From fef5b47f6bfc9bfec619bb2e6e66b027e7ff21a3 Mon Sep 17 00:00:00 2001 From: Fujii Masao Date: Thu, 14 Jan 2021 12:27:11 +0900 Subject: [PATCH] Ensure that a standby is able to follow a primary on a newer timeline. Commit 709d003fbd refactored WAL-reading code, but accidentally caused WalSndSegmentOpen() to fail to follow a timeline switch while reading from a historic timeline. This issue caused a standby to fail to follow a primary on a newer timeline when WAL archiving is enabled. If there is a timeline switch within the segment, WalSndSegmentOpen() should read from the WAL segment belonging to the new timeline. But previously since it failed to follow a timeline switch, it tried to read the WAL segment with old timeline. When WAL archiving is enabled, that WAL segment with old timeline doesn't exist because it's renamed to .partial. This leads a primary to have tried to read non-existent WAL segment, and which caused replication to faill with the error "ERROR: requested WAL segment ... has already been removed". This commit fixes WalSndSegmentOpen() so that it's able to follow a timeline switch, to ensure that a standby is able to follow a primary on a newer timeline even when WAL archiving is enabled. This commit also adds the regression test to check whether a standby is able to follow a primary on a newer timeline when WAL archiving is enabled. Back-patch to v13 where the bug was introduced. Reported-by: Kyotaro Horiguchi Author: Kyotaro Horiguchi, tweaked by Fujii Masao Reviewed-by: Alvaro Herrera, Fujii Masao Discussion: https://postgr.es/m/20201209.174314.282492377848029776.horikyota.ntt@gmail.com --- src/backend/replication/walsender.c | 2 +- src/test/recovery/t/004_timeline_switch.pl | 42 ++++++++++++++++++++-- 2 files changed, 40 insertions(+), 4 deletions(-) diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c index fe0d368a35b..8545c6c4231 100644 --- a/src/backend/replication/walsender.c +++ b/src/backend/replication/walsender.c @@ -2491,7 +2491,7 @@ WalSndSegmentOpen(XLogReaderState *state, XLogSegNo nextSegNo, XLogSegNo endSegNo; XLByteToSeg(sendTimeLineValidUpto, endSegNo, state->segcxt.ws_segsize); - if (state->seg.ws_segno == endSegNo) + if (nextSegNo == endSegNo) *tli_p = sendTimeLineNextTLI; } diff --git a/src/test/recovery/t/004_timeline_switch.pl b/src/test/recovery/t/004_timeline_switch.pl index 1ecdb0eba0d..8dad044db4b 100644 --- a/src/test/recovery/t/004_timeline_switch.pl +++ b/src/test/recovery/t/004_timeline_switch.pl @@ -1,15 +1,16 @@ # Test for timeline switch -# Ensure that a cascading standby is able to follow a newly-promoted standby -# on a new timeline. use strict; use warnings; use File::Path qw(rmtree); use PostgresNode; use TestLib; -use Test::More tests => 2; +use Test::More tests => 3; $ENV{PGDATABASE} = 'postgres'; +# Ensure that a cascading standby is able to follow a newly-promoted standby +# on a new timeline. + # Initialize primary node my $node_primary = get_new_node('primary'); $node_primary->init(allows_streaming => 1); @@ -66,3 +67,38 @@ $node_standby_1->wait_for_catchup($node_standby_2, 'replay', my $result = $node_standby_2->safe_psql('postgres', "SELECT count(*) FROM tab_int"); is($result, qq(2000), 'check content of standby 2'); + + +# Ensure that a standby is able to follow a primary on a newer timeline +# when WAL archiving is enabled. + +# Initialize primary node +my $node_primary_2 = get_new_node('primary_2'); +$node_primary_2->init(allows_streaming => 1, has_archiving => 1); +$node_primary_2->start; + +# Take backup +$node_primary_2->backup($backup_name); + +# Create standby node +my $node_standby_3 = get_new_node('standby_3'); +$node_standby_3->init_from_backup($node_primary_2, $backup_name, + has_streaming => 1); + +# Restart primary node in standby mode and promote it, switching it +# to a new timeline. +$node_primary_2->set_standby_mode; +$node_primary_2->restart; +$node_primary_2->promote; + +# Start standby node, create some content on primary and check its presence +# in standby, to ensure that the timeline switch has been done. +$node_standby_3->start; +$node_primary_2->safe_psql('postgres', + "CREATE TABLE tab_int AS SELECT 1 AS a"); +$node_primary_2->wait_for_catchup($node_standby_3, 'replay', + $node_primary_2->lsn('write')); + +my $result_2 = + $node_standby_3->safe_psql('postgres', "SELECT count(*) FROM tab_int"); +is($result_2, qq(1), 'check content of standby 3');