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Re: Nova and asynchronous instance launching

 

On 06/29/2012 04:25 AM, Huang Zhiteng wrote:
Sound like a performance issue.  I think this symptom can be much
eased if we spend sometime fixing whatever bottleneck causing this
(slow AMQP, scheduler, or network)?  Now that Nova API has got
multprocess enabled, we'd move to next bottleneck in long path of
'launching instance'.
Devin, is it possible that you provide more details about this issue
so that someone else can reproduce it?

Actually, Vish, David Kranz and I had a discussion about similar stuff on IRC yesterday. I think that an easy win for this would be to add much more fine-grained DEBUG logging statements in the various nova service pieces -- nova-compute, nova-network, etc. Right now, there are areas that seem to look like performance or locking culprits (iptables save/restore for example), but because there isn't very fine-grained logging statements, it's tough to say whether:

a) A process (or greenthread) has simply yielded to another while it waits for something

b) A process is doing something that is blocking

or

c) A process is doing some other work but no log statements are being logged about that work, which makes it seem like some other work is taking much longer than it really is

This would be a really easy win for a beginner developer or someone looking for something to assist with -- simply add informative LOG.debug() statements at various points in the API call pipelines

Best,
-jay


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