Having started to get some rhythm back in to the publishing of my personal blog posts, I thought it was about time that I started posting some technical content again too. I’m having to do lots of new learning at the moment and, if nothing else, writing about it makes sure that I’ve understood it and helps me remember at least some of what I’ve learnt. As before, these posts in no way indicate the position of my employer nor, in general, should you read in to them anything about technical direction. On the whole, they are just about topics that I’ve found sufficiently interesting to write a little about. There is, I have found, no knowing what will be of interest to other people (my all-time top post relates to Remote Desktop!). From an entirely selfish perspective, I don’t care if anyone reads what I write as it’s largely the writing that gives me value!
Having said all the above, the subject of this post is Jenkins X which is very much in the domain of my new employer! When it was announced back in March, I have to admit that I was somewhat sceptical. It was clearly aiming at much the same space that we were with the dev-ops part of Microclimate. My view wasn’t helped by the fact that I couldn’t actually get it to run. It did (and still does) run best out on public cloud but I used up my free quotas on AWS and GCP a long time ago. I tried to run it on minikube and failed. It was also developed by the team behind Fabric8 which, although it showed lots of promise, was never incorporated in to any of RedHat’s commercial offerings. The same was not set to be true of Jenkins X and, six months later, my new employer has just announced that it now forms part of the CloudBees Core offering under the name of Kube CD. I’ll save details of that commercial offering for another post and restrict myself to talking about the open source Jenkins X project here.
So what exactly is Jenkins X? It enables Continuous Integration and Continuous Deployment, of applications on Kubernetes. It happens to use Jenkins as the engine to perform those actions but, at least at a first pass, that is immaterial. Around that Jenkins is wrapped lots of Kubernetes-native goodness and, most importantly, a CLI by the name of jx. Thankfully this time around the minikube experience worked for me just fine and getting up and running was as simple as:
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brew install jenkins-x/jx/jx jx create cluster minikube |
I have to say that I’m not a big fan of ‘verb followed by noun’ when it comes to CLI arguments as, although perhaps more readable, it makes end-user discovery harder (jx create tells me about a whole long list of largely unrelated things) but thankfully just typing jx gives a reasonable overview of the main options. Beware though that the CLI is heavily overloaded: it’s not only used for initialisation, but also subsequent actions performed by the developer, and those performed by the pipeline.
Perhaps the quickest way to demonstrate the capabilities is to then use a quick start:
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brew install jenkins-x/jx/jx jx create quickstart |
This allows you to select a technology stack (everything from Android to Vert.X via Rust, Rails and React!) which lays down a skeleton application on disk. It then uses Draft to add a Dockerfile and Helm chart(s). It doesn’t stop there though. It will then help you create a repo on GitHub, check your code in, set up a multi-branch pipeline on the Jenkins instance it provisioned, and set up the web hook to trigger Jenkins on subsequent updates. (Webhooks don’t tend to work too well unless your minikube is internet facing but, given a bit more time, polling does the job eventually.) The default pipeline (defined by a Jenkinsfile in your application repository) uses Skaffold to build the application Docker image and push to a registry. The Helm chart is published to the provided instance of ChartMuseum.
Jenkins X follows the GitOps model promulgated by Alexis Richardson and the team at Weaveworks. By default, it sets up two GitHub repositories that map to staging and production namespaces in the Kubernetes cluster. Additional environments can easily be defined via, you guessed it, jx create environment. These repositories make good use of ‘umbrella’ Helm charts to deploy specific versions of each of the application charts. By default, the master branch is automatically deployed to the staging environment but promotion to production is performed manually, for example:
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jx promote --version 0.0.1 --env production |
There is also the concept of a preview environment. Typically created for reviewing a pull request, they can also be created manually via the CLI. These allow a specific version of the application to be accessed in a temporary namespace created just for that purpose. All of the Jenkins X configuration (environments, releases, …) are represented in the Kubernetes way: as Custom Resource Definitions.
There’s plenty more to say about Jenkins X but I’ll save that for another post on another day. Hopefully this has given you enough of a flavour to encourage you to download the CLI and give it a try for yourself.
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