Jenkins is a continuous integration server that detects code changes, runs automated builds and tests, and can deploy code. It supports defining build pipelines as code to make them version controlled and scalable. Popular plugins allow Jenkins pipelines to integrate with tools for testing, reporting, notifications, and deployments. Pipelines can define stages, run steps in parallel, and leverage existing Jenkins functionality.

1. Jenkins
& Continuous Integration

2. What is Continuous integration
 A development methodology
 Of daily developer integrations
 Verified by automated builds
 Every commit triggers a build
As soon as you have completed an independent functionality
A full build on another, empty machine

3. Why use continuous integration
 Automate the build
 Make the build self testing
 Keep the build fast
 Test in a clone of the production environment
 Everyone can see what's happening
 Automate deployment

4. Self-testing build
 Directly go from source to running build
No manual copying
No click on dialog boxes
No configuration file editing
 Test with
Unit tests
Functional tests (web tests)
Performance tests
 Responsible persons should be notified when
anything fails
 Tests web in more browsers

5. Why Jenkins?
● Continuous integration server - detects changes
in Subversion, performs tasks, repeatedly.
(Build, Test, Deploy, Test, Package)
● Seven years old approx
● 47000+ installations
● 600+ plugins
● Free !!!!!!

6. Jenkins Demo
docker run -p 8080:8080 -p 50000:50000
jenkins/jenkins:lts
java -jar jenkins.war -httpPort=8080

7. Configuration as Code
• Define jobs/pipelines as code
• Avoid point & click
• In version control
• Can live with the application
• Scales better
• Example: .travis.yml (from TravisCI)
• Similar to GitlabCI

8. Job Pipelines
●Job - a unit of work for a project
You can chain jobs together in a pipeline.
Promotion occurs when a job succeeds
Then the next job in the pipeline executes
(based on some conditions)

9. Jenkins Pipeline Plugins
• Whole suite of plugins (10+), open-sourced in 2016
• Shipped with Jenkins 2.0
• Formerly commercially available by CloudBees, called Work
• Define pipeline as code (again Groovy DSL)

10. Pipeline as code
• Introduce “Pipeline” as a new type in Jenkins
• Codify an implicit series of stages into an explicit pip
• Resumability/durability of pipeline state
• Extend the DSL to meet organizational needs

11. Jenkins Job DLS Steps
Jenkinsfile describe pipeline using Jenkins Pipeline DSL
Jenkins Pipeline DSL consist of steps like:
stage: starts a new pipeline stage
node: executes steps on an agent (node) with the
corresponding name / label
checkout: checkouts code from SCM (e.g. Git or SVN)
sh: executes command line or shell script
bat: executes Windows command line or script
junit: publishes JUnit test results

12. Sample nodejs pipeline
node('testing') {
stage('Initialize') {
echo 'Initializing...'
def node = tool name: 'Node-7.4.0', type: 'jenkins.plugins.nodejs.tools.NodeJSInstallation'
env.PATH = "${node}/bin:${env.PATH}"
}
stage('Checkout') {
echo 'Getting source code...'
checkout scm
}
stage('Build') {
echo 'Building dependencies...'
sh 'npm i'
}
stage('Test') {
echo 'Testing...'
sh 'npm test'
}
stage('Publish') {
echo ‘Publishing report...'
}
}

13. Workflow-stage
●https://jenkins.cloudops.careerbuilder.com/job/RecruitmentPlatform/job/wfa-ts/job/Publish/workflow-stage/

14. Plugins that support Pipeline
• A few plugins which provide custom steps for Pipeline scripts:
- Tooling: Credentials binding, SSH Agent, Parallel Test
- Reporters: JUnit, Brakeman, HTML Publisher, Cucumber Test
- Notifiers: Slack, HipChat, email-ext
- Wrappers: Timestamper
• Plugins work within Pipelines
- SCM: Git, SVN, Mercurial, P4, CV
- Wrappers: Ansi Color, NodeJS
- Build steps: Ant, etc

15. Parallel Execution of Steps
parallel(
//Both deployments are executed in parallel
deployToEnv1: {
node('environment-1') {
deploy(…)
}
},
deployToEnv2: {
node(environment-2') {
deploy(…)
}
}
)
//Execution continues after the longer step
finishes

16. Use existing plugins in pipeline
 It is possible to use existing Jenkins Plug-ins if they added Pipeline support
 Majority of popular Jenkins plug-ins support Pipeline already (see list here)
 E.g. Email-Ext plug-in:
emailext(
subject: "Build #$buildNumber, $status",
recipientProviders:'CulpritsRecipientProvider'
…
)

17. Docker Support
Jenkins Pipeline also provides Docker support
See Orchestrating Workflows with Jenkins and Docker
docker.image('.../java8-maven').inside {
checkout svn
sh 'mvn -B clean install'
}

18. wfa-ts/Publish.Jenkinsfile
CloudOps/blob/master/Jenkins/Pipelines/RecruitmentPlatform/wfa

19. Blue Ocean Plugin
 Jenkins will soon get a new UI optimized for pipelines:
Blue Ocean – see the following slides
 It can be installed from the experimental update center:
http://updates.jenkins-ci.org/experimental/update-
center.json
New UI –Blue Ocean