mirror of https://github.com/postgres/postgres
Replication slots are useful to retain data that may be needed by a replication system. But experience has shown that allowing them to retain excessive data can lead to the primary failing because of running out of space. This new feature allows the user to configure a maximum amount of space to be reserved using the new option max_slot_wal_keep_size. Slots that overrun that space are invalidated at checkpoint time, enabling the storage to be released. Author: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com> Reviewed-by: Jehan-Guillaume de Rorthais <jgdr@dalibo.com> Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/20170228.122736.123383594.horiguchi.kyotaro@lab.ntt.co.jppull/51/head
Alvaro Herrera
6 years ago
parent
b63c293bcb
commit
c655077639
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# Test for replication slot limit |
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# Ensure that max_slot_wal_keep_size limits the number of WAL files to |
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# be kept by replication slots. |
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use strict; |
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use warnings; |
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use TestLib; |
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use PostgresNode; |
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use File::Path qw(rmtree); |
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use Test::More tests => 13; |
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use Time::HiRes qw(usleep); |
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$ENV{PGDATABASE} = 'postgres'; |
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# Initialize master node, setting wal-segsize to 1MB |
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my $node_master = get_new_node('master'); |
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$node_master->init(allows_streaming => 1, extra => ['--wal-segsize=1']); |
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$node_master->append_conf('postgresql.conf', qq( |
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min_wal_size = 2MB |
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max_wal_size = 4MB |
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log_checkpoints = yes |
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)); |
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$node_master->start; |
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$node_master->safe_psql('postgres', "SELECT pg_create_physical_replication_slot('rep1')"); |
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# The slot state and remain should be null before the first connection |
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my $result = $node_master->safe_psql('postgres', "SELECT restart_lsn is NULL, wal_status is NULL, min_safe_lsn is NULL FROM pg_replication_slots WHERE slot_name = 'rep1'"); |
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is($result, "t|t|t", 'check the state of non-reserved slot is "unknown"'); |
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# Take backup |
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my $backup_name = 'my_backup'; |
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$node_master->backup($backup_name); |
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# Create a standby linking to it using the replication slot |
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my $node_standby = get_new_node('standby_1'); |
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$node_standby->init_from_backup($node_master, $backup_name, has_streaming => 1); |
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$node_standby->append_conf('postgresql.conf', "primary_slot_name = 'rep1'"); |
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$node_standby->start; |
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# Wait until standby has replayed enough data |
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my $start_lsn = $node_master->lsn('write'); |
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$node_master->wait_for_catchup($node_standby, 'replay', $start_lsn); |
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# Stop standby |
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$node_standby->stop; |
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# Preparation done, the slot is the state "normal" now |
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$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, min_safe_lsn is NULL FROM pg_replication_slots WHERE slot_name = 'rep1'"); |
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is($result, "$start_lsn|normal|t", 'check the catching-up state'); |
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# Advance WAL by five segments (= 5MB) on master |
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advance_wal($node_master, 1); |
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$node_master->safe_psql('postgres', "CHECKPOINT;"); |
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# The slot is always "safe" when fitting max_wal_size |
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$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, min_safe_lsn is NULL FROM pg_replication_slots WHERE slot_name = 'rep1'"); |
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is($result, "$start_lsn|normal|t", 'check that restart_lsn is in max_wal_size'); |
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advance_wal($node_master, 4); |
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$node_master->safe_psql('postgres', "CHECKPOINT;"); |
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# The slot is always "safe" when max_slot_wal_keep_size is not set |
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$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, min_safe_lsn is NULL FROM pg_replication_slots WHERE slot_name = 'rep1'"); |
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is($result, "$start_lsn|normal|t", 'check that slot is working'); |
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# The standby can reconnect to master |
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$node_standby->start; |
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$start_lsn = $node_master->lsn('write'); |
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$node_master->wait_for_catchup($node_standby, 'replay', $start_lsn); |
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$node_standby->stop; |
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# Set max_slot_wal_keep_size on master |
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my $max_slot_wal_keep_size_mb = 6; |
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$node_master->append_conf('postgresql.conf', qq( |
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max_slot_wal_keep_size = ${max_slot_wal_keep_size_mb}MB |
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)); |
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$node_master->reload; |
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# The slot is in safe state. The distance from the min_safe_lsn should |
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# be as almost (max_slot_wal_keep_size - 1) times large as the segment |
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# size |
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$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, pg_size_pretty(pg_current_wal_lsn() - min_safe_lsn) FROM pg_replication_slots WHERE slot_name = 'rep1'"); |
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is($result, "$start_lsn|normal|5120 kB", 'check that max_slot_wal_keep_size is working'); |
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# Advance WAL again then checkpoint, reducing remain by 2 MB. |
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advance_wal($node_master, 2); |
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$node_master->safe_psql('postgres', "CHECKPOINT;"); |
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# The slot is still working |
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$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, pg_size_pretty(pg_current_wal_lsn() - min_safe_lsn) FROM pg_replication_slots WHERE slot_name = 'rep1'"); |
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is($result, "$start_lsn|normal|2048 kB", 'check that min_safe_lsn gets close to the current LSN'); |
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# The standby can reconnect to master |
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$node_standby->start; |
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$start_lsn = $node_master->lsn('write'); |
