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help / color / mirror / Atom feedFrom: Fujii Masao <[email protected]>
To: shveta malik <[email protected]>
Cc: Nisha Moond <[email protected]>
Cc: Amit Kapila <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Use SIGTERM instead of SIGUSR1 for slotsync worker to exit during promotion?
Date: Wed, 1 Apr 2026 00:33:27 +0900
Message-ID: <CAHGQGwFC1qK3XiVi47VfJDNXE05HRA6AJmqrnAj55SK3kWTBkw@mail.gmail.com> (raw)
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On Tue, Mar 31, 2026 at 7:42 PM shveta malik <[email protected]> wrote:
> > > One idea would be to prevent the restart altogether. For example,
> > > ProcessSlotSyncMessage() could set SlotSyncCtx->last_start_time to
> > > a special value (like -1), and SlotSyncWorkerCanRestart() could return
> > > false (i.e., prevent postmater from starting up slotsync worker) when
> > > it sees that. Alternatively, SlotSyncWorkerCanRestart() could simply
> > > check SlotSyncCtx->stopSignaled.
> > >
> > > That said, as far as I remember correctly, postmaster is generally not
> > > supposed to touch shared memory (per the comments in postmaster.c),
> > > so I'm not sure this approach is acceptable. On the other hand,
> > > postmaster and the slotsync worker already rely on SlotSyncCtx->last_start_time,
> > > so perhaps there's some precedent here.
> > >
> > IIUC, checking SlotSyncCtx->stopSignaled in SlotSyncWorkerCanRestart()
> > may not be ideal, as it requires a spinlock to avoid races with the
> > startup process and it is disallowed to take lock in postmaster main
> > loop. Whereas, SlotSyncCtx->last_start_time doesn’t need a lock since
> > the postmaster accesses it only when the worker is not alive.
> >
>
> I agree.
Could you clarify what issue might arise from checking
SlotSyncCtx->stopSignaled without holding a spinlock in
SlotSyncWorkerCanRestart()? Is it actually problematic?
That said, since the postmaster should generally avoid
touching shared memory, it doesn't seem like a good idea
for it to check SlotSyncCtx->stopSignaled. So I'm fine with
instead lowering the log level for the "worker will not start"
message to DEBUG1.
Regards,
--
Fujii Masao
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To: [email protected]
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Subject: Re: Use SIGTERM instead of SIGUSR1 for slotsync worker to exit during promotion?
In-Reply-To: <CAHGQGwFC1qK3XiVi47VfJDNXE05HRA6AJmqrnAj55SK3kWTBkw@mail.gmail.com>
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