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Re: [Qemu-devel] [RFC PATCH v2 00/10] Add colo-proxy based on netfilter


From: Li Zhijian
Subject: Re: [Qemu-devel] [RFC PATCH v2 00/10] Add colo-proxy based on netfilter
Date: Thu, 31 Dec 2015 16:02:20 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0



On 12/31/2015 10:36 AM, Jason Wang wrote:


On 12/22/2015 06:42 PM, Zhang Chen wrote:
From: zhangchen <address@hidden>

Hi,all

This patch add an colo-proxy object, COLO-Proxy is a part of COLO,
based on qemu netfilter and it's a plugin for qemu netfilter. the function
keep Secondary VM connect normal to Primary VM and compare packets
sent by PVM to sent by SVM.if the packet difference,notify COLO do
checkpoint and send all primary packet has queued.

Thanks for the work. I don't object this method but still not convinced
that qemu is the best place for this.

As been raised in the past discussion, it's almost impossible to
cooperate with vhost backends. If we want this to be used in production
environment, need to think of a solution for vhost. There's no such
worry if we decouple this from qemu.

Yes, I agree with you. But not everything is perfect at the beginning.
If we implement proxy as kernel modules, maybe some one will ask how
about the packet(e.g. vhost-user) that host kernel can not touch.

As you said, colo-proxy in qemu will not support vhost scene, but it can make
colo more easier to be used so that more and more pepole will join us to test 
it.
I'm looking forward to that day.

if everything goes fine, I think colo can support vhost scene in other way(such 
as
introduce extra proxy module in kernel) in the feature.

So, I think colo-proxy in qemu is a good choice for current COLO.

Thanks
Li



You can also get the series from:

https://github.com/zhangckid/qemu/tree/colo-v2.2-periodic-mode-with-colo-proxyV2

Usage:

primary:
-netdev tap,id=bn0 -device e1000,netdev=bn0
-object colo-proxy,id=f0,netdev=bn0,queue=all,mode=primary,addr=host:port

secondary:
-netdev tap,id=bn0 -device e1000,netdev=bn0
-object colo-proxy,id=f0,netdev=bn0,queue=all,mode=secondary,addr=host:port

Have a quick glance at how secondary mode work. What it does is just
forwarding packets between a nic and a socket, qemu socket backend did
exact the same job. You could even use socket in primary node and let
packet compare module talk to both primary and secondary node.


NOTE:
queue must set "all". See enum NetFilterDirection for detail.
colo-proxy need queue all packets
colo-proxy V2 just can compare ip packet


## 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.

V2:
   rebase colo-proxy with qemu-colo-v2.2-periodic-mode
   fix dave's comments
   fix wency's comments
   fix zhanghailiang's comments

v1:
   initial patch.



zhangchen (10):
   Init colo-proxy object based on netfilter
   Jhash: add linux kernel jhashtable in qemu
   Colo-proxy: add colo-proxy framework
   Colo-proxy: add data structure and jhash func
   net/colo-proxy: Add colo interface to use proxy
   net/colo-proxy: add socket used by forward func
   net/colo-proxy: Add packet enqueue & handle func
   net/colo-proxy: Handle packet and connection
   net/colo-proxy: Compare pri pkt to sec pkt
   net/colo-proxy: Colo-proxy do checkpoint and clear

  include/qemu/jhash.h |  61 ++++
  net/Makefile.objs    |   1 +
  net/colo-proxy.c     | 939 +++++++++++++++++++++++++++++++++++++++++++++++++++
  net/colo-proxy.h     |  24 ++
  qemu-options.hx      |   6 +
  trace-events         |   8 +
  vl.c                 |   3 +-
  7 files changed, 1041 insertions(+), 1 deletion(-)
  create mode 100644 include/qemu/jhash.h
  create mode 100644 net/colo-proxy.c
  create mode 100644 net/colo-proxy.h





.


--
Best regards.
Li Zhijian (8555)





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