Re: Detect streaming replication failure

you can run select * from pg_stat_replication on master to check all the
salve stats.

On Fri, Jul 18, 2014 at 6:50 AM, Lists <lists(at)benjamindsmith(dot)com> wrote:

> For reference:
> https://wiki.postgresql.org/wiki/Streaming_Replication
>
> Assume a master -> slave streaming replication configuration, Postgresql
> 9.2.
> Assume that the master has been chugging away, but the slave PG service
> has been offline
> for a while and the wal archive has updated enough that the slave cannot
> catch up.
>
> When I start the slave PG instance, pg launches and "runs" but doesn't
> update. It also doesn't seem to throw any errors. The only outward sign
> that I can see that anything is wrong is that
> pg_last_xlog_replay_location() doesn't update. I can look in
> /var/lib/pgsql/9.2/data/pg_log/postgresql-Thu.csv and see errors there EG:
>
> 2014-07-17 22:38:23.851 UTC,,,21310,,53c8505f.533e,2,,2014-07-17 22:38:23
> UTC,,0,FATAL,XX000,"could not receive data from WAL stream: FATAL:
> requested WAL segment 000000070000000500000071 has already been removed
>
> Is that the only way to detect this condition? I guess I'm looking for
> something like
>
> select * from pg_is_replicating_ok();
> 1
>
> on the slave. At the moment, it appears that I can either parse the log
> file, or look for pg_last_xact_replay_timestamp() > acceptable threshold
> minutes in the past.
>
> http://www.postgresql.org/docs/9.2/static/functions-admin.html
>
> Thanks,
>
> Ben
>
>
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