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Disable cache clobber to avoid breaking postgres_fdw termination test.
Commit 93f4146 improved a pre-existing test case so that it would show whether or not termination of the "remote" worker process happened. This soon exposed that, when debug_invalidate_system_caches_always (nee CLOBBER_CACHE_ALWAYS) is enabled, no such termination occurs. That's because cache invalidation forces postgres_fdw connections to be dropped at end of transaction, so that there's no worker to terminate. There's a race condition as to whether the worker will manage to get out of the BackendStatusArray before we look, but at least on buildfarm member hyrax, it's failed twice in two attempts. Rather than re-lobotomizing the test, let's fix this by transiently disabling debug_invalidate_system_caches_always. (Hooray for that being just a GUC nowadays, rather than a compile-time option.) If this proves not to be enough to make the test stable, we can do the other thing instead. Discussion: https://postgr.es/m/3854538.1620081771@sss.pgh.pa.us
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‎contrib/postgres_fdw/expected/postgres_fdw.out

Lines changed: 10 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -9204,6 +9204,12 @@ WARNING: there is no transaction in progress
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-- Change application_name of remote connection to special one
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-- so that we can easily terminate the connection later.
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ALTER SERVER loopback OPTIONS (application_name 'fdw_retry_check');
9207+
-- If debug_invalidate_system_caches_always is active, it results in
9208+
-- dropping remote connections after every transaction, making it
9209+
-- impossible to test termination meaningfully. So turn that off
9210+
-- for this test.
9211+
SET debug_invalidate_system_caches_always = 0;
9212+
-- Make sure we have a remote connection.
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SELECT 1 FROM ft1 LIMIT 1;
92089214
?column?
92099215
----------
@@ -9227,9 +9233,8 @@ SELECT 1 FROM ft1 LIMIT 1;
92279233
1
92289234
(1 row)
92299235

9230-
-- If the query detects the broken connection when starting new remote
9231-
-- subtransaction, it doesn't reestablish new connection and should fail.
9232-
-- The text of the error might vary across platforms, so don't show it.
9236+
-- If we detect the broken connection when starting a new remote
9237+
-- subtransaction, we should fail instead of establishing a new connection.
92339238
-- Terminate the remote connection and wait for the termination to complete.
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SELECT pg_terminate_backend(pid, 180000) FROM pg_stat_activity
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WHERE application_name = 'fdw_retry_check';
@@ -9239,11 +9244,13 @@ SELECT pg_terminate_backend(pid, 180000) FROM pg_stat_activity
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(1 row)
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92419246
SAVEPOINT s;
9247+
-- The text of the error might vary across platforms, so only show SQLSTATE.
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\set VERBOSITY sqlstate
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SELECT 1 FROM ft1 LIMIT 1; -- should fail
92449250
ERROR: 08006
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\set VERBOSITY default
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COMMIT;
9253+
RESET debug_invalidate_system_caches_always;
92479254
-- =============================================================================
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-- test connection invalidation cases and postgres_fdw_get_connections function
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-- =============================================================================

‎contrib/postgres_fdw/sql/postgres_fdw.sql

Lines changed: 13 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2795,6 +2795,14 @@ ROLLBACK;
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-- Change application_name of remote connection to special one
27962796
-- so that we can easily terminate the connection later.
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ALTER SERVER loopback OPTIONS (application_name 'fdw_retry_check');
2798+
2799+
-- If debug_invalidate_system_caches_always is active, it results in
2800+
-- dropping remote connections after every transaction, making it
2801+
-- impossible to test termination meaningfully. So turn that off
2802+
-- for this test.
2803+
SET debug_invalidate_system_caches_always = 0;
2804+
2805+
-- Make sure we have a remote connection.
27982806
SELECT 1 FROM ft1 LIMIT 1;
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28002808
-- Terminate the remote connection and wait for the termination to complete.
@@ -2806,18 +2814,20 @@ SELECT pg_terminate_backend(pid, 180000) FROM pg_stat_activity
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BEGIN;
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SELECT 1 FROM ft1 LIMIT 1;
28082816

2809-
-- If the query detects the broken connection when starting new remote
2810-
-- subtransaction, it doesn't reestablish new connection and should fail.
2811-
-- The text of the error might vary across platforms, so don't show it.
2817+
-- If we detect the broken connection when starting a new remote
2818+
-- subtransaction, we should fail instead of establishing a new connection.
28122819
-- Terminate the remote connection and wait for the termination to complete.
28132820
SELECT pg_terminate_backend(pid, 180000) FROM pg_stat_activity
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WHERE application_name = 'fdw_retry_check';
28152822
SAVEPOINT s;
2823+
-- The text of the error might vary across platforms, so only show SQLSTATE.
28162824
\set VERBOSITY sqlstate
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SELECT 1 FROM ft1 LIMIT 1; -- should fail
28182826
\set VERBOSITY default
28192827
COMMIT;
28202828

2829+
RESET debug_invalidate_system_caches_always;
2830+
28212831
-- =============================================================================
28222832
-- test connection invalidation cases and postgres_fdw_get_connections function
28232833
-- =============================================================================

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