Using OpenShift Pipeline Plugin with External Jenkins

OpenShift provides a Jenkins Container as the CI/CD tool to run on an OpenShift cluster. You can use this tool to set up your CI/CD pipelines in order to deploy applications to an OpenShift cluster or elsewhere. However, we do come across use cases where there is a need to run Jenkins outside OpenShift and still deploy applications to an OpenShift cluster. For example, some organizations have invested in CI/CD infrastructure that they want to reuse for workloads deployed to OpenShift.

There are a few ways to use an external Jenkins to deploy applications to OpenShift:

1. You can install an oc command line tool on the external Jenkins server and use oc mechanism to deploy applications to OpenShift.
2. You can use REST APIs to interact with OpenShift.
3. You can use OpenShift plugin to deploy applications to OpenShift.

In this post, we'll focus on the third option.

Step 1: Install Pipeline Plugin

On your Jenkins console, go to "Manage Jenkins" option and "Manage Plugins." Search for OpenShift Pipeline Jenkins Plugin in the "Available" tab and install it.
Note: Make sure that the Jenkins Pipeline Plugin is installed.

Now we are ready to set up a pipeline.

Step 2: Set up a Pipeline

Now go to Jenkins Home and add a "New Item" on the left menu. Input a value for the field "Enter an item name" and choose "Pipeline" and press OK. On the next page:

• Add a "Description" (this is optional).
• Check the box for "This project is parameterized." It will display the Add Parameter button. Add the following parameters:
  • String parameter named KUBERNETES_SERVICE_HOST and set the Default Value as your OpenShift host URL.
  • Boolean parameter named SKIP_TLS checked by default.
  • Password parameter named AUTH_TOKEN set to your token value. You can login to the same OpenShift server using oc login on your workstation and run oc whoami -t to get the token value to use here.
• Scroll down to the end and add the pipeline script in the Pipeline section. For this exercise, we will use the following example script:

node('') {

stage 'buildInDevelopment'

openshiftBuild(namespace: 'development', buildConfig: 'myapp', showBuildLogs: 'true')

stage 'deployInDevelopment'

openshiftDeploy(namespace: 'development', deploymentConfig: 'myapp')

openshiftScale(namespace: 'development', deploymentConfig: 'myapp',replicaCount: '2')

}

This script has two stages:

1. In the buildInDevelopment stage, it starts a build by invoking the build configuration named myapp in the project named development using the openshiftBuild step.
2. In the deployInDevelopment stage, it deploys using the deployment configuration named myapp using the openshiftDeploy step. Then it scales up the application to 2 replicas using the openshiftScale step.

The documentation for these steps from the OpenShift Jenkins Pipelines plugin is available here. I recommend exploring all the possibilities.

Step 3: Create the Build and Deployment Configurations

Because we are trying to use build and deployment configurations in the project named "development" from the pipeline, we will have to first create those following these steps:

• Create a project named "development" from the web console
• Add to project an application (for example, use PHP latest)
• Name the application "myapp"
• Provide a Git URL for source code (for example, https://github.com/openshift/cakephp-ex.git)
• Click on advanced options
• Uncheck the three options under "Build Configuration:"
  • Configure a webhook build trigger
  • Automatically build a new image when the builder image changes
  • Launch the first build when the build configuration is created
• Uncheck the two "Autodeploy" options under "Deployment Configuration"
  • New image is available
  • Deployment configuration changes

Step 4: Start the Pipeline

Now go back to Jenkins and start the pipeline. Observe build, deployment, and scale up on the OpenShift web console while the pipeline stages are executed in the Jenkins console.

Summary

In this article, I showed how to set up a external Jenkins to talk to an OpenShift cluster using Jenkins Pipeline plugin and described how to use it.