Create Jenkins jobs using Docker

This document describes how you create a Jenkins job which deploys as a docker container on our infrastructure. We’ll describe how you do this using a freestyle project, however it can be adapted to any other job types.

Overview

The Docker Custom Build Environment plugin has been installed to allow the ability to run jobs inside of containers. When a job is executed, the Jenkins master node connects to one of the worker nodes, deploys a container on the node and reports the information back.

OSL Pre-built images

We are currently maintaining a list of container images to help assist with usage on the cluster. Here is the current list of images we support:

These images are tested and verified to work on our infrastructure. If you have any issues or want to add support for something, please visit https://github.com/osuosl/osl-dockerfiles.

Notes on using your own containers

The Docker Custom Build Environment plugin allows users to build and run any container they would like, however there are some restrictions that need to be made before using it. The plugin requires the user running the build commands to be the same as the jenkins slave agent user. This means if you need to run root level commands inside of your container, you need to do the following:

  1. Ensure you create a user with the same UID/GID as our slave agent which is currently 10000

  2. Ensure sudo is installed on the container and the user is allowed to run sudo commands

1. Create new Freestyle project

First step is to create a new freestyle project. After you logged in at https://powerci.osuosl.org with you GitHub account, click on the “New Item” option on the left menu as in the image below. Then, enter your item’s name and select “Freestyle project” under the textbox.

../_images/powerci-new-item.png

2. Build inside a Docker container

Next select the Build inside a Docker container under the Build Environment section for the job. You have two options to select:

Pull a Docker image from a repository:

../_images/powerci-build-inside-docker.png

Or build from a Dockerfile:

../_images/powerci-build-dockerfile.png

3. Set any advanced options

To show advanced config options, click on the “Advanced…” button below the “Docker image to use” as in the image below:

../_images/powerci-advance-docker-settings.png

A lot more advanced config options will show up:

../_images/powerci-build-advanced.png

In general, the default settings should work, however there are a few advanced options you can use. You can set things such as:

  • Private docker registries

  • Volumes

  • Running in privileged mode

  • Setting memory limit / CPU shares

Use any of these options at your own risk.

4. Add build step

Next, add a build step. You can choose any that work in the container but for this example we’re just doing a simple shell.

../_images/powerci-docker-execute-shell.png

If all goes well, you should be able run the build and have it succeed!

GitHub Pull Request Integration

We use GitHub Pull Request Builder (ghprb) (repo, wiki) to integrate Jenkins build with GitHub Pull Request. You can check out their detailed official documentation and from many other available guides elsewhere such as this one. We think the availability of such documentation for this plugin is good enough that we don’t need to replicate more of them here.