On Wed, May 19, 2021 at 11:55 AM Kyotaro Horiguchi <horikyota....@gmail.com> wrote: > > At Wed, 19 May 2021 11:19:13 +0530, Dilip Kumar <dilipbal...@gmail.com> wrote > in > > On Wed, May 19, 2021 at 10:16 AM Fujii Masao > > <masao.fu...@oss.nttdata.com> wrote: > > > > > > On 2021/05/18 15:46, Michael Paquier wrote: > > > > On Tue, May 18, 2021 at 12:48:38PM +0900, Fujii Masao wrote: > > > >> Currently a promotion causes all available WAL to be replayed before > > > >> a standby becomes a primary whether it was in paused state or not. > > > >> OTOH, something like immediate promotion (i.e., standby becomes > > > >> a primary without replaying outstanding WAL) might be useful for > > > >> some cases. I don't object to that. > > > > > > > > Sounds like a "promotion immediate" mode. It does not sound difficult > > > > nor expensive to add a small test for that in one of the existing > > > > recovery tests triggerring a promotion. Could you add one based on > > > > pg_get_wal_replay_pause_state()? > > > > > > You're thinking to add the test like the following? > > > #1. Pause the recovery > > > #2. Confirm that pg_get_wal_replay_pause_state() returns 'paused' > > > #3. Trigger standby promotion > > > #4. Confirm that pg_get_wal_replay_pause_state() returns 'not paused' > > > > > > It seems not easy to do the test #4 stably because > > > pg_get_wal_replay_pause_state() needs to be executed > > > before the promotion finishes. > > > > Even for #2, we can not ensure that whether it will be 'paused' or > > 'pause requested'. > > We often use poll_query_until() to make sure some desired state is > reached. And, as Michael suggested, the function > pg_get_wal_replay_pause_state() still works at the time of > recovery_end_command. So a bit more detailed steps are:
Right, if we are polling for the state change in #2 then that makes sense. > #0. Equip the server with recovery_end_command that waits for some > trigger then start the server. > #1. Pause the recovery > #2. Wait until pg_get_wal_replay_pause_state() returns 'paused' > #3. Trigger standby promotion > #4. Wait until pg_get_wal_replay_pause_state() returns 'not paused' > #5. Trigger recovery_end_command to let promotion proceed. +1 -- Regards, Dilip Kumar EnterpriseDB: http://www.enterprisedb.com
