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Jenkins

Overview

OpenShift Container Platform provides a container image for running Jenkins. This image provides a Jenkins server instance, which can be used to set up a basic flow for continuous testing, integration, and delivery.

This image also includes a sample Jenkins job, which triggers a new build of a BuildConfig defined in OpenShift Container Platform, tests the output of that build, and then on successful build, retags the output to indicate the build is ready for production.

Versions

OpenShift Container Platform follows the LTS releases of Jenkins. Currently, OpenShift Container Platform provides versions 1.x and 2.x.

Images

These images come in two flavors, depending on your needs:

  • RHEL 7

  • CentOS 7

RHEL 7 Based Images

The RHEL 7 images are available through the Red Hat Registry:

$ docker pull registry.access.redhat.com/openshift3/jenkins-1-rhel7
$ docker pull registry.access.redhat.com/openshift3/jenkins-2-rhel7

CentOS 7 Based Images

This image is available on Docker Hub:

$ docker pull openshift/jenkins-1-centos7
$ docker pull openshift/jenkins-2-centos7

To use these images, you can either access them directly from these registries or push them into your OpenShift Container Platform Docker registry. Additionally, you can create an ImageStream that points to the image, either in your Docker registry or at the external location. Your OpenShift Container Platform resources can then reference the ImageStream. You can find example ImageStream definitions for all the provided OpenShift Container Platform images.

Configuration and Usage

Initializing Jenkins

You can manage Jenkins authentication in two ways:

  • OpenShift Container Platform OAuth authentication provided by the OpenShift Login plug-in.

  • Standard authentication provided by Jenkins

OpenShift Container Platform OAuth authentication

OAuth authentication is activated by configuring the Configure Global Security panel in the Jenkins UI, or by setting the OPENSHIFT_ENABLE_OAUTH environment variable on the Jenkins Deployment Config to anything other than false. This activates the OpenShift Login plug-in, which retrieves the configuration information from pod data or by interacting with the OpenShift Container Platform API server.

Valid credentials are controlled by the OpenShift Container Platform identity provider. For example, if Allow All is the default identity provider, you can provide any non-empty string for both the user name and password.

Jenkins supports both browser and non-browser access.

Valid users are automatically added to the Jenkins authorization matrix at log in, where OpenShift Container Platform Roles dictate the specific Jenkins permissions the user will have.

Users with the admin role will have the traditional Jenkins administrative user permissions. Users with the edit or view role will have progressively less permissions. See the Jenkins image source repository README for the specifics on the OpenShift roles to Jenkins permissions mappings.

The admin user that is pre-populated in the OpenShift Container Platform Jenkins image with administrative privileges will not be given those privileges when OpenShift Container Platform OAuth is used, unless the OpenShift Container Platform cluster administrator explicitly defines that user in the OpenShift Container Platform identity provider and assigns the admin role to the user.

Jenkins' users permissions can be changed after the users are initially established. The OpenShift Login plug-in polls the OpenShift Container Platform API server for permissions and updates the permissions stored in Jenkins for each user with the permissions retrieved from OpenShift Container Platform. If the Jenkins UI is used to update permissions for a Jenkins user, the permission changes are overwritten the next time the plug-in polls OpenShift Container Platform.

You can control how often the polling occurs with the OPENSHIFT_PERMISSIONS_POLL_INTERVAL environment variable. The default polling interval is five minutes.

The easiest way to create a new Jenkins service using OAuth authentication is to use a template as described below.

Jenkins Standard Authentication

Jenkins authentication is used by default if the image is run directly, without using a template.

The first time Jenkins starts, the configuration is created along with the administrator user and password. The default user credentials are admin and password. Configure the default password by setting the JENKINS_PASSWORD environment variable when using (and only when using) standard Jenkins authentication.

To create a new Jenkins application using standard Jenkins authentication:

$ oc new-app -e \
    JENKINS_PASSWORD=<password> \
    openshift/jenkins-1-centos7

Environment Variables

The Jenkins server can be configured with the following environment variables:

Table 1. Jenkins Environment Variables
Variable name Description

JENKINS_PASSWORD

The password for the admin user when using standard Jenkins authentication. Not applicable when using OpenShift Container Platform OAuth authentication.

OPENSHIFT_ENABLE_OAUTH

Determines whether the OpenShift Login plug-in manages authentication when logging into Jenkins. Enabled when set to any non-empty value other than "false".

OPENSHIFT_PERMISSIONS_POLL_INTERVAL

Specifies in seconds how often the OpenShift Login plug-in polls OpenShift Container Platform for the permissions associated with each user defined in Jenkins.

