From 05676d87e2e69a889abf75ce4f0c1bedde9ed71f Mon Sep 17 00:00:00 2001 From: Amit Kapila Date: Wed, 23 Apr 2025 10:52:36 +0530 Subject: [PATCH] Fix an oversight in 3f28b2fcac. Commit 3f28b2fcac tried to ensure that the replication origin shouldn't be advanced in case of an ERROR in the apply worker, so that it can request the same data again after restart. However, it is possible that an ERROR was caught and handled by a (say PL/pgSQL) function, and the apply worker continues to apply further changes, in which case, we shouldn't reset the replication origin. Ensure to reset the origin only when the apply worker exits after an ERROR. Commit 3f28b2fcac added new function geterrlevel, which we removed in HEAD as part of this commit, but kept it in backbranches to avoid breaking any applications. A separate case can be made to have such a function even for HEAD. Reported-by: Shawn McCoy Author: Hayato Kuroda Reviewed-by: Masahiko Sawada Reviewed-by: vignesh C Reviewed-by: Amit Kapila Backpatch-through: 16, where it was introduced Discussion: https://postgr.es/m/CALsgZNCGARa2mcYNVTSj9uoPcJo-tPuWUGECReKpNgTpo31_Pw@mail.gmail.com --- src/backend/replication/logical/worker.c | 21 +++---- src/test/subscription/t/100_bugs.pl | 77 ++++++++++++++++++++++++ 2 files changed, 87 insertions(+), 11 deletions(-) diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c index 65e22306c48..db09978697f 100644 --- a/src/backend/replication/logical/worker.c +++ b/src/backend/replication/logical/worker.c @@ -416,6 +416,8 @@ static inline void reset_apply_error_context_info(void); static TransApplyAction get_transaction_apply_action(TransactionId xid, ParallelApplyWorkerInfo **winfo); +static void replorigin_reset(int code, Datum arg); + /* * Form the origin name for the subscription. * @@ -4441,6 +4443,14 @@ start_apply(XLogRecPtr origin_startpos) } PG_CATCH(); { + /* + * Reset the origin state to prevent the advancement of origin + * progress if we fail to apply. Otherwise, this will result in + * transaction loss as that transaction won't be sent again by the + * server. + */ + replorigin_reset(0, (Datum) 0); + if (MySubscription->disableonerr) DisableSubscriptionAndExit(); else @@ -4928,23 +4938,12 @@ void apply_error_callback(void *arg) { ApplyErrorCallbackArg *errarg = &apply_error_callback_arg; - int elevel; if (apply_error_callback_arg.command == 0) return; Assert(errarg->origin_name); - elevel = geterrlevel(); - - /* - * Reset the origin state to prevent the advancement of origin progress if - * we fail to apply. Otherwise, this will result in transaction loss as - * that transaction won't be sent again by the server. - */ - if (elevel >= ERROR) - replorigin_reset(0, (Datum) 0); - if (errarg->rel == NULL) { if (!TransactionIdIsValid(errarg->remote_xid)) diff --git a/src/test/subscription/t/100_bugs.pl b/src/test/subscription/t/100_bugs.pl index cb36ca7b16b..3498a90e741 100644 --- a/src/test/subscription/t/100_bugs.pl +++ b/src/test/subscription/t/100_bugs.pl @@ -490,4 +490,81 @@ is( $result, qq(2|f $node_publisher->stop('fast'); $node_subscriber->stop('fast'); +# The bug was that when an ERROR was caught and handled by a (PL/pgSQL) +# function, the apply worker reset the replication origin but continued +# processing subsequent changes. So, we fail to update the replication origin +# during further apply operations. This can lead to the apply worker requesting +# the changes that have been applied again after restarting. + +$node_publisher->rotate_logfile(); +$node_publisher->start(); + +$node_subscriber->rotate_logfile(); +$node_subscriber->start(); + +# Set up a publication with a table +$node_publisher->safe_psql( + 'postgres', qq( + CREATE TABLE t1 (a int); + CREATE PUBLICATION regress_pub FOR TABLE t1; +)); + +# Set up a subscription which subscribes the publication +$node_subscriber->safe_psql( + 'postgres', qq( + CREATE TABLE t1 (a int); + CREATE SUBSCRIPTION regress_sub CONNECTION '$publisher_connstr' PUBLICATION regress_pub; +)); + +$node_subscriber->wait_for_subscription_sync($node_publisher, 'regress_sub'); + +# Create an AFTER INSERT trigger on the table that raises and subsequently +# handles an exception. Subsequent insertions will trigger this exception, +# causing the apply worker to invoke its error callback with an ERROR. However, +# since the error is caught within the trigger, the apply worker will continue +# processing changes. +$node_subscriber->safe_psql( + 'postgres', q{ +CREATE FUNCTION handle_exception_trigger() +RETURNS TRIGGER AS $$ +BEGIN + BEGIN + -- Raise an exception + RAISE EXCEPTION 'This is a test exception'; + EXCEPTION + WHEN OTHERS THEN + RETURN NEW; + END; + + RETURN NEW; +END; +$$ LANGUAGE plpgsql; + +CREATE TRIGGER silent_exception_trigger +AFTER INSERT OR UPDATE ON t1 +FOR EACH ROW +EXECUTE FUNCTION handle_exception_trigger(); + +ALTER TABLE t1 ENABLE ALWAYS TRIGGER silent_exception_trigger; +}); + +# Obtain current remote_lsn value to check its advancement later +my $remote_lsn = $node_subscriber->safe_psql('postgres', + "SELECT remote_lsn FROM pg_replication_origin_status os, pg_subscription s WHERE os.external_id = 'pg_' || s.oid AND s.subname = 'regress_sub'" +); + +# Insert a tuple to replicate changes +$node_publisher->safe_psql('postgres', "INSERT INTO t1 VALUES (1);"); +$node_publisher->wait_for_catchup('regress_sub'); + +# Confirms the origin can be advanced +$result = $node_subscriber->safe_psql('postgres', + "SELECT remote_lsn > '$remote_lsn' FROM pg_replication_origin_status os, pg_subscription s WHERE os.external_id = 'pg_' || s.oid AND s.subname = 'regress_sub'" +); +is($result, 't', + 'remote_lsn has advanced for apply worker raising an exception'); + +$node_publisher->stop('fast'); +$node_subscriber->stop('fast'); + done_testing();