Effectively using Kubernetes plugin with Jenkins

Kubernetes, the container orchestration platform is rapidly becoming popular. There are more and more workloads that you can run on top of Kubernetes. It's becoming an enabling layer of your Hyper-convergenced infrastructure.

If you set up Kubernetes as a Cloud provider in Jenkins, you'll get a very powerful couple for running your workloads. To do that, you can simply install Kubernetes plugin for Jenkins. Kubernetes is able to run your Jenkins workloads as long as they are run in container. And containers are an awesome way if your workload is a build, because you can pack all your application and OS dependencies in a container and then run it anywhere!

Let's imagine that you have been running a Kubernetes cluster setup in your organisation for a while now. First it was all about proof of concept but now its becoming more popular within your developers and you have to think about scaling and orchestration. Resource quotas are a part of that and every responsible operator should set those up both in both development and production clusters. Otherwise people will be lazy and just reserve all the resources of your cluster without actually using those resources for anything. By introducing quotas into your cluster, you can control how many resources should each namespace have.

Quotas are a mature feature of Kubernetes already. You have the possibility to create very fine grained quotas for different hardware resources, for example when it's fast disk, GPUs or CPU time. You can also specify multiple scopes of quota per one namespace. For example, you can have a quota for workloads that are to be run to the infinity like web servers or databases. Or have quota for workloads that are short lived like builds or test automation runs.

Different scopes of Kubernetes quota

Since Jenkins is all about running short workloads, you should aim for the Terminating scope of quota. But how do you specify workloads in Jenkins so that correct scope is used?

If you were to do this in Kubernetes, you have to specify .spec.activeDeadlineSeconds .

Same configuration is available in the Jenkinsfile as well if you don't like static configurations.

podTemplate(label: 'maven', activeDeadlineSeconds: 180, containers: [
    containerTemplate(name: 'maven', image: 'maven:3.5.4-jdk-10-slim')
  ]) {
  // maven magic
}

This was just a small sample of features of the Kubernetes plugin in Jenkins. For more, be sure to check out our talk at Devops World 2018 where we share more of how you can utilise Kubernetes with Jenkins!