kubernetes 部署redis cluster

谁践踏了优雅 2023-06-27 05:44 14阅读 0赞

# kubernetes 部署redis cluster #

## 前言 ##

Redis cluster的集群关系的维系，并非是依赖于ip的，而是依赖于cluster内部的唯一id, ip只在首次建立集群关系时连接彼此使用，不作为成员连接凭据，取而代之的是id。画外音：只要持有id，容器重启ip怎么变化都不会影响到维系redis cluster的成员关系。

那么id怎么保存的呢？redis cluster在建立起来后，每个主备节点都会保存一份cluster节点的元数据文件，因此，为了保证在kubernetes内pod重启后，集群相关的角色配置等不丢失，此文件必须持久化，因此，适合使用statefulSet来部署。

## 部署 ##

直接贴部署的yaml文件：

apiVersion: v1
    data:
      redis.conf: |2
            appendonly no
            save 900 1
            save 300 10
            save 60 300
            maxmemory 4GB
            maxmemory-policy allkeys-lru
            cluster-enabled yes
            cluster-config-file  /var/lib/redis/nodes.conf  # cluster的node元数据文件
            #cluster-node-timeout 5000 # 主从心跳检查的时间间隔
            cluster-node-timeout 500 # 这里临时配置成500ms，为了下方的主备切换的测试
            dir /var/lib/redis
            port 6379
    kind: ConfigMap
    metadata:
      name: app-rds-cluster
      namespace: default
    ---
    apiVersion: v1
    kind: PersistentVolumeClaim
    metadata:
      name: app-rds-cluster
    spec:
      accessModes:
      - ReadWriteMany
      resources:
        requests:
          storage: 50Gi
      storageClassName: cephfs
    ---
    # 用来提供redis cluster对外连接服务的
    apiVersion: v1
    kind: Service
    metadata:
      name: app-rds-cluster
      labels:
        app: redis
    spec:
      ports:
      - name: redis-port
        port: 6379
      selector:
        app: app-rds-cluster
        appCluster: redis-cluster
    ---
    apiVersion: apps/v1beta1
    kind: StatefulSet
    metadata:
      name: app-rds-cluster
    spec:
      serviceName: "app-rds-cluster"
      replicas: 6
      template:
        metadata:
          labels:
            app: app-rds-cluster
            appCluster: redis-cluster
        spec:
          terminationGracePeriodSeconds: 5
          affinity:
            podAntiAffinity:
              preferredDuringSchedulingIgnoredDuringExecution:
              - weight: 100
                podAffinityTerm:
                  labelSelector:
                    matchExpressions:
                    - key: app
                      operator: In
                      values:
                      - app-rds-cluster
                  topologyKey: kubernetes.io/hostname
          containers:
          - name: redis
            env:
            - name: POD_NAME
              valueFrom:
                fieldRef:
                  apiVersion: v1
                  fieldPath: metadata.name
            image: redis:v4.0.14
            command:
              - "redis-server"                  #redis启动命令
            args:
              - "/etc/redis/redis.conf"         # 配置文件
            # command: redis-server /etc/redis/redis.conf
            resources:                          #资源
              requests:                         #请求的资源
                cpu: "100m"                     #m代表千分之,相当于0.1 个cpu资源
                memory: "100Mi"                 #内存100m大小
              limits:                         
                cpu: "1"                        # 1代表1核
                memory: "4096Mi"                 #内存100m大小 
            ports:
                - name: redis
                  containerPort: 6379
                  protocol: "TCP"
                - name: cluster
                  containerPort: 16379
                  protocol: "TCP"
            volumeMounts:
              - name: "redis-conf"              # 挂载configmap生成的文件
                mountPath: "/etc/redis"         
              - name: pvc
                mountPath: "/var/lib/redis"
                subPathExpr: $(POD_NAME)/data/
          nodeSelector:
            RDSDB: ''
          volumes:
          - name: "redis-conf"
            configMap:
              name: app-rds-cluster
          - name: pvc
            persistentVolumeClaim:
              claimName: app-rds-cluster

**部署说明**：

1.  redis配置文件使用configmap挂载
2.  共配置6个节点，3主3从，这也是官方文档中说的推荐最小的集群规模了。
3.  redis cluster node元数据文件很重要，下面会有详细说明。这个文件必须要做持久化，可使用pvc/hostPath等方式。
4.  使用redis-trib工具建立cluster，建立好cluster后，后续cluster关系维护不再需要它。
5.  网上有不少其他文章中都部署了2个service，包含一个headless service，建cluster时用作服务发现；和一个正常的service，给客户端连接使用。但这个headless service其实根本没有必要，建cluster的时候手动取一次pod ip就好，何必多建一个无用的service

