Intro to Cassandra On Kubernetes

Learning Workshop

In this session we will be taking a look at running a distributed system on top of another distributed system while using persistant storage to make sure our data stays in tact.

Before starting

Workshop attendees will be able to message Prasson in discord for a training instance.

Notice that training cloud instances will be available only during the workshop and will be terminated 24 hours later. If you are in our workshop we recommend using the provided cloud instance, you can relax as we have you covered: prerequisites are installed already.

⚡ IMPORTANT NOTE: Everywhere in this repo you see <YOURADDRESS> replace with the URL for the instance you were given.

Table of content

Title	Description
1 - Getting Connected	Instructions
2 - Setting Up Storage	Instructions
3 - Setting Up Cassandra	Instructions
4 - Connecting To Cassandra	Instructions
5 - Resources	Instructions

1. Getting Connected

✅ Step 1a: The first step in the section.

In your browser window, navigate to the url :3000 where your address is the one provided by Prasson.

When you arrive at the webpage you should be greeted by something similar to this.

Click in the Terminal menu from the top of the page and select new terminal as shown below

Once you have opened the terminal run

kubectl get nodes

📃output

NAME                        STATUS   ROLES    AGE   VERSION
learning-cluster-master     Ready    master   49m   v1.19.4
learning-cluster-worker-0   Ready    <none>   49m   v1.19.4
learning-cluster-worker-1   Ready    <none>   49m   v1.19.4
ubuntu@learning-cluster-master:~/workshop$ 

If you see the above output you are ready for the lab.

2. Setting Up Storage

✅ Step 2a: Setting Up Block Devices.

Show the current pods that are running.

kubectl get pods --all-namespaces

📃output

NAMESPACE     NAME                                                READY   STATUS    RESTARTS   AGE
kube-system   coredns-f9fd979d6-pbs8m                             1/1     Running   0          10m
kube-system   coredns-f9fd979d6-wzcgn                             1/1     Running   0          10m
kube-system   etcd-learning-cluster-0-master                      1/1     Running   0          10m
kube-system   kube-apiserver-learning-cluster-0-master            1/1     Running   0          10m
kube-system   kube-controller-manager-learning-cluster-0-master   1/1     Running   0          10m
kube-system   kube-flannel-ds-cvjvp                               1/1     Running   0          3m
kube-system   kube-flannel-ds-xflrq                               1/1     Running   0          3m
kube-system   kube-flannel-ds-xw4m9                               1/1     Running   0          3m
kube-system   kube-proxy-9rzw4                                    1/1     Running   0          3m7s
kube-system   kube-proxy-jns28                                    1/1     Running   0          3m8s
kube-system   kube-proxy-mjgqj                                    1/1     Running   0          10m
kube-system   kube-scheduler-learning-cluster-0-master            1/1     Running   0          10m

Install OpenEBS

wget https://openebs.github.io/charts/openebs-operator.yaml
kubectl apply -f openebs-operator.yaml
kubectl get pods --all-namespaces

📃output

NAMESPACE     NAME                                                READY   STATUS              RESTARTS   AGE
kube-system   coredns-f9fd979d6-pbs8m                             1/1     Running             0          10m
kube-system   coredns-f9fd979d6-wzcgn                             1/1     Running             0          10m
kube-system   etcd-learning-cluster-0-master                      1/1     Running             0          11m
kube-system   kube-apiserver-learning-cluster-0-master            1/1     Running             0          11m
kube-system   kube-controller-manager-learning-cluster-0-master   1/1     Running             0          11m
kube-system   kube-flannel-ds-cvjvp                               1/1     Running             0          3m23s
kube-system   kube-flannel-ds-xflrq                               1/1     Running             0          3m23s
kube-system   kube-flannel-ds-xw4m9                               1/1     Running             0          3m23s
kube-system   kube-proxy-9rzw4                                    1/1     Running             0          3m30s
kube-system   kube-proxy-jns28                                    1/1     Running             0          3m31s
kube-system   kube-proxy-mjgqj                                    1/1     Running             0          10m
kube-system   kube-scheduler-learning-cluster-0-master            1/1     Running             0          11m
openebs       maya-apiserver-747fbf7f89-vgs86                     0/1     ContainerCreating   0          2s
openebs       openebs-admission-server-555b957648-dwls5           0/1     ContainerCreating   0          1s
openebs       openebs-localpv-provisioner-7d7c74fbbb-c78js        0/1     ContainerCreating   0          1s
openebs       openebs-ndm-4tcxw                                   0/1     ContainerCreating   0          1s
openebs       openebs-ndm-kbxdq                                   0/1     ContainerCreating   0          1s
openebs       openebs-ndm-operator-6bd5949967-66zw6               0/1     ContainerCreating   0          1s
openebs       openebs-provisioner-cd9474fb8-rvdj6                 0/1     ContainerCreating   0          2s
openebs       openebs-snapshot-operator-897d78956-2k8qq           0/2     ContainerCreating   0          2s

For each blockdevice listed you will need to add the learning tag so that it can be consumed as a resource by our pods.

kubectl get blockdevice -n openebs

📃output

NAME                                           NODENAME                      SIZE          CLAIMSTATE   STATUS   AGE
blockdevice-6073c1a6970805a0c5f63b04dedb1f5b   learning-cluster-0-worker-0   75000000000   Unclaimed    Active   19s
blockdevice-6dcd4d6f4ff6be74c0b5fb0517244b53   learning-cluster-0-worker-1   75000000000   Unclaimed    Active   19s

kubectl label bd -n openebs BLOCKDEVICENAMEHERE openebs.io/block-device-tag=learning
kubectl label bd -n openebs BLOCKDEVICENAMEHERE openebs.io/block-device-tag=learning

