In the Buildbarn event at Snowflake this week, Ed Schouten presented the work on the Bonanza project. Bonanza is a prototype for a drop in replacement Bazel with improvements to its communication protocols and written as client that performs all of its actions remotely, deduplicated and cacheable.

How is it different from Bazel?

Bazel is written in an interesting manner. It is designed from the ground up to represent a stable description of a build that is reproducible from any developer's machine. Any developer can check out the same source code ask Bazel to analyze it and get the exact commands which Bazel would run to perform the build.

This involves a lot of computation: Resolving bazel modules, downloading repository rules, executing them, analyzing the .bzl and BUILD.bazel files, and finally executing the actions themselves.

Bazel internally represents these computation steps as pure functions returning deterministic values from a stable key, internally represented as SkyFunctions returning SkyValues from SkyKeys.

A SkyFunction should return the same SkyValue given the same SkyKey which makes it a good candidate for being computed only once and have the result cached and fed throught to the next step. But peculiarly only the action execution itself has been offloaded to remote cache and execution.

This is what Bonanza attempts to resolve. Instead of having all of that state computed and represented locally, repeated by each developer and discarded whenever a flag changes, Bonanza is designed from the ground up to offload all computations, downloads, and analysis to a remote cacheable system. This essentially reduces the client side to a very light weight program with the primary purpose of scanning the source code for modifications and uploading any local changes.

What's the current state?

The project is still in an early state prototype state. In the presentation Ed demonstrated how far the prototype has come, and it was very impressive. The Bonanza client as of today is capable of analyzing the bb-storage codebase.

There is still a lot remaining before it's a production ready system but it is very impressive progress. Bonanza is capable of running the full bzlmod resolution, fetching all relevant repository rules from upstream, run those repository rules, and analyzing the resulting codebase, basically performing everything a Bazel cquery does, all with fully remote and cacheable manner.

For shops which lean heavily into remote caching and execution the remaining local load is often the bottleneck for your builds, the ability to offload the remaining pieces to your build cluster may be the next evolution of your build system.