Continuous integration (CI) is all the rage these days because merging, building, and testing (shared) configurations early-and-often is a good thing. Actually, it’s a great thing! After all, finding problems sooner rather than later benefits everyone. For some, CI means simply testing compilation. (Phew… it works. Ship it! haha). For those investing time in a full test harness, CI may mean frequently executing a suite of tests at various levels (unit, functional, system) to validate functionality and identify regressions. I’ve even seen other levels of CI to include lab testing, flight testing, or even customer acceptance testing for even the smallest of changes. Regardless of how you ‘do’ CI, I’ll show how I use AccuRev for continuous integration. [Keep in mind that this is one interpretation of the subject matter]

The Pattern. The stream-based nature of AccuRev makes it very natural to define separate areas for development, integration, testing, and release. As seen in my example stream structure, I have an Integration stream as the first point of merging between individual project streams. This Integration stream is a great place to hook up a CI tool [Cruise Control, CC.NET, FinalBuilder, QuickBuild] and perform nightly or per-promote builds. I prefer to create a snapshot before doing the build mainly because snapshot creation is atomic and their immutable configurations guarantee reproducibility. After creating the snapshot, I will pull the build from the snapshot name. You could build from the Integration stream directly (similar to the concept of a moving label), but creating snapshots makes it easy to visually identify with the build process and compare good builds from bad builds with simple stream diffs.  [Note: integrating any of the above mentioned CI tools is as simple as telling the build tool to pull code from a stream (by name) and then configure the build tool to execute at some frequency and notify people of the build status]

What about all those snapshots? At first, you may think, “Isn’t this going to create a gazillion snapshots? Won’t that take up a ton of (disk) space and totally clutter the stream browser view?” Well… No.

• Snapshots are cheap. Snapshots are extremely cheap server-side entities consuming ~100bytes regardless of the number of elements they label… so go nuts! Snapshots mark transaction numbers, not elements! I say, always do what you need to solve important problems and answer tough questions even if that means creating a gazillion snapshots; just be sure to organize them.
• Clean up as you go. Your CI build script (build.xml, Makefile, or doBuild.sh) can easily be instructed to remove a snapshot for every snapshot created. I’d recommend keeping around enough snapshots (say 3 to 10) to do valuable work such as comparing builds or serving as temporary baselines for developers who want to reparent. As you can see in the stream structure, AccuRev stores both active and inactive snapshots and it is easy to reactivate any snapshot if necessary (I’ve enabled the stream browser to show both; lower left corner option).
• Group snapshots. I prefer to tuck logically related sets of snapshots behind a locked pass-through stream. The pass-through stream lets me collapse them all as a group and the lock prevents the pass-through stream from being accidentally being reparented.

Tip for very-long build/test cycles. Over the past few years I’ve encountered a few shops with single build/test cycles ranging from hours to days to complete. In this case, the concept of CI is slightly challenging because the notion of frequent builds is constrained. In this case, I’d recommend setting up two distinct test phases; quick and full. The “quick phase” is a quick pass sanity test only performing tasks such as compilation and unit testing — enough to let developers know they can continue on forward progress with little concern. The “full phase” is the full blown cycle, taking hours/days to complete, that completes all levels of testing such as compilation, unit testing, functional testing, system testing, etc. I would execute the quick phase early and often while the full phase may be once per week. As an additional step, I would mark the snapshot used for the full phase with a pass-through stream for the purpose of reporting configuration diffs or letting developers reparent their project streams/workspaces on the latest known good “certified” build.

Interested in continuous integration? Perhaps you’d also be interested in multistage continuous integration…

/happy building/ – dave

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