Re: Optional message to user when terminating/cancelling backend

From: Daniel Gustafsson <daniel(at)yesql(dot)se>
To: Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
Cc: PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Optional message to user when terminating/cancelling backend
Date: 2017-06-22 13:48:27
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> On 22 Jun 2017, at 10:24, Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp> wrote:
> On Thu, 22 Jun 2017 09:24:54 +0900
> Michael Paquier <michael(dot)paquier(at)gmail(dot)com> wrote:
>> On Wed, Jun 21, 2017 at 11:42 PM, Daniel Gustafsson <daniel(at)yesql(dot)se> wrote:
>>> The message is truncated in SetBackendCancelMessage() for safety, but
>>> pg_{cancel|terminate}_backend() could throw an error on too long message, or
>>> warning truncation, to the caller as well. Personally I think a warning is the
>>> appropriate response, but I don’t really have a strong opinion.
>> And a NOTICE? That's what happens for relation name truncation. You
>> are right that having a check in SetBackendCancelMessage() makes the
>> most sense as bgworkers could just call the low level API. Isn't the
>> concept actually closer to just a backend message? This slot could be
>> used for other purposes than cancellation.
> +1 for NOTICE. The message truncation seems to be a kind of helpful
> information rather than a likely problem as long as pg_terminated_backend
> exits successfully.

Good point. I’ve attached a new version which issues a NOTICE on truncation
and also addresses all other comments so far in this thread. Thanks a lot for
the early patch reviews!

cheers ./daniel

Attachment Content-Type Size
terminate_msg_v3.patch application/octet-stream 17.2 KB

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