Add regression tests for csvlog with the logging collector

These are added in the existing tests of pg_ctl for log rotation, that
already tested stderr.  The same amount of coverage is added for csvlog:
- Checks for pg_current_logfile().
- Log rotation with expected file name.
- Log contents generated.

This test is refactored to minimize the amount of work required to add
tests for new log formats, easing some upcoming work.

Author: Michael Paquier, Sehrope Sarkuni
Discussion: https://postgr.es/m/CAH7T-aqswBM6JWe4pDehi1uOiufqe06DJWaU5=X7dDLyqUExHg@mail.gmail.com

src/bin/pg_ctl/t/004_logrotate.pl

@@ -6,15 +6,64 @@ use warnings;
 
 use PostgresNode;
 use TestLib;
-use Test::More tests => 5;
+use Test::More tests => 10;
 use Time::HiRes qw(usleep);
 
+# Extract the file name of a $format from the contents of
+# current_logfiles.
+sub fetch_file_name
+{
+	my $logfiles = shift;
+	my $format   = shift;
+	my @lines    = split(/\n/, $logfiles);
+	my $filename = undef;
+	foreach my $line (@lines)
+	{
+		if ($line =~ /$format (.*)$/gm)
+		{
+			$filename = $1;
+		}
+	}
+
+	return $filename;
+}
+
+# Check for a pattern in the logs associated to one format.
+sub check_log_pattern
+{
+	my $format   = shift;
+	my $logfiles = shift;
+	my $pattern  = shift;
+	my $node     = shift;
+	my $lfname   = fetch_file_name($logfiles, $format);
+
+	my $max_attempts = 180 * 10;
+
+	my $logcontents;
+	for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
+	{
+		$logcontents = slurp_file($node->data_dir . '/' . $lfname);
+		last if $logcontents =~ m/$pattern/;
+		usleep(100_000);
+	}
+
+	like($logcontents, qr/$pattern/,
+		"found expected log file content for $format");
+
+	# While we're at it, test pg_current_logfile() function
+	is( $node->safe_psql('postgres', "SELECT pg_current_logfile('$format')"),
+		$lfname,
+		"pg_current_logfile() gives correct answer with $format");
+	return;
+}
+
 # Set up node with logging collector
 my $node = PostgresNode->new('primary');
 $node->init();
 $node->append_conf(
 	'postgresql.conf', qq(
 logging_collector = on
+log_destination = 'stderr, csvlog'
 # these ensure stability of test results:
 log_rotation_age = 0
 lc_messages = 'C'
@@ -44,26 +93,12 @@ note "current_logfiles = $current_logfiles";
 
 like(
 	$current_logfiles,
-	qr|^stderr log/postgresql-.*log$|,
+	qr|^stderr log/postgresql-.*log
+csvlog log/postgresql-.*csv$|,
 	'current_logfiles is sane');
 
-my $lfname = $current_logfiles;
-$lfname =~ s/^stderr //;
-chomp $lfname;
-
-my $first_logfile;
-for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
-{
-	$first_logfile = slurp_file($node->data_dir . '/' . $lfname);
-	last if $first_logfile =~ m/division by zero/;
-	usleep(100_000);
-}
-
-like($first_logfile, qr/division by zero/, 'found expected log file content');
-
-# While we're at it, test pg_current_logfile() function
-is($node->safe_psql('postgres', "SELECT pg_current_logfile('stderr')"),
-	$lfname, 'pg_current_logfile() gives correct answer');
+check_log_pattern('stderr', $current_logfiles, 'division by zero', $node);
+check_log_pattern('csvlog', $current_logfiles, 'division by zero', $node);
 
 # Sleep 2 seconds and ask for log rotation; this should result in
 # output into a different log file name.
@@ -84,28 +119,14 @@ note "now current_logfiles = $new_current_logfiles";
 
 like(
 	$new_current_logfiles,
-	qr|^stderr log/postgresql-.*log$|,
+	qr|^stderr log/postgresql-.*log
+csvlog log/postgresql-.*csv$|,
 	'new current_logfiles is sane');
 
-$lfname = $new_current_logfiles;
-$lfname =~ s/^stderr //;
-chomp $lfname;
-
 # Verify that log output gets to this file, too
-
 $node->psql('postgres', 'fee fi fo fum');
 
-my $second_logfile;
-for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
-{
-	$second_logfile = slurp_file($node->data_dir . '/' . $lfname);
-	last if $second_logfile =~ m/syntax error/;
-	usleep(100_000);
-}
-
-like(
-	$second_logfile,
-	qr/syntax error/,
-	'found expected log file content in new log file');
+check_log_pattern('stderr', $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('csvlog', $new_current_logfiles, 'syntax error', $node);
 
 $node->stop();