Note_Tech

All technological notes.

Project maintained by simonangel-fong Hosted on GitHub Pages — Theme by mattgraham

Jenkins - Agent

Jenkins - Agent

Jenkins Agent

Jenkins agent
- formerly “slave” or simply “node”
- a separate machine, virtual machine, or container that connects to a Jenkins controller to execute build, test, and deployment jobs

Agent Type	Description
Built-in agent	Runs jobs directly on the Jenkins controller itself Jenkins controller runs jobs locally
Static agent	A fixed VM, physical server, or long-running machine connected to Jenkins
Dynamic agent	An agent created on demand when a job starts and removed after the job finishes

Docker agent needs to mount host Docker socket: -v /var/run/docker.sock:/var/run/docker.sock

Static Docker Agent

Architecture:
- Jenkins controller (Docker)
- Separate container running:
  - long-running
  - jenkins-agent image

docker network create jenkins-net

# connect jenkins
docker network connect jenkins-net jenkins

Setup agent
- Manage Jenkins -> Nodes -> New node

Create agent

docker run -d \
  --name jenkins-agent \
  --network jenkins-net \
  -e JENKINS_URL=http://jenkins:8080/ \
  -e JENKINS_AGENT_NAME=docker-agent \
  -e JENKINS_SECRET=<secret>  \
  -v jenkins-agent-work:/home/jenkins/agent \
  jenkins/inbound-agent

run pipeline

pipeline {
    agent { label 'docker' }

    stages {
        stage('Hello') {
            steps {
                sh 'echo Hello World from agent'
                sh 'hostname'
            }
        }
    }
}

Dynamic Agents

Docker Agents

need:
- mount host Docker socket: -v /var/run/docker.sock:/var/run/docker.sock
Spins up a fresh container per build
production standard
Example:

pipeline {
    agent {
        docker {
            image 'node:18'
        }
    }
    stages {
        stage('Build') {
            steps {
                sh 'node -v'
                sh 'npm install'
            }
        }
    }
}

Kubernetes Agents

MOST COMMON in production
- EKS / GKE / AKS environments
With Kubernetes plugin:
- Jenkins dynamically creates pods as agents

pipeline {
    agent {
        kubernetes {
            yaml """
apiVersion: v1
kind: Pod
spec:
  containers:
  - name: node
    image: node:18
    command:
    - cat
    tty: true
"""
        }
    }
    stages {
        stage('Build') {
            steps {
                container('node') {
                    sh 'node -v'
                }
            }
        }
    }
}