Re: speed up a logical replica setup - Mailing list pgsql-hackers

On Thu, 22 Feb 2024 at 21:17, Hayato Kuroda (Fujitsu)
<kuroda.hayato@fujitsu.com> wrote:
>
> Dear Vignesh,
>
> > Few comments on the tests:
> > 1) If the dry run was successful because of some issue then the server
> > will be stopped so we can check for "pg_ctl status" if the server is
> > running otherwise the connection will fail in this case. Another way
> > would be to check if it does not have "postmaster was stopped"
> > messages in the stdout.
> > +
> > +# Check if node S is still a standby
> > +is($node_s->safe_psql('postgres', 'SELECT pg_catalog.pg_is_in_recovery()'),
> > +       't', 'standby is in recovery');
>
> Just to confirm - your suggestion is to add `pg_ctl status`, right? Added.

Yes, that is correct.

> > 2) Can we add verification of  "postmaster was stopped" messages in
> > the stdout for dry run without --databases testcase
> > +# pg_createsubscriber can run without --databases option
> > +command_ok(
> > +       [
> > +               'pg_createsubscriber', '--verbose',
> > +               '--dry-run', '--pgdata',
> > +               $node_s->data_dir, '--publisher-server',
> > +               $node_p->connstr('pg1'), '--subscriber-server',
> > +               $node_s->connstr('pg1')
> > +       ],
> > +       'run pg_createsubscriber without --databases');
> > +
>
> Hmm, in case of --dry-run, the server would be never shut down.
> See below part.
>
> ```
>         if (!dry_run)
>                 stop_standby_server(pg_ctl_path, opt.subscriber_dir);
> ```

One way to differentiate whether the server is run in dry_run mode or
not is to check if the server was stopped or not. So I mean we can
check that the stdout does not have a "postmaster was stopped" message
from the stdout. Can we add validation based on this code:
+       if (action)
+               pg_log_info("postmaster was started");

Or another way is to check pg_ctl status to see that the server is not shutdown.

> > 3) This message "target server must be running" seems to be wrong,
> > should it be cannot specify cascading replicating standby as standby
> > node(this is for v22-0011 patch :
> > +               'pg_createsubscriber', '--verbose', '--pgdata',
> > $node_c->data_dir,
> > +               '--publisher-server', $node_s->connstr('postgres'),
> > +               '--port', $node_c->port, '--socketdir', $node_c->host,
> > +               '--database', 'postgres'
> >         ],
> > -       'primary server is in recovery');
> > +       1,
> > +       [qr//],
> > +       [qr/primary server cannot be in recovery/],
> > +       'target server must be running');
>
> Fixed.
>
> > 4) Should this be "Wait for subscriber to catch up"
> > +# Wait subscriber to catch up
> > +$node_s->wait_for_subscription_sync($node_p, $subnames[0]);
> > +$node_s->wait_for_subscription_sync($node_p, $subnames[1]);
>
> Fixed.
>
> > 5) Should this be 'Subscriptions has been created on all the specified
> > databases'
> > +);
> > +is($result, qq(2),
> > +       'Subscriptions has been created to all the specified databases'
> > +);
>
> Fixed, but "has" should be "have".
>
> > 6) Add test to verify current_user is not a member of
> > ROLE_PG_CREATE_SUBSCRIPTION, has no create permissions, has no
> > permissions to execution replication origin advance functions
> >
> > 7) Add tests to verify insufficient max_logical_replication_workers,
> > max_replication_slots and max_worker_processes for the subscription
> > node
> >
> > 8) Add tests to verify invalid configuration of  wal_level,
> > max_replication_slots and max_wal_senders for the publisher node
>
> Hmm, but adding these checks may increase the test time. we should
> measure the time and then decide.

We can check and see if it does not take significantly more time, then
we can have these tests.

Regards,
Vignesh