From a53547b859eb5c48d919c7e0d794bc2fd12f12b9 Mon Sep 17 00:00:00 2001
From: Sunil S <sunil.s@broadcom.com>
Date: Mon, 7 Jul 2025 11:36:56 +0530
Subject: [PATCH v6 3/3] Test archive recovery takes precedence over streaming
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Since archive recovery is typically faster and more efficient than streaming,
initiating the WAL receiver early—before attempting recovery from archived WAL
files—is not ideal.
Furthermore, determining the correct starting point for streaming by examining
the last valid WAL segment restored from the archive adds complexity and potential risk.

Therefore, even when the configuration parameter wal_receiver_start_at is set to consistency,
archive recovery should take precedence, and the WAL receiver should only be
started after archive recovery is exhausted or deemed unavailable.

Co-authors: Sunil S<sunilfeb26@gmail.com>, Soumyadeep Chakraborty <soumyadeep2007@gmail.com>, Ashwin Agrawal, Asim Praveen, Wu Hao, Konstantin Knizhnik
Discussion: https://www.postgresql.org/message-id/flat/CANXE4Tc3FNvZ_xAimempJWv_RH9pCvsZH7Yq93o1VuNLjUT-mQ%40mail.gmail.com
---
 .../recovery/t/049_archive_enabled_standby.pl | 77 +++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 src/test/recovery/t/049_archive_enabled_standby.pl

diff --git a/src/test/recovery/t/049_archive_enabled_standby.pl b/src/test/recovery/t/049_archive_enabled_standby.pl
new file mode 100644
index 00000000000..5dddcb0b00c
--- /dev/null
+++ b/src/test/recovery/t/049_archive_enabled_standby.pl
@@ -0,0 +1,77 @@
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+# Test that a standby with archive recovery enabled does not start WAL receiver early:
+# - Verifies that wal_receiver_start_at = 'consistency'
+# - Ensures WAL receiver is not started when restore_command is specified
+
+use strict;
+use warnings;
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use File::Copy;
+use Test::More tests => 1;
+
+# Initialize primary node with archving enabled and start it.
+my $node_primary = PostgreSQL::Test::Cluster->new('test');
+$node_primary->init(allows_streaming => 1, has_archiving => 1);
+$node_primary->start;
+
+# Initial workload.
+$node_primary->safe_psql(
+	'postgres', qq {
+CREATE TABLE test_walreceiver_start(i int);
+INSERT INTO test_walreceiver_start VALUES(1);
+SELECT pg_switch_wal();
+});
+
+# Take backup.
+my $backup_name = 'my_backup';
+$node_primary->backup($backup_name);
+
+# Run a post-backup workload
+$node_primary->safe_psql(
+	'postgres', qq {
+INSERT INTO test_walreceiver_start VALUES(2);
+SELECT pg_switch_wal();
+});
+
+# Initialize standby node from the backup with restore enabled from archived WAL
+my $node_standby = PostgreSQL::Test::Cluster->new('standby');
+$node_standby->init_from_backup($node_primary, $backup_name,
+	has_streaming => 1,  has_restoring => 1);
+
+# Set up a long delay to prevent the standby from replaying past the first
+# commit outside the backup.
+$node_standby->append_conf('postgresql.conf',
+	"recovery_min_apply_delay = '2h'");
+# Set up the walreceiver to start as soon as consistency is reached.
+$node_standby->append_conf('postgresql.conf',
+	"wal_receiver_start_at = 'consistency'");
+
+$node_standby->start();
+
+# The standby should have reached consistency and should be blocked waiting for
+# recovery_min_apply_delay.
+$node_standby->poll_query_until(
+	'postgres', qq{
+SELECT wait_event = 'RecoveryApplyDelay' FROM pg_stat_activity
+WHERE backend_type='startup';
+}) or die "Timed out checking if startup is in recovery_min_apply_delay";
+
+# The walreceiver should not have started
+$node_standby->poll_query_until('postgres',
+	"SELECT COUNT(1) = 1 FROM pg_stat_wal_receiver;", 'f')
+	or die "Timed out while waiting for streaming to start";
+
+# Now clear the delay so that the standby can replay the received WAL.
+$node_standby->safe_psql('postgres',
+	'ALTER SYSTEM SET recovery_min_apply_delay TO 0;');
+$node_standby->reload;
+
+# Now the replay should catch up.
+$node_primary->wait_for_catchup('standby', 'replay');
+is( $node_standby->safe_psql(
+	'postgres', 'SELECT count(*) FROM test_walreceiver_start;'),
+	2,
+	"querying test_walreceiver_start now should return 2 rows");
\ No newline at end of file
-- 
2.49.0