Re: [RFC] Should we fix postmaster to avoid slow shutdown?

Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> Well, the problem is that the stats data is not on disk while the system
> is in operation, as far as I recall -- it's only in the collector's
> local memory. On shutdown we tell it to write it down to a file, and on
> startup we tell it to read it from the file and then delete it. I think
> the rationale for this is to avoid leaving a file with stale data on
> disk while the system is running.

Maybe a workable compromise would be to leave the file present, and have
the stats collector re-write it every (say) five minutes. Then I'd be
okay with having an immediate shutdown skip writing the file; you'd be
losing up to five minutes' worth of activity, but not going completely
nuts. So the stats collector's normal activities would include writing
the temp file on-demand and the permanent file on a timed cycle.

The other components of the fix (deleting on PITR rewind or stats
collector crash) would remain the same.

regards, tom lane