Debug-action-cache

Keep "Before" and "After" execution logs whenever you make changes to your build infrastructure. Conclusion

Set ACTIONS_RUNNER_DEBUG to true to view low-level background runner events.

: Create a repository secret named ACTIONS_STEP_DEBUG with the value true .

If an action's input hash changes, the action key changes, leading to a cache miss and re-execution. 2. Common Causes of Action Cache Misses

If you suspect the cache is the problem, the first step is to force a "cache miss" to see if a clean slate fixes the build. Key Rotation: debug-action-cache

The ability to see the exact key being generated, the internal version of the cache, and the step-by-step restore and save process is the difference between guessing at a problem and solving it. So, the next time your CI pipeline slows down or fails without explanation, don't just stare at the green checkmark. Remember to flip the debug switch, dive into the logs, and let debug-action-cache guide you to the solution.

Bazel is renowned for its speed, largely due to its advanced caching mechanisms, particularly the . By caching the output of every build step (action) based on its inputs, Bazel avoids redundant work, providing near-instant builds for minor changes. However, when Bazel decides an action is "dirty" and must be re-executed, it results in a cache miss, slowing down your pipeline.

Do not guess what is inside your system's storage backend. Use administrative tools to audit your current cache footprint.

GitHub Actions relies heavily on the actions/cache utility. When a cache hit causes errors, use the following sequence to isolate and fix the problem. 1. Enable Step and System Diagnostics Keep "Before" and "After" execution logs whenever you

Append a version suffix to your cache key in your YAML file (e.g.,

In modern DevOps, the "action cache" stores intermediate build artifacts and dependencies. However, debugging these caches is notoriously difficult because they are often opaque, immutable, and distributed across various runner environments. A debug-action-cache utility serves as a diagnostic bridge, allowing engineers to inspect the state of cached assets without manual intervention.

debug-action-cache is less a single command and more of an investigative methodology. It involves a structured sequence of steps to diagnose and resolve caching issues. Typically, a seasoned engineer will approach a cache failure in the following order:

Enable runner diagnostic logging by setting the secret ACTIONS_RUNNER_DEBUG to true . Step 2: Extract and Compare Cache Keys If an action's input hash changes, the action

Modify the key temporarily to force the creation of a fresh cache.

Run your build with execution logging enabled: bazel build //... --execution_log_json_file=/tmp/exec_log.json

To debug an action cache effectively, a developer must move from guessing to empirical comparison.