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$node_master->wait_for_catchup($node_standby, 'replay', $start_lsn); |
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$node_standby->stop; |
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# wal_keep_segments overrides max_slot_wal_keep_size |
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$result = $node_master->safe_psql('postgres', "ALTER SYSTEM SET wal_keep_segments to 8; SELECT pg_reload_conf();"); |
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# Advance WAL again then checkpoint, reducing remain by 6 MB. |
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advance_wal($node_master, 6); |
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$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, pg_size_pretty(pg_current_wal_lsn() - min_safe_lsn) as remain FROM pg_replication_slots WHERE slot_name = 'rep1'"); |
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is($result, "$start_lsn|normal|8192 kB", 'check that wal_keep_segments overrides max_slot_wal_keep_size'); |
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# restore wal_keep_segments |
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$result = $node_master->safe_psql('postgres', "ALTER SYSTEM SET wal_keep_segments to 0; SELECT pg_reload_conf();"); |
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# The standby can reconnect to master |
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$node_standby->start; |
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$start_lsn = $node_master->lsn('write'); |
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$node_master->wait_for_catchup($node_standby, 'replay', $start_lsn); |
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$node_standby->stop; |
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# Advance WAL again without checkpoint, reducing remain by 6 MB. |
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advance_wal($node_master, 6); |
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# Slot gets into 'reserved' state |
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$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, pg_size_pretty(restart_lsn - min_safe_lsn) as remain FROM pg_replication_slots WHERE slot_name = 'rep1'"); |
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is($result, "$start_lsn|reserved|216 bytes", 'check that the slot state changes to "reserved"'); |
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# do checkpoint so that the next checkpoint runs too early |
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$node_master->safe_psql('postgres', "CHECKPOINT;"); |
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# Advance WAL again without checkpoint; remain goes to 0. |
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advance_wal($node_master, 1); |
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# Slot gets into 'lost' state |
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$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, min_safe_lsn is NULL FROM pg_replication_slots WHERE slot_name = 'rep1'"); |
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is($result, "$start_lsn|lost|t", 'check that the slot state changes to "lost"'); |
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# The standby still can connect to master before a checkpoint |
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$node_standby->start; |
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$start_lsn = $node_master->lsn('write'); |
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$node_master->wait_for_catchup($node_standby, 'replay', $start_lsn); |
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$node_standby->stop; |
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ok(!find_in_log($node_standby, |
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"requested WAL segment [0-9A-F]+ has already been removed"), |
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'check that required WAL segments are still available'); |
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# Advance WAL again, the slot loses the oldest segment. |
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my $logstart = get_log_size($node_master); |
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advance_wal($node_master, 7); |
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$node_master->safe_psql('postgres', "CHECKPOINT;"); |
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# WARNING should be issued |
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ok(find_in_log($node_master, |
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"invalidating slot \"rep1\" because its restart_lsn [0-9A-F/]+ exceeds max_slot_wal_keep_size", |
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$logstart), |
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'check that the warning is logged'); |
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# This slot should be broken |
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$result = $node_master->safe_psql('postgres', "SELECT slot_name, active, restart_lsn, wal_status, min_safe_lsn FROM pg_replication_slots WHERE slot_name = 'rep1'"); |
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is($result, "rep1|f|||", 'check that the slot became inactive'); |
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# The standby no longer can connect to the master |
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$logstart = get_log_size($node_standby); |
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$node_standby->start; |
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my $failed = 0; |
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for (my $i = 0; $i < 10000; $i++) |
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{ |
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if (find_in_log($node_standby, |
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"requested WAL segment [0-9A-F]+ has already been removed", |
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$logstart)) |
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{ |
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$failed = 1; |
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last; |
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} |
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usleep(100_000); |
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} |
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ok($failed, 'check that replication has been broken'); |
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$node_standby->stop; |
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##################################### |
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# Advance WAL of $node by $n segments |
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sub advance_wal |
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{ |
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my ($node, $n) = @_; |
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# Advance by $n segments (= (16 * $n) MB) on master |
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for (my $i = 0 ; $i < $n ; $i++) |
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{ |
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$node->safe_psql('postgres', "CREATE TABLE t (); DROP TABLE t; SELECT pg_switch_wal();"); |
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} |
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} |
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# return the size of logfile of $node in bytes |
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sub get_log_size |
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{ |
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my ($node) = @_; |
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return (stat $node->logfile)[7]; |
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} |
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# find $pat in logfile of $node after $off-th byte |
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sub find_in_log |
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{ |
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my ($node, $pat, $off) = @_; |
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$off = 0 unless defined $off; |
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my $log = TestLib::slurp_file($node->logfile); |
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return 0 if (length($log) <= $off); |
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$log = substr($log, $off); |
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return $log =~ m/$pat/; |
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} |
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