Re: Helper functions for wait_for_catchup() in Cluster.pm

Hi,

On 1/17/23 12:23 PM, Alvaro Herrera wrote:
> On 2023-Jan-17, Drouvot, Bertrand wrote:
>
>> The idea has been raised in [1], where we are adding more calls to
>> wait_for_catchup() in 'replay' mode.
>
> This seems mostly useless as presented. Maybe if you're able to reduce
> the noise on the second argument it would be worth something -- namely,
> if the wrapper function receives a node instead of an LSN: perhaps
> wait_for_replay_catchup() would use the flush LSN from the given node,
> wait_for_write_catchup() would use the write LSN, and
> wait_for_sent_catchup() would use the insert LSN. (I didn't check in
> your patch if there are callsites that do something else). This would
> in several cases let you also remove the line with the assignment of
> appropriate LSN to a separate variable. If you did it that way, maybe
> the code would become a tiny bit smaller overall.
>

Thanks for looking at it!

The current calls are done that way:

wait_for_replay_catchup called:
- 8 times with write LSN as an argument
- 1 time with insert LSN as an argument
- 16 times with flush LSN as an argument

wait_for_write_catchup called:
- 5 times with write LSN as an argument

So it looks like that providing a node as a second argument
would not help for the wait_for_replay_catchup() case.

Worth to use the node as an argument for wait_for_write_catchup()? (though it would be
weird to have different types of arguments between wait_for_replay_catchup() and wait_for_write_catchup()).

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com