup_cb(ctx, opt, is_init);
@@ -650,6 +676,9 @@ shutdown_cb_wrapper(LogicalDecodingContext *ctx)
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.shutdown_cb(ctx);
@@ -685,6 +714,9 @@ begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn)
ctx->write_xid = txn->xid;
ctx->write_location = txn->first_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.begin_cb(ctx, txn);
@@ -716,6 +748,9 @@ commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn; /* points to the end of the record */
+ /* set lsn state */
+ ctx->end_xact = true;
+
/* do the actual work: call callback */
ctx->callbacks.commit_cb(ctx, txn, commit_lsn);
@@ -754,6 +789,9 @@ change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
ctx->callbacks.change_cb(ctx, txn, relation, change);
/* Pop the error context stack */
@@ -794,6 +832,9 @@ truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
ctx->callbacks.truncate_cb(ctx, txn, nrelations, relations, change);
/* Pop the error context stack */
@@ -821,6 +862,9 @@ filter_by_origin_cb_wrapper(LogicalDecodingContext *ctx, RepOriginId origin_id)
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ret = ctx->callbacks.filter_by_origin_cb(ctx, origin_id);
@@ -858,6 +902,9 @@ message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
ctx->write_location = message_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.message_cb(ctx, txn, message_lsn, transactional, prefix,
message_size, message);
diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index 79735da21a..2ae00a70cb 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -385,6 +385,8 @@ pgoutput_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
RelationSyncEntry *relentry;
Relation ancestor = NULL;
+ OutputPluginUpdateProgress(ctx);
+
if (!is_publishable_relation(relation))
return;
@@ -514,6 +516,8 @@ pgoutput_truncate(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
int nrelids;
Oid *relids;
+ OutputPluginUpdateProgress(ctx);
+
old = MemoryContextSwitchTo(data->context);
relids = palloc0(nrelations * sizeof(Oid));
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index fe0d2ee2ed..b885fac833 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -240,6 +240,7 @@ static void ProcessStandbyMessage(void);
static void ProcessStandbyReplyMessage(void);
static void ProcessStandbyHSFeedbackMessage(void);
static void ProcessRepliesIfAny(void);
+static void ProcessPendingWrites(void);
static void WalSndKeepalive(bool requestReply);
static void WalSndKeepaliveIfNecessary(void);
static void WalSndCheckTimeOut(void);
@@ -1295,6 +1296,16 @@ WalSndWriteData(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
}
/* If we have pending write here, go to slow path */
+ ProcessPendingWrites();
+}
+
+/*
+ * Wait until there is no pending write. Also process replies from the other
+ * side and check timeouts during that.
+ */
+static void
+ProcessPendingWrites(void)
+{
for (;;)
{
int wakeEvents;
@@ -1348,24 +1359,44 @@ WalSndWriteData(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
* LogicalDecodingContext 'update_progress' callback.
*
* Write the current position to the lag tracker (see XLogSendPhysical).
+ *
+ * In logical replication, if too many changes are processed then try to send a
+ * keepalive message. It might avoid a timeout in the subscriber.
*/
static void
WalSndUpdateProgress(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid)
{
static TimestampTz sendTime = 0;
TimestampTz now = GetCurrentTimestamp();
+ bool end_xact = ctx->end_xact;
/*
* Track lag no more than once per WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS to
* avoid flooding the lag tracker when we commit frequently.
+ *
+ * We don't have a mechanism to get the ack for any LSN other than end xact
+ * LSN from the downstream. So, we track lag only for end of transaction
+ * LSN.
*/
#define WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS 1000
- if (!TimestampDifferenceExceeds(sendTime, now,
+ if (end_xact && TimestampDifferenceExceeds(sendTime, now,
WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS))
- return;
+ {
+ LagTrackerWrite(lsn, now);
+ sendTime = now;
+ }
- LagTrackerWrite(lsn, now);
- sendTime = now;
+ /*
+ * Try to send a keepalive if required. We don't need to try sending keep
+ * alive messages at the transaction end as that will be done at a later
+ * point in time. This is required only for large transactions where we
+ * don't send any changes to the downstream and the receiver can timeout
+ * due to that.
