Re: Get memory contexts of an arbitrary backend process

Hi,

On Thu, Sep 10, 2020 at 8:53 PM torikoshia <torikoshia(at)oss(dot)nttdata(dot)com> wrote:
>
> On 2020-09-04 21:46, Tomas Vondra wrote:
> > On Fri, Sep 04, 2020 at 11:47:30AM +0900, Kasahara Tatsuhito wrote:
> >> On Fri, Sep 4, 2020 at 2:40 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >>> Kasahara Tatsuhito <kasahara(dot)tatsuhito(at)gmail(dot)com> writes:
> >>> > Yes, but it's not only for future expansion, but also for the
> >>> > usability and the stability of this feature.
> >>> > For example, if you want to read one dumped file multiple times and analyze it,
> >>> > you will want the ability to just read the dump.
> >>>
> >>> If we design it to make that possible, how are we going to prevent
> >>> disk
> >>> space leaks from never-cleaned-up dump files?
> >> In my thought, with features such as a view that allows us to see a
> >> list of dumped files,
> >> it would be better to have a function that simply deletes the dump
> >> files associated with a specific PID,
> >> or to delete all dump files.
> >> Some files may be dumped with unexpected delays, so I think the
> >> cleaning feature will be necessary.
> >> ( Also, as the pgsql_tmp file, it might better to delete dump files
> >> when PostgreSQL start.)
> >>
> >> Or should we try to delete the dump file as soon as we can read it?
> >>
> >
> > IMO making the cleanup a responsibility of the users (e.g. by exposing
> > the list of dumped files through a view and expecting users to delete
> > them in some way) is rather fragile.
> >
> > I don't quite see what's the point of designing it this way. It was
> > suggested this improves stability and usability of this feature, but
> > surely making it unnecessarily complex contradicts both points?
> >
> > IMHO if the user needs to process the dump repeatedly, what's
> > preventing
> > him/her from storing it in a file, or something like that? At that
> > point
> > it's clear it's up to them to remove the file. So I suggest to keep the
> > feature as simple as possible - hand the dump over and delete.
Yeah, it might be better to avoid making the user responsible for removal.

I think it's fine to have an interface to delete in an emergency, but
I agree that
users shouldn't be made aware of the existence or deletion of dump
files, basically.

> +1.
> If there are no other objections, I'm going to accept this
> suggestion.
So +1

Best regards,

--
Tatsuhito Kasahara
kasahara.tatsuhito _at_ gmail.com