On Fri, May 2, 2025 at 6:30 PM Andrey Borodin <x4...@yandex-team.ru> wrote: > > 3. Allow reading LSN written by walreciever, but not flushed yet > > Problem: if we have synchronous_standby_names = ANY(node1,node2), node2 might > be ahead of node1 by flush LSN, but before by written LSN. If we do a > failover we choose node2 instead of node1 and loose data recently committed > with synchronous_commit=remote_write. >
In which case, can we rely on written WAL that is not yet flushed? Because say you decide based on written WAL and choose node-1 in above case for failover, what if it restarts without flushing the written WAL? > Caveat: we already have a function pg_last_wal_receive_lsn(), which in fact > returns flushed LSN, not written. I propose to add a new function which > returns LSN actually written. Internals of this function are already > implemented (GetWalRcvWriteRecPtr()), but unused. > It seems to me that this is less controversial than your other two proposals. So, we can discuss this in a separate thread as well. -- With Regards, Amit Kapila.
