How many Kubernetes clusters do I need?
First, we want to separate the non-production and production environments:
- Create two Kubernetes clusters for every application or application suite. One for pre-production and one for production.
We also want to separate each non-production and production like environment. Kubernetes offers namespaces to create segregated areas, resources in separate namespaces cannot see each other. Create a namespace for each environment:
- In the non-production cluster
- Dev namespace
- QA namespace
- UAT namespace
- In the production cluster
- Demo namespace
- Stage namespace
- Production namespace
To list all resources in a namespace use the -n option in the commands
kubectl get all -n MY_NAMESPACE
Load balancers are external to the cluster and point to the nodes to expose the applications outside of the cluster.
For security reasons large organizations don’t allow the creation of multiple load balancers. During the cluster creation they temporarily lift the restriction and one ingress load balancer is created. All inbound communication to the cluster passes through that load balancer.
Do not use the :latest version, as it is hard to control the actual version of the launched image and to roll back to an earlier (unidentified) version.
Use the imagePullPolicy: Always. The Docker caching semantics makes it very efficient, as the layers are cached in the cluster to avid unnecessary downloads..
Order of resource creation
Install the CoreDNS add-on to provide in-cluster DNS service for pods, so all pods can find all services by name within the cluster.
Create the service before the deployment it refers to, because the service passes environment variables into the deployment when the containers start.
Create the target service and deployment before the caller deployment, so the target is available when the request is generated.
Switch between Kubernetes clusters
Companies launch multiple Kubernetes clusters, and the DevOps team needs access to all of them. The kubectl command line utility can only work with one cluster at a time. To work with multiple Kubernetes clusters you need to switch between Kubernetes configurations on your workstation.
Get the list of configured Kubernetes clusters. The asterisk in the first column of the output shows the currently selected cluster.
kubectl config get-contexts
Switch to another cluster
kubectl config set-context MY_CLUSTER_NAME