**Course Title:** Continuous Integration and Continuous Deployment (CI/CD) **Section Title:** Building CI Pipelines **Topic:** Defining Build Triggers: On Push, Pull Requests, and Scheduled Builds **Introduction** In the previous topic, we learned about creating build configurations in CI tools. However, to automate the build process, we need to define when the build should be triggered. In this topic, we will explore the different types of build triggers that can be used to automate the build process in a CI/CD pipeline. We will cover the concepts of on-push, pull request, and scheduled builds, and provide examples of how to configure these triggers in popular CI tools. **On-Push Builds** On-push builds are triggered automatically whenever code is pushed to the repository. This is the most common type of build trigger and is useful for quickly detecting and fixing errors in the code. When an on-push build is triggered, the CI tool will automatically fetch the latest code from the repository, run the build process, and report any errors or warnings. **Example:** In GitHub Actions, you can configure an on-push build by specifying a `push` event in the workflow file. For example: ```yml name: Build and Test on: push: branches: - main jobs: build-and-test: runs-on: ubuntu-latest steps: - name: Checkout code uses: actions/checkout@v2 - name: Build and test run: | npm install npm run build npm run test ``` In this example, the build is triggered whenever code is pushed to the `main` branch. **Pull Request Builds** Pull request builds are triggered automatically whenever a pull request is created or updated. This type of build trigger is useful for reviewing and testing code changes before they are merged into the main branch. **Example:** In CircleCI, you can configure a pull request build by specifying a `pull_request` event in the configuration file. For example: ```yml version: 2.1 jobs: build-and-test: docker: - image: circleci/node:latest steps: - checkout - run: | npm install npm run build npm run test workflows: build-and-test: jobs: - build-and-test: filters: branches: only: /.*/ tags: ignore: /.*/ pull-requests: only: - match: head: /.*/ src: /.*/ ``` In this example, the build is triggered whenever a pull request is created or updated. **Scheduled Builds** Scheduled builds are triggered at regular intervals, such as daily or weekly. This type of build trigger is useful for running automated tests or building releases at regular intervals. **Example:** In Jenkins, you can configure a scheduled build by specifying a cron-like schedule in the job configuration. For example: ```bash H 0 * * * * # every hour ``` In this example, the build is triggered every hour. **Conclusion** In this topic, we learned about the different types of build triggers that can be used to automate the build process in a CI/CD pipeline. On-push builds are triggered whenever code is pushed to the repository, pull request builds are triggered whenever a pull request is created or updated, and scheduled builds are triggered at regular intervals. We also provided examples of how to configure these triggers in popular CI tools. **Practical Takeaways:** * On-push builds are useful for quickly detecting and fixing errors in the code. * Pull request builds are useful for reviewing and testing code changes before they are merged into the main branch. * Scheduled builds are useful for running automated tests or building releases at regular intervals. * When configuring build triggers, consider the needs of your project and the goals of your CI/CD pipeline. **Additional Resources:** * [GitHub Actions documentation on events](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#on) * [CircleCI documentation on workflows](https://circleci.com/docs/2.0/workflows/) * [Jenkins documentation on cron-like schedules](https://jenkins.io/doc/book/pipeline/syntax/#cron-schedule) **Leave a comment:** If you have any questions or need further clarification on this topic, please leave a comment below. **What's next:** In the next topic, we will learn about **Understanding Build Artifacts and Storage**.