Cross Project Access

If you are going to run Jenkins somewhere other than as a deployment within your same project, you will need to provide an access token to Jenkins to access your project.

  1. Identify the secret for the service account that has appropriate permissions to access the project Jenkins needs to access:

    $ oc describe serviceaccount default
Name:       default
Labels:     <none>
Secrets:    {  default-token-uyswp    }
            {  default-dockercfg-xcr3d    }
Tokens:     default-token-izv1u
            default-token-uyswp

    In this case the secret is named default-token-uyswp

  2. Retrieve the token from the secret:

    $ oc describe secret <secret name from above> # e.g. default-token-izv1u
Name:       default-token-izv1u
Labels:     <none>
Annotations:    kubernetes.io/service-account.name=default,kubernetes.io/service-account.uid=32f5b661-2a8f-11e5-9528-3c970e3bf0b7
Type:   kubernetes.io/service-account-token
Data
====
ca.crt: 1066 bytes
token:  eyJhbGc..<content cut>....wRA

The token field contains the token value Jenkins needs to access the project.

Volume Mount Points

The Jenkins image can be run with mounted volumes to enable persistent storage for the configuration:

  • /var/lib/jenkins - This is the data directory where Jenkins stores configuration files including job definitions.

Creating a Jenkins Service from a Template

Templates provide parameter fields to define all the environment variables (password) with predefined defaults. OpenShift Container Platform provides templates to make creating a new Jenkins service easy. The Jenkins templates should have been registered in the default openshift project by your cluster administrator during the initial cluster setup. See Loading the Default Image Streams and Templates for more details, if required.

The two available templates both define a deployment configuration and a service. The templates differ in their storage strategy, which affects whether or not the Jenkins content persists across a pod restart.

A pod may be restarted when it is moved to another node, or when an update of the deployment configuration triggers a redeployment.

  • jenkins-ephemeral uses ephemeral storage. On pod restart, all data is lost. This template is useful for development or testing only.

  • jenkins-persistent uses a persistent volume store. Data survives a pod restart. To use a persistent volume store, the cluster administrator must define a persistent volume pool in the OpenShift Container Platform deployment.

Once you have selected which template you want, you must instantiate the template to be able to use Jenkins:

Creating a New Jenkins Service

  1. Ensure the the default image streams and templates are already installed.

  2. Create a new Jenkins application using:

    1. A persistent volume:

$ oc new-app jenkins-persistent

  1. Or an emptyDir type volume (where configuration does not persist across pod restarts):

$ oc new-app jenkins-ephemeral

If you instantiate the template against releases prior to v3.4 of OpenShift Container Platform, standard Jenkins authentication is used, and the default admin account will exist with password password. See Jenkins Standard Authentication for details about changing this password.

Using Jenkins as a Source-To-Image builder

To customize the official OpenShift Container Platform Jenkins image, you have two options:

  • Use Docker layering.

  • Use the image as a Source-To-Image builder, described here.

You can use S2I to copy your custom Jenkins Jobs definitions, additional plug-ins or replace the provided config.xml file with your own, custom, configuration.

In order to include your modifications in the Jenkins image, you need to have a Git repository with the following directory structure:

plugins

This directory contains those binary Jenkins plug-ins you want to copy into Jenkins.

plugins.txt

This file lists the plug-ins you want to install:

pluginId:pluginVersion
configuration/jobs

This directory contains the Jenkins job definitions.

configuration/config.xml

This file contains your custom Jenkins configuration.

The contents of the configuration/ directory will be copied into the /var/lib/jenkins/ directory, so you can also include additional files, such as credentials.xml, there.

The following is an example build configuration that customizes the Jenkins image in OpenShift Container Platform:

apiVersion: v1
kind: BuildConfig
metadata:
  name: custom-jenkins-build
spec:
  source:                       (1)
    git:
      uri: https://github.com/custom/repository
    type: Git
  strategy:                     (2)
    sourceStrategy:
      from:
        kind: ImageStreamTag
        name: jenkins:latest
        namespace: openshift
    type: Source
  output:                       (3)
    to:
      kind: ImageStreamTag
      name: custom-jenkins:latest
1 The source field defines the source Git repository with the layout described above.
2 The strategy field defines the original Jenkins image to use as a source image for the build.
3 The output field defines the resulting, customized Jenkins image you can use in deployment configuration instead of the official Jenkins image.

