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Hello,
On 2012-08-24 17:14, David Coulson wrote:
>
> On 8/24/12 8:53 AM, Dmitry Akindinov wrote:
>>
>> So, again, routing is fine, the traffic does go as it should (to the
>> new balancer and then to the old one, as a part of the "real server
>> pool" or "farm"). The problem is that ipvs software on the "old"
>> balancer drops some of the packets when it is running the sync daemon.
>> As soon as the sync daemon is stopped, the problem disappears.
> Sorry, I totally missed that your IPVS boxes are also your 'real'
> servers - I had an issue like that a while ago. Basically as far as I
> can tell, if there is a connection in the sync table, the kernel will
> use it even if you don't have ipvs rules entered, or even if you are
> using fwm and you don't have an applicable iptables rule.
>
> Someone who knows the internals of ipvs better can probably get more
> specific, but I was unable to find a workaround for it that did not
> involve disabling the sync daemon.
>
> On my end, I either changed my scheduler to SH and stopped using the
> sync daemon, or separated the ipvs and real servers into separate
> systems to avoid the issue altogether.
We are trying to make ipvs balancing a part of our product and would
rather avoid requiring additional nodes for our cluster.
Actually, there is one more observation:
as soon as the a first "troubled" connection is established, the Linux
kernel thread ksoftirqd starts to consume 100% of CPU, and as new
connections come in, more ksoftirqd threads appear in the "top" output,
all looping somewhere - 100% CPU utlization, till all 8 CPUs on that
server are consumed by them.
It looks like a real bug in the ipvs software - we hav most probably to
move this discussion to the lvs-devel list...
--
Best regards,
Dmitry Akindinov
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