From 0be6949498ec53011a6e62733e31a42dc2a754d8 Mon Sep 17 00:00:00 2001 From: Khanna Date: Tue, 24 Dec 2024 12:27:27 +0530 Subject: [PATCH v3] Validate-max_slot_wal_keep_size-in-pg_createsubscriber This patch introduces validation for the 'max_slot_wal_keep_size' GUC in the 'pg_createsubscriber' utility. The utility now checks that the publisher's 'max_slot_wal_keep_size' is set to '-1' during subscription creation. This ensures proper functioning of logical replication slots. The 'pg_createsubscriber' utility is updated to fetch and validate the 'max_slot_wal_keep_size' setting from the publisher. A warning is raised during the '--dry-run' mode if the configuration is set to a non-default value. By ensuring 'max_slot_wal_keep_size' is -1, this patch prevents the potential deletion of required WAL files on the publisher that could disrupt logical replication. A test case has been added to validate correct warning reporting when 'max_slot_wal_keep_size' is misconfigured. These changes ensure that logical replication does not fail due to improper configuration of 'max_slot_wal_keep_size' on the publisher. --- src/bin/pg_basebackup/pg_createsubscriber.c | 23 ++++++++++++++++++- .../t/040_pg_createsubscriber.pl | 23 ++++++++++++++++--- 2 files changed, 42 insertions(+), 4 deletions(-) diff --git a/src/bin/pg_basebackup/pg_createsubscriber.c b/src/bin/pg_basebackup/pg_createsubscriber.c index e96370a9ec..057ffc64eb 100644 --- a/src/bin/pg_basebackup/pg_createsubscriber.c +++ b/src/bin/pg_basebackup/pg_createsubscriber.c @@ -849,6 +849,7 @@ check_publisher(const struct LogicalRepInfo *dbinfo) int max_walsenders; int cur_walsenders; int max_prepared_transactions; + int max_slot_wal_keep_size; pg_log_info("checking settings on publisher"); @@ -880,7 +881,8 @@ check_publisher(const struct LogicalRepInfo *dbinfo) " (SELECT count(*) FROM pg_catalog.pg_replication_slots)," " pg_catalog.current_setting('max_wal_senders')," " (SELECT count(*) FROM pg_catalog.pg_stat_activity WHERE backend_type = 'walsender')," - " pg_catalog.current_setting('max_prepared_transactions')"); + " pg_catalog.current_setting('max_prepared_transactions')," + " pg_catalog.current_setting('max_slot_wal_keep_size')"); if (PQresultStatus(res) != PGRES_TUPLES_OK) { @@ -895,6 +897,7 @@ check_publisher(const struct LogicalRepInfo *dbinfo) max_walsenders = atoi(PQgetvalue(res, 0, 3)); cur_walsenders = atoi(PQgetvalue(res, 0, 4)); max_prepared_transactions = atoi(PQgetvalue(res, 0, 5)); + max_slot_wal_keep_size = atoi(PQgetvalue(res, 0, 6)); PQclear(res); @@ -905,6 +908,8 @@ check_publisher(const struct LogicalRepInfo *dbinfo) pg_log_debug("publisher: current wal senders: %d", cur_walsenders); pg_log_debug("publisher: max_prepared_transactions: %d", max_prepared_transactions); + pg_log_debug("publisher: max_slot_wal_keep_size: %d", + max_slot_wal_keep_size); disconnect_database(conn, false); @@ -939,6 +944,22 @@ check_publisher(const struct LogicalRepInfo *dbinfo) "Prepared transactions will be replicated at COMMIT PREPARED."); } +/* + * Validate max_slot_wal_keep_size + * Logical replication requires max_slot_wal_keep_size to be set to -1 on the + * publisher to prevent the deletion of WAL files that are still needed by + * replication slots. If this parameter is set to a non-default value, it may + * cause replication failures due to required WAL files being + * prematurely removed. + */ + if (dry_run && max_slot_wal_keep_size != -1) + { + pg_log_warning("publisher requires max_slot_wal_keep_size to be -1, but is set to %d", + max_slot_wal_keep_size); + pg_log_warning_detail("Change the configuration parameter \"%s\" on the publisher to %d.", + "max_slot_wal_keep_size", -1); + } + pg_free(wal_level); if (failed) diff --git a/src/bin/pg_basebackup/t/040_pg_createsubscriber.pl b/src/bin/pg_basebackup/t/040_pg_createsubscriber.pl index 0a900edb65..9f57ceb085 100644 --- a/src/bin/pg_basebackup/t/040_pg_createsubscriber.pl +++ b/src/bin/pg_basebackup/t/040_pg_createsubscriber.pl @@ -318,8 +318,14 @@ $node_p->safe_psql($db1, $node_p->wait_for_replay_catchup($node_s); $node_s->stop; -# dry run mode on node S -command_ok( +# Configure 'max_slot_wal_keep_size = 1' on the publisher and +# reload configuration +$node_p->append_conf('postgresql.conf', 'max_slot_wal_keep_size = 1'); +$node_p->reload; + +# dry run mode on node S and verify the warning message for misconfigured +# 'max_slot_wal_keep_size' +command_checks_all( [ 'pg_createsubscriber', '--verbose', '--recovery-timeout', "$PostgreSQL::Test::Utils::timeout_default", @@ -335,7 +341,18 @@ command_ok( $db1, '--database', $db2 ], - 'run pg_createsubscriber --dry-run on node S'); + 0, + [qr/./], + [ + qr/pg_createsubscriber: warning: publisher requires max_slot_wal_keep_size to be -1/, + qr/Change the configuration parameter "max_slot_wal_keep_size" on the publisher to -1./, + ], + 'Validate warning for misconfigured max_slot_wal_keep_size on the publisher' +); + +# Reset 'max_slot_wal_keep_size' to default after the test +$node_p->append_conf('postgresql.conf', 'max_slot_wal_keep_size = -1'); +$node_p->reload; # Check if node S is still a standby $node_s->start; -- 2.41.0.windows.3