Re: [BUG] non archived WAL removed during production crash recovery - Mailing list pgsql-bugs
From | Jehan-Guillaume de Rorthais |
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Subject | Re: [BUG] non archived WAL removed during production crash recovery |
Date | |
Msg-id | 20200402154915.4984cff2@firost Whole thread Raw |
In response to | Re: [BUG] non archived WAL removed during production crash recovery (Fujii Masao <masao.fujii@oss.nttdata.com>) |
Responses |
Re: [BUG] non archived WAL removed during production crash recovery
Re: [BUG] non archived WAL removed during production crash recovery |
List | pgsql-bugs |
On Thu, 2 Apr 2020 19:38:59 +0900 Fujii Masao <masao.fujii@oss.nttdata.com> wrote: > On 2020/04/02 16:23, Kyotaro Horiguchi wrote: > > At Thu, 2 Apr 2020 14:19:15 +0900, Fujii Masao > > <masao.fujii@oss.nttdata.com> wrote in [...] > >> is whether to remove such WAL files in archive recovery case with > >> archive_mode=on. Those WAL files would be required when recovering > >> from the backup taken before that archive recovery happens. > >> So it seems unsafe to remove them in that case. > > > > I'm not sure I'm getting the intention correctly, but I think it > > responsibility of the operator to provide a complete set of archived > > WAL files for a backup. Could you elaborate what operation steps are > > you assuming of? > > Please imagine the case where you need to do archive recovery > from the database snapshot taken while there are many WAL files > with .ready files. Those WAL files have not been archived yet. > In this case, ISTM those WAL files should not be removed until > they are archived, when archive_mode = on. If you rely on snapshot without pg_start/stop_backup, I agree. Theses WAL should be archived if: * archive_mode >= on for primary * archive_mode = always for standby > >> Therefore, IMO that the patch should change the code so that > >> no unarchived WAL files are removed not only in crash recovery > >> but also archive recovery. Thought? > > > > Agreed if "an unarchived WAL" means "a WAL file that is marked .ready" > > and it should be archived immediately. My previous mail is written > > based on the same thought. > > Ok, so our *current* consensus seems the followings. Right? > > - If archive_mode=off, any WAL files with .ready files are removed in > crash recovery, archive recoery and standby mode. yes > - If archive_mode=on, WAL files with .ready files are removed only in > standby mode. In crash recovery and archive recovery cases, they keep > remaining and would be archived after recovery finishes (i.e., during > normal processing). yes > - If archive_mode=always, in crash recovery, archive recovery and > standby mode, WAL files with .ready files are archived if WAL archiver > is running. yes > That is, WAL files with .ready files are removed when either > archive_mode!=always in standby mode or archive_mode=off. sounds fine to me. [...] > >>>>>> Another is to make the startup process remove .ready file if > >>>>>> necessary. > >>>>> > >>>>> I'm not sure to understand this one. > >> > >> I was thinking to make the startup process remove such unarchived WAL > >> files > >> if archive_mode=on and StandbyModeRequested/ArchiveRecoveryRequested > >> is true. Ok, understood. > > As mentioned above, I don't understand the point of preserving WAL > > files that are either marked as .ready or not marked at all on a > > standby with archive_mode=on. > > Maybe yes. But I'm not confident about that there is no such case. Well, it seems to me that this is what you suggested few paragraph away: «.ready files are removed when either archive_mode!=always in standby mode»
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