假设你的持久化没有问题，那么，你现在应该有6个运行正常的pod了：

[root@008019 redis-cluster]# kubectl get pods -o wide --all-namespaces | grep app-rds-cluster
    default       app-rds-cluster-0                                 1/1     Running   0          5m1s    172.36.4.43      008031   <none>           <none>
    default       app-rds-cluster-1                                 1/1     Running   0          4m58s   172.36.1.30      008020   <none>           <none>
    default       app-rds-cluster-2                                 1/1     Running   0          4m56s   172.36.6.21      020203   <none>           <none>
    default       app-rds-cluster-3                                 1/1     Running   0          4m53s   172.36.5.25      008032   <none>           <none>
    default       app-rds-cluster-4                                 1/1     Running   0          4m51s   172.36.0.198     008019   <none>           <none>
    default       app-rds-cluster-5                                 1/1     Running   0          4m48s   172.36.3.134     020204   <none>           <none>
    
    # 获取到这些pod 的ip，下面会用到
    [root@008019 redis-cluster]# echo `kubectl get pods -o wide --all-namespaces | grep app-rds-cluster | awk '{print $7":6379"}'`
    
    172.36.4.43:6379 172.36.1.30:6379 172.36.6.21:6379 172.36.5.25:6379 172.36.0.198:6379 172.36.3.134:6379

## 建立集群 ##

因此建立集群的操作只需要执行一次，后续集群关系redis节点之间会基于节点元数据文件自动维护，所以，专门部署一个环境，用来初始化配置集群，部署文件如下：

apiVersion: extensions/v1beta1
    kind: Deployment
    metadata:
      labels:
        app: redis-cluster-manager
      name: redis-cluster-manager
      namespace: default
    spec:
      replicas: 1
      selector:
        matchLabels:
          app: redis-cluster-manager
      template:
        metadata:
          labels:
            app: redis-cluster-manager
        spec:
          containers:
          - command:
              - tail
            args:
              - -f
              - /dev/null
            env:
            - name: DB_NAME
              value: redis-cluster-manager
            image: centos:centos7
            imagePullPolicy: Always
            name: redis-cluster-manager
            resources:
              limits:
                cpu: 500m
                memory: 300Mi
              requests:
                cpu: 100m
                memory: 100Mi
            terminationMessagePath: /dev/termination-log
            terminationMessagePolicy: File
          dnsPolicy: ClusterFirst
          restartPolicy: Always
          schedulerName: default-scheduler
          securityContext: { }
          terminationGracePeriodSeconds: 30

[root@008019 redis-cluster]# kubectl get pods -o wide --all-namespaces | grep redis-cluster-manager
    default       redis-cluster-manager-5468b99f7f-lxpw7            1/1     Running   0          87m     172.36.4.42      008031   <none>           <none>
    [root@008019 redis-cluster]# kubectl exec -it redis-cluster-manager-5468b99f7f-lxpw7 bash
    [root@redis-cluster-manager-5468b99f7f-lxpw7 /]#

安装集群配置工具:

cat >> /etc/yum.repos.d/epel.repo<<'EOF' [epel] name=Extra Packages for Enterprise Linux 7 - $basearch baseurl=https://mirrors.tuna.tsinghua.edu.cn/epel/7/$basearch #mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-7&arch=$basearch failovermethod=priority enabled=1 gpgcheck=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7 EOF
    
    
    yum -y install redis-trib.noarch

初始化集群:

# 拿到上面获取到的pod ip,执行命令，交互步骤输入yes,不出意外，集群初始化成功
    # 解释一下，这里的6个节点，--replicas 1，前3个会是master，后3个会是前3个的slave
    redis-trib create --replicas 1 \
    172.36.4.43:6379 172.36.1.30:6379 172.36.6.21:6379 172.36.5.25:6379 172.36.0.198:6379 172.36.3.134:6379
    
    ...
    [OK] All nodes agree about slots configuration.
    >>> Check for open slots...
    >>> Check slots coverage...
    [OK] All 16384 slots covered.

## 连接 ##

选择其中一个

[root@008019 redis-cluster]# kubectl exec -it redis-cluster-manager-5468b99f7f-lxpw7 bash
    [root@redis-cluster-manager-5468b99f7f-lxpw7 /]#
    [root@redis-cluster-manager-5468b99f7f-lxpw7 /]# exit
    exit
    [root@008019 redis-cluster]# kubectl exec -it app-rds-cluster-0 bash
    
    # redis-cli连接cluster记得加-c参数
    root@app-rds-cluster-0:/var/lib/redis# redis-cli -c
    # 设一个key
    127.0.0.1:6379> get a
    -> Redirected to slot [15495] located at 172.36.6.21:6379
    (nil)
    172.36.6.21:6379> set a 1
    OK
    172.36.6.21:6379> get a
    "1"
    # 查看角色
    172.36.6.21:6379> role
    1) "master"
    2) (integer) 1954
    3) 1) 1) "172.36.3.134"
          2) "6379"
          3) "1954"
    172.36.6.21:6379> quit
    
