On 10/03/17 05:59, Petr Jelinek wrote:
> Hi,
>
> while discussing with Craig issues around restarting logical replication
> stream related to the patch he posted [1], I realized that we track
> wrong origin LSN in the logical replication apply.
>
> We currently track commit_lsn which is *start* of commit record, what we
> need to track is end_lsn which is *end* of commit record otherwise we
> might request transaction that was already replayed if the subscription
> instance has crashed right after commit.
>
> Attached patch fixes that.
>
Rebase after table copy patch got committed.
--
Petr Jelinek http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
>From 2a312a4ecce09aab6c72f5f039c49b2300b3f3a4 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmo...@pjmodos.net>
Date: Thu, 9 Mar 2017 12:54:43 +0100
Subject: [PATCH] Fix remote position tracking in logical replication
We need to set the origin remote position to end_lsn and not commit_lsn
as commit_lsn is start of commit record and we use the origin remote
position as start position when restarting replication stream. If we'd
use commit_lsn we could request data that we already received from
remote server after crash of downstream server.
---
src/backend/replication/logical/worker.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index bbf3506..c2ccab7 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -421,9 +421,6 @@ apply_handle_begin(StringInfo s)
logicalrep_read_begin(s, &begin_data);
- replorigin_session_origin_timestamp = begin_data.committime;
- replorigin_session_origin_lsn = begin_data.final_lsn;
-
remote_final_lsn = begin_data.final_lsn;
in_remote_transaction = true;
@@ -443,14 +440,18 @@ apply_handle_commit(StringInfo s)
logicalrep_read_commit(s, &commit_data);
- Assert(commit_data.commit_lsn == replorigin_session_origin_lsn);
- Assert(commit_data.committime == replorigin_session_origin_timestamp);
-
Assert(commit_data.commit_lsn == remote_final_lsn);
/* The synchronization worker runs in single transaction. */
if (IsTransactionState() && !am_tablesync_worker())
{
+ /*
+ * Update origin state so we can restart streaming from correct
+ * position in case of crash.
+ */
+ replorigin_session_origin_lsn = commit_data.end_lsn;
+ replorigin_session_origin_timestamp = commit_data.committime;
+
CommitTransactionCommand();
store_flush_position(commit_data.end_lsn);
--
2.7.4
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