📃output

blockdevice.openebs.io/blockdevice-6073c1a6970805a0c5f63b04dedb1f5b labeled
blockdevice.openebs.io/blockdevice-6dcd4d6f4ff6be74c0b5fb0517244b53 labeled

Setup the storage class.

kubectl apply -f local-device-sc.yaml

Verify storage class.

kubectl get sc local-device

📃output

NAME           PROVISIONER        RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
local-device   openebs.io/local   Delete          WaitForFirstConsumer   false                  1s

3. Setting Up Cassandra

✅ Step 3a: Install Helm

curl -fsSL -o get_helm.sh https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3
chmod 700 get_helm.sh
./get_helm.sh

📃output

Downloading https://get.helm.sh/helm-v3.5.3-linux-amd64.tar.gz
Verifying checksum... Done.
Preparing to install helm into /usr/local/bin
helm installed into /usr/local/bin/helm

✅ Step 3b: Add the K8ssandra repo

helm repo add k8ssandra https://helm.k8ssandra.io/stable
helm repo update

✅ Step 3c: Setup the Ingress

helm repo add traefik https://helm.traefik.io/traefik
helm repo update
helm install traefik traefik/traefik -f traefik.yaml

📃output

NAME: traefik
LAST DEPLOYED: Mon Mar 15 15:54:45 2021
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None

✅ Step 3d: configure the k8ssandra.yaml

Open the file in the browser and add in your IP address where it says <YOURADDRESS>

✅ Step 3e: Install the Cassandra Cluster

helm install -f k8ssandra.yaml k8ssandra k8ssandra/k8ssandra

📃output

NAME: k8ssandra
LAST DEPLOYED: Mon Mar 15 15:55:46 2021
NAMESPACE: default
STATUS: deployed
REVISION: 1

kubectl get cassandradatacenters

📃output

NAME   AGE
dc1    98s

kubectl describe CassandraDataCenter dc1

📃output

Name:         dc1
Namespace:    default
Labels:       app.kubernetes.io/instance=k8ssandra
              app.kubernetes.io/managed-by=Helm
              app.kubernetes.io/name=k8ssandra
              app.kubernetes.io/part-of=k8ssandra-k8ssandra-default
              helm.sh/chart=k8ssandra-1.0.0
Annotations:  meta.helm.sh/release-name: k8ssandra
              meta.helm.sh/release-namespace: default
              reaper.cassandra-reaper.io/instance: k8ssandra-reaper
API Version:  cassandra.datastax.com/v1beta1
Kind:         CassandraDatacenter
...
Events:
  Type    Reason             Age                From           Message
  ----    ------             ----               ----           -------
  Normal  CreatedResource    95s                cass-operator  Created service k8ssandra-dc1-service
  Normal  CreatedResource    95s                cass-operator  Created service k8ssandra-seed-service
  Normal  CreatedResource    95s                cass-operator  Created service k8ssandra-dc1-all-pods-service
  Normal  CreatedResource    87s                cass-operator  Created statefulset k8ssandra-dc1-default-sts
  Normal  ScalingUpRack      87s (x2 over 87s)  cass-operator  Scaling up rack default
  Normal  LabeledPodAsSeed   31s                cass-operator  Labeled pod a seed node k8ssandra-dc1-default-sts-0
  Normal  StartingCassandra  26s                cass-operator  Starting Cassandra for pod k8ssandra-dc1-default-sts-0

4. Connecting To Cassandra

✅ Step 4a: Retreave the Cluster username

kubectl get secret k8ssandra-superuser -o jsonpath="{.data.username}" | base64 --decode

Your output should look something like this.

📃output

k8ssandra-superuser

✅ Step 4b: Retreave the Cluster password

kubectl get secret k8ssandra-superuser -o jsonpath="{.data.password}" | base64 --decode

Your output should look something like this.

📃output

xvKAjJ5CO9F2LOthC5GT

✅ Step 4c: Testing our database

kubectl exec --stdin --tty k8ssandra-dc1-default-sts-0 -- /bin/bash
cqlsh -u YOURUSERNAME -p YOURPASSWORD

This will bring you into the CQLSH prompt where you can directly interact with the database. 📃output

Connected to k8ssandra at 127.0.0.1:9042.
[cqlsh 5.0.1 | Cassandra 3.11.10 | CQL spec 3.4.4 | Native protocol v4]
Use HELP for help.
k8ssandra-superuser@cqlsh> 

✅ Step 4d: Insert Data

CREATE KEYSPACE test WITH REPLICATION = { 'class' : 'NetworkTopologyStrategy', 'dc1' : 3 };
CREATE TABLE test.users (username text, name text, age int, PRIMARY KEY(username));
INSERT INTO test.users(username,name,age) VALUES ('EricZ','Eric Zietlow',67);
SELECT * FROM test.users;

📃output

 username | age | name
----------+-----+--------------
    EricZ |  67 | Eric Zietlow

5. Resources

For further reading go to the OpenEBS Docs

Check out our new Discord server Invite

Get into more with the Data On Kubernetes Community DOKc

For the K8ssandra Project k8ssandra.io

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