Book Image

Kubernetes for Developers

By : Joseph Heck
Book Image

Kubernetes for Developers

By: Joseph Heck

Overview of this book

Kubernetes is documented and typically approached from the perspective of someone running software that has already been built. Kubernetes may also be used to enhance the development process, enabling more consistent testing and analysis of code to help developers verify not only its correctness, but also its efficiency. This book introduces key Kubernetes concepts, coupled with examples of how to deploy and use them with a bit of Node.js and Python example code, so that you can quickly replicate and use that knowledge. You will begin by setting up Kubernetes to help you develop and package your code. We walk you through the setup and installation process before working with Kubernetes in the development environment. We then delve into concepts such as automating your build process, autonomic computing, debugging, and integration testing. This book covers all the concepts required for a developer to work with Kubernetes. By the end of this book, you will be in a position to use Kubernetes in development ecosystems.
Table of Contents (16 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Getting a local cluster up and running


Once Minikube and Kubectl are installed, get a cluster up and running. It is worthwhile to know the versions of the tools you're using, as Kubernetes is a fairly fast-moving project, and if you need to get assistance from the community, knowing which versions of these common tools will be important.

The versions of Minikube and kubectl I used while writing this are:

  • Minikube: version 0.22.3
  • kubectl: version 1.8.0

You can check the version of your copy with the following commands:

minikube version

This will output a version:

minikube version: v0.22.3

If you haven't already done so while following the installation instructions, start a Kubernetes with Minikube. The simplest way is using the following command:

minikube start

This will download a virtual machine image and start it, and Kubernetes on it, as a single-machine cluster. The output will look something like the following:

Downloading Minikube ISO
 106.36 MB / 106.36 MB [============================================] 100.00% 0s
Getting VM IP address...
Moving files into cluster...
Setting up certs...
Connecting to cluster...
Setting up kubeconfig...
Starting cluster components...
Kubectl is now configured to use the cluster.

Minikube will automatically create the files needed for kubectl to access the cluster and control it. Once this is complete, you can get information about the cluster to verify it is up and running.

First, you can ask minikube about its status directly:

minikube status
minikube: Running
cluster: Running
kubectl: Correctly Configured: pointing to minikube-vm at 192.168.64.2

And if we ask kubectl about its version, it will report both the version of the client and the version of the cluster that it is communicating with:

kubectl version

The first output is the version of the kubectl client:

Client Version: version.Info{Major:"1", Minor:"7", GitVersion:"v1.7.5", GitCommit:"17d7182a7ccbb167074be7a87f0a68bd00d58d97", GitTreeState:"clean", BuildDate:"2017-08-31T19:32:26Z", GoVersion:"go1.9", Compiler:"gc", Platform:"darwin/amd64"}

Immediately after, it will communicate and report the version of Kubernetes on your cluster:

Server Version: version.Info{Major:"1", Minor:"7", GitVersion:"v1.7.5", GitCommit:"17d7182a7ccbb167074be7a87f0a68bd00d58d97", GitTreeState:"clean", BuildDate:"2017-09-11T21:52:19Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"linux/amd64"}

And we can use kubectl to ask for information about the cluster as well:

kubectl cluster-info

And see something akin to the following:

Kubernetes master is running at https://192.168.64.2:8443

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.

This command primarily lets you know the API server that you're communicating with is up and running. We can ask for the specific status of the key internal components using an additional command:

kubectl get componentstatuses
NAME                 STATUS    MESSAGE              ERROR
scheduler            Healthy   ok
etcd-0               Healthy   {"health": "true"}
controller-manager   Healthy   ok

Kubernetes also reports and stores a number of events that you can request to see. These show what is happening within the cluster:

kubectl get events
LASTSEEN   FIRSTSEEN   COUNT     NAME       KIND      SUBOBJECT   TYPE      REASON                    SOURCE                 MESSAGE
2m         2m          1         minikube   Node                  Normal    Starting                  kubelet, minikube      Starting kubelet.
2m         2m          2         minikube   Node                  Normal    NodeHasSufficientDisk     kubelet, minikube      Node minikube status is now: NodeHasSufficientDisk
2m         2m          2         minikube   Node                  Normal    NodeHasSufficientMemory   kubelet, minikube      Node minikube status is now: NodeHasSufficientMemory
2m         2m          2         minikube   Node                  Normal    NodeHasNoDiskPressure     kubelet, minikube      Node minikube status is now: NodeHasNoDiskPressure
2m         2m          1         minikube   Node                  Normal    NodeAllocatableEnforced   kubelet, minikube      Updated Node Allocatable limit across pods
2m         2m          1         minikube   Node                  Normal    Starting                  kube-proxy, minikube   Starting kube-proxy.
2m         2m          1         minikube   Node                  Normal    RegisteredNode            controllermanager      Node minikube event: Registered Node minikube in NodeController