Re: [Patch] ALTER SYSTEM READ ONLY

On Wed, Jul 28, 2021 at 5:03 PM Amul Sul <sulamul(at)gmail(dot)com> wrote:
>
> I was too worried about how I could miss that & after thinking more
> about that, I realized that the operation for ArchiveRecoveryRequested
> is never going to be skipped in the startup process and that never
> left for the checkpoint process to do that later. That is the reason
> that assert was added there.
>
> When ArchiveRecoveryRequested, the server will no longer be in
> the wal prohibited mode, we implicitly change the state to
> wal-permitted. Here is the snip from the 0003 patch:
>
> @@ -6614,13 +6629,30 @@ StartupXLOG(void)
> (errmsg("starting archive recovery")));
> }
>
> - /*
> - * Take ownership of the wakeup latch if we're going to sleep during
> - * recovery.
> - */
> if (ArchiveRecoveryRequested)
> + {
> + /*
> + * Take ownership of the wakeup latch if we're going to sleep during
> + * recovery.
> + */
> OwnLatch(&XLogCtl->recoveryWakeupLatch);
>
> + /*
> + * Since archive recovery is requested, we cannot be in a wal prohibited
> + * state.
> + */
> + if (ControlFile->wal_prohibited)
> + {
> + /* No need to hold ControlFileLock yet, we aren't up far enough */
> + ControlFile->wal_prohibited = false;
> + ControlFile->time = (pg_time_t) time(NULL);
> + UpdateControlFile();
> +

Is there some reason why we are forcing 'wal_prohibited' to off if we
are doing archive recovery? It might have already been discussed, but
I could not find it on a quick look into the thread.

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com