Horton

Re: Exit walsender before confirming remote flush in logical replication

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: sawada.mshk@gmail.com, kuroda.hayato@fujitsu.com, andres@anarazel.de, michael@paquier.xyz, peter.eisentraut@enterprisedb.com, dilipbalaut@gmail.com, pgsql-hackers@postgresql.org
Date: 2023-02-02T05:53:30Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add wal_sender_shutdown_timeout GUC to limit shutdown wait for replication

  2. pg_upgrade: Add --copy option

  3. Prevent possibility of panics during shutdown checkpoint.

  4. Support clean switchover.

On Thu, Feb 2, 2023 at 10:04 AM Kyotaro Horiguchi
<horikyota.ntt@gmail.com> wrote:
>
> At Wed, 1 Feb 2023 14:58:14 +0530, Amit Kapila <amit.kapila16@gmail.com> wrote in
> > On Wed, Feb 1, 2023 at 2:09 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > >
> > > Otherwise, we will end up terminating
> > > the WAL stream without the done message. Which will lead to an error
> > > message "ERROR:  could not receive data from WAL stream: server closed
> > > the connection unexpectedly" on the subscriber even at a clean
> > > shutdown.
> > >
> >
> > But will that be a problem? As per docs of shutdown [1] ( “Smart” mode
> > disallows new connections, then waits for all existing clients to
> > disconnect. If the server is in hot standby, recovery and streaming
> > replication will be terminated once all clients have disconnected.),
> > there is no such guarantee. I see that it is required for the
> > switchover in physical replication to ensure that all the WAL is sent
> > and replicated but we don't need that for logical replication.
>
> +1
>
> Since publisher is not aware of apply-delay (by this patch), as a
> matter of fact publisher seems gone before sending EOS in that
> case. The error message is correctly describing that situation.
>

This can happen even without apply-delay patch. For example, when
apply process is waiting on some lock.

-- 
With Regards,
Amit Kapila.