Horton

RE: speed up a logical replica setup

Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>

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From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: 'Euler Taveira' <euler@eulerto.com>
Cc: "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>, vignesh C <vignesh21@gmail.com>, Michael Paquier <michael@paquier.xyz>, Peter Eisentraut <peter@eisentraut.org>, Andres Freund <andres@anarazel.de>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Shlok Kyal <shlok.kyal.oss@gmail.com>, Fabrízio de Royes Mello <fabriziomello@gmail.com>
Date: 2024-02-08T03:04:05Z
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. pg_createsubscriber: Remove obsolete comment

  2. pg_createsubscriber: Fix an unpredictable recovery wait time.

  3. Fix unstable test in 040_pg_createsubscriber.

  4. Fix the testcase introduced in commit 81d20fbf7a.

  5. Further weaken new pg_createsubscriber test on Windows.

  6. Temporarily(?) weaken new pg_createsubscriber test on Windows.

  7. Make pg_createsubscriber warn if publisher has two-phase commit enabled.

  8. Make pg_createsubscriber more wary about quoting connection parameters.

  9. pg_createsubscriber: Remove failover replication slots on subscriber

  10. pg_createsubscriber: Remove replication slot check on primary

  11. pg_createsubscriber: Only --recovery-timeout controls the end of recovery process

  12. pg_createsubscriber: creates a new logical replica from a standby server

  13. Add some const decorations

  14. Add option force_initdb to PostgreSQL::Test::Cluster:init()

  15. Remove MSVC scripts

Dear Euler,

>
Remember the target server was a standby (read only access). I don't expect an
application trying to modify it; unless it is a buggy application.
>

What if the client modifies the data just after the promotion?
Naively considered, all the changes can be accepted, but are there any issues?

>
Regarding
GUCs, almost all of them is PGC_POSTMASTER (so it cannot be modified unless the
server is restarted). The ones that are not PGC_POSTMASTER, does not affect the
pg_createsubscriber execution [1].
>

IIUC,  primary_conninfo and primary_slot_name is PGC_SIGHUP.

>
I'm just pointing out that this case is a different from pg_upgrade (from which
this idea was taken). I'm not saying that's a bad idea. I'm just arguing that
you might be preventing some access read only access (monitoring) when it is
perfectly fine to connect to the database and execute queries. As I said
before, the current UI allows anyone to setup the standby to accept only local
connections. Of course, it is an extra step but it is possible. However, once
you apply v16-0007, there is no option but use only local connection during the
transformation. Is it an acceptable limitation?
>

My remained concern is written above. If they do not problematic we may not have
to restrict them for now. At that time, changes 

1) overwriting a port number,
2) setting listen_addresses = ''

are not needed, right? IIUC inconsistency of -P may be still problematic.

>
pglogical_create_subscriber does nothing [2][3].
>

Oh, thanks.
Just to confirm - pglogical set shared_preload_libraries to '', should we follow or not?

Best Regards,
Hayato Kuroda
FUJITSU LIMITED
https://www.fujitsu.com/global/