Re: PGAgent Connection Pool Leaking

Neel, can you assist with this please?

On Thu, Oct 19, 2017 at 9:51 AM, Rob Emery <re-pgsql(at)codeweavers(dot)net> wrote:

> Hiya,
>
> We run postgresql-9.5 (9.5.5-1.pgdg80+1) on debian jessie (using the
> postgres apt repo) with replication between two servers. We have pgagent
> running on both the master and the slave using:
> /usr/bin/pgagent -f host=pgserver dbname=postgres user=username
> password=password -l 2 -s /home/robertemery/test/pgagent.log
> where pgserver is a CNAME that we use to direct traffic to the current
> master.
>
> We are finding that over-time, the pgagent user ends up with hundreds of
> connections into the postgresql cluster from both pgagents. If we kill and
> restart the pgagent process, it returns to 1.
>
> When we run a job the number of connections goes from 1 -> 3 then back to
> 1 again; however this morning (for example) one of the servers has ended up
> with 2 connections for the pgagent user:
>
> SELECT * FROM pg_stat_activity WHERE usename LIKE '%pgagent%'; looks like
> :
>
> 12379;"postgres";14853;22872466;"pgagent_login_role";
> "";"192.168.1.1";"";58223;"2017-10-18 08:20:29.481096+01";"";"2017-10-19
> 09:16:25.656794+01";"2017-10-19 09:16:25.657219+01";f;"idle";;;"SELECT
> J.jobid FROM pgagent.pga_job J WHERE jobenabled AND jobagentid IS
> NULL AND jobnextrun <= now() AND (jobhostagent = '' OR jobhostagent =
> 'pgsqla02') ORDER BY jobnextrun"
> 12379;"postgres";10184;22872466;"pgagent_login_role";
> "";"192.168.1.2";"";34501;"2017-10-18 15:20:53.282212+01";"";"2017-10-19
> 09:16:29.061761+01";"2017-10-19 09:16:29.062225+01";f;"idle";;;"SELECT
> J.jobid FROM pgagent.pga_job J WHERE jobenabled AND jobagentid IS
> NULL AND jobnextrun <= now() AND (jobhostagent = '' OR jobhostagent =
> 'pgsqla01') ORDER BY jobnextrun"
> 12379;"postgres";13060;22872466;"pgagent_login_role";
> "";"192.168.1.2";"";34518;"2017-10-19 07:20:02.680711+01";"";"2017-10-19
> 07:20:02.70995+01";"2017-10-19 07:20:02.723907+01";f;"idle";;;"UPDATE
> pgagent.pga_job SET jobagentid=10184, joblastrun=now() WHERE jobagentid IS
> NULL AND jobid=2"
>
> It looks like the UPDATE statement is the new connection that's leaking.
>
> Looking at the pgagent log for 07:20 (we have a job that runs at 07:10,
> 07:20, 07:30, 07:40) I can see:
>
> Thu Oct 19 07:19:57 2017 : DEBUG: Clearing inactive connections
> Thu Oct 19 07:19:57 2017 : DEBUG: Connection stats: total - 1, free - 0,
> deleted - 0
> Thu Oct 19 07:19:57 2017 : DEBUG: Checking for jobs to run
> Thu Oct 19 07:19:57 2017 : DEBUG: Sleeping...
> Thu Oct 19 07:20:02 2017 : DEBUG: Clearing inactive connections
> Thu Oct 19 07:20:02 2017 : DEBUG: Connection stats: total - 1, free - 0,
> deleted - 0
> Thu Oct 19 07:20:02 2017 : DEBUG: Checking for jobs to run
> Thu Oct 19 07:20:02 2017 : DEBUG: Creating job thread for job 2
> Thu Oct 19 07:20:02 2017 : DEBUG: Creating DB connection:
> user=pgagent_login_role host=pgserver password=password dbname=postgres
> Thu Oct 19 07:20:02 2017 : DEBUG: Allocating new connection to database
> postgres
> Thu Oct 19 07:20:02 2017 : DEBUG: Starting job: 2
> Thu Oct 19 07:20:02 2017 : DEBUG: Destroying job thread for job 2
> Thu Oct 19 07:20:02 2017 : DEBUG: Sleeping...
> Thu Oct 19 07:20:07 2017 : DEBUG: Clearing inactive connections
> Thu Oct 19 07:20:07 2017 : DEBUG: Connection stats: total - 2, free - 0,
> deleted - 0
> Thu Oct 19 07:20:07 2017 : DEBUG: Checking for jobs to run
> Thu Oct 19 07:20:07 2017 : DEBUG: Sleeping...
>
> which looks like it allocates a connection but never gives it up again.
> From this point on DEBUG: Connection stats: total - 2, free - 0, deleted -
> 0 always shows 2.
>
> Looking at the run at 07:10 it looks different:
>
> Thu Oct 19 07:09:55 2017 : DEBUG: Clearing inactive connections
> Thu Oct 19 07:09:55 2017 : DEBUG: Connection stats: total - 1, free - 0,
> deleted - 0
> Thu Oct 19 07:09:55 2017 : DEBUG: Checking for jobs to run
> Thu Oct 19 07:09:55 2017 : DEBUG: Sleeping...
> Thu Oct 19 07:10:00 2017 : DEBUG: Clearing inactive connections
> Thu Oct 19 07:10:00 2017 : DEBUG: Connection stats: total - 1, free - 0,
> deleted - 0
> Thu Oct 19 07:10:00 2017 : DEBUG: Checking for jobs to run
> Thu Oct 19 07:10:00 2017 : DEBUG: Creating job thread for job 2
> Thu Oct 19 07:10:01 2017 : DEBUG: Creating DB connection:
> user=pgagent_login_role host=pgserver password=password dbname=postgres
> Thu Oct 19 07:10:01 2017 : DEBUG: Allocating new connection to database
> postgres
> Thu Oct 19 07:10:01 2017 : DEBUG: Starting job: 2
> Thu Oct 19 07:10:01 2017 : DEBUG: Sleeping...
> Thu Oct 19 07:10:01 2017 : DEBUG: Creating DB connection:
> user=pgagent_login_role host=pgserver password=password dbname=postgres
> dbname=ourdatabasename
> Thu Oct 19 07:10:01 2017 : DEBUG: Allocating new connection to database
> ourdatabasename
> Thu Oct 19 07:10:01 2017 : DEBUG: Executing SQL step 3 (part of job 2)
> Thu Oct 19 07:10:01 2017 : DEBUG: Returning connection to database
> ourdatabasename
> Thu Oct 19 07:10:01 2017 : DEBUG: Returning connection to database postgres
> Thu Oct 19 07:10:01 2017 : DEBUG: Completed job: 2
> Thu Oct 19 07:10:01 2017 : DEBUG: Destroying job thread for job 2
> Thu Oct 19 07:10:06 2017 : DEBUG: Checking for jobs to run
> Thu Oct 19 07:10:06 2017 : DEBUG: Sleeping...
>
>
> I'm at a bit of a loss to debug this further now, it looks like a bug in
> the connection pooling to me?
>
> Many Thanks,
> Rob
>
> --
> Robert Emery
>
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