OpenShift CI/CD Concepts

External

• https://docs.openshift.com/container-platform/latest/install_config/configuring_pipeline_execution.html
• https://docs.openshift.com/container-platform/latest/using_images/other_images/jenkins.html#jenkins-as-s2i-builder
• https://blog.openshift.com/cicd-with-openshift/, youtu.be demos: 65BnTLcDAJI, wSFyg6Etwx8
• https://github.com/OpenShiftDemos/openshift-cd-demo, https://github.com/OpenShiftDemos/openshift-cd-demo/tree/ocp-3.5
• https://github.com/openshift/jenkins

Internal

• Jenkins
• OpenShift Concepts
• OpenShift CI/CD Operations

Overview

OpenShift provides a certified Jenkins container for building Continuous Delivery pipelines. When necessary, it scales the pipeline execution by on-demand provisioning of multiple Jenkins containers, allowing Jenkins to run many jobs in parallel. OpenShift can integrate with Git-based source code repositories. When a developer pushes code to the GIt repository, Jenkins pulls the code and performs a project build. After the build is complete, Jenkins invokes the OpenShift master node API to initiate a "source-to-image" (S2I) build. As part of the SI process, the latest project artifact is downloaded from Jenkins and included in the image that runs in the OpenShift node.

Resources

This is the memory consumption based on a test installation:

• jenkins/jenkins-jnlp pod: 720 MB
• nexus pod: 610 MB
• gogs pod: 110 MB

Jenkins Pods and Projects

Jenkins infrastructure can run in an arbitrary project, on a per-project basis, but a more common setup is to create a dedicated CI/CD project and configure it to perform CI/CD services for other "client" projects.

The Jenkins application that is deployed with an OpenShift template comes pre-configured for slave pods - they are configured in Jenkins system configuration as Kubernetes bods. Jenkins executes builds in separated pods in the same project it belongs. However, the builds do not use Jenkins pod resources. The slave pods included with OpenShift are the base pod to build custom slave pods, Node.js and Maven ("jenkins-slave-maven-rhel7").

Security Considerations

Jenkins components need to access the OpenShift API exposed by the master for various operations: to access container images, to trigger a build, to check the status of a build, etc. so special privileges need to be assigned to the service account under whose credentials Jenkins runs. By default, Jenkins authenticates to the API using the "system:serviceaccount:<project-name>:default service account, where <project-name> is the name of the project the Jenkins pod runs in. The service account must be granted the "admin" role:

oc policy add-role-to-user admin system:serviceaccount:<jenkins-project-name>:default

"default" is a generic account, so in general is a good idea to created a dedicated "jenkins" service account, to be used by the Jenkins processes: "system:serviceaccount:<project-name>:jenkins. When Jenkins is created from template, the "jenkins" service account is created automatically.

oc policy add-role-to-user admin system:serviceaccount:<jenkins-project-name>:jenkins

Jenkins performs CI/CD services for other projects, so the service account running the Jenkins pods in the Jenkins project must be granted elevated privileges in the projects serviced by it:

oc policy add-role-to-user edit system:serviceaccount:<jenkins-project-name>:jenkins -n <client-project>

To list the roles associated with a service account, use oc get rolebindings or oc describe policyBindings.

Also see:

Grant Jenkins Needed Privileges for the Projects that Require CI/CD Services

State Persistence Considerations

The "jenkins-persistent" template requires a persistent volume, which is configured upon creation of the new application.

Pipeline

https://jenkins.io/doc/book/pipeline/overview/

Pipelines can be defined in-line in the Jenkins job, or in the source code repository, in a file named "Jenkinsfile". The pipelines are written in Groovy. Jenkins drives the pipeline, but it uses OpenShift to perform the build and the deployment, by invoking OpenShift API via "openshiftBuild", "openshiftVerifyBuild", "openshiftDeploy", "openshiftVerifyDeployment", "openshiftVerifyService". Used by the pipeline build.

The pipeline definition starts with a node() statement.

node('maven') {
...
}

defines a pipeline that runs inside of a Maven pod.

node {
...
}

defines a pipeline that executes in a Jenkins pod.

Possible node values: "maven", "nodejs", "custom".

A pipeline consists of stages, which have graphical representation in Jenkins or OpenShift UI. A stage can be used to group tasks, and they should be scoped with { and }.

Pipeline Definition

node {

 stage ("Build") {
   ...
   openshiftBuild 
                  apiURL: 'https://openshift.default.svc.cluster.local', 
                  authToken: , 
                  bldCfg: 'hello-nodejs', 
                  buildName: , 
                  checkForTriggeredDeployments: 'false', 
                  commitID: , 
                  namespace: , 
                  showBuildLogs: 'false', 
                  verbose: 'false', 
                  waitTime: 
   openshiftVerifyBuild 
                  apiURL: 'https://openshift.default.svc.cluster.local', 
                  authToken: ,
                   bldCfg: 'hello-nodejs',
                   checkForTriggeredDeployments: 
                  'false', namespace: , 
                  verbose: 'false'
   openshiftTag 
                  ...
 }
 stage ("Deploy") {
   ...
   openshiftDeploy  
                  apiURL: 'https://openshift.default.svc.cluster.local', 
                  authToken: , 
                  depCfg: 'hello-nodejs', 
                  namespace: , 
                  verbose: 'false', 
                  waitTime: 
   openshiftVerifyDeployment  
                  apiURL: 'https://openshift.default.svc.cluster.local', 
                  authToken: , 
                  depCfg: 'hello-nodejs', 
                  namespace: , 
                  replicaCount: '1',                    
                  verbose: 'false', 
                  verifyReplicaCount: 'false', 
                  waitTime: 
 }
 stage ("Verify") {
   ...
    openshiftVerifyService  
                  apiURL: 'https://openshift.default.svc.cluster.local', 
                  authToken: , 
                  namespace: , 
                  svcName: 'hello-nodejs', 
                  verbose: 'false'
 }
}

Jenkins Operations

OpenShift CI/CD Operations