+ */
+ if (!end_xact &&
+ now >= TimestampTzPlusMilliseconds(last_reply_timestamp,
+ wal_sender_timeout / 2))
+ ProcessPendingWrites();
}
/*
diff --git a/src/include/replication/logical.h b/src/include/replication/logical.h
index c2f2475e5d..6455c2d2bf 100644
--- a/src/include/replication/logical.h
+++ b/src/include/replication/logical.h
@@ -49,6 +49,11 @@ typedef struct LogicalDecodingContext
*/
bool fast_forward;
+ /*
+ * Is the end of transaction LSN?
+ */
+ bool end_xact;
+
OutputPluginCallbacks callbacks;
OutputPluginOptions options;
--
2.23.0.windows.1
[application/octet-stream] REL12-REL11_v1-0001-Fix-the-logical-replication-timeout-during-large-.patch (8.7K, ../OS3PR01MB62754DF6581A3904A78A37CB9EF49@OS3PR01MB6275.jpnprd01.prod.outlook.com/5-REL12-REL11_v1-0001-Fix-the-logical-replication-timeout-during-large-.patch)
download | inline diff:
From d5b8314813f5d513a3a7feb9d7febfb3fef2e655 Mon Sep 17 00:00:00 2001
From: wangw <[email protected]>
Date: Thu, 21 Apr 2022 15:06:07 +0800
Subject: [PATCH v1] Fix the logical replication timeout during large
transactions.
The problem is that we don't send keep-alive messages for a long time
while processing large transactions during logical replication where we
don't send any data of such transactions. This can happen when the table
modified in the transaction is not published. We do try to send the keep_alive
if necessary at the end of the transaction (via WalSndWriteData()) but
by that time the subscriber-side can timeout and exit.
To fix this we try to send the keepalive message if required after
processing certain threshold of changes.
---
src/backend/replication/logical/logical.c | 51 ++++++++++++++++++++-
src/backend/replication/pgoutput/pgoutput.c | 4 ++
src/backend/replication/walsender.c | 39 ++++++++++++++--
src/include/replication/logical.h | 5 ++
4 files changed, 93 insertions(+), 6 deletions(-)
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index a0fc480646..010aa6ab8c 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -548,15 +548,38 @@ OutputPluginWrite(struct LogicalDecodingContext *ctx, bool last_write)
}
/*
- * Update progress tracking (if supported).
+ * Update progress tracking and try to send a keepalive message (if supported).
+ *
+ * For a large transaction, if we don't send any change to the downstream for a
+ * long time (exceeds the wal_receiver_timeout of standby) then it can timeout.
+ * This can happen when all or most of the changes are not published.
*/
void
OutputPluginUpdateProgress(struct LogicalDecodingContext *ctx)
{
+ static int changes_count = 0;
+
if (!ctx->update_progress)
return;
- ctx->update_progress(ctx, ctx->write_location, ctx->write_xid);
+ /*
+ * We don't want to try sending a keepalive message after processing each
+ * change as that can have overhead. Tests revealed that there is no
+ * noticeable overhead in doing it after continuously processing 100 or so
+ * changes.
+ */
+#define CHANGES_THRESHOLD 100
+
+ /*
+ * If we are at the end of transaction LSN, update progress tracking.
+ * Otherwise, after continuously processing CHANGES_THRESHOLD changes, we
+ * try to send a keepalive message if required.
