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

1 files changed, 3 insertions, 14 deletions

diff --git a/src/test/authentication/t/003_peer.pl b/src/test/authentication/t/003_peer.pl
index 3272e52cae8..d8e49760726 100644
--- a/src/test/authentication/t/003_peer.pl
+++ b/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';
 }