Using the Jenkins Kubernetes Plug-in to Run Jobs

The official OpenShift Container Platform Jenkins image includes the pre-installed Kubernetes plug-in that allows Jenkins slaves to be dynamically provisioned on multiple container hosts using Kubernetes and OpenShift Container Platform.

To use the Kubernetes plug-in, OpenShift Container Platform provides three images suitable for use as Jenkins slaves: the Base, Maven, and Node.js images.

The first is a base image for Jenkins slaves:

  • It pulls in both the required tools (headless Java, the Jenkins JNLP client) and the useful ones (including git, tar, zip, and nss among others).

  • It establishes the JNLP slave agent as the entrypoint.

  • It includes the oc client tooling for invoking command line operations from within Jenkins jobs, and

  • It provides Dockerfiles for both CentOS and RHEL images.

Two additional images that extend the base image are also provided:

Both the Maven and Node.js slave images are configured as Kubernetes Pod Template images within the OpenShift Container Platform Jenkins image’s configuration for the Kubernetes plugin. That configuration includes labels for each of the images that can be applied to any of your Jenkins jobs under their "Restrict where this project can be run" setting. If the label is applied, execution of the given job will be done under an OpenShift Container Platform pod running the respective slave image.

The Maven and Node.js Jenkins slave images provide Dockerfiles for both CentOS and RHEL that you can reference when building new slave images. Also note the contrib and contrib/bin subdirectories. They allow for the insertion of configuration files and executable scripts for your image.

The Jenkins image also provides auto-discovery and auto-configuration of slave images for the Kubernetes plug-in. The Jenkins image searches for these in the existing image streams within the project that it is running in. The search specifically looks for image streams that have the label role set to jenkins-slave.

When it finds an image stream with this label, it generates the corresponding Kubernetes plug-in configuration so you can assign your Jenkins jobs to run in a pod running the container image provided by the image stream.

Note: this scanning is only performed once, when the Jenkins master is starting. If you label additional imagestreams, the Jenkins master will need to be restarted to pick up the additional images.

To use a container image as a Jenkins slave, the image must run the slave agent as an entrypoint. For more details about this, refer to the official Jenkins documentation.

Tutorial

For more details on the sample job included in this image, see this tutorial.

OpenShift Container Platform Pipeline Plug-in

The Jenkins image’s list of pre-installed plug-ins includes a plug-in which assists in the creating of CI/CD workflows that run against an OpenShift Container Platform server. A series of build steps, post-build actions, as well as SCM-style polling are provided which equate to administrative and operational actions on the OpenShift Container Platform server and the API artifacts hosted there.

In addition to being accessible from the classic "freestyle" form of Jenkins job, the build steps as of version 1.0.14 of the OpenShift Container Platform Pipeline Plug-in are also available to Jenkins Pipeline jobs via the DSL extension points provided by the Jenkins Pipeline Plug-in. The OpenShift Jenkins Pipeline build strategy sample illustrates how to use the OpenShift Pipeline plugin DSL versions of its steps.

The sample Jenkins job that is pre-configured in the Jenkins image utilizes the OpenShift Container Platform pipeline plug-in and serves as an example of how to leverage the plug-in for creating CI/CD flows for OpenShift Container Platform in Jenkins.

See the the plug-in’s README for a detailed description of what is available.

OpenShift Container Platform Client Plug-in

The experiences gained working with users of the OpenShift Pipeline plug-in, coupled with the rapid evolution of both Jenkins and OpenShift, have provided valuable insight into how to integrate OpenShift Container Platform from Jenkins jobs.

As such, the new experimental OpenShift Client Plug-in for Jenkins is now offered as a technical preview and is included in the OpenShift Jenkins images on CentOS (docker.io/openshift/jenkins-1-centos7:latest and docker.io/openshift/jenkins-2-centos7:latest). The plug-in is also available from the Jenkins Update Center. The OpenShift Client plug-in will eventually replace the OpenShift Pipeline plug-in as the tool for OpenShift integration from Jenkins jobs. The OpenShift Client Plug-in provides:

  • A Fluent-style syntax for use in Jenkins Pipelines

  • Use of and exposure to any option available with oc

  • Integration with Jenkins credentials and clusters

  • Continued support for classic Jenkins Freestyle jobs

OpenShift Container Platform Sync Plug-in

To facilitate OpenShift Container Platform Pipeline build strategy for integration between Jenkins and OpenShift Container Platform, the OpenShift Sync plug-in monitors the API server of OpenShift Container Platform for updates BuildConfigs and Builds that employ the Pipeline strategy and either creates Jenkins Pipeline projects (when a BuildConfig is created) or starts jobs in the resulting projects (when a Build is started).