Add ability to deploy a Cassandra cluster to Kubernetes

[ossarga]

With this ability we could launch clusters on local or cloud infrastructure.

Command integration

After some discussion with @jsanda we think the commands would perform the following actions when deploying a cluster to Kubernetes

Init

• Point to existing kubernetes cluster OR
• Provision a Kubernetes cluster in AWS, Azure, GCP - This is a feature we add once we have the provisioning of the Cassandra nodes working

Up

• No-op if pointing to an existing kube cluster
• Creates Kubernetes cluster in AWS, Azure, GCP - This is a feature we add once we have the provisioning of the Cassandra nodes working

Use

• Cassandra:
  • Select Cassandra version
  • Update cassandra.yaml
  • Assemble Dockerfile from a template
• Prometheus:
  • Update operator YAML file
• Grafana:
  • Update operator YAML file (https://github.com/integr8ly/grafana-operator)
• Reaper:
  • Update operator YAML file (https://github.com/thelastpickle/reaper-operator)

Install

• Build the Cassandra container from Dockerfile

Start

• Start Cassandra containers
• Push up operators
• Deploy Grafana dashboards via controller

Stop

• Stop Cassandra containers
• Update operators to have no pods running

Down

• Tear down pods and operators
• If tlp-cluster created the Kubernetes cluster, tear it down as well.

Things that need to be thought about

• How will tlp-cluster communicate with Kubernetes?

  • We could use a client library (https://github.com/kubernetes-client/java, https://github.com/fabric8io/kubernetes-client). OR
  • Use a container similar to what we do with Terraform (https://hub.docker.com/r/gbraad/kubernetes-client/, https://hub.docker.com/r/bitnami/kubectl/, https://hub.docker.com/r/lachlanevenson/k8s-kubectl)

• A constant storage backing will be needed for the pods. This is so a pod can be restarted or terminated and when it resumes it will use the existing system and user data