In "write-back" scenarios, there is a delay between the action finishing and the cache being fully uploaded to the storage provider. If a job crashes mid-upload, the next run might pull a partial, corrupted archive. Summary Checklist for Debugging Check the Key: actually change when your dependencies change? Verify the Path:
When logs are not enough, you can pause a running workflow execution to inspect the cache directories directly. Third-party actions like mxschmitt/action-tmate or csexton/debugger-action let you trigger a secure SSH or web-terminal session directly into the virtual environment during the build phase. Dependency caching reference - GitHub Docs
The first and most critical step in your debugging journey is to enable the secret, detailed logging that GitHub Actions normally hides from you. There are two primary levels of debug logging you need to know about.
The Debug Action Cache is a valuable component of the debugging process, offering improved performance and reduced overhead. However, to ensure its effectiveness and reliability, it is essential to address potential issues related to cache invalidation, size management, and concurrency. By implementing the recommended strategies, developers can ensure a robust and efficient Debug Action Cache. debug-action-cache
Once you have basic visibility, you can move to advanced diagnostics.
If your debug logs confirm that a corrupted cache is locked behind an immutable key, you must manually evict it to force your pipeline to rebuild from a clean slate. Method A: Deleting Caches via the GitHub UI Navigate to the main page of your GitHub repository. Click on the tab located under the repository name.
Then, in a workflow or locally:
Here, you can manually delete old or corrupted caches to force a fresh rebuild. 4. Interactive Debugging with tmate
Create a secret named ACTIONS_RUNNER_DEBUG and set its value to true .
is a common necessity for optimizing CI/CD pipelines. If you are facing "cache misses" or slow workflows, you can use several built-in methods to troubleshoot the actions/cache mechanism. 1. Enable Verbose Logging In "write-back" scenarios, there is a delay between
Check for "restore-keys." GitHub will try to find the closest match if an exact key isn't found. If your restore-keys
gh api repos/owner/repo/actions/caches --jq '.actions_caches[] | key: .key, size: .size_in_bytes, last_accessed_at: .last_accessed_at'
Your hashFiles('requirements.txt') changed (maybe a whitespace change), causing the exact key to miss. The restore key Linux-pip- matched a cache from the staging branch instead of main . Verify the Path: When logs are not enough,
GitHub provides a management interface to see what is currently stored: Navigate to your repository on GitHub. Click the tab. In the left sidebar, under Management , click Caches .