Open Stack

Hi Matt,

This is awesome feedback and it's great for the user committee to know. I think it would be even more appropriate and definitely get more discussion if you sent this, as is, to the openstack-dev mailing list.

Cheers,
Everett

On Apr 5, 2013, at 9:01 AM, Matt Van Winkle wrote:

Hello again, folks!

When I reached out a couple weeks ago, I mentioned that I was hoping that, along with being a large developer of OpenStack, Rackspace, could also contribute the committee's work as one of it's largest users via our public cloud.  We just found our first opportunity.  This week we deployed an early release of Grizzly code to one of our data centers.

Going in, we knew there were quite a few database migrations.  As we studied them, however, they presented some challenges in the manner that they were executed.  Using them as they were would have meant extended downtime for the databases given the size of our production data (row counts, etc).  That downtime is problematic since it translates to the Public APIs being unavailable – something we aim to impact as minimally as possible during code deploys. Ultimately, we had to rewrite them ourselves to achieve the same out comes with less DB unavailability.  There is plenty of work the community can do, and the committee can help guide, around better ways to change database structure while maintaining as much uptime as possible.  If you need more details, I'm happy to bring the folks that worked on the rewrite into the conversation.  Both will actually be at the summit.

The bigger surprise - and full disclosure, we learned a lot about the things we aren't testing in our deployment pipeline - was the dramatic increase in network traffic following the deploy.  The new table structures, increased meta data and new queries in this version translated to about 10X in the amount of data being returned for some queries.  Add to that, the fact that compute nodes are regularly querying for certain information or often performing a "check in", and we saw a 3X (or more) increase in network traffic on the management network we have for this particular DC (and it's a smaller one as our various deployments go).  For now we have improved things slightly by turning off the following periodic tasks:

reboot_timeout
rescue_timeout
resize_confirm_window

These not running has the potential to create some other issues (zombies and such), but that can be managed.

It does look like the developers are already working on getting some of the queries updated:

https://review.openstack.org/#/c/26136/
https://review.openstack.org/#/c/26109/

All in all, I wanted to reach back out to you to follow up from before, because I think this particular experience is an excellent highlight that there is often a disconnect between some of the changes that come through to trunk and use of the code at scale.  Almost everyone who was dealt with the above will be in Oregon week after next, so I'm happy to drag any and all into the mix to discuss further.

Thanks so much!
Matt
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