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Re: Sync Rep v17

From: Jaime Casanova <jaime(at)2ndquadrant(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org, Daniel Farina <daniel(at)heroku(dot)com>
Subject: Re: Sync Rep v17
Date: 2011-02-22 19:43:29
Message-ID: AANLkTinmmPD_d4WnX8PqG111b_Q4UEBczbQtUMXZAwQ0@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sat, Feb 19, 2011 at 11:26 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> DEBUG:  write 0/3027BC8 flush 0/3014690 apply 0/3014690
> DEBUG:  released 0 procs up to 0/3014690
> DEBUG:  write 0/3027BC8 flush 0/3027BC8 apply 0/3014690
> DEBUG:  released 2 procs up to 0/3027BC8
> WARNING:  could not locate ourselves on wait queue
> server closed the connection unexpectedly
>        This probably means the server terminated abnormally
>        before or while processing the request.
> The connection to the server was lost. Attempting reset: DEBUG:

you can make this happen more easily, i just run "pgbench -n -c10 -j10
test" and qot that warning and sometimes a segmentation fault and
sometimes a failed assertion

and the problematic code starts at
src/backend/replication/syncrep.c:277, here my suggestions on that
code.
still i get a failed assertion because of the second Assert (i think
we should just remove that one)

*************** SyncRepRemoveFromQueue(void)
*** 288,299 ****

                        if (proc->lwWaitLink == NULL)
                                elog(WARNING, "could not locate
ourselves on wait queue");
!                       proc = proc->lwWaitLink;
                }

                if (proc->lwWaitLink == NULL)   /* At tail */
                {
!                       Assert(proc == MyProc);
                        /* Remove ourselves from tail of queue */
                        Assert(queue->tail == MyProc);
                        queue->tail = proc;
--- 288,300 ----

                        if (proc->lwWaitLink == NULL)
                                elog(WARNING, "could not locate
ourselves on wait queue");
!                       else
!                               proc = proc->lwWaitLink;
                }

                if (proc->lwWaitLink == NULL)   /* At tail */
                {
!                       Assert(proc != MyProc);
                        /* Remove ourselves from tail of queue */
                        Assert(queue->tail == MyProc);
                        queue->tail = proc;

-- 
Jaime Casanova         www.2ndQuadrant.com
Professional PostgreSQL: Soporte y capacitación de PostgreSQL

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Next:From: Daniel FarinaDate: 2011-02-22 19:45:30
Subject: Re: Sync Rep v17
Previous:From: Robert HaasDate: 2011-02-22 19:29:26
Subject: Re: Re: [COMMITTERS] pgsql: Make a hard state change from catchup to streaming mode.

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