Day 27 - Jenkins Declarative Pipeline with Docker

Welcome back to our Jenkins journey! We've already mastered the basics of Declarative Pipelines in Jenkins. Now, let's take it up a notch by integrating Docker into our pipeline. This will enable us to build and run our applications in a containerized environment. In this article, we'll walk through two tasks to achieve this: one using the sh command for Docker commands and another using Docker's Groovy syntax within the stage block.

Task 01: Using sh Command for Docker

In this task, we will use the familiar sh command to execute Docker build and run commands within our Jenkins Declarative Pipeline.

pipeline {
    agent any

    stages {
        stage('Build') {
            steps {
                sh 'docker build -t trainwithshubham/django-app:latest .'
            }
        }

        stage('Run') {
            steps {
                sh 'docker run -d trainwithshubham/django-app:latest'
            }
        }
    }
}        

In the above code, we define a simple pipeline with two stages: 'Build' and 'Run.' In the 'Build' stage, we use the docker build command to create an image tagged as trainwithshubham/django-app:latest. In the 'Run' stage, we then use docker run to start a container from the built image.

Note: Running this pipeline multiple times may lead to errors as the Docker container might already exist. We'll address this in Task 02.

Task 02: Using Docker Groovy Syntax

To overcome the potential errors of running the job twice, we can leverage Docker's Groovy syntax within the stage block. This allows us to manage Docker containers more efficiently.

pipeline {
    agent any

    stages {
        stage('Build') {
            steps {
                script {
                    docker.image('trainwithshubham/django-app:latest').build()
                }
            }
        }

        stage('Run') {
            steps {
                script {
                    docker.image('trainwithshubham/django-app:latest').run('-d')
                }
            }
        }
    }
}        

In this version, we use the docker.image syntax to manage Docker images. The build() method is used for building the Docker image, and the run('-d') method is used for running the container in detached mode.

By adopting this approach, we ensure that the Docker container is managed more gracefully, preventing errors when the pipeline is run multiple times.

This powerful combination allows us to containerize your applications efficiently, providing consistency and reproducibility in your CI/CD workflows.