Horton

Re: [HACKERS] make async slave to wait for lsn to be replayed

Alexander Korotkov <aekorotkov@gmail.com>

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From: Alexander Korotkov <aekorotkov@gmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Pavel Borisov <pashkin.elfe@gmail.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Kartyshov Ivan <i.kartyshov@postgrespro.ru>, Euler Taveira <euler@eulerto.com>, Thomas Munro <thomas.munro@gmail.com>, Peter Eisentraut <peter@eisentraut.org>, Amit Kapila <amit.kapila16@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Peter Smith <smithpb2250@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2024-04-06T21:52:47Z
Lists: pgsql-hackers 
Hi, Alvaro!

Thank you for your care on this matter.

On Fri, Apr 5, 2024 at 9:15 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> BTW I noticed that
> https://coverage.postgresql.org/src/backend/commands/waitlsn.c.gcov.html
> says that lsn_cmp is not covered by the tests.  This probably indicates
> that the tests are a little too light, but I'm not sure how much extra
> effort we want to spend.

I'm aware of this.  Ivan promised to send a patch to improve the test.
If he doesn't, I'll care about it.

> I'm still concerned that WaitLSNCleanup is only called in ProcKill.
> Does this mean that if a process throws an error while waiting, it'll
> not get cleaned up until it exits?  Maybe this is not a big deal, but it
> seems odd.

I've added WaitLSNCleanup() to the AbortTransaction().  Just pushed
that together with the improvements upthread.

------
Regards,
Alexander Korotkov

Commits

  1. Ensure standby promotion point in 043_wal_replay_wait.pl

  2. Minor cleanup related to pg_wal_replay_wait() procedure

  3. Adjust pg_wal_replay_wait() procedure behavior on promoted standby

  4. pg_wal_replay_wait(): Fix typo in the doc

  5. Implement pg_wal_replay_wait() stored procedure

  6. Revert: Implement pg_wal_replay_wait() stored procedure

  7. Call WaitLSNCleanup() in AbortTransaction()

  8. Clarify what is protected by WaitLSNLock

  9. Use an LWLock instead of a spinlock in waitlsn.c

  10. Use the pairing heap instead of a flat array for LSN replay waiters

  11. Minor improvements for waitlsn.c

  12. Make the order of the header file includes consistent