[pgpool-hackers: 3316] Re: Adding new columns to show pool_status

Tatsuo Ishii ishii at sraoss.co.jp
Fri Apr 19 11:59:48 JST 2019

> Hi,
> I would like to add new columns to existing "show pool_status" command
> toward 4.1. New columns will be brought by calling pg_stat_replication
> view. From the PostgreSQL docs of pg_stat_replication:
> state: Current WAL sender state. Possible values are:
>     startup: This WAL sender is starting up.
>     catchup: This WAL sender's connected standby is catching up with the primary.
>     streaming: This WAL sender is streaming changes after its
>     	       connected standby server has caught up with the primary.
>     backup: This WAL sender is sending a backup.
>     stopping: This WAL sender is stopping.
> sync_state: Synchronous state of this standby server. Possible values are:
>     async: This standby server is asynchronous.
>     potential: This standby server is now asynchronous, but can
>     	       potentially become synchronous if one of current synchronous ones fails.
>     sync: This standby server is synchronous.
>     quorum: This standby server is considered as a candidate for quorum standbys. 
> These should be useful information for streaming replication users. Of
> course users could call pg_stat_replication as usual but I think
> showing them in "show pool_status" is handy for users so that they
> could grasp overview status of the cluster managed by Pgpool-II.
> To implement this, I will add new members to BackendInfo struct
> sitting on the shared memory. Existing replication delay collecting
> process will be in charge of calling the view.

Please note that those two columns are only available in PostgreSQL
9.2 or later. So we need to check PostgreSQL version.

Best regards,
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php

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