Horton

Re: PQcancel does not use tcp_user_timeout, connect_timeout and keepalive settings

Zhihong Yu <zyu@yugabyte.com>

View thread View on postgr.es
From: Zhihong Yu <zyu@yugabyte.com>
To: Jelte Fennema <Jelte.Fennema@microsoft.com>
Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2021-09-30T14:52:22Z
Lists: pgsql-hackers 
On Thu, Sep 30, 2021 at 7:45 AM Jelte Fennema <Jelte.Fennema@microsoft.com>
wrote:

> The new connection made by PQcancel does not use the tcp_user_timeout,
> connect_timeout or any of the keepalive settings that are provided in the
> connection string. This means that a call to PQcancel can block for a much
> longer time than intended if there are network issues. This can be
> especially impactful, because PQcancel is a blocking function an there is
> no non blocking version of it.
>
> I attached a proposed patch to use the tcp_user_timeout from the
> connection string when connecting to Postgres in PQcancel. This resolves
> the issue for me, since this will make connecting timeout after a
> configurable time. So the other options are not strictly needed. It might
> still be nice for completeness to support them too though. I didn't do this
> yet, because I first wanted some feedback and also because implementing
> connect_timeout would require using non blocking TCP to connect and then
> use select to have a timeout.


Hi,

    int         be_key;         /* key of backend --- needed for cancels */
+   int         pgtcp_user_timeout; /* tcp user timeout */

The other field names are quite short. How about naming the field
tcp_timeout ?

Cheers

Commits

  1. Make PQcancel use the PGconn's tcp_user_timeout and keepalives settings.

  2. Avoid calling gettext() in signal handlers.

  3. Avoid calling strerror[_r] in PQcancel().