DevOps Classroom notes 26/Nov/2023

Jenkins contd

Configuring email notifications in jenkins

• Manage Jenkins => System => Email Notification
• use mailtrap details with tls enabled on port 587 and test configuration
  

Environment variables in jenkins

• Jenkins master injects environmetal variables with information about various aspects such as
  • GIT DETAILS
  • BUILD DETAILS
  • WORKSPACE DETAILS
• Navigate below for the whole list

JENKINS_HOME=/var/lib/jenkins
GIT_PREVIOUS_SUCCESSFUL_COMMIT=c4081c09f8231a44e7d8d898a1ad4476f827da36
USER=jenkins
CI=true
RUN_CHANGES_DISPLAY_URL=http://34.222.10.63:8080/job/spring-petclnic-daybuild/5/display/redirect?page=changes
NODE_LABELS=built-in
HUDSON_URL=http://34.222.10.63:8080/
GIT_COMMIT=c4081c09f8231a44e7d8d898a1ad4476f827da36
HOME=/var/lib/jenkins
BUILD_URL=http://34.222.10.63:8080/job/spring-petclnic-daybuild/5/
HUDSON_COOKIE=29a01ce1-e58d-4b7a-9b23-ae1975c228d1
JENKINS_SERVER_COOKIE=c55384f90aa648b4
NOTIFY_SOCKET=/run/systemd/notify
SYSTEMD_EXEC_PID=375
WORKSPACE=/var/lib/jenkins/workspace/spring-petclnic-daybuild
LOGNAME=jenkins
NODE_NAME=built-in
JOURNAL_STREAM=8:17665
RUN_ARTIFACTS_DISPLAY_URL=http://34.222.10.63:8080/job/spring-petclnic-daybuild/5/display/redirect?page=artifacts
EXECUTOR_NUMBER=1
GIT_BRANCH=origin/main
RUN_TESTS_DISPLAY_URL=http://34.222.10.63:8080/job/spring-petclnic-daybuild/5/display/redirect?page=tests
BUILD_DISPLAY_NAME=#5
HUDSON_HOME=/var/lib/jenkins
JOB_BASE_NAME=spring-petclnic-daybuild
PATH=/usr/lib/jvm/java-1.17.0-openjdk-amd64/bin:/usr/lib/jvm/java-1.17.0-openjdk-amd64/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin
INVOCATION_ID=a1556e10e7bb446795e87a1e2a56deca
BUILD_ID=5
BUILD_TAG=jenkins-spring-petclnic-daybuild-5
LANG=C.UTF-8
JENKINS_URL=http://34.222.10.63:8080/
JOB_URL=http://34.222.10.63:8080/job/spring-petclnic-daybuild/
GIT_URL=https://github.com/dummyrepos/spring-petclinic-nov23.git
BUILD_NUMBER=5
SHELL=/bin/bash
RUN_DISPLAY_URL=http://34.222.10.63:8080/job/spring-petclnic-daybuild/5/display/redirect
HUDSON_SERVER_COOKIE=c55384f90aa648b4
JOB_DISPLAY_URL=http://34.222.10.63:8080/job/spring-petclnic-daybuild/display/redirect
JOB_NAME=spring-petclnic-daybuild
JAVA_HOME=/usr/lib/jvm/java-1.17.0-openjdk-amd64
PWD=/var/lib/jenkins/workspace/spring-petclnic-daybuild
GIT_PREVIOUS_COMMIT=c4081c09f8231a44e7d8d898a1ad4476f827da36
WORKSPACE_TMP=/var/lib/jenkins/workspace/spring-petclnic-daybuild@tmp

• Using environmental variables we have copied the jar into /tmp folder

#!/bin/bash
# create a folder in /tmp
TARGET="/tmp/$JOB_BASE_NAME/$BUILD_ID"
SOURCE="$WORKSPACE/target/spring-petclinic*.jar"
mkdir -p $TARGET
cp $SOURCE $TARGET

• For custom needs ENVIRONMENTAL Variables are useful
• Lets assume i need to copy the jar file in the folder which user will pass.
• To enable users passing information we have parameters in Jenkins
• Lets create a parameter where user can enter folder
  
  
  
  
  
  

Executors in Jenkins

• In jenkins every node will have executors.
• The number of parallel projects which you can build depend on number of executors
• Always ensure you terminate the jobs by defining the hard limits of time to keep your executors ready to serve other projects
  

Distributed Builds in jenkins

• Jenkins allows to add nodes to Master
• Each node will have labels
• Every Jenkins job that needs to run on a specific node should match the label.
  
• There are two ways of connecting nodes
  • Linux: By configuring ssh connections
  • Windows: Configure using
    • JNLP
    • Windows Service

Scenario: Lets create two nodes

• Lets create two nodes
• first node:
  • LABEL: MAVEN, JDK_17
  • Softwares:
    • Openjdk 17
    • maven
  • Executor: 4
• Screenshots for first node:
  
  
  
  
  
  
  
  
  
  
  
• second node:
  • LABEL: DOTNET, DOCKER
  • Softwares:
    • Dotnet 7 Refer Here
    • Docker Refer Here
  • Executors: 2
• Third node:
  • LABEL: TERRAFORM, K8S
  • Softwares:
    • Terraform Refer Here
    • Kubectl
• On Linux nodes, Jenkins expects JDK to be present

Jenkins Plugins

• Plugins provide additional functionality to jenkins
• In free style projects the functionality will be provided as UI (User interface) and for pipeline projects it provides steps.
• Jenkins plugins can be developed in java language.
• Jenkins custom plugins will have two valid extensions
  • hpi (hudson plugin interface)
  • jpi (jenkins plugin interface)