+ */
+ if (ctx->end_xact || ++changes_count >= CHANGES_THRESHOLD)
+ {
+ ctx->update_progress(ctx, ctx->write_location, ctx->write_xid);
+ changes_count = 0;
+ }
}
/*
@@ -625,6 +648,9 @@ startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool i
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.startup_cb(ctx, opt, is_init);
@@ -652,6 +678,9 @@ shutdown_cb_wrapper(LogicalDecodingContext *ctx)
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.shutdown_cb(ctx);
@@ -687,6 +716,9 @@ begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn)
ctx->write_xid = txn->xid;
ctx->write_location = txn->first_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.begin_cb(ctx, txn);
@@ -718,6 +750,9 @@ commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn; /* points to the end of the record */
+ /* set lsn state */
+ ctx->end_xact = true;
+
/* do the actual work: call callback */
ctx->callbacks.commit_cb(ctx, txn, commit_lsn);
@@ -756,6 +791,9 @@ change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
ctx->callbacks.change_cb(ctx, txn, relation, change);
/* Pop the error context stack */
@@ -796,6 +834,9 @@ truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
ctx->callbacks.truncate_cb(ctx, txn, nrelations, relations, change);
/* Pop the error context stack */
@@ -823,6 +864,9 @@ filter_by_origin_cb_wrapper(LogicalDecodingContext *ctx, RepOriginId origin_id)
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ret = ctx->callbacks.filter_by_origin_cb(ctx, origin_id);
@@ -860,6 +904,9 @@ message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
ctx->write_location = message_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.message_cb(ctx, txn, message_lsn, transactional, prefix,
message_size, message);
diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index d317fd7006..cff24fb44f 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -309,6 +309,8 @@ pgoutput_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
MemoryContext old;
RelationSyncEntry *relentry;
+ OutputPluginUpdateProgress(ctx);
+
if (!is_publishable_relation(relation))
return;
@@ -389,6 +391,8 @@ pgoutput_truncate(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
int nrelids;
Oid *relids;
+ OutputPluginUpdateProgress(ctx);
+
old = MemoryContextSwitchTo(data->context);
relids = palloc0(nrelations * sizeof(Oid));
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 3698135e49..2373ebd57c 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -244,6 +244,7 @@ static void ProcessStandbyMessage(void);
static void ProcessStandbyReplyMessage(void);
static void ProcessStandbyHSFeedbackMessage(void);
static void ProcessRepliesIfAny(void);
+static void ProcessPendingWrites(void);
static void WalSndKeepalive(bool requestReply);
static void WalSndKeepaliveIfNecessary(void);
static void WalSndCheckTimeOut(void);
@@ -1214,6 +1215,16 @@ WalSndWriteData(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
}
/* If we have pending write here, go to slow path */
+ ProcessPendingWrites();
+}
+
+/*
+ * Wait until there is no pending write. Also process replies from the other
+ * side and check timeouts during that.
+ */
+static void
+ProcessPendingWrites(void)
+{
for (;;)
{
int wakeEvents;
@@ -1267,24 +1278,44 @@ WalSndWriteData(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
* LogicalDecodingContext 'update_progress' callback.
*
* Write the current position to the lag tracker (see XLogSendPhysical).
+ *
+ * In logical replication, if too many changes are processed then try to send a
+ * keepalive message. It might avoid a timeout in the subscriber.
*/
static void
WalSndUpdateProgress(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid)
{
static TimestampTz sendTime = 0;
TimestampTz now = GetCurrentTimestamp();
+ bool end_xact = ctx->end_xact;
/*
* Track lag no more than once per WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS to
* avoid flooding the lag tracker when we commit frequently.
+ *
+ * We don't have a mechanism to get the ack for any LSN other than end xact
+ * LSN from the downstream. So, we track lag only for end of transaction
+ * LSN.
*/
#define WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS 1000
- if (!TimestampDifferenceExceeds(sendTime, now,
+ if (end_xact && TimestampDifferenceExceeds(sendTime, now,
WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS))
- return;
+ {
+ LagTrackerWrite(lsn, now);
+ sendTime = now;
+ }
- LagTrackerWrite(lsn, now);
- sendTime = now;
+ /*
+ * Try to send a keepalive if required. We don't need to try sending keep
+ * alive messages at the transaction end as that will be done at a later
+ * point in time. This is required only for large transactions where we
+ * don't send any changes to the downstream and the receiver can timeout
+ * due to that.
