by John Turner
Posted on February 07, 2017
Kubernetes, Docker, Jenkins
Quick on the heels of my recent overview of the Kubernetes Fundamentals I wanted to dive into deploying something familiar (Jenkins) so that I could focus in on some of the Kubernetes specifics.
Before going any further I’ll describe my local Kubernetes environment. I’ve previously explored Kubernetes on Google Container Engine and found it effortless. I’ve also used the community provided kube-up scripts to create a local cluster but it appears that this approach has been deprecated. The recommended approach to creating a local Kubernetes environment is using MiniKube.
If you are using Mac, it is fairly trivial to install the components required for MiniKube:
Note: If you don’t have brew installed you can find the brew installation instructions here.
To start minikube simply invoke:
At this point there is a single node Kubernates environment running within a VirtualBox VM. To validate the environment simply invoke:
This command will return URL’s for the Kubernetes Master, DNS service and Dashboard.
So now we have a single node Kubernetes environment running locally it’s time to define our Jenkins deployment. A simple deployment is defined below:
Some points of note:
To create the deployment execute:
To validate that creating the deployment was successful you can invoke:
It’s worth noting that the Kubernetes command line is very consistent in its naming and syntax. You can invoke kubectl get RESOURCE for any Kubernetes resource. If all has worked as expected you will be presented with output similar to that below:
We can also see that a single Pod has been created by invoking:
As it stands we have a Jenkins instance deployed but it is still not accessible. The jenkins Pod has been assigned an IP address which is internal to the Kubernetes cluster. Of course it’s possible to log into the Kubernetes Node and access Jenkins from there but that’s not a very useful way to access the service.
To make Jenkins accessible outside the Kubernetes cluster the Pod needs to be exposed as a Service. With a local deployment this means creating a NodePort service type. A NodePort service type exposes a service on a port on each node in the cluster. It’s then possible to access the service given the Node IP address and the service nodePort. A simple service is defined below:
Some points of note:
To create the service execute:
To validate that creating the service was successful you can invoke:
So now we have created a deployment and service how do we access Jenkins?
From the output above we can see that the service has been exposed on port 30104. We also know that because the service is of type NodeType the service will route requests made to any node on this port to the jenkins pod. All that’s left for us is to determine the IP address of the minikube VM. Minikube have made this really simple by including a specific command that outputs the IP address of the running cluster:
Now we can access the jenkins instance at http://192.168.99.100:30104/
So that is a bit of a world wind tour of deploying Jenkins on Kubernetes. I plan on developing this use case in future posts so as to explore Kubernetes further so stay tuned if you are finding this useful. On the other hand, if you are experienced with Kubernetes and spot any rookie mistakes I’d appreciate you drawing my attention to them using the comment section below.