Jenkins Master (Server)

Jenkins’s server or master node holds all key configurations. The Jenkins master server is like a control server that orchestrates all the workflow defined in the pipelines. For example, scheduling a job, monitoring the jobs, etc.

Jenkins Agent

An agent is typically a machine or container that connects to a Jenkins master and this agent actually executes all the steps mentioned in a Job. When you create a Jenkins job, you have to assign an agent to it. Every agent has a label as a unique identifier.

When you trigger a Jenkins job from the master, the actual execution happens on the agent node that is configured in the job.

A single, monolithic Jenkins installation can work great for a small team with a relatively small number of projects. As your needs grow, however, it often becomes necessary to scale up.

Jenkins provides a way to do this called “master to agent connection.” Instead of serving the Jenkins UI and running build jobs all on a single system, you can provide Jenkins with agents to handle the execution of jobs while the master serves the Jenkins UI and acts as a control node.

Pre-requisites

Let’s say we’re starting with a fresh Ubuntu 22.04 Linux installation. To get an agent working make sure you install Java ( same version as Jenkins master server ) and Docker on it.

Note:- While creating an agent, be sure to separate rights, permissions, and ownership for jenkins users.

Task-01

• Create an agent by setting up a node on Jenkins

• Create a new AWS EC2 Instance and connect it to the master(Where Jenkins is installed)

• The connection of master and agent requires SSH and the public-private key pair exchange.

• Verify its status under "Nodes" section.

• You can follow this article for the same

Task-02

• Run your previous Jobs (which you built on Day 26, and Day 27) on the new agent

• Use labels for the agent, your master server should trigger builds for the agent server.

Pre-requisites:

-Java should be installed on both instances Jenkins-master and Jenkins-agent.
-Docker and Docker-compose should be installed on both instances Jenkins-master and Jenkins-agent

Points to be remembered:

1. ssh-keygen command will be run on Jenkins-master.

2. id_rsa.pub will be copied on Jenkins-agent at '.ssh' location under authorised.keys file

3. id_rsa will be copied and pasted under the private key section of Jenkins Credentials Providers while creating Agent Node on Jenkins-master Dashboard.

Steps:

1. Create two EC2-instance one for Jenkins-server and the other for Jenkins-agent (Slave)

   

2. Generate SSH keys on 'Jenkins-server' through 'ssh-keygen'.

   

3. Go to the .ssh folder to get generated public and private keys.

   

4. Copy <id_rsa.pub> key from the 'Jenkins-master' server and add it to Jenkins-agent at '.ssh/authorized_keys' location.

   

5. Login to Jenkins-server Dashboard and go to Manage Jenkins.

   

6. Go to 'Nodes'

   

7. Click on +New Node and add details of the Jenkins-agent node

   

   

   

   Add the private key of the Jenkins-master server at the private key option

   

   

   

8. Save and refresh the icon, the agent dev created.

   

9. Created a declarative pipeline job for node-todo-app

   

   

   

   

10. Deploy the code

    

11. Console output

    

    

12. Access deployed todo-app through Jenkins-agent ip.

    

"Thank you for reading my blog! Happy Learning!!!😊

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