Hi
I met a problem in synchronous logical replication. The client hangs when TRUNCATE TABLE at publisher.
Example of the procedure:
------publisher------
create table test (a int primary key);
create publication pub for table test;
------subscriber------
create table test (a int primary key);
create subscription sub connection 'dbname=postgres' publication pub;
Then, set synchronous_standby_names = 'sub’ on publisher, and reload publisher.
------publisher------
truncate test;
Then the client of publisher will wait for a long time. A moment later, the publisher and subscriber will report
followingerrors.
Subscriber log
2021-04-07 12:13:07.700 CST [3542235] logical replication worker ERROR: terminating logical replication worker due to
timeout
2021-04-07 12:13:07.722 CST [3542217] postmaster LOG: background worker "logical replication worker" (PID 3542235)
exitedwith exit code 1
2021-04-07 12:13:07.723 CST [3542357] logical replication worker LOG: logical replication apply worker for
subscription"sub" has started
2021-04-07 12:13:07.745 CST [3542357] logical replication worker ERROR: could not start WAL streaming: ERROR:
replicationslot "sub" is active for PID 3542236
Publisher log
2021-04-07 12:13:07.745 CST [3542358] walsender ERROR: replication slot "sub" is active for PID 3542236
2021-04-07 12:13:07.745 CST [3542358] walsender STATEMENT: START_REPLICATION SLOT "sub" LOGICAL 0/169ECE8
(proto_version'2', publication_names '"pub"')
I checked the PG-DOC, found it says that “Replication of TRUNCATE commands is supported”[1], so maybe TRUNCATE is not
supportedin synchronous logical replication?
If my understanding is right, maybe PG-DOC can be modified like this. Any thought?
Replication of TRUNCATE commands is supported
->
Replication of TRUNCATE commands is supported in asynchronous mode
[1]https://www.postgresql.org/docs/devel/logical-replication-restrictions.html
Regards,
Tang
