Introduction

Continuous Integration/Continuous Deployment (CI/CD) has established itself as a transformative force, enabling organizations to iterate rapidly, deliver efficiently, and innovate consistently. GitLab, with its built-in CI/CD feature, is one of the prominent tools that facilitate this culture of automation. When coupled with Kubernetes—a scalable, open-source container orchestration system—developers can achieve automated, efficient, and scalable deployment cycles.

In this blog post, we dive deep into how to integrate GitLab CI/CD with a Kubernetes cluster, empowering teams to automate the build, test, and deployment processes in a streamlined manner.

Understanding the Basics

Before we delve into the integration, it's essential to understand the core components:

  • GitLab CI/CD: A part of the GitLab platform, GitLab CI/CD is a powerful tool that automates the software delivery process. It allows you to define pipeline configurations using a YAML file, called .gitlab-ci.yml,' enabling the execution of scripts at predefined stages.
  • Kubernetes: Kubernetes is a container-orchestration system designed to automate the deployment, scaling, and management of containerized applications. It groups containers into Pods, facilitating communications and the management of resources.

Setting Up the Prerequisites

  • A running Kubernetes cluster (either locally via tools like Minikube or through cloud providers such as AWS, Google Cloud, or Azure).
  • A project repository on GitLab.
  • kubectl (Kubernetes command-line tool) is configured to communicate with your cluster.

Integrating Kubernetes with GitLab

  • Navigate to your project’s “Operate”  > “Kubernetes Clusters” in your GitLab dashboard.

  • Click “Add Kubernetes cluster” and follow the instructions to connect your Kubernetes cluster. You can choose between adding an existing cluster or creating a new cluster on the cloud services that GitLab supports. Select the kind of Kubernetes cluster you want to create.

Install GitLab Runner

  • Once connected, install GitLab Runner. GitLab Runner is an application that processes jobs by running the scripts contained in .gitlab-ci.yml. It interacts with GitLab CI/CD as part of your project's pipeline.
  • In the “Kubernetes” section, after connecting your cluster, click on the “GitLab Runner” option and then Install.

Configuring the CI/CD Pipeline

Define the Pipeline Configuration

  • In your project repository, create a file named .gitlab-ci.yml. This file defines the configuration of your CI/CD pipeline.
  • Specify the stages of the pipeline (e.g., build, test, deploy) and the scripts to run at each stage. Ensure you're using the appropriate Docker images and that your scripts interact correctly with your Kubernetes cluster.
stages:
  - build
  - test
  - deploy

build:
  stage: build
  script:
    - echo "Building the application..."
    # Add build commands here

test:
  stage: test
  script:
    - echo "Testing the application..."
    # Add test commands here

deploy:
  stage: deploy
  script:
    - echo "Deploying the application..."
    - kubectl apply -f deployment.yml  # This is your Kubernetes deployment script

Kubernetes Deployment Script

  • Create a Kubernetes deployment configuration file (e.g., deployment.yml) in your project repository. This file contains the specifications of your Pods, container images, resource limits, and other crucial deployment settings.
apiVersion: apps/v1
kind: Deployment
metadata:
  name: sample-deployment
spec:
  replicas: 2
  selector:
    matchLabels:
      app: sample-app
  template:
    metadata:
      labels:
        app: sample-app
    spec:
      containers:
      - name: sample-app
        image: <YOUR_CONTAINER_IMAGE>
        ports:
        - containerPort: 80

Commit and Push

  • Commit the .gitlab-ci.yml and deployment.yml files and push them to your GitLab repository.
git add .gitlab-ci.yml deployment.yml
git commit -m "Add GitLab CI/CD pipeline and Kubernetes deployment configurations"
git push origin main


Automating the Deployment

Once you've pushed the configurations, GitLab CI/CD is triggered:

  • The GitLab Runner processes the pipeline, executing jobs for each stage defined in .gitlab-ci.yml.
  • During the deploy stage, the Runner applies the deployment.yml file, instructing Kubernetes to update the application deployment if it exists or create it if it doesn't.

Conclusion

Integrating GitLab CI/CD with Kubernetes clusters unifies and automates the software deployment lifecycle, offering fast, consistent, and reliable application delivery. This synergy not only accelerates development cycles but also minimizes the risks associated with manual deployment processes.