[Openstack-operators] memcached redundancy

Joe Topjian joe at topjian.net
Thu Aug 14 19:38:13 UTC 2014

Thanks all for the input! Aggregating all replies:

Juan: I've seen that patch and was curious about it. When you say it worked
for you, have you used it in OpenStack for similar reasons?

Daneyon: ah - sticky sessions are a good idea. I will look into that.

John: Another component is a very good possibility. I'll try this out in a
dev environment or if we have planned maintenance where I can try this
prior to the maintenance window. Thank you for the insight on what the
memcached client should be doing.


On Thu, Aug 14, 2014 at 1:22 PM, Juan José Pavlik Salles <jjpavlik at gmail.com
> wrote:

> It might not be the best idea ever, but it worked for me. There's a
> memcached patch called repcached that allows you to have 2 memcached
> servers sincronized (as far as I now, it just works for 2 servers) with
> each other, this way you get HA and LB. The patch source is
> https://github.com/usecide/repcached/blob/master/repcached-2.3.1-1.4.13.patch and
> here you've got a little example
> http://viviendolared.blogspot.com.ar/2014/01/memcached-replicado-en-ubuntu-1204-lts.html running
> on Ubuntu 12.04 (sorry about the spanish link, but the steps are pretty
> straight forward).
> 2014-08-14 16:05 GMT-03:00 Daneyon Hansen (danehans) <danehans at cisco.com>:
>>  It has been a while, but I believe I load-balanced memcached using
>> HAProxy (using sticky sessions) and observed no issues with fail-over.
>>  Regards,
>> Daneyon Hansen
>> Software Engineer
>> Email: danehans at cisco.com
>> Phone: 303-718-0400
>> http://about.me/daneyon_hansen
>>   From: Joe Topjian <joe at topjian.net>
>> Date: Thursday, August 14, 2014 10:09 AM
>> To: "openstack-operators at lists.openstack.org" <
>> openstack-operators at lists.openstack.org>
>> Subject: [Openstack-operators] memcached redundancy
>>   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
>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators
> --
> Pavlik Salles Juan José
> Blog - http://viviendolared.blogspot.com
> _______________________________________________
> OpenStack-operators mailing list
> OpenStack-operators at lists.openstack.org
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