Open Stack

On Oct 30, 2013, at 11:11 AM, Alex Glikson <GLIKSON at il.ibm.com> wrote:

> There is a ZK-backed driver in Nova service heartbeat mechanism (https://blueprints.launchpad.net/nova/+spec/zk-service-heartbeat) -- would be interesting to know whether it is widely used (might be worth asking at the general ML, or user groups). There have been also discussions on using it for other purposes (some listed towards the bottom at https://wiki.openstack.org/wiki/NovaZooKeeperHeartbeat). While I am not aware of any particular progress with implementing any of them, I think they still make sense and could be useful. 
> 
> Regards, 
> Alex 

Zookeeper is very useful, and we already deploy it on our clusters here at Y!.  But we only use it for leader election of nova scheduler and network processes, not for service groups yet.  I've been meaning to try it for service groups, though, because I see the service group database queries eating a lot of time in the scheduler process on large (hundreds of nodes) clusters.  Presumably the ZK driver would be cheaper, and would hopefully also not leave such a long window before it notices a node is down.  Just haven't gotten around to it yet.

I have yet to see any other mature open source distributed coordination service.  Yahoo has run zookeeper in production for ages now, since long before we started using openstack.

For yahoo, python is the new language that we're not sure is good for production.  Each process effectively constrained to a single CPU, no good static checker, so many random little libraries.  Obviously we're using it, but it's new to us.  But Java?  It must be the number one or maybe number two language for production code the world over right now.


Cheers,
Tim