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?
