Introduction :-

CircleCI is a robust continuous integration and delivery (CI/CD) platform designed to automate the build, test, and deployment processes. This guide provides a comprehensive, step-by-step approach to setting up CircleCI for your project, configuring pipelines, and utilizing advanced features like branch filtering.

Step 1: Register and Connect to Your Version Control System (VCS)

1.1 Create a CircleCI Account

• Sign Up or Log In:

• Visit CircleCI and sign up using GitHub, Bitbucket, or email.

• If you already have an account, simply log in.

1.2 Connect Your Repository

• After logging in, connect your VCS (GitHub or Bitbucket) to CircleCI.

• This integration allows CircleCI to access your code and trigger builds based on your configuration.

Step 2: Set Up Your Project in CircleCI

2.1 Access Your Projects

• Navigate to the “Projects” page in CircleCI.

• A list of repositories linked to your VCS account will be displayed.

2.2 Configure a New Project

• Locate your repository and click “Set Up Project.”

• Follow the prompts to complete the initial setup process.

Step 3: Create the .circleci Directory and config.yml File

3.1 Create Configuration Directory

• In your project’s root directory, create a new folder:

mkdir .circleci

3.2 Create and Edit config.yml

• Inside the .circleci directory, create a configuration file:

touch .circleci/config.yml

• Open the config.yml file using a text editor to define your CI/CD workflows.

Step 4: Configuring the CircleCI Pipeline

4.1 Basic Configuration Example

version: 2.1
jobs:
  setup_workspace:
    docker:
      - image: maven:3.8.5-openjdk-11
    steps:
      - checkout
      - run:
          name: Setup Workspace
          command: |
            mkdir -p /home/circleci/project
      - persist_to_workspace:
          root: /home/circleci/project
          paths:
            - .
  build_test:
    docker:
      - image: maven:3.8.5-openjdk-11
    steps:
      - attach_workspace:
          at: /home/circleci/project
      - run:
          name: Build and Test
          command: mvn clean install
  lint_code:
    docker:
      - image: maven:3.8.5-openjdk-11
    steps:
      - attach_workspace:
          at: /home/circleci/project
      - run:
          name: Lint Code
          command: mvn com.coveo:fmt-maven-plugin:format
  snyk_scan:
    docker:
      - image: maven:3.8.5-openjdk-11
    steps:
      - attach_workspace:
          at: /home/circleci/project
      - run:
          name: Snyk Scan
          command: snyk test
  build_docker_image:
    docker:
      - image: maven:3.8.5-openjdk-11
    steps:
      - attach_workspace:
          at: /home/circleci/project
      - setup_remote_docker:
          docker_layer_caching: true
      - run:
          name: Build Docker Image
          command: |
            docker build -t myapp:latest .
            docker push myapp:latest
workflows:
  version: 2
  build_and_deploy:
    jobs:
      - setup_workspace
      - build_test:
          requires:
            - setup_workspace
      - lint_code:
          requires:
            - build_test
      - snyk_scan:
          requires:
            - lint_code
      - build_docker_image:
          requires:
            - snyk_scan

Advanced Configuration

5.1 Branch Filtering

• Apply branch filters to control workflow execution:

filters:
   branches:
     only: main

5.2 Environment Variables

• Securely manage credentials like API tokens in the CircleCI Project Settings > Environment Variables section.

5.3 Custom Workflows

• Utilize matrix builds, reusable commands, and parameterized jobs to streamline complex workflows.

Conclusion :-

By following this guide, you can effectively set up and optimize CircleCI for your project, enabling automated builds, tests, and deployments. For further details, explore CircleCI Documentation.