From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:49723)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <jasowang@redhat.com>) id 1ZKfNg-00078u-Nt
	for qemu-devel@nongnu.org; Thu, 30 Jul 2015 00:23:46 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <jasowang@redhat.com>) id 1ZKfNd-0002AD-GH
	for qemu-devel@nongnu.org; Thu, 30 Jul 2015 00:23:44 -0400
Received: from mx1.redhat.com ([209.132.183.28]:55557)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <jasowang@redhat.com>) id 1ZKfNd-000285-AB
	for qemu-devel@nongnu.org; Thu, 30 Jul 2015 00:23:41 -0400
Message-ID: <55B9A6C6.6010008@redhat.com>
Date: Thu, 30 Jul 2015 12:23:34 +0800
From: Jason Wang <jasowang@redhat.com>
MIME-Version: 1.0
References: <55AC9859.3050100@cn.fujitsu.com>
In-Reply-To: <55AC9859.3050100@cn.fujitsu.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [POC] colo-proxy in qemu
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Li Zhijian <lizhijian@cn.fujitsu.com>, qemu-devel@nongnu.org, stefanha@redhat.com
Cc: zhanghailiang <zhang.zhanghailiang@huawei.com>, jan.kiszka@siemens.com, dgilbert@redhat.com, "peter.huangpeng" <peter.huangpeng@huawei.com>, "Gonglei (Arei)" <arei.gonglei@huawei.com>, Yang Hongyang <yanghy@cn.fujitsu.com>



On 07/20/2015 02:42 PM, Li Zhijian wrote:
> Hi, all
>
> We are planning to implement colo-proxy in qemu to cache and compare
> packets.
> This module is one of the important component of COLO project and now
> it is
> still in early stage, so any comments and feedback are warmly welcomed,
> thanks in advance.
>
> ## Background
> COLO FT/HA (COarse-grain LOck-stepping Virtual Machines for Non-stop
> Service)
> project is a high availability solution. Both Primary VM (PVM) and
> Secondary VM
> (SVM) run in parallel. They receive the same request from client, and
> generate
> responses in parallel too. If the response packets from PVM and SVM are
> identical, they are released immediately. Otherwise, a VM checkpoint
> (on demand)
> is conducted.
> Paper:
> http://www.socc2013.org/home/program/a3-dong.pdf?attredirects=0
> COLO on Xen:
> http://wiki.xen.org/wiki/COLO_-_Coarse_Grain_Lock_Stepping
> COLO on Qemu/KVM:
> http://wiki.qemu.org/Features/COLO
>
> By the needs of capturing response packets from PVM and SVM and
> finding out
> whether they are identical, we introduce a new module to qemu
> networking called
> colo-proxy.

A question here, the packet comparing may be very tricky. For example,
some protocol use random data to generate unpredictable id or something
else. One example is ipv6_select_ident() in Linux. So COLO needs a
mechanism to make sure PVM and SVM can generate same random data?