On Tue, Sep 21, 2021 at 1:52 PM Fabrice Chapuis <fabrice636...@gmail.com> wrote: > > If I understand, the instruction to send keep alive by the wal sender has not > been reached in the for loop, for what reason? > ... > * Check for replication timeout. */ > WalSndCheckTimeOut(); > > /* Send keepalive if the time has come */ > WalSndKeepaliveIfNecessary(); > ... >
Are you sure that these functions have not been called? Or the case is that these are called but due to some reason the keep-alive is not sent? IIUC, these are called after processing each WAL record so not sure how is it possible in your case that these are not reached? > The data load is performed on a table which is not replicated, I do not > understand why the whole transaction linked to an insert is copied to snap > files given that table does not take part of the logical replication. > It is because we don't know till the end of the transaction (where we start sending the data) whether the table will be replicated or not. I think specifically for this purpose the new 'streaming' feature introduced in PG-14 will help us to avoid writing data of such tables to snap/spill files. See 'streaming' option in Create Subscription docs [1]. > We are going to do a test by modifying parameters > wal_sender_timeout/wal_receiver_timeout from 1' to 5'. The problem is that > these parameters are global and changing them will also impact the physical > replication. > Do you mean you are planning to change from 1 minute to 5 minutes? I agree with the global nature of parameters and I think your approach to finding out the root cause is good here because otherwise, under some similar or more heavy workload, it might lead to the same situation. > Concerning the walsender timeout, when the worker is started again after a > timeout, it will trigger a new walsender associated with it. > Right, I know that but I was curious to know if the walsender has exited before walreceiver. [1] - https://www.postgresql.org/docs/devel/sql-createsubscription.html -- With Regards, Amit Kapila.