    # 查看集群节点元数据文件，第一列是id号，后面则是ip与角色信息， myself指的是自身
    root@app-rds-cluster-0:/var/lib/redis# cat nodes.conf
    bdcda6ce963add5bc9706e912b6fcf4b355e2add 172.36.3.134:6379@16379 slave d24da6b03aa3b614a1429847b3a47836f89dbc07 0 1578042761171 6 connected
    f85ce96851823832a9bda4233cc6e3066e97c050 172.36.5.25:6379@16379 slave 561f70b2c94c6e46f7b9588705f2cb48861b1e89 0 1578042760571 4 connected
    561f70b2c94c6e46f7b9588705f2cb48861b1e89 172.36.4.43:6379@16379 myself,master - 0 1578042760000 1 connected 0-5460
    e5c64aa60dcc73746e196b6c1630019ec0c10ad5 172.36.0.198:6379@16379 slave 7e2a3fa95ef9402bfba7b2e08a27812272640179 0 1578042760000 5 connected
    7e2a3fa95ef9402bfba7b2e08a27812272640179 172.36.1.30:6379@16379 master - 0 1578042760000 2 connected 5461-10922
    d24da6b03aa3b614a1429847b3a47836f89dbc07 172.36.6.21:6379@16379 master - 0 1578042759569 3 connected 10923-16383
    vars currentEpoch 6 lastVoteEpoch 0
    root@app-rds-cluster-0:/var/lib/redis#
    root@app-rds-cluster-0:/var/lib/redis#

使用service 固定ip连接：

[root@008019 ~]# kubectl get service --all-namespaces | grep app-rds-cluster
    default       app-rds-cluster                        ClusterIP   10.123.80.163    <none>        6379/TCP                   48m
    
    [root@008019 ~]# kubectl exec -it redis-cluster-manager-5468b99f7f-lxpw7 bash
    [root@redis-cluster-manager-5468b99f7f-lxpw7 /]# redis-cli -h 10.123.80.163 -c
    10.123.80.163:6379> get a
    -> Redirected to slot [15495] located at 172.36.6.22:6379
    "1"

## 主备切换 ##

作为一个高可用集群，主备切换是基本能力，看一看切换过程发生了什么:

# 重启一个master
    [root@008019 ~]# kubectl delete pod app-rds-cluster-0
    pod "app-rds-cluster-0" deleted
    [root@008019 ~]#
    [root@008019 ~]# kubectl get pods -o wide --all-namespaces | grep app-rds-cl
    default       app-rds-cluster-0                                 1/1     Running   0          20s     172.36.4.44      008031   <none>           <none>
    default       app-rds-cluster-1                                 1/1     Running   0          31m     172.36.1.30      008020   <none>           <none>
    default       app-rds-cluster-2                                 1/1     Running   0          31m     172.36.6.21      020203   <none>           <none>
    default       app-rds-cluster-3                                 1/1     Running   0          31m     172.36.5.25      008032   <none>           <none>
    default       app-rds-cluster-4                                 1/1     Running   0          31m     172.36.0.198     008019   <none>           <none>
    default       app-rds-cluster-5                                 1/1     Running   0          31m     172.36.3.134     020204   <none>           <none>
    
    # 对比上面可以发现，redis-0的ip从172.36.4.43变成了172.36.4.44，那么连接看看数据和角色
    # 可以看到，此时master已经变成了slave, 但nodes.conf内的ip没有随着容器ip变化而修改，只是修改了从属关系的记录。当然，数据也没有丢失。
    root@app-rds-cluster-0:/var/lib/redis# cat nodes.conf
    7e2a3fa95ef9402bfba7b2e08a27812272640179 172.36.1.31:6379@16379 master - 1578044978612 1578044978607 2 connected 5461-10922
    e5c64aa60dcc73746e196b6c1630019ec0c10ad5 172.36.0.199:6379@16379 slave 7e2a3fa95ef9402bfba7b2e08a27812272640179 0 1578044978614 5 connected
    561f70b2c94c6e46f7b9588705f2cb48861b1e89 172.36.4.43:6379@16379 myself,slave f85ce96851823832a9bda4233cc6e3066e97c050 0 1578044978608 9 connected
    bdcda6ce963add5bc9706e912b6fcf4b355e2add 172.36.3.135:6379@16379 slave d24da6b03aa3b614a1429847b3a47836f89dbc07 1578044978612 1578044978608 10 connected
    f85ce96851823832a9bda4233cc6e3066e97c050 172.36.5.26:6379@16379 master - 0 1578044978614 11 connected 0-5460
    d24da6b03aa3b614a1429847b3a47836f89dbc07 172.36.6.22:6379@16379 master - 1578044978612 1578044978608 10 connected 10923-16383
    vars currentEpoch 11 lastVoteEpoch 10
    root@app-rds-cluster-0:/var/lib/redis# redis-cli -c
    127.0.0.1:6379> get a
    -> Redirected to slot [15495] located at 172.36.6.22:6379
    "1"

有兴趣可以同时删除多个节点试试，6节点，3个为主，按照raft的算法，外加主挂了之后还有备接替上，因此，除非2主+2备或更多节点同时挂掉，不然不会影响redis的服务。