Jenkins Distributed Builds

• When we try to build a jenkins job, jenkins will try to find an executor. Jenkins server has by default 2 executor. This implies we can build two jobs in parallel.
• In an enterprise scenario, each project has its set of tools/softwares which might be different, to support this jenkins has node concept
• A node is a VM or Physical or docker container with preconfigured set of tools installed.
• We need to configure the connection b/w jenkins Server and node and also configure number of executors. Each node will/should have a label.
• Now once this configuration is done, then we can have our jobs build on different node than jenkins server
• This gives an option to have various builds configured from one highly available jenkins.
• Adding nodes to jenkins server gives us the flexibility to create various environments (QA,Dev, Staging, pre-prod)

How to configure a node to Jenkins server

• Jenkins tries to login into remote node and execute the job for this jenkins uses an agent from jenkins called as jenkins-agent
• On the jenkins node java 8 or java 11 has to be installed
• For our lab set up lets create a ubuntu 18 node install java and maven

sudo apt update
sudo apt install openjdk-8-jdk -y
sudo apt install maven -y

• To configure a linux node we need to configure the ssh communication between jenkins server and node
  • Jenkins server needs to know the username and password of the node
• Ensure password authentication is enabled by checking PasswordAuthentication value in /etc/ssh/sshd_config
• Ensure a user is created for running builds on jenkins node

sudo adduser jenkins

• Give the user necessary permissions
• Try to login into jenkins node from jenkins server as jenkins user
• Now lets try to configure this node from jenkins ui
• Now since the node is healthy lets try to build a game of life on the node
• Next Steps:
  • We have configured a linux node with ssh username and password, we need to configure with name and ssh-key
  • Other aspects of jenkins such as periodic builds, mail notifications, post build actions etc..