jenkins-limited-shared-library

A project-scoped ("limited") Jenkins shared library bundling custom pipeline steps for a full CI/CD flow:

• building a Maven JAR,
• building Docker images,
• pushing them to Docker Hub or AWS ECR,
• deploying to AWS EC2 (via SSH or SSM),
• and cleaning up old images.

Used as a Git submodule of PART3-Core / 9. Jenkins CI-CD.

What is a "limited" shared library?

Unlike a global shared library (available to every job on the controller), a project-scoped library is declared at the level of a specific folder or job, so its reach is "limited" to that project.

Each file in vars/ becomes a step that can be called directly by name into a Jenkinsfile.

Requirements

On the Jenkins agent: mvn, docker, the aws CLI (for the ECR/SSM steps), and SSH or SSM access to the target EC2 instances.

Environment variables expected by the steps:

Variable	Purpose
APP_IMAGE_NAME	image / repository name
APP_IMAGE_TAG	tag to build / keep
ECR_REGISTRY	ECR registry URL (ECR/SSM steps)

Jenkins credentials referenced:

ID	Usage
DOCKER_USERNAME	Docker Hub username
dockerhub-pat	Docker Hub access token
(AWS)	credentials / IAM role for ECR, SSM and EC2

Usage

Declare the library in the job or folder configuration (Pipeline Libraries section), then call the steps by name:

@Library('jenkins-limited-shared-library') _

pipeline {
    agent any
    environment {
        APP_IMAGE_NAME = 'my-app'
        APP_IMAGE_TAG  = "${env.BUILD_NUMBER}"
    }
    stages {
        stage('Build')  { steps { buildJar() } }
        stage('Image')  { steps { dockerhubBuildAndPushImage() } }
        stage('Deploy') { steps { ec2DeployDockerCmdSSH() } }
        stage('Clean')  { steps { dockerhubCleanImageExceptTag() } }
    }
}

Step catalogue (vars/)

Build

Step	Purpose
buildJar	mvn clean package -DskipTests to produce the JAR
localBuildJar	same, for a local run

Docker Hub

Step	Purpose
dockerhubBuildAndPushImage	builds the image and pushes it to Docker Hub
dockerhubCleanImageExceptTag	removes old tags via the registry API
localCleanDockerhubImageExceptTag	same cleanup, run locally

AWS ECR

Step	Purpose
ecrBuildAndPushImageSSM	builds the image, creates the repo if needed, pushes to ECR
ecrCleanImageExceptTagSSM	cleans ECR images via SSM
localCleanEcrImageExceptTag	cleans ECR locally

AWS EC2 deployment

Step	Purpose
ec2DeployDockerCmdSSH	deploys via SSH + docker run
ec2DeployDockerComposeSSM	deploys a docker-compose via SSM
ec2DeployEnvDockerComposeSSM	deploys compose + an environment file via SSM
ec2CleanImageExceptTagSSH	cleans images on the instance via SSH
ec2CleanImageExceptTagSSM	cleans images on the instance via SSM

Local cleanup

Step	Purpose
localCleanImageExceptTag(repository)	removes local Docker images except the current tag and <none> ones

SSH or SSM?

Several steps come in two variants:

• SSH — direct connection to the instance; requires opening port 22 and managing a key.
• SSM (AWS Systems Manager) — runs commands without opening a port or distributing a key. This is the preferred option when Jenkins runs inside AWS with an IAM role: authentication goes through the role, with no credentials or ports to expose.

Pick the variant based on where your Jenkins controller lives.

Skills demonstrated

Jenkins CI/CD (declarative pipeline, project-scoped shared library) · Groovy · Docker (build, push, cleanup) · Docker Hub & AWS ECR · AWS EC2 deployment over SSH and SSM · secure secret handling (withCredentials) · Maven.