Subject: [PATCH] Fix timeline-tracking failure while sending a historic timeline

From: Kyotaro Horiguchi <[email-masked]>
Date: Tue, 5 Jan 2021 13:34:36 +0900

Walsender should track timeline switches while sending a historic
timeline. Regain that behavior, which was broken in PG13, by a thinko
of 709d003fbd. Backpatch to PG13.
---
 src/backend/replication/walsender.c       |  2 +-
 src/test/perl/PostgresNode.pm             | 36 ++++++++++++++++++++
 src/test/recovery/t/001_stream_rep.pl     | 41 ++++++++++++++++++++++-
 src/test/recovery/t/019_replslot_limit.pl | 37 ++++----------------
 4 files changed, 83 insertions(+), 33 deletions(-)

diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 7f87eb7f19..04f6c3ebb4 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -2478,7 +2478,7 @@ 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/perl/PostgresNode.pm b/src/test/perl/PostgresNode.pm
index 980f1f1533..a08c71b549 100644
--- a/src/test/perl/PostgresNode.pm
+++ b/src/test/perl/PostgresNode.pm
@@ -2138,6 +2138,42 @@ sub pg_recvlogical_upto
 
 =pod
 
+=item $node->current_log_position()
+
+Return the current position of server log.
+
+=cut
+
+sub current_log_position
+{
+	my $self = shift;
+
+	return (stat $self->logfile)[7];
+}
+
+=pod
+
+=item $node->find_in_log($pattern, $startpos)
+
+Returns whether the $pattern occurs after $startpos in the server log.
+
+=cut
+
+sub find_in_log
+{
+	my ($self, $pattern, $startpos) = @_;
+
+	$startpos = 0 unless defined $startpos;
+	my $log = TestLib::slurp_file($self->logfile);
+	return 0 if (length($log) <= $startpos);
+
+	$log = substr($log, $startpos);
+
+	return $log =~ m/$pattern/;
+}
+
+=pod
+
 =back
 
 =cut
diff --git a/src/test/recovery/t/001_stream_rep.pl b/src/test/recovery/t/001_stream_rep.pl
index 778f11b28b..8d2b24fe55 100644
--- a/src/test/recovery/t/001_stream_rep.pl
+++ b/src/test/recovery/t/001_stream_rep.pl
@@ -2,8 +2,9 @@
 use strict;
 use warnings;
 use PostgresNode;
+use Time::HiRes qw(usleep);
 use TestLib;
-use Test::More tests => 36;
+use Test::More tests => 37;
 
 # Initialize master node
 my $node_master = get_new_node('master');
@@ -409,3 +410,41 @@ ok( ($phys_restart_lsn_pre cmp $phys_restart_lsn_post) == 0,
 my $master_data = $node_master->data_dir;
 ok(!-f "$master_data/pg_wal/$segment_removed",
 	"WAL segment $segment_removed recycled after physical slot advancing");
+
+#
+# Check if timeline-increment works while reading a historic timeline.
+my $node_primary_2 = get_new_node('primary_2');
+# archiving is needed to create .paritial segment
+$node_primary_2->init(allows_streaming => 1, has_archiving => 1);
+$node_primary_2->start;
+$node_primary_2->backup($backup_name);
+my $node_standby_3 = get_new_node('standby_3');
+$node_standby_3->init_from_backup($node_primary_2, $backup_name,
+								  has_streaming => 1);
+$node_primary_2->stop;
+$node_primary_2->set_standby_mode; # increment primary timeline
+$node_primary_2->start;
+$node_primary_2->promote;
+my $logstart = $node_standby_3->current_log_position();
+$node_standby_3->start;
+
+my $success = 0;
+for (my $i = 0 ; $i < 1000; $i++)
+{
+	if ($node_standby_3->find_in_log(
+			"requested WAL segment [0-9A-F]+ has already been removed",
+			$logstart))
+	{
+		last;
+	}
+	elsif ($node_standby_3->find_in_log(
+			"End of WAL reached on timeline",
+			   $logstart))
+	{
+		$success = 1;
+		last;
+	}
+	usleep(100_000);
+}
+
+ok($success, 'Timeline increment while reading a historic timeline');
diff --git a/src/test/recovery/t/019_replslot_limit.pl b/src/test/recovery/t/019_replslot_limit.pl
index a7231dcd47..8b3c5de057 100644
--- a/src/test/recovery/t/019_replslot_limit.pl
+++ b/src/test/recovery/t/019_replslot_limit.pl
@@ -165,19 +165,17 @@ $node_master->wait_for_catchup($node_standby, 'replay', $start_lsn);
 
 $node_standby->stop;
 
-ok( !find_in_log(
-		$node_standby,
-		"requested WAL segment [0-9A-F]+ has already been removed"),
+ok( !$node_standby->find_in_log(
+		 "requested WAL segment [0-9A-F]+ has already been removed"),
 	'check that required WAL segments are still available');
 
 # Advance WAL again, the slot loses the oldest segment.
-my $logstart = get_log_size($node_master);
+my $logstart = $node_master->current_log_position();
 advance_wal($node_master, 7);
 $node_master->safe_psql('postgres', "CHECKPOINT;");
 
 # WARNING should be issued
-ok( find_in_log(
-		$node_master,
+ok( $node_master->find_in_log(
 		"invalidating slot \"rep1\" because its restart_lsn [0-9A-F/]+ exceeds max_slot_wal_keep_size",
 		$logstart),
 	'check that the warning is logged');
@@ -190,14 +188,13 @@ is($result, "rep1|f|t|lost|",
 	'check that the slot became inactive and the state "lost" persists');
 
 # The standby no longer can connect to the master
-$logstart = get_log_size($node_standby);
+$logstart = $node_standby->current_log_position();
 $node_standby->start;
 
 my $failed = 0;
 for (my $i = 0; $i < 10000; $i++)
 {
-	if (find_in_log(
-			$node_standby,
+	if ($node_standby->find_in_log(
 			"requested WAL segment [0-9A-F]+ has already been removed",
 			$logstart))
 	{
@@ -264,25 +261,3 @@ sub advance_wal
 	}
 	return;
 }
-
-# return the size of logfile of $node in bytes
-sub get_log_size
-{
-	my ($node) = @_;
-
-	return (stat $node->logfile)[7];
-}
-
-# find $pat in logfile of $node after $off-th byte
-sub find_in_log
-{
-	my ($node, $pat, $off) = @_;
-
-	$off = 0 unless defined $off;
-	my $log = TestLib::slurp_file($node->logfile);
-	return 0 if (length($log) <= $off);
-
-	$log = substr($log, $off);
-
-	return $log =~ m/$pat/;
-}
-- 
2.27.0

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