BazelCon 2024

In this session I will discuss remote action deduplication, a feature of some Bazel RBE backends. I will explain the problem it solves, how it works, and some details about how well it has worked for us. I'll also quickly touch on merge queues, and mention some RBE backends that support the feature. --- If you run builds on every master commit, and you have commits landing more quickly than your slowest action can finish, you'll end up rebuilding unnecessarily. We estimated that our slowest webpack action was being re-run unnecessarily 66% of the time! This action is an input to a large number of expensive integration tests so it's very likely that we're also wasting a lot of compute on those tests as well. The web page builds and tests account for the vast majority of the compute we use in CI. The number of wasted builds would be even higher if we were using a merge queue, so we have been forced to stick to a conventional merge strategy. By running these builds remotely and using an RBE backend that supports action deduplication, we've massively (25%, more expected by BazelCon) reduced the amount of compute needed to build and test web pages.

In this talk, you'll gain practical insights from our experience migrating Airbnb's web monorepo (which houses millions of lines of TS/JS code) to Bazel. We developed methods and tooling to trim down input sizes, share the cache between MacOS and Linux, persist caches through local and remote builds, catch and fix non-deterministic builds, and automatically generate BUILD files from JS/TS code. This helped us create a robust system for adopting Bazel without compromising on developer experience. These insights are designed to help you navigate similar migrations, improve build performance, and reuse builds across platforms.

Aspect authors many of the Bazel rules you know and love. We also provide the missing CI/CD and developer platform to integrate Bazel into your team's workflows and achieve the promised incremental build&test speed while reducing your cloud spend! This talk will update you on our latest and greatest.