README.md

3 Running multiple jobs in parallel

Navigation

0. Getting started
1. Creating a workflow
2. Building code in a workflow
3. Running multiple jobs in parallel (this task)
4. Running jobs in sequence
5. Deploying to GitHub Pages
6. Using other events to run workflows
7. Outputs from steps and jobs
8. Keeping dependencies up to date with Dependabot
9. Matrices
10. Workflow dispatch inputs and security verification
11. Learn more about GitHub Actions

In the previous task we created a workflow that runs a single job. Each step in a job is run in sequence:

jobs:
  job1:
    runs-on: ubuntu-latest
    steps:
      - name: Step 1
        run: echo "Step 1"
      - name: Step 2
        run: echo "Step 2"

However, we can also run multiple jobs in parallel:

jobs:
  job1:
    runs-on: ubuntu-latest
    steps:
      - name: Step 1
        run: echo "Step 1"
      - name: Step 2
        run: echo "Step 2"
  job2:
    runs-on: ubuntu-latest
    steps:
      - name: Step 1
        run: echo "Step 1"
      - name: Step 2
        run: echo "Step 2"

We can have as many jobs as we want and they will all run in parallel. Jobs are great for grouping up steps that are related to each other, and to otherwise keep the workflow file clean. They often can be run entire independently of each other, therefore making them great for parallelization.

Tip

Each job has its own fresh virtual machine, so they don't share any state. This means that you need to check out the repository and install dependencies for each job, even if they're within the same workflow file.

3.1 Test and lint

In the previous task, we learned how to build the project. We're still missing some safeguards though. We should run our unit tests, and we should check that we have no linting errors (i.e. check that there are no mistakes that can lead to bugs).

We can see in the package.json file that we have a few scripts available. These can all be run with npm run <script name>:

"scripts": {
  "start": "vite",
  "build": "vite build",
  "test": "vitest run",
  "lint:check": "eslint . --ext .ts,.tsx",
  "lint:fix": "npm run lint:check -- --fix",
  "format:check": "prettier --check .",
  "format:fix": "prettier --write ."
}

In the workflow file we've already created, create one job for the test script and one for the lint:check script.

Tip

Remember: To run the scripts, type npm run <script name> (if you already have npm installed).

Now if we commit and see how the workflow runs, we can see that all jobs are run at the same time.

Tip

If you get an error saying that package.json is not found, or that the vitest or eslint commands aren't found, remember that each job gets its own fresh virtual machine. The latest version of Node and npm (and .NET and a few others) come pre-installed, but we need to both clone the repository and install dependencies before we can run the scripts, just as we did for the build job in the previous task.

If we open up the repository settings page again and take a look at our branch protection rule, we can now search for the new jobs we added. Jobs will show up in search after they've been run at least once.

Note

You could also add a job that runs the format:check script. If you did, you would also need to format your workflow file by the rules set by Prettier. That is not what we're learning right now, so we skipped it, but it's a good idea to do it in your own projects.

Did everything pass? If yes, move on to task 4!