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

On Thu, Mar 28, 2024, at 9:39 AM, Alexander Korotkov wrote:

[I didn't read the whole thread. I'm sorry if I missed something ...]

You renamed the function in a previous version but let me suggest another one:

pg_wal_replay_wait. It uses the same pattern as the other recovery control

functions [1]. I think "for" doesn't add much for the function name and "lsn" is

used in functions that return an LSN (that's not the case here).

postgres=# \df pg_wal_replay*

List of functions

-[ RECORD 1 ]-------+---------------------

Schema              | pg_catalog

Name                | pg_wal_replay_pause

Result data type    | void

Argument data types | 

Type                | func

-[ RECORD 2 ]-------+---------------------

Schema              | pg_catalog

Name                | pg_wal_replay_resume

Result data type    | void

Argument data types | 

Type                | func

Regarding the arguments, I think the timeout should be bigint. There is at least

another function that implements a timeout that uses bigint. 

postgres=# \df pg_terminate_backend

List of functions

-[ RECORD 1 ]-------+--------------------------------------

Schema              | pg_catalog

Name                | pg_terminate_backend

Result data type    | boolean

Argument data types | pid integer, timeout bigint DEFAULT 0

Type                | func

I also suggests that the timeout unit should be milliseconds, hence, using

bigint is perfectly fine for the timeout argument.

+       <para>

+        Throws an ERROR if the target <acronym>lsn</acronym> was not replayed

+        on standby within given timeout.  Parameter <parameter>timeout</parameter>

+        is the time in seconds to wait for the <parameter>target_lsn</parameter>

+        replay. When <parameter>timeout</parameter> value equals to zero no

+        timeout is applied.

+       </para></entry>

[1] https://www.postgresql.org/docs/current/functions-admin.html#FUNCTIONS-RECOVERY-CONTROL