Re: pg_rewind just doesn't fsync *anything*?

On 2016-03-09 19:43:52 -0800, Andres Freund wrote:
> Hi,
>
> how come that the only comment in pg_rewind about fsyncing is '
> void
> close_target_file(void)
> {
> ...
> /* fsync? */
> }
>
> Isn't that a bit, uh, minimal for a utility that's likely to be used in
> failover scenarios?
>
> I think we might actually be "saved" due to
> http://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=2ce439f33
> because pg_rewind appears to leave the cluster in
>
> ControlFile_new.state = DB_IN_ARCHIVE_RECOVERY;
> updateControlFile(&ControlFile_new);
>
> a state that StartupXLOG will treat as needing recovery:
>
> if (ControlFile->state != DB_SHUTDOWNED &&
> ControlFile->state != DB_SHUTDOWNED_IN_RECOVERY)
> SyncDataDirectory();
>
> but that code went in after pg_rewind, so this certainly can't be an
> intentional save.
>
> I also don't think it's ok that you need to start the cluster to make it
> safe against a crash?
>
> I guess the easiest fix would be to shell out to initdb -s?

I've pushed a modified version of the fix that Michael posted in
http://archives.postgresql.org/message-id/CAB7nPqRmM%2BCX6bVxw0Y7mMVGMFj1S8kwhevt8TaP83yeFRfbXA%40mail.gmail.com

Andres