On GitHub merge queues, reliability, and multiplexed serial connections

Assuming anyone was paying attention, which I suspect they are not, they would have noticed that there are a lot of queued up pull requests for Shaken Fist right now. There are a couple of factors leading to that — there are now several bots which do automated pull requests for code hygiene purposes; and a couple of months ago I decided to give GitHub’s new merge queue functionality a go in order to keep the CI resource requirements for Shaken Fist under control. All CI runs on four machines in my home office, and there were periods of time where the testing backlog would be more than 24 hours long. I can’t simply buy more hardware, and I didn’t really want to test things less.

The basic idea of GitHub merge queues is that you have a quick set of initial tests which determine if the pull request smells, and then only run the full test suite on non-stinky code which a human has signed off on. Once the human signs off, the code will only merge if the full suite passes, and GitHub manages a queue of merge attempts to keep that reasonable.

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On Continuous Integration testing for Nova DB

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To quote Homer Simpson: "All my life I've had one dream, to achieve my many goals.". One of my more recent goals is a desire to have real continuous integration testing for database migrations in Nova. You see, at the moment, database migrations can easily make upgrades painful for deployers, normally by taking a very long time to run. This is partially because we test on trivial datasets on our laptops, but it is also because it is hard to predict the scale of the various dimensions in the database -- for example: perhaps one deployment has lots of instances; whilst another might have a smaller number of instances but a very large number of IP addresses. The team I work with at Rackspace Australia has therefore been cooking up a scheme to try and fix this. For example, Josh Hesketh has been working on what we call Turbo Hipster, which he has blogged about. We've started off with a prototype to prove we can get meaningful testing results, which is running now. Since we finished the prototype we've been working on a real implementation, which is known as Turbo Hipster. I know it's an odd name, but we couldn't…

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Nova database continuous integration

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I've had some opportunity recently to spend a little quality time off line, and I spent some of that time working on a side project I've wanted to do for a while -- continuous integration testing of nova database migrations. Now, the code isn't perfect at the moment, but I think its an interesting direction to take and I will keep pursuing it. One of the problems nova developers have is that we don't have a good way of determining whether a database migration will be painful for deployers. We can eyeball code reviews, but whether code looks reasonable or not, its still hard to predict how it will perform on real data. Continuous integration is the obvious solution -- if we could test patch sets on real databases as part of the code review process, then reviewers would have more data about whether to approve a patch set or not. So I did that. At the moment the CI implementation I've built isn't posting to code reviews, but that's because I want to be confident that the information it gathers is accurate before wasting other reviewers' time. You can see results at openstack.stillhq.com/ci. For now, I am keeping an…

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