From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9AF2DC32792 for ; Mon, 30 Sep 2019 16:07:06 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 70870215EA for ; Mon, 30 Sep 2019 16:07:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 70870215EA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:54538 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iEyCX-0000Vn-44 for qemu-devel@archiver.kernel.org; Mon, 30 Sep 2019 12:07:05 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:38619) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iEy8v-0005yn-Ni for qemu-devel@nongnu.org; Mon, 30 Sep 2019 12:03:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iEy8u-0004kd-KB for qemu-devel@nongnu.org; Mon, 30 Sep 2019 12:03:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54577) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iEy8u-0004kE-EI for qemu-devel@nongnu.org; Mon, 30 Sep 2019 12:03:20 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A2CB320FD; Mon, 30 Sep 2019 16:03:19 +0000 (UTC) Received: from work-vm (ovpn-117-232.ams2.redhat.com [10.36.117.232]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C3F4719C6A; Mon, 30 Sep 2019 16:03:18 +0000 (UTC) Date: Mon, 30 Sep 2019 17:03:16 +0100 From: "Dr. David Alan Gilbert" To: Felipe Franciosi Subject: Re: Thoughts on VM fence infrastructure Message-ID: <20190930160316.GH2759@work-vm> References: <42837590-2563-412B-ADED-57B8A10A8E68@nutanix.com> <20190930142954.GA2801@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.71]); Mon, 30 Sep 2019 16:03:19 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Aditya Ramesh , qemu-devel Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Felipe Franciosi (felipe@nutanix.com) wrote: > Hi David, > > > On Sep 30, 2019, at 3:29 PM, Dr. David Alan Gilbert wrote: > > > > * Felipe Franciosi (felipe@nutanix.com) wrote: > >> Heyall, > >> > >> We have a use case where a host should self-fence (and all VMs should > >> die) if it doesn't hear back from a heartbeat within a certain time > >> period. Lots of ideas were floated around where libvirt could take > >> care of killing VMs or a separate service could do it. The concern > >> with those is that various failures could lead to _those_ services > >> being unavailable and the fencing wouldn't be enforced as it should. > >> > >> Ultimately, it feels like Qemu should be responsible for this > >> heartbeat and exit (or execute a custom callback) on timeout. > > > > It doesn't feel doing it inside qemu would be any safer; something > > outside QEMU can forcibly emit a kill -9 and qemu *will* stop. > > The argument above is that we would have to rely on this external > service being functional. Consider the case where the host is > dysfunctional, with this service perhaps crashed and a corrupt > filesystem preventing it from restarting. The VMs would never die. Yeh that could fail. > It feels like a Qemu timer-driven heartbeat check and calls abort() / > exit() would be more reliable. Thoughts? OK, yes; perhaps using a timer_create and telling it to send a fatal signal is pretty solid; it would take the kernel to do that once it's set. IMHO the safer way is to kick the host off the network by reprogramming switches; so even if the qemu is actually alive it can't get anywhere. Dave > Felipe > > > > >> Does something already exist for this purpose which could be used? > >> Would a generic Qemu-fencing infrastructure be something of interest? > > Dave > > > > > >> Cheers, > >> F. > >> > > -- > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK