DevOps Classroomnotes 13/May/2022

Jenkins Project

• In Jenkins the traditional way of creating project/job is called as Free Style
• The Free Style Jenkins Job Contains the following sections
  • General
    • Basic information about project
  • Source Code Management:
    • Section for configuring SCM
  • Build Triggers:
    • Section for configuring when to start the build
  • Build Environment:
    • Has information and options to control workspace and logs
  • Build:
    • This is section used to configure the builds
  • Post Build:
    • Actions to be performed after the build is complete
• Jenkins is a plugin based tool, the Functionality to show UI to the user and converting the interaction into low level commands is done by Plugin.
• Plugins can be developed by using Java Language
• There are lot of community plugins. Plugins generally have the format of hpi (hudson plugin interface) or jpi (jenkins plugin interface)
• Before installing subversion plugin
  
• Lets install a plugin for Subversion
  
  
  
  
  
• Plugins of the jenkins are available at Refer Here
• Plugins can be installed in 3 ways
  • Using the Plugins UI
  • Using the Jenkins-cli
  • Direct Upload
    
• Lets directly upload the plugin
  
  
  

Distributed Builds

• When we work with any CI/CD system, Working with one server is not possible due to various reasons
  • Projects might have different build environments
  • Every build on one server will make this a single point of failure
    
• So jenkins supports distributed builds, where we can have a jenkins master is the central server to create and configure jobs and then to run the jenkins jobs, we create jenkins nodes.
• Jenkins node is a different machine with jenkins agent in it.
• Jenkins nodes have labels and Jenkins master will try to identify the best fit node for the project based on the labels on the node.
• If the labels on the project/job match node, then jenkins will execute the job on a particular node as mentioned in the below image
  
• To establish the communication between jenkins master and nodes, jenkins has by default two ways
  • Controller based
  • SSH Based
• Refer Here for the official docs to connect to nodes
• Lets create two more linux servers. On these server lets create a user called as jenkins and give admin permissions (sudo permission without password)
  • In one server i will be install java 8
    
  • In other server i will be install java 11
• Now lets configure Node-1 (jdk 8 and mvn) as a node via ssh to the jenkins server
• Manage Jenkins => Manage Nodes
  
  
  
  
  
• Lets create a project to run on node-1 to build game of life Refer Here. In this project i will be using the forked verson Refer Here
  
  
  
  
  
  
  
  
• Now lets configure the node2 with jdk11 and maven
  
  
• Jenkins can run multiple projects in parallel, but one project will be assigned to only one executor
  
• If you want to change this, we need to configure concurrent builds
  
  
• When we execute any jenkins project a build id which is by default a running number (Start from 1 ) is assigned.