K8ssandra入门教程之Linux上部署K8ssandra到Kubernetes的过程

1 什么是k8ssandra

cassandra是一款非常优秀的开源的分布式nosql数据库，被许多优秀的大公司采用，具有高可用、弹性扩展、性能好等特点。

正应cassandra的优势，我们经常需要在云上服务使用，则需要部署cassandra到k8s上，这就有了k8ssandra。k8ssandra不仅帮助我们可以快速可靠地在kubernetes上部署cassandra，同时提供了许多组件，如监控、备份、同步、访问等。而这些都是一个production-ready的产品不可或缺的。

k8ssandra的组件架构图如下：

cass-operator：保证整个集群正常运行；
reaper：保证一致性的同步工具；
medusa：数据备份工具，支持s3、gcp cloud storage等；
stargate：对数据访问提供api；
prometheus+grafana：云原生的常用监控组件。

2 安装k8ssandra

2.1 安装kubenetes

如何在ubuntu上搭建kubernetes，在文章《virtualbox+ubuntu16搭建kubernetes集群的实现》已经有详细的介绍，这里不再赘述。为了更好的兼容性，我们指定了kubernetes的版本，命令如下：

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

因为要用到pvc，我们创建一个storageclass：

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

2.2 安装helm3

我们需要使用helm来部署k8ssandra，下载helm3如下：

# 下载安装包
curl -lo https://get.helm.sh/helm-v3.7.0-linux-amd64.tar.gz
# 解压
tar -zxvf helm-v3.7.0-linux-amd64.tar.gz
# 移动到bin目录
mv linux-amd64/helm /usr/local/bin/helm

添加helm的仓库：

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

查找一下k8ssandra相关的包：

$ 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...

我们安装k8ssandra/k8ssandra就可以了。

2.3 用helm安装k8ssandra

helm是一个chart+value的管理方式，我们准备一个yaml文件（k8ssandra-values.yaml）来放一些变量：

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

安装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

做一些必要的检查如下：

$ 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

检查一下pod和service：

获取k8ssandra超级用户的用户名和密码

$ 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 增加节点

我们为了高可用和容量，创建更多的cassandra node，直接修改k8ssandra-values.yaml如下：

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

修改完之后，升级配置：

$ 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

查看kubernetes的相关资源：

3 查看监控

我们对外暴露grafana服务来看看：

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

找到对应的nodeport的端口30348，访问：http://外网ip:30348

账号：admin/admin123

界面如下，提供良好的监控界面：

4 总结

k8ssandra真是一个不错的开源项目，后续再介绍如何在开发中通过k8ssandra使用cassandra吧。

代码请查看：https://github.com/larrydpk/pkslow-samples

reference:

apache cassandra operations in kubernetes

k8ssandra get started

install k8ssandra on gke

k8ssandra helm chart

用helm部署kubernetes应用，支持多环境部署与版本回滚

附：

使用到的镜像：

root@k8ssandra:~# docker images | sort | grep -v repository | grep -v k8s.gcr.io
alpine                                                   3.12.2            b14afc6dfb98   9 months ago    5.57mb
busybox                                                  1.33.1            16ea53ea7c65   2 weeks ago     1.24mb
busybox                                                  latest            16ea53ea7c65   2 weeks ago     1.24mb
datastax/cass-config-builder                             1.0.4             907e52ff2f78   4 months ago    354mb
gcr.io/k8s-minikube/storage-provisioner                  v5                6e38f40d628d   6 months ago    31.5mb
grafana/grafana                                          7.3.5             71716d95fc52   9 months ago    187mb
jettech/kube-webhook-certgen                             v1.5.0            344297e197b6   11 months ago   44.7mb
k8ssandra/cass-management-api                            3.11.10-v0.1.27   e88cc3a8ce75   2 months ago    877mb
k8ssandra/cass-management-api                            4.0.0-v0.1.28     59b9869dd160   7 weeks ago     726mb
k8ssandra/cass-operator                                  v1.7.1            dd57363b0794   4 months ago    49.4mb
k8ssandra/k8ssandra-tools                                latest            43e4bd91cf9b   42 hours ago    49mb
k8ssandra/reaper-operator                                v0.3.3            b4cb9084a5e5   2 months ago    45.9mb
k8ssandra/system-logger                                  9c4c3692          4dda0db106cb   4 months ago    5.66mb
kiwigrid/k8s-sidecar                                     1.1.0             f4bb3bf1ddc7   11 months ago   82mb
quay.io/prometheus-operator/prometheus-config-reloader   v0.44.0           73bc771f8028   10 months ago   13.4mb
quay.io/prometheus-operator/prometheus-operator          v0.44.0           f5ab8d7a1a64   10 months ago   42.6mb
quay.io/prometheus/prometheus                            v2.22.1           7cc97b58fb0e   10 months ago   168mb
rancher/local-path-provisioner                           v0.0.20           933989e1174c   2 months ago    35mb
stargateio/stargate-3_11                                 v1.0.29           c276fffd9964   3 months ago    537mb
stargateio/stargate-4_0                                  v1.0.29           be4bae3748e1   3 months ago    546mb
thelastpickle/cassandra-reaper                           2.3.1             8ad2c2784ead   2 months ago    418mb

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