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

Hi,

On 1/26/23 10:42 AM, Alvaro Herrera wrote:
> On 2023-Jan-26, Drouvot, Bertrand wrote:
> 
>> On 1/24/23 7:27 PM, Alvaro Herrera wrote:
> 
>>> 1. I don't think wait_for_write_catchup is necessary, because
>>> calling wait_for_catchup() and omitting the 'mode' and 'lsn' arguments
>>> would already do the same thing. 

Having a closer look, it does not seem to be the case. The default mode
in wait_for_catchup() is 'replay' and the default mode for the lsn is 'write'.

But in wait_for_write_catchup() we are making use of 'write' for both.

> 
>>> 2. Because wait_for_replay_catchup is an instance method, passing the
>>> second node as argument is needlessly noisy, because that's already
>>> known as $self.  So we can just say
>>>
>>>     $primary_node->wait_for_replay_catchup($standby_node);
>>
>> Yeah, but same here, there is places where the node passed as the second argument is not the "$self":
>>
>> src/bin/pg_rewind/t/007_standby_source.pl:$node_b->wait_for_replay_catchup('node_c', $node_a);
>> src/test/recovery/t/001_stream_rep.pl:$node_standby_1->wait_for_replay_catchup($node_standby_2, $node_primary);
>> src/test/recovery/t/001_stream_rep.pl:$node_standby_1->wait_for_replay_catchup($node_standby_2, $node_primary);
>> src/test/recovery/t/001_stream_rep.pl:  $node_standby_1->wait_for_replay_catchup($node_standby_2, $node_primary);
>>
>> So it looks like there is still a need for wait_for_replay_catchup() with 2 parameters.
> 
> Ah, cascading replication.  In that case, let's make the second
> parameter optional.  If it's not given, $self is used.
> 

Good point, done in V3 attached.

Regards,

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