Docker Cookbook

134 | Chapter 5: Kubernetes

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Discussion
Kubernetes assumes a network model in which each pod gets an IP. Each pod can
then connect to other pods, regardless of which physical node they happen to be run‐
ning on.
However, just because pods can connect directly doesn’t mean that is the best or easi‐
est way to communicate between pods. In the event that a pod fails or is replaced on a
new node, the calling code would have to know to reconnect to a new address. This
dynamic reconnection is hard to integrate with many existing servers and frame‐
works. Kubernetes services are the answer to this problem (see 
Recipe 5.8
).
See Also
• Administration guide for 
Networking in Kubernetes
5.3 Creating a Multinode Kubernetes Cluster with Vagrant
Problem
You want to get started with Kubernetes and would like to create a small cluster on
your local machine using Vagrant.
Solution
You will need to install 
Vagrant
 and 
VirtualBox
 if you have not done so already. Then
set two environment variables: 
KUBERNETES_PROVIDER
to specify that you will use
Vagrant, and 
NUM_MINIONS
to set the number of nodes in your cluster (in addition to
the master node). Then you will use the installation 
script
provided by the Kuber‐
netes community. It will read the environment variables, detect your operating sys‐
tem, download the latest stable release of Kubernetes, and untar it in a 
kubernetes
directory. The following commands show you these steps on the command line:
export KUBERNETES_PROVIDER=vagrant
export NUM_MINIONS=2
curl -sS https://get.k8s.io | bash
If you do not specify the 
NUM_MINIONS
environment variables, only
one node will be started in addition to the master node.