Action Merging

BuildBuddy's remote execution engine optimizes performance by merging identical in-flight executions of actions, effectively saving time and resources for users. This process, integral to the efficiency of the Bazel build tool, addresses issues with redundant action executions when results can't be shared between pending tasks. By using a system that identifies and merges identical actions, BuildBuddy has demonstrated significant resource savings, especially for long-running tests, and manages state using Redis to alleviate database loads. Challenges such as stalled executions and scaling bugs have prompted the introduction of concepts like "hedging," which dispatches parallel executions to prevent deadlocks. Despite its success, the system faces certain complexities, such as managing flaky tests and improving cancellation correctness, prompting ongoing improvements. This intricate system exemplifies the complexities of distributed system designs, highlighting both its importance and the challenges it seeks to address.