OpenShift CI/CD Concepts
External
- https://docs.openshift.com/container-platform/latest/using_images/other_images/jenkins.html
- https://blog.openshift.com/cicd-with-openshift/, youtu.be demos: 65BnTLcDAJI, wSFyg6Etwx8
- Practical Examples:
Internal
Overview
Jenkins can be deployed as a pod in OpenShift. OpenShift comes with two templates ("jerkins-ephemeral" and "jenkins-persistent", both available in the "openshift" namespace), which can be used to deploy an "ephemeral" or a "persistent" Jenkins. The "persistent" Jenkins will save its state between the pod restarts, and needs a persistent volume with sufficient storage space to be available at the time of the installation.
Once deployed, Jenkins spins up two pods: the main "jenkins" pod which contains the functionality that drives the build logic, and a "jenkins-jnlp" pod that is an auxiliary service used for master/slave communication. Why doesn't the CI/CD project have a jenkins-jnlp pod? The service exists, maybe the pod was not needed yet? There is no container template for jenkins-jnlp. The template also creates a "jenkins" service account used by the Jenkins pod to authenticate. The service account is automatically bound to the "edit" role in the target project.
The Jenkins instance can be configured build environment.
Build Environment
OpenShift Jenkins image comes pre-preconfigured to allow access to a Kubernetes CLI (kubectl) build environment, which uses the Kubernetes plugin to provision Kubernetes-based Jenkins agents.
For more details about Jenkins build environment, see:
Kubernetes Plugin
The Kubernetes plug-in is a Jenkins extension that uses a Kubernetes cluster to dynamically provision Jenkins agents, use them to run builds and then dispose of them. It does do by using Kubernetes scheduling mechanism to optimize the load.
TO DEPLETE
Deplete anything under this.
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.
Jenkins
The Jenkins Docker image for OpenShift: https://github.com/openshift/jenkins
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 pods. Jenkins executes builds in separated pods in the same project it belongs. This is possible due to the Jenkins Kubernetes Plug-in. 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").
Jenkins Kubernetes Plug-in
OpenShift Plug-in for Jenkins
What is the difference between OpenShift Plug-in for Jenkins and Jenkins Kubernetes Plug-in.
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:
TODO: OAuth authentication: https://docs.openshift.com/container-platform/latest/using_images/other_images/jenkins.html#jenkins-openshift-oauth-authentication
TODO: Standard authentication: https://docs.openshift.com/container-platform/latest/using_images/other_images/jenkins.html#jenkins-jenkins-standard-authentication
TODO: Cross-project access: https://docs.openshift.com/container-platform/latest/using_images/other_images/jenkins.html#jenkins-cross-project-access
State Persistence Considerations
The "jenkins-persistent" template requires a persistent volume, which is configured upon creation of the new application.
Pipeline
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'
}
}