Refactor routine to find single log content pattern in TAP tests

The same routine to check if a specific pattern can be found in the
server logs was copied over four different test scripts.  This refactors
the whole to use a single routine located in PostgreSQL::Test::Cluster,
named log_contains, to grab the contents of the server logs and check
for a specific pattern.

On HEAD, the code previously used assumed that slurp_file() could not
handle an undefined offset, setting it to zero, but slurp_file() does
do an extra fseek() before retrieving the log contents only if an offset
is defined.  In two places, the test was retrieving the full log
contents with slurp_file() after calling substr() to apply an offset,
ignoring that slurp_file() would be able to handle that.

Backpatch all the way down to ease the introduction of new tests that
could rely on the new routine.

Author: Vignesh C
Reviewed-by: Andrew Dunstan, Dagfinn Ilmari Mannsåker, Michael Paquier
Discussion: https://postgr.es/m/CALDaNm0YSiLpjCmajwLfidQrFOrLNKPQir7s__PeVvh9U3uoTQ@mail.gmail.com
Backpatch-through: 11

src/test/authentication/t/003_peer.pl

@@ -69,17 +69,6 @@ sub test_role
 	}
 }
 
-# Find $pattern in log file of $node.
-sub find_in_log
-{
-	my ($node, $offset, $pattern) = @_;
-
-	my $log = PostgreSQL::Test::Utils::slurp_file($node->logfile, $offset);
-	return 0 if (length($log) <= 0);
-
-	return $log =~ m/$pattern/;
-}
-
 my $node = PostgreSQL::Test::Cluster->new('node');
 $node->init;
 $node->append_conf('postgresql.conf', "log_connections = on\n");
@@ -91,9 +80,9 @@ reset_pg_hba($node, 'peer');
 # Check if peer authentication is supported on this platform.
 my $log_offset = -s $node->logfile;
 $node->psql('postgres');
-if (find_in_log(
-		$node, $log_offset,
-		qr/peer authentication is not supported on this platform/))
+if ($node->log_contains(
+		qr/peer authentication is not supported on this platform/,
+		$log_offset))
 {
 	plan skip_all => 'peer authentication is not supported on this platform';
 }

src/test/perl/PostgreSQL/Test/Cluster.pm

@@ -2547,6 +2547,22 @@ sub log_check
 
 =pod
 
+=item log_contains(pattern, offset)
+
+Find pattern in logfile of node after offset byte.
+
+=cut
+
+sub log_contains
+{
+	my ($self, $pattern, $offset) = @_;
+
+	return PostgreSQL::Test::Utils::slurp_file($self->logfile, $offset) =~
+	  m/$pattern/;
+}
+
+=pod
+
 =item $node->run_log(...)
 
 Runs a shell command like PostgreSQL::Test::Utils::run_log, but with connection parameters set

src/test/recovery/t/019_replslot_limit.pl

@@ -161,8 +161,7 @@ $node_primary->wait_for_catchup($node_standby);
 
 $node_standby->stop;
 
-ok( !find_in_log(
-		$node_standby,
+ok( !$node_standby->log_contains(
 		"requested WAL segment [0-9A-F]+ has already been removed"),
 	'check that required WAL segments are still available');
 
