From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ludovic =?UTF-8?Q?Court=C3=A8s?= <ludo@gnu.org>
Subject: bug#34033: Offloading sometimes hangs
Date: Mon, 14 Jan 2019 23:45:56 +0100
Message-ID: <87fttuq2mz.fsf@gnu.org>
References: <87o98obikk.fsf@gnu.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Return-path: <bug-guix-bounces+gcggb-bug-guix=m.gmane.org@gnu.org>
Received: from eggs.gnu.org ([209.51.188.92]:33614)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <Debian-debbugs@debbugs.gnu.org>) id 1gjB0a-0001n3-8G
	for bug-guix@gnu.org; Mon, 14 Jan 2019 17:47:04 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <Debian-debbugs@debbugs.gnu.org>) id 1gjB0Y-0005IO-CX
	for bug-guix@gnu.org; Mon, 14 Jan 2019 17:47:04 -0500
Received: from debbugs.gnu.org ([209.51.188.43]:60145)
	by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16)
	(Exim 4.71) (envelope-from <Debian-debbugs@debbugs.gnu.org>)
	id 1gjB0Y-0005Hv-7q
	for bug-guix@gnu.org; Mon, 14 Jan 2019 17:47:02 -0500
Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2)
	(envelope-from <Debian-debbugs@debbugs.gnu.org>) id 1gjB0X-0002gc-Rc
	for bug-guix@gnu.org; Mon, 14 Jan 2019 17:47:01 -0500
Sender: "Debbugs-submit" <debbugs-submit-bounces@debbugs.gnu.org>
Resent-Message-ID: <handler.34033.B34033.154750596110221@debbugs.gnu.org>
In-Reply-To: <87o98obikk.fsf@gnu.org> ("Ludovic
	\=\?utf-8\?Q\?Court\=C3\=A8s\=22'\?\=
	\=\?utf-8\?Q\?s\?\= message of "Thu, 10 Jan 2019 17:09:31 +0100")
List-Id: Bug reports for GNU Guix <bug-guix.gnu.org>
List-Unsubscribe: <https://lists.gnu.org/mailman/options/bug-guix>,
	<mailto:bug-guix-request@gnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/archive/html/bug-guix/>
List-Post: <mailto:bug-guix@gnu.org>
List-Help: <mailto:bug-guix-request@gnu.org?subject=help>
List-Subscribe: <https://lists.gnu.org/mailman/listinfo/bug-guix>,
	<mailto:bug-guix-request@gnu.org?subject=subscribe>
Errors-To: bug-guix-bounces+gcggb-bug-guix=m.gmane.org@gnu.org
Sender: "bug-Guix" <bug-guix-bounces+gcggb-bug-guix=m.gmane.org@gnu.org>
To: 34033@debbugs.gnu.org

Hello,

Ludovic Court=C3=A8s <ludo@gnu.org> skribis:

> A simple thing would be to somehow get libssh to pass POLLIN | POLLRDHUP
> instead of just POLLIN.

Reported here:

  https://www.libssh.org/archive/libssh/2019-01/0000000.html

A fix has been proposed by upstream and should be committed shortly.

> Additionally, we could change Guile-SSH so that we can specify a timeout
> when reading from a channel.

Turns out we can set a per-session timeout, which we already do (see
#:timeout in =E2=80=98open-ssh-session=E2=80=99 in (guix scripts offload)) =
but
=E2=80=98ssh_channel_read=E2=80=99 would ignore it and instead pass an infi=
nite timeout
to poll(2):

  https://www.libssh.org/archive/libssh/2019-01/0000001.html

This issue happens to be fixed in libssh 0.8.x, so I upgraded our libssh
package in commit a8b0556ea1e439c89dc1ba33c8864e8b9b811f08.

(That still doesn=E2=80=99t tell us why our =E2=80=98guix offload=E2=80=99 =
processes would
occasionally be stuck but at least it ensures the build farm keeps
making progress even when that happens.)

Ludo=E2=80=99.