Open Stack

On 01/03/2014 11:38 PM, Xu (Simon) Chen wrote:
> Hi folks,
>
> I am having trouble with using memcache as the keystone token backend. 
> I have three keystone nodes running active/active. Each is running 
> keystone on apache (for kerberos auth). I recently switched from using 
> sql backend to memcache, while have memcached running on all three of 
> the keystone nodes.

This triggers a memory of htere being something wonky with 
Greenthreads,  the threading override in Eventlet, and Memcached. But 
you said Apache, so I think that you are not running with greenthreads?

There are numerous things out there about apache and memcached 
performance.  For example, one article talks about filling up 
partitions, etc.


>
> This setup would run well for a while, but then apache would start to 
> hog CPUs, and memcached would increase to 30% or so. I tried to 
> increase memcached cluster from 3 to 6 nodes, but in general the 
> performance is much worse compared to sql backend.
Probably due to the need for replication.  In order to keep it anywhere 
close to in sync,  it is going to require some non-trivial subset of 
fully connectedness.



>
> Any ideas?
>
> Thanks.
> -Simon
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