+ */
+ if (!end_xact &&
+ now >= TimestampTzPlusMilliseconds(last_reply_timestamp,
+ wal_sender_timeout / 2))
+ ProcessPendingWrites();
}
/*
diff --git a/src/include/replication/logical.h b/src/include/replication/logical.h
index 31c796b765..0864475c6b 100644
--- a/src/include/replication/logical.h
+++ b/src/include/replication/logical.h
@@ -50,6 +50,11 @@ typedef struct LogicalDecodingContext
*/
bool fast_forward;
+ /*
+ * Is the end of transaction LSN?
+ */
+ bool end_xact;
+
OutputPluginCallbacks callbacks;
OutputPluginOptions options;
--
2.23.0.windows.1
[application/octet-stream] REL10_v1-0001-Fix-the-logical-replication-timeout-during-large-.patch (8.2K, ../OS3PR01MB62754DF6581A3904A78A37CB9EF49@OS3PR01MB6275.jpnprd01.prod.outlook.com/6-REL10_v1-0001-Fix-the-logical-replication-timeout-during-large-.patch)
download | inline diff:
From aaa79d6c340c146fb02c4afbebd31f729da406be Mon Sep 17 00:00:00 2001
From: wangw <[email protected]>
Date: Thu, 21 Apr 2022 15:53:29 +0800
Subject: [PATCH v1] Fix the logical replication timeout during large
transactions.
The problem is that we don't send keep-alive messages for a long time
while processing large transactions during logical replication where we
don't send any data of such transactions. This can happen when the table
modified in the transaction is not published. We do try to send the keep_alive
if necessary at the end of the transaction (via WalSndWriteData()) but
by that time the subscriber-side can timeout and exit.
To fix this we try to send the keepalive message if required after
processing certain threshold of changes.
---
src/backend/replication/logical/logical.c | 48 ++++++++++++++++++++-
src/backend/replication/pgoutput/pgoutput.c | 2 +
src/backend/replication/walsender.c | 39 +++++++++++++++--
src/include/replication/logical.h | 1 +
4 files changed, 84 insertions(+), 6 deletions(-)
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 1851a626f9..7cc3b5ac60 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -515,15 +515,38 @@ OutputPluginWrite(struct LogicalDecodingContext *ctx, bool last_write)
}
/*
- * Update progress tracking (if supported).
+ * Update progress tracking and try to send a keepalive message (if supported).
+ *
+ * For a large transaction, if we don't send any change to the downstream for a
+ * long time (exceeds the wal_receiver_timeout of standby) then it can timeout.
+ * This can happen when all or most of the changes are not published.
*/
void
OutputPluginUpdateProgress(struct LogicalDecodingContext *ctx)
{
+ static int changes_count = 0;
+
if (!ctx->update_progress)
return;
- ctx->update_progress(ctx, ctx->write_location, ctx->write_xid);
+ /*
+ * We don't want to try sending a keepalive message after processing each
+ * change as that can have overhead. Tests revealed that there is no
+ * noticeable overhead in doing it after continuously processing 100 or so
+ * changes.
+ */
+#define CHANGES_THRESHOLD 100
+
+ /*
+ * If we are at the end of transaction LSN, update progress tracking.
+ * Otherwise, after continuously processing CHANGES_THRESHOLD changes, we
+ * try to send a keepalive message if required.
