Horton

Re: [Patch] ALTER SYSTEM READ ONLY

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Amul Sul <sulamul@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2021-03-03T06:37:53Z
Lists: pgsql-hackers 
On Tue, Mar 2, 2021 at 9:01 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:

> >
> > We don't want that to happen in cases where previous recovery-end-checkpoint is
> > skipped in startup. We want Checkpointer first to convey the barrier to all
> > backends but, the backend shouldn't write wal until the Checkpointer writes
> > recovery-end-checkpoint record.
> >
> > To refrain these backends from writing WAL I think we should keep the server in
> > crash recovery mode until UpdateFullPageWrites(),
> > end-of-recovery-checkpoint, and XLogReportParameters() are performed.

I did not read the code for this, but let me ask something about this
case.  Why do we want checkpointer to convey the barrier to all the
backend before completing the end of recovery checkpoint and other
stuff? Is it because the system is still in WAL prohibited state?  Is
it possible that as soon as we get the pg_prohibit_wal(false) request
the receiving backend start allowing the WAL writing for itself and
finish the all post-recovery pending work and then inform the
checkpointer to inform all other backends?

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

Commits

  1. Initialize variable to placate compiler.

  2. StartupXLOG: Don't repeatedly disable/enable local xlog insertion.

  3. StartupXLOG: Call CleanupAfterArchiveRecovery after XLogReportParameters.

  4. Postpone some end-of-recovery operations related to allowing WAL.

  5. Refactor some end-of-recovery code out of StartupXLOG().

  6. Re-enable contrib/bloom's TAP tests.

  7. Remove unnecessary call to ReadCheckpointRecord().

  8. Allow for error or refusal while absorbing a ProcSignalBarrier.

  9. Add comment to explain an unused function parameter

  10. Extend the ProcSignal mechanism to support barriers.

  11. At promotion, don't leave behind a partial segment on the old timeline.