On Sun, Jan 17, 2021 at 5:19 PM Dilip Kumar <dilipbal...@gmail.com> wrote: > > On Sat, Jan 16, 2021 at 8:59 AM Masahiko Sawada <sawada.m...@gmail.com> wrote: > > > > On Wed, Jan 13, 2021 at 9:20 PM Dilip Kumar <dilipbal...@gmail.com> wrote: > > > > > > On Wed, Jan 13, 2021 at 3:35 PM Dilip Kumar <dilipbal...@gmail.com> wrote: > > > > > > > > On Wed, Jan 13, 2021 at 3:27 PM Yugo NAGATA <nag...@sraoss.co.jp> wrote: > > > > > > > > > > On Thu, 10 Dec 2020 11:25:23 +0530 > > > > > Dilip Kumar <dilipbal...@gmail.com> wrote: > > > > > > > > > > > > > However, I wonder users don't expect pg_is_wal_replay_paused to > > > > > > > > wait. > > > > > > > > Especially, if max_standby_streaming_delay is -1, this will be > > > > > > > > blocked forever, > > > > > > > > although this setting may not be usual. In addition, some users > > > > > > > > may set > > > > > > > > recovery_min_apply_delay for a large. If such users call > > > > > > > > pg_is_wal_replay_paused, > > > > > > > > it could wait for a long time. > > > > > > > > > > > > > > > > At least, I think we need some descriptions on document to > > > > > > > > explain > > > > > > > > pg_is_wal_replay_paused could wait while a time. > > > > > > > > > > > > > > Ok > > > > > > > > > > > > Fixed this, added some comments in .sgml as well as in function > > > > > > header > > > > > > > > > > Thank you for fixing this. > > > > > > > > > > Also, is it better to fix the description of pg_wal_replay_pause from > > > > > "Pauses recovery." to "Request to pause recovery." in according with > > > > > pg_is_wal_replay_paused? > > > > > > > > Okay > > > > > > > > > > > > > > > > > Also, how about adding a new boolean argument to > > > > > > > > pg_is_wal_replay_paused to > > > > > > > > control whether this waits for recovery to get paused or not? > > > > > > > > By setting its > > > > > > > > default value to true or false, users can use the old format > > > > > > > > for calling this > > > > > > > > and the backward compatibility can be maintained. > > > > > > > > > > > > > > So basically, if the wait_recovery_pause flag is false then we > > > > > > > will > > > > > > > immediately return true if the pause is requested? I agree that > > > > > > > it is > > > > > > > good to have an API to know whether the recovery pause is > > > > > > > requested or > > > > > > > not but I am not sure is it good idea to make this API serve both > > > > > > > the > > > > > > > purpose? Anyone else have any thoughts on this? > > > > > > > > > > > > > > > > > I think the current pg_is_wal_replay_paused() already has another > > > > > purpose; > > > > > this waits recovery to actually get paused. If we want to limit this > > > > > API's > > > > > purpose only to return the pause state, it seems better to fix this > > > > > to return > > > > > the actual state at the cost of lacking the backward compatibility. > > > > > If we want > > > > > to know whether pause is requested, we may add a new API like > > > > > pg_is_wal_replay_paluse_requeseted(). Also, if we want to wait > > > > > recovery to actually > > > > > get paused, we may add an option to pg_wal_replay_pause() for this > > > > > purpose. > > > > > > > > > > However, this might be a bikeshedding. If anyone don't care that > > > > > pg_is_wal_replay_paused() can make user wait for a long time, I don't > > > > > care either. > > > > > > > > I don't think that it will be blocked ever, because > > > > pg_wal_replay_pause is sending the WakeupRecovery() which means the > > > > recovery process will not be stuck on waiting for the WAL. > > > > > > > > > > > > As another comment, while pg_is_wal_replay_paused is blocking, > > > > > > > > I can not cancel > > > > > > > > the query. I think CHECK_FOR_INTERRUPTS() is necessary in the > > > > > > > > waiting loop. > > > > > > > > > > How about this fix? I think users may want to cancel > > > > > pg_is_wal_replay_paused() during > > > > > this is blocking. > > > > > > > > Yeah, we can do this. I will send the updated patch after putting > > > > some more thought into these comments. Thanks again for the feedback. > > > > > > > > > > Please find the updated patch. > > > > I've looked at the patch. Here are review comments: > > > > + /* Recovery pause state */ > > + RecoveryPauseState recoveryPause; > > > > Now that the value can have tri-state, how about renaming it to > > recoveryPauseState? > > This makes sense to me. > > > --- > > bool > > RecoveryIsPaused(void) > > +{ > > + bool recoveryPause; > > + > > + SpinLockAcquire(&XLogCtl->info_lck); > > + recoveryPause = (XLogCtl->recoveryPause == RECOVERY_PAUSED) ? > > true : false; > > + SpinLockRelease(&XLogCtl->info_lck); > > + > > + return recoveryPause; > > +} > > + > > +bool > > +RecoveryPauseRequested(void) > > { > > bool recoveryPause; > > > > SpinLockAcquire(&XLogCtl->info_lck); > > - recoveryPause = XLogCtl->recoveryPause; > > + recoveryPause = (XLogCtl->recoveryPause != > > RECOVERY_IN_PROGRESS) ? true : false; > > SpinLockRelease(&XLogCtl->info_lck); > > > > return recoveryPause; > > } > > > > We can write like recoveryPause = (XLogCtl->recoveryPause == > > RECOVERY_PAUSED); > > In RecoveryPauseRequested, we just want to know whether the pause is > requested or not, even if the pause requested and not yet pause then > also we want to return true. So how > recoveryPause = (XLogCtl->recoveryPause == RECOVERY_PAUSED) will work?
Sorry for the late response. What I wanted to say is that the ternary operator is not necessary in those cases. The codes, recoveryPause = (XLogCtl->recoveryPause == RECOVERY_PAUSED) ? true : false; recoveryPause = (XLogCtl->recoveryPause != RECOVERY_IN_PROGRESS) ? true : false; are equivalent with, recoveryPause = (XLogCtl->recoveryPause == RECOVERY_PAUSED); recoveryPause = (XLogCtl->recoveryPause != RECOVERY_IN_PROGRESS); respectively. Regards, -- Masahiko Sawada EDB: https://www.enterprisedb.com/