Re: Improve shutdown during online backup

On Tue, 2008-04-01 at 17:42 +0100, Simon Riggs wrote:

> Few comments:
>
> * smart shutdown waits for sessions to complete, yet this just ignores
> smart shutdowns which is something a little different. I think we
> should wait for the backup to complete and then shutdown.

> * The #defines at top of postmaster.c are duplicated from xlog.c
> If we can't agree on a common header file then we should at least add a
> comment to mention they are duplicated (in both locations).

If we add a function called something like BackupInProgress() to xlog.c,
exported via miscadmin.h then we can use it within the
PostmasterStateMachine() function like this

if (pmState == PM_WAIT_BACKENDS)
{
if (CountChildren() == 0 &&
StartupPID == 0 &&
(BgWriterPID == 0 || !FatalError) &&
WalWriterPID == 0 &&
AutoVacPID == 0 &&
!BackupInProgress()) <---- new line

so that the postmaster doesn't need to know about how we do backups.

That way you don't need any of the special cases in your patch, nor is
there any need to duplicate the #defines.

--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com

PostgreSQL UK 2008 Conference: http://www.postgresql.org.uk