Lab: Speed Up Node.js CI with GitHub Actions Cache

Introduction

In this lab, you will learn how to use caching in GitHub Actions to speed up a Node.js application’s build by avoiding redundant dependency installation. You’ll compare two workflows: one without caching and one using the actions/cache action.

You’ll use the existing express-hello-world Node.js project located at /src/javascript/express-hello-world

Estimated Duration: 20–30 minutes

Instructions

Step 1: Open your repository

  1. Navigate to the repository containing the express-hello-world project.
  2. Ensure the following file exists ` src/javascript/express-hello-world/package.json`
  3. If needed, test the app locally to verify it’s working:
cd src/javascript/express-hello-world
npm install
node server.js

Step 2: Create the workflow without cache

  1. In the GitHub web UI, go to the Code tab.

  2. Navigate to the .github/workflows directory. Create the folders if they don’t exist:

    • Click Add file > Create new file
    • Name the file: .github/workflows/build-no-cache.yml

  3. Paste the following content:

    name: Express Server without cache

on:
  workflow_dispatch:

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v3

      - name: Setup Node.js
        uses: actions/setup-node@v3
        with:
          node-version: '18'

      - name: Install dependencies
        run: |
          cd src/javascript/express-hello-world
          npm install

      - name: Show installed packages
        run: |
          cd src/javascript/express-hello-world
          npm list

  4. Scroll down and click Commit new file.

Step 3: Run the workflow and check time taken

  1. Go to the Actions tab.
  2. Click on the Node.js CI without cache workflow.
  3. Click Run workflow > Run workflow (manually trigger it).
  4. After it completes, expand the Install dependencies step and note the duration.

Step 4: Create the workflow with cache

  1. In the same .github/workflows folder, create another file named build-with-cache.yml

  2. Paste the following content:

    name: Express Server with cache

on:
  workflow_dispatch:

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v3

      - name: Setup Node.js
        uses: actions/setup-node@v3
        with:
          node-version: '18'

      - name: Cache npm dependencies
        uses: actions/cache@v3
        with:
          path: ~/.npm
          key: $-node-$
          restore-keys: |
            $-node-

      - name: Install dependencies
        run: |
          cd src/javascript/express-hello-world
          npm install

      - name: Show installed packages
        run: |
          cd src/javascript/express-hello-world
          npm list

  3. Commit the file.

Step 5: Run the workflow twice and compare

  1. Navigate to the Actions tab.

  2. Run the Node.js CI with cache workflow manually.

    • First run: Installs dependencies and creates the cache.
    • Second run: Restores the cache and speeds up installation.

  3. Expand the Install dependencies step in both runs and compare durations.

Summary

In this lab, you created two GitHub Actions workflows for a Node.js app — one with caching and one without. You observed how dependency installation time was significantly reduced when using the actions/cache step with .npm as the cache path.

Caching is useful when:

Additional Resources