Re: Optional message to user when terminating/cancelling backend

David G. Johnston <david.g.johnston@gmail.com>

From: "David G. Johnston" <david.g.johnston@gmail.com>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Satyanarayana Narlapuram <Satyanarayana.Narlapuram@microsoft.com>, Pavel Stehule <pavel.stehule@gmail.com>, Daniel Gustafsson <daniel@yesql.se>, PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
Date: 2017-06-20T19:43:39Z
Lists: pgsql-hackers
On Tue, Jun 20, 2017 at 11:54 AM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> Satyanarayana Narlapuram wrote:

> Unless you have a lot of users running psql manually, I don't see how
> this is actually very useful or actionable.  What would the user do with
> the information?  Hopefully your users already trust that you'd keep the
> downtime to the minimum possible.
>

Why wouldn't this be useful in application logs?  Spurious dropped
connections during application execution would be alarming.  Seeing a
message from the DBA when looking into those would be a painless and
quick way to alleviate stress.

pg_cancel_backend(<pid>, 'please try not to leave sessions in an "idle
in transaction" state...') would also seem like a useful message to
communicate; to user or application.  Sure, some of this can, and
maybe would also need to, be done out-of-band but this communication
channel seems worthy enough to at least evaluate the provided
implementation.

David J.


Commits

  1. Refactor user-facing SQL functions signalling backends

  2. Introduce 64-bit hash functions with a 64-bit seed.