Open Stack

On Nov 12, 2012, at 1:12 PM, Vishvananda Ishaya <vishvananda at gmail.com> wrote:

> And fwiw I think the plan of starting small with db writes and building up us the right one. But I wonder about the requirement of a new service. For cleanliness I like separating into a new service but for ease of deployment it seems far easier to make this a part of nova-scheduler.
> 

If it's something that is modularized well enough to make it optional to run as a separate service, I think this makes sense for (the more common case of) smaller deployments, and have nova-scheduler be the default.

As a side note, we really need to get DB writes non-blocking again, preferably ahead of any changes to move DB updates over to a single service.  As it stands, moving the DB updates to a single service is going to completely serialize all DB calls that are currently distributed across many nova-computes.  I can attest to there being a huge performance issue when doing this, as nova-cells at the global level essentially has this functionality.  It's largely a DB writer… and at Rackspace scale, it's doing quite a bit of writes.  Because there's so many DB calls going on, it tends to affect its ability to simply route messages.  The DB calls blocking steal a lot of time where other work can be happening.  So, if you're going to move this to the scheduler, that's something to consider, also.

- Chris




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