Jenkins nodes on Docker containers

Jenkins is most popular an open source automation server written in Java. It has many interesting plugins and features. Today, I’m going to show you one of them – how to set up Jenkins master server with one slave instance connected to master. So that we will be able to run distributed builds using few docker containers. For that sample we use docker images of Jenkins (jenkins) and Jenkins slave (jenkinsci/jnlp-slave). Let’s start from running Jenkins docker container.

docker run -d --name jenkins -p 50000:50000 -p 50080:8080 jenkins

Go to management console (http://192.168.99.100:50080) and select Manage Jenkins -> Manage Nodes and then click New Node. In the next page you have to put the slave name – for that sample is slave-1. After clicking OK you will see new node on the list. Now, you can configure it by clicking setting button and display node details by clicking node name on the list.

New node is created by is still disabled. After clicking node you will see the page with details. The important information is in command secret line property. Copy that token.

Now, we are going to run docker image with JNLP agent. In the docker run command we paste Jenkins master URL, secret token and chosen node name (slave-1). If you would like to set up it without docker container you should download slave agent JAR file by clicking Launch button and run agent from command line like in the picture above.

docker run -d --name jenkins-slave1 jenkinsci/jnlp-slave -url http://192.168.99.100:50080 5d681c12e9c68f14373d62375e852d0874ea9daeca3483df4c858ad3556d406d slave-1

After running slave container you should see name slave-1 in the Build Executor Status below master node.

Now, we could configure sample Jenkins pipeline to test our new slave. Pipeline builds could be ran on master node or on slave node. Here sample pipeline fragment. For trying that sample you need to have Pipeline Plugin installed on your Jenkins server.

node() {
    stage('Checkout') {
        ...
    }

    stage('Build') {
        ...
    }
}

You can select the node for running your pipeline by providing node name. Now, build always run on slave-1 node.

node('slave-1') {
    stage('Checkout') {
        ...
    }

    stage('Build') {
        ...
    }
}