Re: Make wal_receiver_timeout configurable per subscription

On 2025/05/20 18:13, vignesh C wrote:
> If we set the wal_receiver_timeout configuration using ALTER ROLE for
> the subscription owner's role, the apply worker will start with that
> value. However, any changes made via ALTER ROLE ... SET
> wal_receiver_timeout will not take effect for an already running apply
> worker unless the subscription is disabled and re-enabled. In
> contrast, this is handled automatically during CREATE SUBSCRIPTION,
> where parameter changes are detected.

Yes, this is one of the limitations of the user-settable wal_receiver_timeout
approach. If we want to change the timeout used by the apply worker without
restarting it, storing the value in pg_subscription (similar to how
synchronous_commit is handled) would be a better solution.

In that case, for example, we could set the default value of
pg_subscription.wal_receiver_timeout to -1, meaning the apply worker should
use the global wal_receiver_timeout from postgresql.conf. If the value is 0
or higher, the apply worker would use the value stored in pg_subscription.

On further thought, another downside of the user-settable approach is that
it doesn't work for parameters like wal_retrieve_retry_interval, which is
used by the logical replication launcher not the apply worker. So if we
want to support per-subscription control for non-apply workers, storing
the settings in pg_subscription might be more appropriate.

Regards,

--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION