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

[Jason Wang]

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.

>
> 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
>