[pgpool-general: 3971] Re: How does one terminate/cancel queries via PGPool safely?

[Pablo Sanchez]

[ Comments below, in-line ]


On 08/14/2015 10:51 PM, Tatsuo Ishii wrote:
>> The PGPool manual has a dire warning about not using
>> >pg_terminate_backend().
>> >
>> >http://www.pgpool.net/docs/latest/pgpool-en.html#restriction
>> >
>> >Under "Functionality of PostgreSQL" it states:
>> >
>> >    If you use pg_terminate_backend() to stop a backend, this will
>> >    trigger a failover.
> This is still correct. PostgreSQL returns the same error code when
> PostgreSQL is shutting down.

Hi Tatsuo,

This morning we had an issue this morning where a query needed to be
killed.

I tried to _cancel() it via PGPool and the connection did not die.

Next, I went to the DB Server and issued a _terminate().  This caused
PGPool to degenerate.  Is this expected?

I think the answer is yes.

That is, for any connection which is initiated via PGPool, you cannot
issue a pg_terminate_backend() to kill a connection.  Either from
PGPool or psql.

If the above is true, I suggest we update the documentation to not the
above.

My next test, either in Production (yikes!) or in my sandbox is to try
and issue a signal from the DB server to emulate the _cancel.

Cheers,
--
Pablo Sanchez - Blueoak Database Engineering, Inc
Ph:    819.459.1926         Blog:  http://pablo-blog.blueoakdb.com
iNum:  883.5100.0990.1054