Horton

Re: speed up a logical replica setup

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: vignesh C <vignesh21@gmail.com>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Euler Taveira <euler@eulerto.com>, pgsql-hackers@lists.postgresql.org, Andres Freund <andres@anarazel.de>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Date: 2024-01-03T09:19:01Z
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

On Wed, Jan 3, 2024 at 12:09 PM vignesh C <vignesh21@gmail.com> wrote:
>
> On Wed, 1 Nov 2023 at 19:28, Ashutosh Bapat
> <ashutosh.bapat.oss@gmail.com> wrote:
> >
> > At this stage the standby would have various replication objects like
> > publications, subscriptions, origins inherited from the upstream
> > server and possibly very much active. With failover slots, it might
> > inherit replication slots. Is it intended that the new subscriber also
> > acts as publisher for source's subscribers OR that the new subscriber
> > should subscribe to the upstreams of the source? Some use cases like
> > logical standby might require that but a multi-master multi-node setup
> > may not. The behaviour should be user configurable.
>
> How about we do like this:
> a) Starting the server in binary upgrade mode(so that the existing
> subscriptions will not try to connect to the publishers)
>

Can't we simply do it by starting the server with
max_logical_replication_workers = 0 or is there some other need to
start in binary upgrade mode?

 b) Disable
> the subscriptions
>

Why not simply drop the subscriptions?

 c) Drop the replication slots d) Drop the
> publications
>

I am not so sure about dropping publications because, unlike
subscriptions which can start to pull the data, there is no harm with
publications. Similar to publications there could be some user-defined
functions or other other objects which may not be required once the
standby replica is converted to subscriber. I guess we need to leave
those to the user.

 e) Then restart the server in normal(non-upgrade) mode.
> f) The rest of pg_subscriber work like
> create_all_logical_replication_slots, create_subscription,
> set_replication_progress, enable_subscription, etc
> This will be done by default. There will be an option
> --clean-logical-replication-info provided to allow DBA not to clean
> the objects if DBA does not want to remove these objects.
>

I agree that some kind of switch to control this action would be useful.

-- 
With Regards,
Amit Kapila.