Invalidate Cache

When you add or remove dependencies in your package.json, it’s crucial to invalidate the existing cache so Jenkins reinstalls packages based on the updated lock file. Below is a step-by-step guide to demonstrate how cache invalidation works in a Jenkins pipeline using the Job Cache plugin’s cacheValidityDecidingFile option.

1. Navigate to Your Repository

Switch back to your Solar System project:

cd ~/solar-system

Verify you’re on the correct feature branch:

git status
# On branch feature/advanced-demo

2. Add a New Dependency

Install a new package (e.g., localtunnel) to trigger a change in package-lock.json:

npm install localtunnel

This command updates both package.json and package-lock.json, altering the lock file’s hash.

3. Commit & Push

Stage and commit the updated dependency files:

git add package.json package-lock.json
git commit -m "chore: install localtunnel to trigger cache invalidation"
git push

Pushing these changes starts a new Jenkins build. The install stage will reveal the cache behavior.

4. Observe Cache Invalidation in Jenkins

In the pipeline’s console output, look for entries related to the cache plugin:

17:06:25  + node -v
17:06:25  v22.6.0
17:06:26  + npm install --no-audit
17:06:27  added 7 packages in 2s
17:06:27  45 packages are looking for funding
17:06:27  run `npm fund` for details
17:06:30  Stashed 5131 file(s)

17:06:25  {cache for node_modules (npm-dependency-cache) with id 3ec03583f8eace275cb2183db769ff47}
17:06:25  got hash 5a159d4c8ba0a6882fd4b8ef16c2 for cacheValidityDecidingFile(s): /var/lib/jenkins/workspace/lar-system_feature_advanced-demo/package-lock.json
17:06:25  cache outdated; skipping restore
17:06:30  creating cache...
17:06:32  cache created in 2179ms

Key observations:

1. Jenkins computes a new hash for package-lock.json.
2. Since the hash differs from the previous build, the old cache is skipped.
3. A fresh cache is created based on the updated dependencies.

5. Cache Invalidation Logic

By specifying cacheValidityDecidingFile: package-lock.json in your Job Cache plugin configuration, you ensure your Node.js dependencies are always in sync with the lock file.

Links and References

• Jenkins Job Cache Plugin
• npm install documentation
• package-lock.json specification