@@ -184,9 +183,8 @@ $node_primary->safe_psql('postgres', "CHECKPOINT;");
 my $invalidated = 0;
 for (my $i = 0; $i < 10 * $PostgreSQL::Test::Utils::timeout_default; $i++)
 {
-	if (find_in_log(
-			$node_primary, 'invalidating obsolete replication slot "rep1"',
-			$logstart))
+	if ($node_primary->log_contains(
+			'invalidating obsolete replication slot "rep1"', $logstart))
 	{
 		$invalidated = 1;
 		last;
@@ -207,7 +205,7 @@ is($result, "rep1|f|t|lost|",
 my $checkpoint_ended = 0;
 for (my $i = 0; $i < 10 * $PostgreSQL::Test::Utils::timeout_default; $i++)
 {
-	if (find_in_log($node_primary, "checkpoint complete: ", $logstart))
+	if ($node_primary->log_contains("checkpoint complete: ", $logstart))
 	{
 		$checkpoint_ended = 1;
 		last;
@@ -237,8 +235,7 @@ $node_standby->start;
 my $failed = 0;
 for (my $i = 0; $i < 10 * $PostgreSQL::Test::Utils::timeout_default; $i++)
 {
-	if (find_in_log(
-			$node_standby,
+	if ($node_standby->log_contains(
 			"requested WAL segment [0-9A-F]+ has already been removed",
 			$logstart))
 	{
@@ -381,8 +378,7 @@ my $msg_logged = 0;
 my $max_attempts = $PostgreSQL::Test::Utils::timeout_default;
 while ($max_attempts-- >= 0)
 {
-	if (find_in_log(
-			$node_primary3,
+	if ($node_primary3->log_contains(
 			"terminating process $senderpid to release replication slot \"rep3\"",
 			$logstart))
 	{
@@ -406,9 +402,8 @@ $msg_logged = 0;
 $max_attempts = $PostgreSQL::Test::Utils::timeout_default;
 while ($max_attempts-- >= 0)
 {
-	if (find_in_log(
-			$node_primary3, 'invalidating obsolete replication slot "rep3"',
-			$logstart))
+	if ($node_primary3->log_contains(
+			'invalidating obsolete replication slot "rep3"', $logstart))
 	{
 		$msg_logged = 1;
 		last;
@@ -446,18 +441,4 @@ sub get_log_size
 	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 $log = PostgreSQL::Test::Utils::slurp_file($node->logfile);
-	return 0 if (length($log) <= $off);
-
-	$log = substr($log, $off);
-
-	return $log =~ m/$pat/;
-}
-
 done_testing();

src/test/recovery/t/033_replay_tsp_drops.pl

@@ -135,8 +135,7 @@ while ($max_attempts-- >= 0)
 {
 	last
 	  if (
-		find_in_log(
-			$node_standby,
+		$node_standby->log_contains(
 			qr!WARNING: ( [A-Z0-9]+:)? creating missing directory: pg_tblspc/!,
 			$logstart));
 	usleep(100_000);
@@ -144,13 +143,3 @@ while ($max_attempts-- >= 0)
 ok($max_attempts > 0, "invalid directory creation is detected");
 
 done_testing();
-
-# find $pat in logfile of $node after $off-th byte
-sub find_in_log
-{
-	my ($node, $pat, $off) = @_;
-
-	my $log = PostgreSQL::Test::Utils::slurp_file($node->logfile, $off);
-
-	return $log =~ m/$pat/;
-}

src/test/recovery/t/035_standby_logical_decoding.pl

@@ -28,20 +28,6 @@ my $res;
 my $primary_slotname = 'primary_physical';
 my $standby_physical_slotname = 'standby_physical';
 
-# find $pat in logfile of $node after $off-th byte
-sub find_in_log
-{
-	my ($node, $pat, $off) = @_;
-
-	$off = 0 unless defined $off;
-	my $log = PostgreSQL::Test::Utils::slurp_file($node->logfile);
-	return 0 if (length($log) <= $off);
-
-	$log = substr($log, $off);
-
-	return $log =~ m/$pat/;
-}
-
 # Fetch xmin columns from slot's pg_replication_slots row, after waiting for
 # given boolean condition to be true to ensure we've reached a quiescent state.
 sub wait_for_xmins
@@ -235,14 +221,12 @@ sub check_for_invalidation
 	my $inactive_slot = $slot_prefix . 'inactiveslot';
 
 	# message should be issued
-	ok( find_in_log(
-			$node_standby,
+	ok( $node_standby->log_contains(
 			"invalidating obsolete replication slot \"$inactive_slot\"",
 			$log_start),
 		"inactiveslot slot invalidation is logged $test_name");
 
-	ok( find_in_log(
-			$node_standby,
+	ok( $node_standby->log_contains(
 			"invalidating obsolete replication slot \"$active_slot\"",
 			$log_start),
 		"activeslot slot invalidation is logged $test_name");
@@ -657,14 +641,12 @@ $node_primary->safe_psql(
 $node_primary->wait_for_replay_catchup($node_standby);
 
 # message should not be issued
-ok( !find_in_log(
-		$node_standby,
+ok( !$node_standby->log_contains(
 		"invalidating obsolete slot \"no_conflict_inactiveslot\"", $logstart),
 	'inactiveslot slot invalidation is not logged with vacuum on conflict_test'
 );
 
-ok( !find_in_log(
-		$node_standby,
+ok( !$node_standby->log_contains(
 		"invalidating obsolete slot \"no_conflict_activeslot\"", $logstart),
 	'activeslot slot invalidation is not logged with vacuum on conflict_test'
 );