Re: Terminating a backend - Mailing list pgsql-patches

From Bruce Momjian
Subject Re: Terminating a backend
Date
Msg-id 200804151353.m3FDrWB09489@momjian.us
Whole thread Raw
In response to Terminating a backend  (Bruce Momjian <bruce@momjian.us>)
List pgsql-patches
Applied.

---------------------------------------------------------------------------

Bruce Momjian wrote:
> oikBruce Momjian wrote:
> > Bruce Momjian wrote:
> > > > > When we get the termination signal, why can't we just set a global
> > > > > boolean, do a query cancel, and in the setjmp() code block check the
> > > > > global and exit --- at that stage we know we have released all locks and
> > > > > can exit cleanly.
> > > >
> > > > I have implemented this idea with the attached patch.
> > >
> > > One problem I have with my patch is that SIGTERM is currently used by
> > > the postmaster to shut down backends.  Now because the postmaster knows
> > > that all backend are terminating, it can accept a dirtier shutdown than
> > > one where we are terminating just one backend and the rest are going to
> > > keep running.  The new SIGTERM coding is going to exit a backend only in
> > > a place where cancel is checked.
> >
> > I have a idea --- to have pg_terminate_backend() set a PGPROC boolean
> > and then send a query cancel signal to the backend --- the backend can
> > then check the boolean and exit if required.  I will work on a new
> > version of this patch tomorrow/Monday.
>
> Updated patch attached.  I didn't modify SIGTERM at all but set a PRPROC
> boolean and piggybacked on SIGINT.  I think I got the PGPROC locking
> right.  I had to split apart pg_signal_backend() so I could do the
> permission and pid checks independent of the signalling, because I
> pg_terminate_backend() needs to check, then set the PGPROC variable,
> then send the signal.
>
> I also added an administration doc mention about when to use
> pg_terminate_backend().
>
> --
>   Bruce Momjian  <bruce@momjian.us>        http://momjian.us
>   EnterpriseDB                             http://enterprisedb.com
>
>   + If your life is a hard drive, Christ can be your backup. +


>
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--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

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