Uphill Forever

In many ways this is the follow up to hard is good and the post I promised recounting the lessons of the buildcloth v0.2.0 release

This release of buildcloth is in some ways, the first real piece of software I've written from the ground up. I've written a bunch of code, and I've implemented a decent amount of functionality as extensions and additions to other programs, written some very small programs, and written an endless number of throw away scripts, but never something quite on this scale. The remainder of this post is

Whats the coolest thing about Buildcloth 0.2.0?

The buildsystem feature is pretty awesome, mostly because it makes it possible to have legitimate, honest-to-goodness build systems running with an Python project. Integration is a sweet thing.

Why make another build tool? Aren't there enough of those already?

I started working on this for two reasons, first because the MongoDB documentation build process was lagging under some process creation overhead and using buildcloth as a meta-build system was clearly not holding up.

Second, I wanted to write a static site generator that used a fully concurrent internal model. My initial plan was to use the buildcloth meta-build system, but that clearly wouldn't hold up at scale so I needed something like buildcloth.

Finally, there aren't actually a lot of generalized build automation tools: Make, Ninja, SCons, Waf, and Rake plus a small cluster of Java tools (Ant, Maven, sbt, Gradle). See the wikipedia list of build automation tools.

How can I use Buildcloth? Is Buildcloth right for my project?

If you want, you can use Buildcloth as a Make replacement, using the buildc front end. For build systems that already have Python code to wrap or implement build steps, Buildcloth may be much more efficient than using something like Make. For other kinds of builds, the benefits may be less pronounced.

You can also use Buildcloth as a library in your own Python programs if you need a way of ruining build-jobs in a parallel, dependency aware mode.

I've started to think think buildcloth is really a sort of embedable, small-scale, local version of something like celery. Or maybe it's just a collections of decent wrappers around multiprocessing.Pool. Regardless, there aren't a lot of really intuitive tools around that make async processing/parallel execution easy and fun in Python, so if you need to do this kind of processing work, take a look.

How well tested is Buildcloth?

There's a complete unit test suite with 400 tests (last count) that should ensure that things stay stable as the product continues to develop. In this respect buildcloth is really well tested (particularly for a project of its age.) In other respects, its less well tested.

Now that things are comparatively stable, I'm pretty eager to begin using the buildsystem and make sure all of the higher-level aspects work well.

What aspects need the most improvement?

I need to devise a way to save some state between builds so that buildcloth can check to see if a target needs to be rebuilt by seeing if the content of the dependent files has changed. Currently, (like many tools,) buildcloth must rebuild things based on a comparison of modified times from the file system, which do not necessarily indicate a required rebuild.

This isn't really a buildcloth problem, but I also find myself frustrated by the error reporting of tasks running inside the multiprocessing pool. I'm thinking of wrapping tasks right before calling them in a way that will capture output and make it easier to kill zombie tasks and dead pools.

What would you do differently next time?

I wrote the implementation in a very bottom-up sort of way, and as a result the design and testing suite feels a little bottom up. In the long term I think it was the right decision, but I think that in the medium term it will lead to some awkwardness.

Furthermore, build systems are fundamentally static and there's no good way to "add jobs to the top of the pipe." I don't yet have a good answer to this problem (yet,) but shouldn't be insurmountable.

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