Build tools frequently use environment variables to configure compilers. If a cloud runner injects a fluctuating variable (like a unique RUNNER_TRACKING_ID ), the cache engine assumes the build environment has changed and invalidates the previous cache. 3. Non-Deterministic Build Outputs
If the log says "Cache restored from key...", the action did its job, but the data inside might be stale. Cache Miss: If it says "Cache not found for input keys," it means your
[debug] restoreKeys: [ 'Linux-pip-', 'Linux-' ] [debug] GET response for key 'Linux-pip-main-2d711b': 404 [debug] GET response for key 'Linux-pip-': 200 (Stored key: 'Linux-pip-staging-9c4a7b')
Caching not working · community · Discussion #163260 - GitHub debug-action-cache
Set ACTIONS_STEP_DEBUG=true . Run the workflow.
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Caching is the backbone of fast Continuous Integration and Continuous Deployment (CI/CD) pipelines. By reusing unchanged dependencies, build artifacts, and compiled code, caches cut down deployment times from thirty minutes to three. However, when a cache becomes corrupted, stale, or misconfigured, it introduces silent bugs that are notoriously difficult to track down. Non-Deterministic Build Outputs If the log says "Cache
Let's map error symptoms to debug-action-cache insights.
If your build is not achieving the expected cache hit rate, it is usually due to one of these reasons:
to get system-level information about the runner environment. 2. Verify Your Cache Keys Cache misses often occur because the generated by hashFiles() doesn't match what was previously saved. This public link is valid for 7 days
Set ACTIONS_RUNNER_DEBUG to true to view low-level background runner events.
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:
: When a developer initiates an action or computation (e.g., running a test, compiling code, or executing a script), the system first checks if the result of this action is already cached.