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

On Tue, Nov 22, 2016 at 4:15 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> 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.

Sounds great.

--
Robert Haas
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