[Openstack-operators] memcached redundancy

Abel Lopez alopgeek at gmail.com
Thu Aug 14 16:23:57 UTC 2014

I played with this in the lab for a little bit, it didn’t seem to be a huge deal.
My setup was three ‘controller’ nodes each running Multi-master Percona DB, rabbit-ha cluster, and memcached. Killing DB, no worries as it’s behind LB, killing rabbit? Usually not a problem especially after 3.2.x. Memcached? I noticed a brief period of invalid tokens, but within a few seconds, everything goes back to normal. I think the client software has a built-in retry when auth fails, or at least that was the observation. This was on Havana 1

On Aug 14, 2014, at 9:09 AM, Joe Topjian <joe at topjian.net> wrote:

> Hello,
> I have an OpenStack cloud with two HA cloud controllers. Each controller runs the standard controller components: glance, keystone, nova minus compute and network, cinder, horizon, mysql, rabbitmq, and memcached.
> Everything except memcached is accessed through haproxy and everything is working great (well, rabbit can be finicky ... I might post about that if it continues).
> The problem I currently have is how to effectively work with memcached in this environment. Since all components are load balanced, they need access to the same memcached servers. That's solved by the ability to specify multiple memcached servers in the various openstack config files.
> But if I take a server down for maintenance, I notice a 2-3 second delay in all requests. I've confirmed it's memcached by editing the list of memcached servers in the config files and the delay goes away.
> I'm wondering how people deploy memcached in environments like this? Are you using some type of memcached replication between servers? Or if a memcached server goes offline are you reconfiguring OpenStack to remove the offline memcached server?
> Thanks,
> Joe
> _______________________________________________
> OpenStack-operators mailing list
> OpenStack-operators at lists.openstack.org
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