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19 November 2012

Building Code at Logos: Build Repositories

As mentioned in my last post (Sharing Code Across Projects), developers work on the head of the master branch “by convention”. This is fine for day-to-day work, but we’d like something a little more rigorous for our continuous integration builds.

For this, we use “build repositories”. A build repository contains a submodule for each repository required to build the project. (In the App1 example, the App1 build repo would have App1, Framework and Utility submodules.) The CI server simply gets the most recent commit on the master branch of the build repo, recursively updates all the submodules, then builds the code.

The problem now: how is the build repository updated? We solve this using a tool we developed named Leeroy. (So named because we use Jenkins as a CI server, and Leeroy starts the Jenkins builds. We weren’t the first ones to think of this.)

Leeroy uses the GitHub API on our GitHub Enterprise instance to watch for changes to the submodules in a build repo. When it detects one, it creates a new commit (again, through the GitHub API) that updates that submodule in the build repo. After committing, it requests the “force build” URL on the Jenkins server to start a build. Jenkins’ standard git plugin updates the code to the current commit in each submodule and builds it.

The benefit is that we now have a permanent record of the code included in each build (by finding the commit in the build repo for that build, then following the submodules). For significant public releases, we also tag the build repo and each of the submodules (for convenience).

We’ve made Leeroy available at GitHub.

Posts in the “Building Code at Logos” series:

Posted by Bradley Grainger at November 19, 2012 01:40 PM