Re: Timeout failure in 019_replslot_limit.pl

On Mon, Sep 27, 2021 at 11:32 AM Michael Paquier <michael@paquier.xyz> wrote:
>
> On Sat, Sep 25, 2021 at 05:12:42PM +0530, Amit Kapila wrote:
> > Now, in the failed run, it appears that due to some reason WAL sender
> > has not released the slot. Is it possible to see if the WAL sender is
> > still alive when a checkpoint is stuck at ConditionVariableSleep? And
> > if it is active, what is its call stack?
>
> I got again a failure today, so I have used this occasion to check that
> when the checkpoint gets stuck the WAL sender process getting SIGCONT
> is still around, waiting for a write to happen:
> * thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
>     frame #0: 0x00007fff20320c4a libsystem_kernel.dylib`kevent + 10
>     frame #1: 0x000000010fe50a43 postgres`WaitEventSetWaitBlock(set=0x00007f884d80a690, cur_timeout=-1,
occurred_events=0x00007ffee0395fd0,nevents=1) at latch.c:1601:7
 
>     frame #2: 0x000000010fe4ffd0 postgres`WaitEventSetWait(set=0x00007f884d80a690, timeout=-1,
occurred_events=0x00007ffee0395fd0,nevents=1, wait_event_info=100663297) at latch.c:1396:8
 
>     frame #3: 0x000000010fc586c4 postgres`secure_write(port=0x00007f883eb04080, ptr=0x00007f885006a040, len=122694)
atbe-secure.c:298:3
 
..
..
>     frame #15: 0x000000010fe91eb8 postgres`PostgresMain(dbname="", username="mpaquier") at postgres.c:4493:12
>
> It logs its FATAL "terminating connection due to administrator
> command" coming from ProcessInterrupts(), and then it sits idle on
> ClientWrite.
>

So, it seems on your machine it has passed  the following condition in
secure_write:
if (n < 0 && !port->noblock && (errno == EWOULDBLOCK || errno == EAGAIN))

If so, this indicates write failure which seems odd to me and probably
something machine-specific or maybe some different settings in your
build or machine. BTW, if SSL or GSS is enabled that might have caused
it in some way. I think the best way is to debug the secure_write
during this occurrence.

-- 
With Regards,
Amit Kapila.