Why is my Bazel build so slow?
The promise of Bazel is the promise of fast builds. So what do you do if your build was slow? Curse out the developer that convinced your company to migrate to Bazel? Of course not! You’d never do that, right? 🙂
BuildBuddy is here to help. Bazel provides a lot of helpful information to debug slow builds, but it can be overwhelming to know where to look.
Maybe you ran two builds and you’re surprised the second build ran so slowly, when you’d expected it to be cached. Or maybe you ran one build, and you just want to understand where all the time was spent. Here are some good places to start, with some real-world examples of why our own builds were slow.
This post frequently references the BuildBuddy UI. While most of these steps are possible without it, it will be a lot more work to find and parse the info from the build event stream yourself. If you’re not already using it, you can stream build events to our servers for free by adding the following flags to your builds (more setup docs here):
Once you’ve added these flags, you’ll see a line like Streaming build results to: https://app.buildbuddy.io/invocation/XXX in your build logs. If you follow that link to our UI, you’ll have access to many of the features discussed below.
