Horton

Re: Synchronizing slots from primary to standby

Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>

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From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
To: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
Cc: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, shveta malik <shveta.malik@gmail.com>, Ajin Cherian <itsajin@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Peter Smith <smithpb2250@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, Bruce Momjian <bruce@momjian.us>, Ashutosh Sharma <ashu.coek88@gmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>, Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: 2024-04-01T04:31:19Z
Lists: pgsql-hackers 
On Thu, Mar 28, 2024 at 10:08 AM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> [2] The steps to reproduce the data miss issue on a primary->standby setup:

I'm trying to reproduce the problem with [1], but I can see the
changes after the standby is promoted. Am I missing anything here?

ubuntu:~/postgres/pg17/bin$ ./psql -d postgres -p 5433 -c "select *
from pg_logical_slot_get_changes('lrep_sync_slot', NULL, NULL);"
    lsn    | xid |                    data
-----------+-----+---------------------------------------------
 0/30000B0 | 738 | BEGIN 738
 0/3017FC8 | 738 | COMMIT 738
 0/3017FF8 | 739 | BEGIN 739
 0/3019A38 | 739 | COMMIT 739
 0/3019A38 | 740 | BEGIN 740
 0/3019A38 | 740 | table public.dummy1: INSERT: a[integer]:999
 0/3019AA8 | 740 | COMMIT 740
(7 rows)

[1]
-#define LOG_SNAPSHOT_INTERVAL_MS 15000
+#define LOG_SNAPSHOT_INTERVAL_MS 1500000

./initdb -D db17
echo "archive_mode = on
archive_command='cp %p /home/ubuntu/postgres/pg17/bin/archived_wal/%f'
wal_level='logical'
autovacuum = off
checkpoint_timeout='1h'" | tee -a db17/postgresql.conf

./pg_ctl -D db17 -l logfile17 start

rm -rf sbdata logfilesbdata
./pg_basebackup -D sbdata

./psql -d postgres -p 5432 -c "SELECT
pg_create_logical_replication_slot('lrep_sync_slot', 'test_decoding',
false, false, true);"
./psql -d postgres -p 5432 -c "SELECT
pg_create_physical_replication_slot('phy_repl_slot', true, false);"

echo "port=5433
primary_conninfo='host=localhost port=5432 dbname=postgres user=ubuntu'
primary_slot_name='phy_repl_slot'
restore_command='cp /home/ubuntu/postgres/pg17/bin/archived_wal/%f %p'
hot_standby_feedback=on
sync_replication_slots=on" | tee -a sbdata/postgresql.conf

touch sbdata/standby.signal

./pg_ctl -D sbdata -l logfilesbdata start
./psql -d postgres -p 5433 -c "SELECT pg_is_in_recovery();"

./psql -d postgres

SESSION1, TXN1
BEGIN;
create table dummy1(a int);

SESSION2, TXN2
SELECT pg_log_standby_snapshot();

SESSION1, TXN1
COMMIT;

SESSION1, TXN1
BEGIN;
create table dummy2(a int);

SESSION2, TXN2
SELECT pg_log_standby_snapshot();

SESSION1, TXN1
COMMIT;

./psql -d postgres -p 5432 -c "SELECT
pg_replication_slot_advance('lrep_sync_slot', pg_current_wal_lsn());"
./psql -d postgres -p 5432 -c "INSERT INTO dummy1 VALUES(999);"

./psql -d postgres -p 5433 -c "SELECT pg_promote();"
./psql -d postgres -p 5433 -c "SELECT pg_is_in_recovery();"

./psql -d postgres -p 5433 -c "select * from
pg_logical_slot_get_changes('lrep_sync_slot', NULL, NULL);"

-- 
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

Commits

  1. Doc: Add the new section "Logical Replication Failover".

  2. Fix the review comments and a bug in the slot sync code.

  3. Fix a test in failover slots regression test.

  4. Fix the intermittent buildfarm failures in 040_standby_failover_slots_sync.

  5. Split XLogCtl->LogwrtResult into separate struct members

  6. Ensure that the sync slots reach a consistent state after promotion without losing data.

  7. Introduce a new GUC 'standby_slot_names'.

  8. Fix BF failure introduced by commit b3f6b14cf4.

  9. Fixups for commit 93db6cbda0.

  10. Fix BF failure in commit 93db6cbda0.

  11. Add a new slot sync worker to synchronize logical slots.

  12. Improve ERROR/LOG messages added by commits ddd5f4f54a and 7a424ece48.

  13. Disable autovacuum on primary in 040_standby_failover_slots_sync test.

  14. Fix the incorrect format specifier used in commit 7a424ece48.

  15. Change the LOG level in 040_standby_failover_slots_sync.pl to DEBUG2.

  16. Add more LOG and DEBUG messages for slot synchronization.

  17. Another try to fix BF failure introduced in commit ddd5f4f54a.

  18. Fix BF introduced in commit ddd5f4f54a.

  19. Add a slot synchronization function.

  20. Clean-ups for 776621a5e4 and 7329240437.

  21. Enhance libpqrcv APIs to support slot synchronization.

  22. Add a failover option to subscriptions.

  23. Allow setting failover property in the replication command.

  24. Allow to enable failover property for replication slots via SQL API.

  25. Add macros for looping through a List without a ListCell.

  26. Track conflict_reason in pg_replication_slots.

  27. Allow upgrades to preserve the full subscription's state.

  28. Add support for incremental backup.

  29. Simplify some logic in CreateReplicationSlot()

  30. Fix uninitialized access to InitialRunningXacts during decoding after ERROR.

  31. Flexible options for CREATE_REPLICATION_SLOT.

  32. Empty search_path in logical replication apply worker and walsender.

  33. Fix oldest xmin and LSN computation across repslots after advancing

  34. Require C99 (and thus MSCV 2013 upwards).