Sometimes, a cache becomes corrupted due to an interrupted build network failure. In these cases, no amount of debugging will fix the broken archive. You must purge the cache.
Use a tool to manually query the Digest. If the Action Cache returns a result, but the ActionResult references a file hash that doesn't exist in the CAS, your cache is "orphaned." Common Culprits of Cache Issues
if [ -f "$CACHE_PATH/.last_hash" ]; then OLD_HASH=$(cat "$CACHE_PATH/.last_hash") if [ "$OLD_HASH" != "$EXPECTED_HASH" ]; then echo "⚠️ WARNING: Cache contains old hash $OLD_HASH. Stale cache detected!" else echo "✅ Hash matches expected value." fi else echo "⚠️ No hash file found inside cache. Cannot verify integrity." fi debug-action-cache
If a compiler includes timestamps or absolute file paths inside compiled binary outputs, the file hashes will change between identical runs. This destroys the determinism needed for remote build caches. 🛠️ Step-by-Step Guide to Debugging an Action Cache
You can scope these variables globally across an entire workflow run like this: Sometimes, a cache becomes corrupted due to an
Avoid reading arbitrary environment variables inside build scripts. If you must use them, explicitly declare them in the build configuration files so the system knows to track them.
Once you’ve mastered debug-action-cache , adopt these best practices to prevent issues: Use a tool to manually query the Digest
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.
To debug a GitHub Actions cache and inspect its , you can use several methods ranging from built-in debug modes to external CLI tools. 1. Enable Action Debug Logging