The following document describes the development of a cloud native Cassandra deployment on Kubernetes. When we say cloud native we mean an application which understands that it is running within a cluster manager, and uses this cluster management infrastructure to help implement the application. In particular, in this instance, a custom Cassandra SeedProvider is used to enable Cassandra to dynamically discover new Cassandra nodes as they join the cluster.
This document also attempts to describe the core components of Kubernetes, Pods, Services and Replication Controllers.
This example assumes that you have a Kubernetes cluster installed and running, and that you have installed the kubectl command line tool somewhere in your path. Please see the getting started for installation instructions for your platform.
The v1beta3 API is not enabled by default. The kube-apiserver process needs to run with the --runtime_config=api/v1beta3 argument. Use the following command to enable it:
$sudo sed -i 's|KUBE_API_ARGS="|KUBE_API_ARGS="--runtime_config=api/v1beta3|' /etc/kubernetes/apiserver
For those of you who are impatient, here is the summary of the commands we ran in this tutorial.
# create a single cassandra node
kubectl create -f cassandra-controller.yaml
# create a service to track all cassandra nodes
kubectl create -f cassandra-service.yaml
$ docker exec <cassandra-container-id> nodetool status
Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns (effective) Host ID Rack
UN 10.244.3.29 72.07 KB 256 100.0% f736f0b5-bd1f-46f1-9b9d-7e8f22f37c9e rack1
# scale up to 2 nodes
kubectl resize rc cassandra --replicas=2
# validate the cluster
$ docker exec <cassandra-container-id> nodetool status
Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns (effective) Host ID Rack
UN 10.244.3.29 72.07 KB 256 100.0% f736f0b5-bd1f-46f1-9b9d-7e8f22f37c9e rack1
UN 10.244.1.10 41.14 KB 256 100.0% 42617acd-b16e-4ee3-9486-68a6743657b1 rack1
# scale up to 4 nodes
kubectl resize rc cassandra --replicas=4
# validate the cluster
$ docker exec <cassandra-container-id> nodetool status
Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns (effective) Host ID Rack
UN 10.244.3.29 72.07 KB 256 49.5% f736f0b5-bd1f-46f1-9b9d-7e8f22f37c9e rack1
UN 10.244.2.14 61.62 KB 256 52.6% 3e9981a6-6919-42c4-b2b8-af50f23a68f2 rack1
UN 10.244.1.10 41.14 KB 256 49.5% 42617acd-b16e-4ee3-9486-68a6743657b1 rack1
UN 10.244.4.8 63.83 KB 256 48.3% eeb73967-d1e6-43c1-bb54-512f8117d372 rack1