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: 'Shubham Khanna' <khannashubham1197@gmail.com>
Cc: Euler Taveira <euler@eulerto.com>, "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: 2024-02-16T11:10:42Z
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 Shubham,

Thanks for testing. It seems you ran with v20 patch, but I confirmed
It could reproduce with v21.

> 
> I found a couple of issues, while verifying the cascaded replication
> with the following scenarios:
> Scenario 1) Create cascade replication like node1->node2->node3
> without using replication slots (attached
> cascade_3node_setup_without_slots has the script for this):
> Then I ran pg_createsubscriber by specifying primary as node1 and
> standby as node3, this scenario runs successfully. I was not sure if
> this should be supported or not?

Hmm. After the script, the cascading would be broken. The replication would be:

```
Node1 -> node2
  |
Node3
```

And the operation is bit strange. The consistent LSN is gotten from the node1,
but node3 waits until it receives the record from NODE2.
Can we always success it?

> Scenario 2) Create cascade replication like node1->node2->node3 using
> replication slots (attached cascade_3node_setup_with_slots has the
> script for this):
> Here, slot name was used as slot1 for node1 to node2 and slot2 for
> node2 to node3. Then I ran pg_createsubscriber by specifying primary
> as node1 and standby as node3. In this case pg_createsubscriber fails
> with the following error:
> pg_createsubscriber: error: could not obtain replication slot
> information: got 0 rows, expected 1 row
> [Inferior 1 (process 2623483) exited with code 01]
> 
> This is failing because slot name slot2 is used between node2->node3
> but pg_createsubscriber is checked for slot1, the slot which is used
> for replication between node1->node2.
> Thoughts?

Right. The inconsistency is quite strange.

Overall, I felt such a case must be rejected. How should we detect at checking phase?

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