Running GitHub Actions in Parallel and Sequentially

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Use Case Explanation:

Imagine you have a workflow that includes multiple tasks such as linting, testing, building, and deploying your code. Some tasks can run simultaneously (in parallel) without depending on each other, while others need to execute in a specific order (sequentially).

Running Actions in Parallel:

1. Parallel Execution Example:

name: Parallel Actions
on:
  push:
    branches: [main]
jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - name: Lint Code
        run: npm run lint
  test:
    runs-on: ubuntu-latest
    steps:
      - name: Test Code
        run: npm test

In this example, lint and test jobs can execute simultaneously as they don't depend on each other.

Breaking it down:

• name: Parallel Actions sets the name for this workflow.
• on specifies that this workflow will trigger on push events to the main branch.
• jobs define separate tasks that can run concurrently.
• lint defines a job to run on ubuntu-latest and contains a single step to execute linting using the command npm run lint.
• test defines another job also running on ubuntu-latest with a single step to execute tests using the command npm test.

Running Actions Sequentially:

1. Sequential Execution Example:

name: Sequential Actions
on:
  push:
    branches: [main]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Build Application
        run: npm run build
  deploy:
    needs: build
    runs-on: ubuntu-latest
    steps:
      - name: Deploy to Production
        run: |
          echo "Deploying to production..."

Here, the deploy job depends on the completion of the build job, ensuring the deployment only occurs after the successful build.

Breaking it down:

• name: Sequential Actions sets the name for this workflow.
• on specifies that this workflow will trigger on push events to the main branch.
• jobs define separate tasks where one job depends on the completion of another.
• build defines a job to run on ubuntu-latest and contains a single step to execute the build process using npm run build.
• deploy defines another job running on ubuntu-latest that has a dependency (needs: build) on the completion of the build job. This job is responsible for deployment, and it executes only after the build job has successfully completed.

Use Cases:

1. Parallel Execution:

• When tasks don’t rely on each other and can execute concurrently, like linting, testing, or running independent checks.
• Speeding up workflows by reducing the overall execution time when tasks can run simultaneously.

1. Sequential Execution:

• Ensuring a specific order of execution, such as building before deploying, to maintain the workflow’s integrity.
• Preventing issues caused by dependencies between tasks.

Benefits of Knowing Both:

• Performance Optimization: Understanding when to run tasks in parallel can significantly reduce the total workflow execution time.
• Workflow Integrity: Knowing how to run tasks sequentially ensures critical steps are completed in the required order without dependencies causing issues.
• Resource Utilization: Parallel execution optimizes resource usage by leveraging available resources effectively.

Conclusion:

Understanding how to run GitHub Actions in parallel and sequentially allows you to optimize your workflows, streamline processes, and ensure tasks are executed efficiently without unnecessary delays or dependencies affecting the workflow’s integrity. It helps in maximizing the benefits of automation and continuous integration/deployment in software development pipelines.