Use a Plain Cluster

A plain IONOS cluster is ready when kubectl get pods, and operator deployment pods are up and running. If all goes well, you will have successfully deployed a Stackable cluster and used it to start three services that should now be ready for you.

Apache ZooKeeper

We can test ZooKeeper by running the ZooKeeper CLI shell. The easiest way to do this is to run the CLI shell on the pod that is running ZooKeeper.

kubectl exec -i -t simple-zk-server-primary-0 -- bin/zkCli.sh

The shell should connect automatically to the ZooKeeper server running on the pod. You can run the ls / command to see the list of znodes in the root path, which should include those created by Apache Kafka and Apache NiFi.

[zk: localhost:2181(CONNECTED) 0] ls /
[nifi, znode-17b28a7e-0d45-450b-8209-871225c6efa1, zookeeper]

More information on how to use Apache Zookeeper can be found here.

Apache Kafka

To test Kafka we’ll create a topic, and verify that it was created. First create the topic with the following command:

kubectl exec -i -t simple-kafka-broker-brokers-0 -c kafka -- \
  bin/kafka-topics.sh --bootstrap-server localhost:9092 --create --topic demo
Created topic demo.

Now let’s check if it was actually created:

kubectl exec -i -t simple-kafka-broker-brokers-0 -c kafka -- \
  bin/kafka-topics.sh --bootstrap-server localhost:9092 --list
demo

More information on how to use Apache Kafka can be found here.

Apache NiFi

Apache NiFi provides a web interface and the easiest way to test it is to view this in a web browser. To access the web interface we first need to get the ip address and port Nifi is listening on. To get the IP address we need to connect to (in this case 172.18.0.2), run:

kubectl get nodes --selector=node=quickstart-1 -o wide

NAME                STATUS   ROLES    AGE   VERSION   INTERNAL-IP   EXTERNAL-IP   OS-IMAGE       KERNEL-VERSION      CONTAINER-RUNTIME
quickstart-worker   Ready    <none>   45m   v1.21.1   172.18.0.2    <none>        Ubuntu 21.04   5.15.0-25-generic   containerd://1.5.2

With the following command we get the port (in this case 30247):

kubectl get svc simple-nifi

NAME          TYPE       CLUSTER-IP    EXTERNAL-IP   PORT(S)          AGE
simple-nifi   NodePort   10.43.75.25   <none>        8443:30247/TCP   49m

Browse to the address of your Kubernetes node on port 30247 e.g. https://172.18.0.2:30247/nifi and you should see the NiFi login screen.

NiFi login screen

The Apache NiFi operator will automatically generate the admin user credentials with a random password and store it as a Kubernetes secret in order to provide some security out of the box. You can retrieve this password for the admin user with the following kubectl command.

kubectl get secrets nifi-admin-credentials-simple \
-o jsonpath="{.data.password}" | base64 -d && echo

Once you have these credentials you can log in and you should see a blank NiFi canvas.

NiFi canvas

More information on how to use Apache NiFi can be found here.

Note that we install and maintain only the Stackable operators' tools, but you have to install tools like Zookeeper, Kafka, Nifi, etc. before you can check that the tools are ready to use in the Cluster.