Open Stack

On Mon, 2014-01-06 at 10:10 -0500, Adam Young wrote:
> 
> 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.

Instead of doing replication of memcache, instead just tell your
loadbalancer to have sticky sessions, and have each keystone server have
its own dedicated memcache instance.

-jay