1 what is k8sandra

Cassandra is an excellent open source distributed NoSQL database, which is adopted by many excellent large companies. It has the characteristics of high availability, elastic expansion and good performance.

Due to the advantages of Cassandra, we often need to use services on the cloud, so we need to deploy Cassandra to K8s, which has k8sandra. K8sandra not only helps us to deploy Cassandra on Kubernetes quickly and reliably, but also provides many components, such as monitoring, backup, synchronization, access, etc. These are indispensable to a production ready product.

The component architecture diagram of K8ssandra is as follows:

• Cass operator: ensure the normal operation of the whole cluster;
• Reaper: a synchronization tool to ensure consistency;
• Medusa: data backup tool, supporting S3, GCP Cloud Storage, etc;
• Stargate: provides API for data access;
• Prometheus+Grafana: common monitoring component of cloud native.

2 install K8ssandra

2.1 installation of Kubenetes

How to quickly start a Kubernetes through Minikube on Ubuntu, in the article< Getting started with Istio in service grid - detailed record of Kubernetes installing Istio and using >It has been introduced in detail and will not be repeated here. For better compatibility, we specify the version of Kubernetes. The command is as follows:

minikube start --driver=none --kubernetes-version=v1.19.13

Because PVC is used, we create a StorageClass:

$ kubectl apply -f https://raw.githubusercontent.com/rancher/local-path-provisioner/master/deploy/local-path-storage.yaml

2.2 installation helm3

We need to use Helm to deploy K8ssandra. Download Helm3 as follows:

# Download installation package
curl -LO https://get.helm.sh/helm-v3.7.0-linux-amd64.tar.gz
# decompression
tar -zxvf helm-v3.7.0-linux-amd64.tar.gz
# Move to bin directory
mv linux-amd64/helm /usr/local/bin/helm

Add Helm's warehouse:

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

$ helm repo list
NAME            URL                             
k8ssandra       https://helm.k8ssandra.io/stable
traefik         https://helm.traefik.io/traefik 

Find k8sandra related packages:

$ helm search repo k8ssandra
NAME                            CHART VERSION   APP VERSION     DESCRIPTION                                       
k8ssandra/k8ssandra             1.3.1                           Provisions and configures an instance of the en...
k8ssandra/k8ssandra-common      0.28.4                          Helper library containing functions used by man...
k8ssandra/k8ssandra-operator    0.31.0          1.0.0           Kubernetes operator which handles the provision...
k8ssandra/backup                0.26.0                          Creates a CassandraBackup custom resource insta...
k8ssandra/cass-operator         0.31.0          1.8.0           Kubernetes operator which handles the provision...
k8ssandra/medusa-operator       0.30.1          0.1.0           Installs and configures the Medusa Operator for...
k8ssandra/reaper-operator       0.32.1          0.1.0           Configures and installs the Reaper Operator for...
k8ssandra/restore               0.27.1                          Creates a CassandraRestore custom resource inst...                       

We can install k8sandra / k8sandra.

2.3 install K8ssandra with Helm

Helm is a Chart+Value management method. We prepare a yaml file (k8sandra values. Yaml) to put some variables:

cassandra:
  version: "4.0.0"
  cassandraLibDirVolume:
    storageClass: local-path
    size: 5Gi
  allowMultipleNodesPerWorker: true
  heap:
    size: 1G
    newGenSize: 1G
  resources:
    requests:
      cpu: 1000m
      memory: 2Gi
    limits:
      cpu: 1000m
      memory: 2Gi
  datacenters:
  - name: dc1
    size: 1
    racks:
    - name: default 
kube-prometheus-stack:
  grafana:
    adminUser: admin
    adminPassword: admin123 
stargate:
  enabled: true
  replicas: 1
  heapMB: 256
  cpuReqMillicores: 200
  cpuLimMillicores: 1000

Install K8ssandra:

$ helm install -f k8ssandra-values.yaml k8ssandra k8ssandra/k8ssandra
NAME: k8ssandra
LAST DEPLOYED: Thu Sep 30 21:20:49 2021
NAMESPACE: default
STATUS: deployed
REVISION: 1

Make some necessary checks as follows:

$ helm list
NAME            NAMESPACE       REVISION        UPDATED                                 STATUS          CHART           APP VERSION
k8ssandra       default         1               2021-09-30 21:20:49.409672869 +0800 CST deployed        k8ssandra-1.3.1            

$ kubectl get cassandradatacenters
NAME   AGE
dc1    4m34s

$ kubectl describe CassandraDataCenter dc1 | grep "Cassandra Operator Progress:"
  Cassandra Operator Progress:  Ready

Check the Pod and Service:

Get the user name and password of k8sandra super user

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

$ kubectl get secret k8ssandra-superuser -o jsonpath="{.data.password}" | base64 --decode ; echo
TNE5xOk45C1aQsj29qxw

2.4 adding nodes

For high availability and capacity, we create more Cassandra nodes and directly modify k8sandra-values.yaml as follows:

cassandra:
  version: "4.0.0"
  cassandraLibDirVolume:
    storageClass: local-path
    size: 5Gi
  allowMultipleNodesPerWorker: true
  heap:
    size: 1G
    newGenSize: 1G
  resources:
    requests:
      cpu: 1000m
      memory: 2Gi
    limits:
      cpu: 1000m
      memory: 2Gi
  datacenters:
  - name: dc1
    size: 3
    racks:
    - name: racks1
    - name: racks2
    - name: racks3
kube-prometheus-stack:
  grafana:
    adminUser: admin
    adminPassword: admin123 
stargate:
  enabled: true
  replicas: 1
  heapMB: 256
  cpuReqMillicores: 200
  cpuLimMillicores: 1000

After modification, upgrade the configuration:

$ helm upgrade -f k8ssandra-values.yaml k8ssandra k8ssandra/k8ssandra
Release "k8ssandra" has been upgraded. Happy Helming!
NAME: k8ssandra
LAST DEPLOYED: Fri Oct  1 00:40:08 2021
NAMESPACE: default
STATUS: deployed
REVISION: 2

Check out Kubernetes resources:

3 view monitoring

Let's expose the Grafana service to see:

kubectl expose deployment k8ssandra-grafana --type=NodePort --name=grafana-out

Find the port 30348 of the corresponding NodePort. Access: http: / / Internet IP:30348

Account No.: admin/admin123

The interface is as follows, providing a good monitoring interface:

4 Summary

K8sandra is really a good open source project. Later, let's introduce how to use Cassandra through k8sandra in development.

Please check the code: https://github.com/LarryDpk/pkslow-samples