Re: pgsql: Add tests for '-f' option in dropdb utility.

On Fri, Nov 29, 2019 at 3:24 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Fri, Nov 29, 2019 at 7:42 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Fri, Nov 29, 2019 at 2:25 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > >
> >
> > > * On all the failing machines, it's very clear from the postmaster
> > > log that the backend knows why it's being terminated:
> > >
> > > 2019-11-28 13:47:56.320 UTC [212024:4] 051_dropdb_force.pl FATAL: terminating connection due to administrator command
> > >
> >
> > Yeah, I can confirm this behavior on the Windows machines. I have
> > also seen that we already expose this behavior in more than one way
> > and all behave similar to this. If I use pg_terminate_backend(<pid>)
> > or pg_ctl kill TERM <pid>, the behavior is exactly the same
> > (terminated backend doesn't get the message (FATAL: terminating
> > connection due to administrator command), but it is present in
> > postmaster log.
> >
> > > So the question seems to be why libpq isn't reporting that
> > > message before it detects connection-closed.
> > >
> > > This triggered a vague memory, and after a bit of archives-digging,
> > > I found this thread from a few months back:
> > >
> > > https://www.postgresql.org/message-id/flat/CA%2BhUKGJowQypXSKsjws9A%2BnEQDD0-mExHZqFXtJ09N209rCO5A%40mail.gmail.com#0629f079bc59ecdaa0d6ac9f8f2c18ac
> > >
> > > in which it's alleged that Windows' TCP stack is flat-out
> > > broken and will drop not-yet-delivered data when the server
> > > closes the connection.
> > >
> > > If that's true, it's pretty nasty. Windows is about the
> > > last platform where I'd want us to have behavior like this,
> > > because we *will* get bug reports about it from novices.
> > >
> > > If there's no other workaround, I'm tempted to propose
> > >
> > > #ifdef WIN32
> > > pg_sleep(1 second);
> > > #endif
> > >
> > > or something close to that, before we close the socket.
> > >
> >
> > I can experiment with this or if something else occurred to me.
> >
>
> The above experiment suggested by you works and the test passes after
> this in the local Windows setup. One more thing, I think we don't
> need to do above for graceful exits and during socket_close we have
> access to exit_status_code which can be used in this context. I have
> attached the patch for this. I think something on these lines is even
> suggested by MSDN [1], but I am not sure.
>

On further reading the Microsoft docs, it seems that even though it
suggests something which can work in our current situation, but it is
in a different context.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com