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Installing the Cassandra Operator

Requirements

  • A running kubernetes cluster setup with Persistent Volumes. We advise running 1 Cassandra pod per k8 node, and hence please plan your environment accordingly.

Note: See AKS notes to properly define parameters for clusters running on AKS.

Note: See Dynamic provisioning for notes to setup the persistent volumes properly for dynamic provisioning.

Note: See Local setup for notes on setting up a local kubernetes cluster

Deploy the Operator

  1. Deploy the CRDs used by the operator to manage Cassandra clusters:

    kubectl apply -f deploy/crds.yaml

  2. Deploy the operator:

    kubectl apply -f deploy/bundle.yaml

  3. Verify the operator is running:

    kubectl get pods | grep cassandra-operator

    cassandra-operator-5755f6855f-t9hvm   1/1     Running   0          65s

Custom Cassandra configurations

It is possible to configure Cassandra by providing custom configuration. Refer to Custom configurations for options to configure your cluster.

Deploy a Cassandra cluster

NOTE: To deploy the Cassandra cluster, one can use an example yaml provided in the examples directory. There are 2 examples included in the repo:

  • example-datacenter.yaml -> a full example will all the fields showing usage. Use it as a template for your usecase.
  • example-datacenter-minimal.yaml -> the minimal example of the yaml. To use this example, you must also create a configMap called "cassandra-operator-default-config" that will have default values used by operator set: 
    apiVersion: v1
kind: ConfigMap
metadata:
  name: cassandra-operator-default-config
data:
  nodes: "3"
  cassandraImage: gcr.io/cassandra-operator/cassandra:3.11.4
  sidecarImage: gcr.io/cassandra-operator/cassandra-sidecar:latest
  memory: 1Gi
  disk: 1Gi

This configMap is already loaded into your k8 environment if you've used deploy/bundle.yaml to load operator's configuration.

  1. Make sure to set all apropriate values and fields in the yaml examples/example-datacenter.yaml

  2. Deploy the cluster

    # kubectl apply -f examples/example-datacenter.yaml

  3. Wait for the pods to become ready:

    NOTE: It could take a few minutes for the pods to converge while persistent volumes are being automatically provisioned and attached to the cluster nodes.

    kubectl get pods | grep cassandra-test

    NAME                                          READY   STATUS             RESTARTS   AGE
cassandra-test-dc-cassandra-west1-a-0   2/2     Running            2          84m
cassandra-test-dc-cassandra-west1-b-0   2/2     Running            0          83m
cassandra-test-dc-cassandra-wesr1-c-0   2/2     Running            0          81m

  4. Verify the Cassandra cluster is healthy:

    kubectl exec cassandra-test-dc-cassandra-west1-a-0 -c cassandra -- nodetool status

    Datacenter: test-dc-cassandra
==========================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address      Load       Tokens       Owns (effective)  Host ID                               Rack
UN  10.244.1.14  87.41 KiB  256          62.9%             dcf940c2-18d2-4a3a-8abf-833acadeca7e  west1-a
UN  10.244.2.9   87.38 KiB  256          69.6%             fd59fa32-aab0-485e-b04b-7ad4b75e54dd  west1-b
UN  10.244.0.10  69.91 KiB  256          67.5%             9e4883a1-e822-472f-920f-f2fc36c340c8  west1-c

  5. Issue a sample query to the cluster:

    kubectl exec cassandra-test-dc-cassandra-west1-a-0 -c cassandra -- cqlsh -e "SELECT now() FROM system.local;" cassandra-test-dc-cassandra-nodes 

     system.now()
--------------------------------------
 243e2fd0-d64a-11e9-b8a4-2dd801fa1b1c

(1 rows)

Resize a Cassandra cluster

  1. Create a Cassandra cluster, if you haven't already:

    $ kubectl apply -f example/example-datacenter.yaml

  2. In example/example-datacenter.yaml the initial cluster size is 3. Modify the file and change replicas from 3 to 5.

    spec:
  replicas: 5
  image: "gcr.io/cassandra-operator/cassandra:latest"

  3. Apply the size change to the cluster CR:

    $ kubectl apply -f example/example-datacenter.yaml

    The Cassandra cluster will scale to 5 members (5 pods):

    $ kubectl get pods
NAME                                    READY     STATUS    RESTARTS   AGE
cassandra-test-dc-cassandra-west1-a-0   2/2       Running   1          10m12s
cassandra-test-dc-cassandra-west1-a-1   2/2       Running   2          3m2s
cassandra-test-dc-cassandra-west1-b-0   2/2       Running   1          8m38s
cassandra-test-dc-cassandra-west1-b-1   2/2       Running   1          1m4s
cassandra-test-dc-cassandra-west1-c-0   2/2       Running   0          5m22s

  4. Similarly we can decrease the size of cluster from 5 back to 3 by changing the size field again and reapplying the change.

    spec:
  replicas: 3
  image: "gcr.io/cassandra-operator/cassandra:latest"

    Then apply the changes

    $ kubectl apply -f example/example-datacenter.yaml

    Note: scaling up/down is a long operation that performs actions in the background that are not visible to kubernetes tools. It might take long time until some "activity" is seen (like nodes in LEAVING state or pods terminating). Please do not rerun this command many times, but just follow the sidecar log (via kubectl logs <pod name> --container sidecar and cassandra status via kubectl exec <pod name> -c cassandra -- bash "nodetool status")

Cleanup

WARNING! The following will delete the Cassandra cluster deployed in the previous steps as well as all of its data.

Delete the Cassandra Cluster

  1. Delete the Cassandra cluster:

    kubectl delete -f examples/example-datacenter.yaml

  2. Delete the PVCs created automatically for the pods:

    kubectl delete pvc data-volume-cassandra-cassandra-test-{rack name}-{num}

Delete the Operator

  1. Delete the operator:

    kubectl delete -f deploy

  2. Delete the RBAC and PSP resources:

    kubectl delete -f deploy/cassandra

  3. Delete the CRDs:

    kubectl delete -f deploy/crds.yaml