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

Ivan Kartyshov <i.kartyshov@postgrespro.ru>

From: Kartyshov Ivan <i.kartyshov@postgrespro.ru>

To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>

Cc: Andy Fan <zhihuifan1213@163.com>, Alexander Korotkov <aekorotkov@gmail.com>, 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: 2024-04-02T15:21:34Z

Lists: pgsql-hackers

On 2024-04-02 13:15, Bharath Rupireddy wrote:
> On Tue, Apr 2, 2024 at 3:41 PM Kartyshov Ivan
> <i.kartyshov@postgrespro.ru> wrote:
>> 
>> 8 years, we tried to add this feature, and now we suggest the best way
>> for this feature is to commit the minimal version first.
> 
> Just curious, do you or anyone else have an immediate use for this
> function? If yes, how are they achieving read-after-write-consistency
> on streaming standbys in their application right now without a
> function like this?

Just now, application runs pg_current_wal_lsn() after update and then
waits on loop pg_current_wal_flush_lsn() until updated.

Or use slow synchronous_commit.

-- 
Ivan Kartyshov
Postgres Professional: www.postgrespro.com

Commits

Ensure standby promotion point in 043_wal_replay_wait.pl
- 2520226c953c 18.0 landed
Minor cleanup related to pg_wal_replay_wait() procedure
- 85b98b8d5a48 18.0 landed
Adjust pg_wal_replay_wait() procedure behavior on promoted standby
- 867d396ccd2a 18.0 landed
pg_wal_replay_wait(): Fix typo in the doc
- 8036d73ae3d4 18.0 landed
Implement pg_wal_replay_wait() stored procedure
- 3c5db1d6b016 18.0 landed
- 06c418e163e9 17.0 landed
Revert: Implement pg_wal_replay_wait() stored procedure
- 772faafca1b2 17.0 landed
Call WaitLSNCleanup() in AbortTransaction()
- 74eaf66f988c 17.0 landed
Clarify what is protected by WaitLSNLock
- ee79928441e7 17.0 landed
Use an LWLock instead of a spinlock in waitlsn.c
- 25f42429e2ff 17.0 landed
Use the pairing heap instead of a flat array for LSN replay waiters
- bf1e65080629 17.0 landed
Minor improvements for waitlsn.c
- e37662f22158 17.0 landed
Make the order of the header file includes consistent
- 97d85be36544 17.0 cited