From 67ff8ceca9a4b49de87bbb9f5e13dabefe0e6253 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Thu, 30 Apr 2026 16:06:06 -0400
Subject: [PATCH] Put pg_combinebackup debug test output in temp file

Having --debug as the default option to pg_combinebackup in
init_from_backup() makes the logs extremely verbose. It is used for
debugging failures, so put the output in a temp file and only keep it
around if tests fail.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Disussion: https://postgr.es/m/y73coty2smkxgvelh4e32kqrt5pyn2pb7cz7x4mrz6yaxitqd5%40nzhkeazqf4bn
Backpatch-through: 17
---
 src/test/perl/PostgreSQL/Test/Cluster.pm | 86 +++++++++++++++++++++++-
 1 file changed, 84 insertions(+), 2 deletions(-)

diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 529f49efee1..0d4fd929b6b 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -125,6 +125,7 @@ our $min_compat = 12;
 
 # list of file reservations made by get_free_port
 my @port_reservation_files;
+my @combinebackup_debug_logs;
 
 # We want to choose a server port above the range that servers typically use
 # on Unix systems and below the range those systems typically use for ephemeral
@@ -924,7 +925,9 @@ pathnames that should be used for the target cluster.
 
 To restore from an incremental backup, pass the parameter combine_with_prior
 as a reference to an array of prior backup names with which this backup
-is to be combined using pg_combinebackup.
+is to be combined using pg_combinebackup.  pg_combinebackup is run with
+--debug, but the output is captured in a temporary file and only copied to the
+test log if pg_combinebackup fails or if a later test fails.
 
 Streaming replication can be enabled on this node by passing the keyword
 parameter has_streaming => 1. This is disabled by default.
@@ -990,7 +993,7 @@ sub init_from_backup
 		}
 		push @combineargs, @prior_backup_path, $backup_path,
 		  '--output' => $data_path;
-		PostgreSQL::Test::Utils::system_or_bail(@combineargs);
+		$self->_run_pg_combinebackup_with_debug_log(@combineargs);
 	}
 	elsif (defined $params{tar_program})
 	{
@@ -1105,6 +1108,85 @@ port = $port
 	return;
 }
 
+sub _run_pg_combinebackup_with_debug_log
+{
+	my ($self, @cmd) = @_;
+	my $debug_log = $self->basedir . '/pg_combinebackup_debug.log';
+
+	print("# Running: " . join(" ", @cmd) . "\n");
+	# If this pg_combinebackup invocation itself fails, print its captured
+	# output immediately. Successful invocations may still be printed later if
+	# some subsequent TAP assertion in this test script fails.
+	if (!IPC::Run::run(\@cmd, '&>' => $debug_log))
+	{
+		_print_pg_combinebackup_debug_log($debug_log);
+
+		if ($? == -1)
+		{
+			BAIL_OUT(
+				sprintf(
+					"failed to execute command \"%s\": $!", join(" ", @cmd)));
+		}
+		elsif ($? & 127)
+		{
+			BAIL_OUT(
+				sprintf(
+					"command \"%s\" died with signal %d",
+					join(" ", @cmd), $? & 127));
+		}
+		else
+		{
+			BAIL_OUT(
+				sprintf(
+					"command \"%s\" exited with value %d",
+					join(" ", @cmd), $? >> 8));
+		}
+	}
+
+	# pg_combinebackup succeeded. Retain its debug log so that, if a later TAP
+	# assertion in this test fails, the END block can print the combine step
+	# that produced the restored state; on a clean run the END block removes it.
+	# On failure above we already printed the log and bailed out, so it is
+	# deliberately not added to the list here (which also avoids printing it
+	# twice).
+	push @combinebackup_debug_logs, $debug_log;
+}
+
+sub _print_pg_combinebackup_debug_log
+{
+	my ($debug_log) = @_;
+
+	return unless -e $debug_log;
+
+	diag("pg_combinebackup debug output from $debug_log:\n" .
+	  PostgreSQL::Test::Utils::slurp_file($debug_log));
+}
+
+# Keep pg_combinebackup debug logs until test exit. If pg_combinebackup itself
+# fails, its log is printed at the failure site above. If pg_combinebackup
+# succeeds but a later TAP assertion fails, print the retained logs here so the
+# regress output includes the combine step that produced the restored state.
+# Remove the logs after a clean run.
+END
+{
+	# take care not to change the script's exit value
+	my $exit_code = $?;
+
+	if ($exit_code == 0 && PostgreSQL::Test::Utils::all_tests_passing())
+	{
+		unlink @combinebackup_debug_logs;
+	}
+	else
+	{
+		foreach my $debug_log (@combinebackup_debug_logs)
+		{
+			_print_pg_combinebackup_debug_log($debug_log);
+		}
+	}
+
+	$? = $exit_code;
+}
+
 =pod
 
 =item $node->rotate_logfile()
-- 
2.47.3