+ */
+ if (ctx->end_xact || ++changes_count >= CHANGES_THRESHOLD)
+ {
+ ctx->update_progress(ctx, ctx->write_location, ctx->write_xid);
+ changes_count = 0;
+ }
}
/*
@@ -590,6 +613,9 @@ startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool i
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.startup_cb(ctx, opt, is_init);
@@ -615,6 +641,9 @@ shutdown_cb_wrapper(LogicalDecodingContext *ctx)
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.shutdown_cb(ctx);
@@ -648,6 +677,9 @@ begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn)
ctx->write_xid = txn->xid;
ctx->write_location = txn->first_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.begin_cb(ctx, txn);
@@ -677,6 +709,9 @@ commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn->xid;
ctx->write_location = txn->end_lsn; /* points to the end of the record */
+ /* set lsn state */
+ ctx->end_xact = true;
+
/* do the actual work: call callback */
ctx->callbacks.commit_cb(ctx, txn, commit_lsn);
@@ -713,6 +748,9 @@ change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
*/
ctx->write_location = change->lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
ctx->callbacks.change_cb(ctx, txn, relation, change);
/* Pop the error context stack */
@@ -738,6 +776,9 @@ filter_by_origin_cb_wrapper(LogicalDecodingContext *ctx, RepOriginId origin_id)
/* set output state */
ctx->accept_writes = false;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ret = ctx->callbacks.filter_by_origin_cb(ctx, origin_id);
@@ -773,6 +814,9 @@ message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
ctx->write_location = message_lsn;
+ /* set lsn state */
+ ctx->end_xact = false;
+
/* do the actual work: call callback */
ctx->callbacks.message_cb(ctx, txn, message_lsn, transactional, prefix,
message_size, message);
diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index 529a5c0b48..12db2ad4fd 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -264,6 +264,8 @@ pgoutput_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
MemoryContext old;
RelationSyncEntry *relentry;
+ OutputPluginUpdateProgress(ctx);
+
if (!is_publishable_relation(relation))
return;
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 3c9b9f5376..2e4e86f409 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -243,6 +243,7 @@ static void ProcessStandbyMessage(void);
static void ProcessStandbyReplyMessage(void);
static void ProcessStandbyHSFeedbackMessage(void);
static void ProcessRepliesIfAny(void);
+static void ProcessPendingWrites(void);
static void WalSndKeepalive(bool requestReply);
static void WalSndKeepaliveIfNecessary(void);
static void WalSndCheckTimeOut(void);
@@ -1190,6 +1191,16 @@ WalSndWriteData(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
}
/* If we have pending write here, go to slow path */
+ ProcessPendingWrites();
+}
+
+/*
+ * Wait until there is no pending write. Also process replies from the other
+ * side and check timeouts during that.
+ */
+static void
+ProcessPendingWrites(void)
+{
for (;;)
{
int wakeEvents;
@@ -1250,24 +1261,44 @@ WalSndWriteData(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
* LogicalDecodingContext 'progress_update' callback.
*
* Write the current position to the log tracker (see XLogSendPhysical).
+ *
+ * In logical replication, if too many changes are processed then try to send a
+ * keepalive message. It might avoid a timeout in the subscriber.
*/
static void
WalSndUpdateProgress(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid)
{
static TimestampTz sendTime = 0;
TimestampTz now = GetCurrentTimestamp();
+ bool end_xact = ctx->end_xact;
/*
* Track lag no more than once per WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS to
* avoid flooding the lag tracker when we commit frequently.
+ *
+ * We don't have a mechanism to get the ack for any LSN other than end xact
+ * LSN from the downstream. So, we track lag only for end of transaction
+ * LSN.
*/
#define WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS 1000
- if (!TimestampDifferenceExceeds(sendTime, now,
+ if (end_xact && TimestampDifferenceExceeds(sendTime, now,
WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS))
- return;
+ {
+ LagTrackerWrite(lsn, now);
+ sendTime = now;
+ }
- LagTrackerWrite(lsn, now);
- sendTime = now;
+ /*
+ * Try to send a keepalive if required. We don't need to try sending keep
+ * alive messages at the transaction end as that will be done at a later
+ * point in time. This is required only for large transactions where we
+ * don't send any changes to the downstream and the receiver can timeout
+ * due to that.
+ */
+ if (!end_xact &&
+ now >= TimestampTzPlusMilliseconds(last_reply_timestamp,
+ wal_sender_timeout / 2))
+ ProcessPendingWrites();
}
/*
diff --git a/src/include/replication/logical.h b/src/include/replication/logical.h
index 7f0e0fa881..b25a935bc0 100644
--- a/src/include/replication/logical.h
+++ b/src/include/replication/logical.h
@@ -80,6 +80,7 @@ typedef struct LogicalDecodingContext
*/
bool accept_writes;
bool prepared_write;
+ bool end_xact;
XLogRecPtr write_location;
TransactionId write_xid;
} LogicalDecodingContext;
--
2.23.0.windows.1
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Subject: RE: Logical replication timeout problem
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