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

[Zhang Chen]

On 01/04/2016 01:37 PM, Jason Wang wrote:
> On 12/31/2015 04:40 PM, Zhang Chen wrote:
> > 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.
> > >
> > > > 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.
> > If we use qemu socket backend , the same netdev will used by qemu
> > socket and
> > qemu netfilter. this will against qemu net design. and then, when colo
> > do failover,
> > secondary do not have backend to use. that's the real problem.
> Then, maybe it's time to implement changing the netdev of a nic. The
> point here is that what secondary mode did is in fact a netdev backend
> instead of a filter ...

Currently, you are right. in colo-proxy V2 code, I just compare IP packet to
decide whether to do checkpoint.
But, in colo-proxy V3 I will compare tcp,icmp,udp packet to decide it.
because that can reduce frequency of checkpoint and improve
performance. To keep tcp connection well, colo secondary need to record
primary guest's init seq and adjust secondary guest's ack. if colo do 
failover,
secondary also need do this to old tcp connection. qemu socket
can't do this job. and another problem is do failover, if we use qemu socket
to be backend in secondary, when colo do failover, I don't know how to 
change
secondary be a normal qemu, if you know, please tell me.


Thanks for your revew
zhangchen

> > Thanks
> > zhangchen
> >
> > > > 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
> > >
> > > .
>
>
>
> .

--
Thanks
zhangchen