Re: BUG #18155: Logical Apply Worker Timeout During TableSync Causes Either Stuckness or Data Loss

On Tue, Oct 17, 2023 at 4:46 AM Callahan, Drew <callaan@amazon.com> wrote:
>
> On the server side, we did not see evidence of WALSenders being launched. As a result, the gap kept increasing
further
> and further since they workers would not transition to the catchup state after several hours due to this.
>

One possibility is that the system has reached
'max_logical_replication_workers' limit due to which it is not
allowing to launch the apply worker. If so, then consider increasing
the value of 'max_logical_replication_workers'. You can query
'pg_stat_subscription' to know more information about workers. See the
description of subscriber-side parameters [1].

[1] - https://www.postgresql.org/docs/devel/runtime-config-replication.html#RUNTIME-CONFIG-REPLICATION-SUBSCRIBER

--
With Regards,
Amit Kapila.