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3fa17d3771
Previously, we used to use the array of size max_replication_slots to store stats for replication slots. But that had two problems in the cases where a message for dropping a slot gets lost: 1) the stats for the new slot are not recorded if the array is full and 2) writing beyond the end of the array if the user reduces the max_replication_slots. This commit uses HTAB for replication slot statistics, resolving both problems. Now, pgstat_vacuum_stat() search for all the dead replication slots in stats hashtable and tell the collector to remove them. To avoid showing the stats for the already-dropped slots, pg_stat_replication_slots view searches slot stats by the slot name taken from pg_replication_slots. Also, we send a message for creating a slot at slot creation, initializing the stats. This reduces the possibility that the stats are accumulated into the old slot stats when a message for dropping a slot gets lost. Reported-by: Andres Freund Author: Sawada Masahiko, test case by Vignesh C Reviewed-by: Amit Kapila, Vignesh C, Dilip Kumar Discussion: https://postgr.es/m/20210319185247.ldebgpdaxsowiflw@alap3.anarazel.de
116 lines
3.7 KiB
Perl
116 lines
3.7 KiB
Perl
# Test replication statistics data in pg_stat_replication_slots is sane after
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# drop replication slot and restart.
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use strict;
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use warnings;
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use File::Path qw(rmtree);
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use PostgresNode;
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use TestLib;
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use Test::More tests => 2;
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# Test set-up
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my $node = get_new_node('test');
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$node->init(allows_streaming => 'logical');
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$node->append_conf('postgresql.conf', 'synchronous_commit = on');
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$node->start;
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# Check that replication slot stats are expected.
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sub test_slot_stats
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{
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my ($node, $expected, $msg) = @_;
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my $result = $node->safe_psql(
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'postgres', qq[
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SELECT slot_name, total_txns > 0 AS total_txn,
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total_bytes > 0 AS total_bytes
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FROM pg_stat_replication_slots
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ORDER BY slot_name]);
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is($result, $expected, $msg);
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}
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# Create table.
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$node->safe_psql('postgres', "CREATE TABLE test_repl_stat(col1 int)");
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# Create replication slots.
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$node->safe_psql(
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'postgres', qq[
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SELECT pg_create_logical_replication_slot('regression_slot1', 'test_decoding');
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SELECT pg_create_logical_replication_slot('regression_slot2', 'test_decoding');
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SELECT pg_create_logical_replication_slot('regression_slot3', 'test_decoding');
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SELECT pg_create_logical_replication_slot('regression_slot4', 'test_decoding');
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]);
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# Insert some data.
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$node->safe_psql('postgres',
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"INSERT INTO test_repl_stat values(generate_series(1, 5));");
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$node->safe_psql(
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'postgres', qq[
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SELECT data FROM pg_logical_slot_get_changes('regression_slot1', NULL,
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NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
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SELECT data FROM pg_logical_slot_get_changes('regression_slot2', NULL,
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NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
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SELECT data FROM pg_logical_slot_get_changes('regression_slot3', NULL,
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NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
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SELECT data FROM pg_logical_slot_get_changes('regression_slot4', NULL,
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NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
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]);
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# Wait for the statistics to be updated.
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$node->poll_query_until(
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'postgres', qq[
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SELECT count(slot_name) >= 4 FROM pg_stat_replication_slots
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WHERE slot_name ~ 'regression_slot'
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AND total_txns > 0 AND total_bytes > 0;
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]) or die "Timed out while waiting for statistics to be updated";
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# Test to drop one of the replication slot and verify replication statistics data is
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# fine after restart.
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$node->safe_psql('postgres',
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"SELECT pg_drop_replication_slot('regression_slot4')");
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$node->stop;
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$node->start;
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# Verify statistics data present in pg_stat_replication_slots are sane after
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# restart.
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test_slot_stats(
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$node,
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qq(regression_slot1|t|t
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regression_slot2|t|t
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regression_slot3|t|t),
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'check replication statistics are updated');
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# Test to remove one of the replication slots and adjust
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# max_replication_slots accordingly to the number of slots. This leads
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# to a mismatch between the number of slots present in the stats file and the
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# number of stats present in the shared memory, simulating the scenario for
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# drop slot message lost by the statistics collector process. We verify
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# replication statistics data is fine after restart.
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$node->stop;
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my $datadir = $node->data_dir;
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my $slot3_replslotdir = "$datadir/pg_replslot/regression_slot3";
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rmtree($slot3_replslotdir);
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$node->append_conf('postgresql.conf', 'max_replication_slots = 2');
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$node->start;
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# Verify statistics data present in pg_stat_replication_slots are sane after
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# restart.
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test_slot_stats(
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$node,
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qq(regression_slot1|t|t
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regression_slot2|t|t),
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'check replication statistics after removing the slot file');
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# cleanup
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$node->safe_psql('postgres', "DROP TABLE test_repl_stat");
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$node->safe_psql('postgres',
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"SELECT pg_drop_replication_slot('regression_slot1')");
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$node->safe_psql('postgres',
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"SELECT pg_drop_replication_slot('regression_slot2')");
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# shutdown
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$node->stop;
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