Aggregating Version Control Info at Mozilla

January 21, 2014 at 10:50 AM | categories: Git, Mercurial, Mozilla, Python | View Comments

Over the winter break, I set out on an ambitious project to create a service to help developers and others manage the flury of patches going into Firefox. While the project is far from complete, I'm ready to unleash the first part of the project upon the world.

If you point your browsers to moztree.gregoryszorc.com, you'll hopefully see some documentation about what I've built. Source code is available and free, of course. Patches very welcome.

Essentially, I built a centralized indexing service for version control repositories with Mozilla's extra metadata thrown in. I tell it what repositories to mirror, and it clones everything, fetches data such as the pushlog and Git SHA-1 mappings, and stores everything in a central database. It then exposes this aggregated data through world-readable web services.

Currently, I have the service indexing the popular project branches for Firefox (central, aurora, beta, release, esr, b2g, inbound, fx-team, try, etc). You can view the full list via the web service. As a bonus, I'm also serving these repositories via hg.gregoryszorc.com. My server appears to be significantly faster than hg.mozilla.org. If you want to use it for your daily needs, go for it. I make no SLA guarantees, however.

I'm also using this service as an opportunity to experiment with alternate forms of Mercurial hosting. I have mirrors of mozilla-central and the try repository with generaldelta and lz4 compression enabled. I may blog about what those are eventually. The teaser is that they can make Mercurial perform a lot faster under some conditions. I'm also using ZFS under the hood to manage repositories. Each repository is a ZFS filesystem. This means I can create repository copies on the server (user repositories anyone?) at a nearly free cost. Contrast this to the traditional method of full clones, which take lots of time, memory, CPU, and storage.

Anyway, some things you can do with the existing web service:

  • Obtain metadata about Mercurial changesets. Example.
  • Look up metadata about Git commits. Example.
  • Obtain a SPORE descriptor describing the web service endpoints. This allows you to auto-generate clients from descriptors. Yay!

Obviously, that's not a lot. But adding new endpoints is relatively straightforward. See the source. It's literally as easy as defining a URL mapping and writing a database query.

The performance is also not the best. I just haven't put in the effort to tune things yet. All of the querying hits the database, not Mercurial. So, making things faster should merely be a matter of database and hosting optimization. Patches welcome!

Some ideas that I haven't had time to implement yet:

  • Return changests in a specific repository
  • Return recently pushed changesets
  • Return pushes for a given user
  • Return commits for a given author
  • Return commits referencing a given bug
  • Obtain TBPL URLs for pushes with changeset
  • Integrate bugzilla metadata

Once those are in place, I foresee this service powering a number of dashboards. Patches welcome.

Again, this service is only the tip of what's possible. There's a lot that could be built on this service. I have ideas. Others have ideas.

The project includes a Vagrant file and Puppet manifests for provisioning the server. It's a one-liner to get a development environment up and running. It should be really easy to contribute to this project. Patches welcome.

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