Effectively using Kubernetes plugin with Jenkins

Published on 8/30/2018 by Niklas Tanskanen
    This is a guest blog by Niklas Tanskanen, consultant at Eficode.
    Jenkins X

    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. 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, whenever 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.

    Table 1. Scopes
    Scope Description

    Terminating

    Match pods where .spec.activeDeadlineSeconds >= 0

    NotTerminating

    Match pods where .spec.activeDeadlineSeconds is nil

    BestEffort

    Match pods that have best effort quality of service.

    NotBestEffort

    Match pods that do not have best effort quality of service.

    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. The same field can also be specified by the Kubernetes plugin when you are specifying a Pod Template.

    time deadline
    Figure 1. Specifying .spec.activeDeadlineSeconds in the Kubernetes plugin

    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
}
    DevOps World | Jenkins World 2018

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

    Come see Niklas Tanskanen and many other Jenkins experts and contributors at Jenkins World on September 16-19th, register with the code JWFOSS for a 30% discount off your pass.
    About the Author
    Niklas Tanskanen
    		Niklas Tanskanen

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