Caching is not "set and forget." It is a living part of your infrastructure. Every time a dependency changes, a runner OS updates, or a new developer joins the team, your cache assumptions can break.
Sometimes the cache hit is correct, but the files it points to are corrupted or missing from the CAS.
- name: Attempt Cache Restore with Full Debug uses: actions/cache@v4 with: path: node_modules key: debug-$ runner.os -$ steps.sim.outputs.hash restore-keys: debug-$ runner.os -
GitHub Actions stores cache-related secrets that you can use for direct API interaction: debug-action-cache
The debug-action-cache technique is not about memorizing YAML syntax. It is about . The silent restore, the missing package, the 10-minute delay—all of these yield to the developer willing to flip the debug switch.
key: my-cache-$ runner.os -$ github.run_id
bazel build //target --execution_log_compact_file=/tmp/exec2.log Caching is not "set and forget
Why would you need to debug? Here are the top five disasters debug-action-cache helps you solve:
Look at:
While different tools have different specific commands, the process of "debugging the action cache" generally follows these steps: 1. Inspecting Input Digests - name: Attempt Cache Restore with Full Debug
Create a secret named ACTIONS_STEP_DEBUG and set its value to true .
Additional information could help me provide a more precise report.
Shows which branch or commit generated the specific cache slice. 3. Clear and Purge the Cache via GitHub CLI
This comprehensive technical guide outlines the architecture of build caching, diagnoses common failure points, and provides step-by-step methodologies to inspect and debug your action cache across platforms like and advanced monorepo build tools like Bazel . The Architecture of an Action Cache
To debug action cache hits/misses, you typically use the following flags in your command line: