How to use DevOps tools such as Jenkins, Docker, Kubernetes, Ansible, etc. to automate software delivery and deployment

DevOps is a practice that involves a cultural change, new management principles, and technology tools that help to implement best practices. DevOps aims to bridge the gap between development and operations teams by enabling faster and more reliable software delivery and deployment.

One of the key aspects of DevOps is automation. Automation reduces manual errors, improves efficiency, and ensures consistency across different environments. Automation also enables continuous integration (CI) and continuous delivery (CD), which are processes that ensure code quality and rapid feedback.

In this article, we will explore some of the most popular DevOps tools that can help you automate various stages of the software development life cycle (SDLC). We will also see how they can work together to create a seamless pipeline for your software projects.

Jenkins

Jenkins is an open-source tool that provides continuous integration and continuous delivery services. Jenkins can build, test, and deploy your code automatically whenever you make changes to your source code repository. Jenkins supports various plugins that integrate with other DevOps tools such as Git, Docker, Kubernetes, Ansible, etc.

To use Jenkins for automation, you need to create a Jenkins file that defines the steps of your pipeline. A Jenkins file is a text file written in Groovy syntax that describes what actions to perform at each stage of your pipeline. For example:

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                sh 'mvn clean package'
            }
        }
        stage('Test') {
            steps {
                sh 'mvn test'
            }
        }
        stage('Deploy') {
            steps {
                sh 'scp target/my-app.jar user@server:/opt/my-app/'
                sh 'ssh user@server "java -jar /opt/my-app/my-app.jar"'
            }
        }
    }
}

This Jenkins file defines a simple pipeline that builds a Java application using Maven, runs unit tests using Maven again, and deploys the application to a remote server using secure copy (scp) and secure shell (ssh) commands.

You can store your Jenkins file in your source code repository or in Jenkins itself. You can also configure triggers for your pipeline such as polling your repository for changes or responding to webhooks from GitHub or Bitbucket.

Docker

Docker is an open-source tool that allows you to create, run, and manage containers. Containers are isolated environments that package your application code and its dependencies into a single unit. Containers make it easy to deploy your application across different platforms without worrying about compatibility issues.

To use Docker for automation, you need to create a Dockerfile that defines how to build your container image. A Dockerfile is a text file written in Docker syntax that describes what base image to use, what commands to run during the build process, what files or directories to copy into the image, what ports to expose, and what command or entrypoint to execute when running the container. For example:

FROM openjdk:11-jdk-slim
COPY target/my-app.jar /opt/my-app/
EXPOSE 8080
CMD ["java", "-jar", "/opt/my-app/my-app.jar"]

This Dockerfile defines a simple container image that uses OpenJDK 11 as the base image, copies the Java application jar file from the target directory into the /opt/my-app/ directory inside the image, exposes port 8080 for external access, and runs the Java command when starting the container.

You can build your container image using docker build command and run it using docker run command. You can also push it to a remote registry such as Docker Hub or Amazon Elastic Container Registry (ECR) using docker push command.

Kubernetes

Kubernetes is an open-source tool that provides orchestration and management services for containers. Kubernetes can scale up or down your containers based on demand, balance load across multiple nodes, handle service discovery and routing, provide health checks and self-healing capabilities, and enforce security policies and resource limits.

To use Kubernetes for automation, you need to create YAML files that define various resources such as pods, services, deployments, ingresses, etc. A pod is a group of one or more containers that share network and storage resources. A service is an abstraction that exposes a set of pods as a network service. A deployment is an object that manages the creation and update of pods based on a desired state. An ingress is an object that defines rules for external access to services in your cluster.

For example, the following YAML file defines a deployment resource that creates two replicas of a pod running an NGINX container:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: web
spec:
  selector:
    matchLabels:
      app: web
  replicas: 2 # tells deployment to run 2 pods matching the template
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2 # use NGINX version 1.14.2 
        ports:
        - containerPort: 80 # expose port 80

You can create your Kubernetes resources using kubectl apply command and delete them using kubectl delete command. You can also view and modify them using kubectl get, kubectl describe, kubectl edit, etc.

Ansible

Ansible is an open-source tool that provides configuration management and automation services. Ansible can install and configure software packages, manage users and groups, run commands and scripts, copy files and directories, etc. on remote servers or machines.

To use Ansible for automation, you need to create playbooks that define the tasks you want to perform on your target hosts. A playbook is a text file written in YAML syntax that describes what modules to use, what parameters to pass, and what conditions to check. For example:

- name: Install Apache on Ubuntu servers # name of the playbook 
  hosts: ubuntu # target hosts group 
  become: yes # use sudo privileges 
  tasks: # list of tasks 
    - name: Update apt cache # name of the task 
      apt: update_cache=yes # use apt module with update_cache parameter 

    - name: Install Apache package # name of another task 
      apt: name=apache2 state=present # use apt module with name and state parameters 

    - name: Start Apache service # name of another task 
      service: name=apache2 state=started enabled=yes # use service module with name, state, and enabled parameters

This playbook defines a simple set of tasks that install and start Apache web server on Ubuntu servers.

You can run your playbooks using ansible-playbook command. You can also test your playbooks using ansible-lint or ansible-test tools.

The bottom line

In this article, we have seen how some of the most popular DevOps tools such as Jenkins, Docker, Kubernetes, Ansible, etc. can help you automate various stages of the software development life cycle (SDLC). These tools can work together to create a seamless pipeline for your software projects that ensures faster and more reliable software delivery and deployment.

There are many other DevOps tools that you can explore such as Git for version control, Maven or Gradle for build automation, Selenium or Cucumber for testing automation, Terraform or CloudFormation for infrastructure as code (IaC), Prometheus or Grafana for monitoring, etc.

DevOps is not just about tools but also about culture and mindset. By adopting DevOps practices, you can improve collaboration between development and operations teams, enhance customer satisfaction, and deliver value faster.