Horton

Re: On login trigger: take three

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Greg Nancarrow <gregn4422@gmail.com>
Cc: Daniel Gustafsson <daniel@yesql.se>, Ivan Panchenko <wao@mail.ru>, Teodor Sigaev <teodor@sigaev.ru>, Ibrar Ahmed <ibrar.ahmad@gmail.com>, vignesh C <vignesh21@gmail.com>, Pavel Stehule <pavel.stehule@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Amit Kapila <amit.kapila16@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>
Date: 2022-03-11T21:10:36Z
Lists: pgsql-hackers 
On Tue, Feb 15, 2022 at 5:07 AM Greg Nancarrow <gregn4422@gmail.com> wrote:
> I've attached a re-based version (no functional changes from the
> previous) to fix cfbot failures.

I tried this:

rhaas=# create function on_login_proc() returns event_trigger as
$$begin perform pg_sleep(10000000); end$$ language plpgsql;
CREATE FUNCTION
rhaas=# create event trigger on_login_trigger on login execute
procedure on_login_proc();

When I then attempt to connect via psql, it hangs, as expected. When I
press ^C, psql exits, but the backend process is not cancelled and
just keeps chugging along in the background. The good news is that if
I connect to another database, I can cancel all of the hung sessions
using pg_cancel_backend(), and all of those processes then promptly
exit, and presumably I could accomplish the same thing by sending them
SIGINT directly. But it's still not great behavior. It would be easy
to use up a pile of connection slots inadvertently and have to go to
some trouble to get access to the server again. Since this is a psql
behavior and not a server behavior, one could argue that it's
unrelated to this patch, but in practice this patch seems to increase
the chances of people running into problems quite a lot.

-- 
Robert Haas
EDB: http://www.enterprisedb.com

Commits

  1. Fix some typos in event trigger docs

  2. Use heap_inplace_update() to unset pg_database.dathasloginevt

  3. Remove the flaky check in event_trigger_login regression test

  4. Fix instable 006_login_trigger.pl test

  5. Add support event triggers on authenticated login

  6. Add GUC for temporarily disabling event triggers

  7. Fix typo in reference to __FreeBSD__.

  8. Restore robustness of TAP tests that wait for postmaster restart.

  9. Restore the portal-level snapshot after procedure COMMIT/ROLLBACK.