Re: PGAgent Connection Pool Leaking

Sure. Dave. I will work on this.

Thanks,
Neel Patel

On Thu, Oct 19, 2017 at 2:25 PM, Dave Page <dpage(at)pgadmin(dot)org> wrote:

> 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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> --
> Dave Page
> Blog: http://pgsnake.blogspot.com
> Twitter: @pgsnake
>
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> The Enterprise PostgreSQL Company
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