redis叢集建構
1.1使用redis-cli建立叢集
# 查看redis的pod对应的ip
kubectl get pod -n jxbp -o wide
>NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
redis-0 1/1 Running 0 18h 10.168.235.196 k8s-master <none> <none>
redis-1 1/1 Running 0 18h 10.168.235.225 k8s-master <none> <none>
redis-2 1/1 Running 0 18h 10.168.235.239 k8s-master <none> <none>
redis-3 1/1 Running 0 18h 10.168.235.198 k8s-master <none> <none>
redis-4 1/1 Running 0 18h 10.168.235.222 k8s-master <none> <none>
redis-5 1/1 Running 0 18h 10.168.235.238 k8s-master <none> <none>
# 进入到redis-0容器
kubectl exec -it redis-0 /bin/bash -n jxbp
# 创建master节点（redis-0、redis-2、redis-4）
redis-cli --cluster create 10.168.235.196:6379 10.168.235.239:6379 10.168.235.222:6379 -a jxbd
> Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
>>> Performing hash slots allocation on 3 nodes...
Master[0] -> Slots 0 - 5460
Master[1] -> Slots 5461 - 10922
Master[2] -> Slots 10923 - 16383
M: bcae187137a9b30d7dab8fe0d8ed4a46c6e39638 10.168.235.196:6379
slots:[0-5460] (5461 slots) master
M: 4367e4a45e557406a3112e7b79f82a44d4ce485e 10.168.235.239:6379
slots:[5461-10922] (5462 slots) master
M: a2cec159bbe2efa11a8f60287b90927bcb214729 10.168.235.222:6379
slots:[10923-16383] (5461 slots) master
Can I set the above configuration? (type 'yes' to accept): yes
>>> Nodes configuration updated
>>> Assign a different config epoch to each node
>>> Sending CLUSTER MEET messages to join the cluster
Waiting for the cluster to join
.
>>> Performing Cluster Check (using node 10.168.235.196:6379)
M: bcae187137a9b30d7dab8fe0d8ed4a46c6e39638 10.168.235.196:6379
slots:[0-5460] (5461 slots) master
M: a2cec159bbe2efa11a8f60287b90927bcb214729 10.168.235.222:6379
slots:[10923-16383] (5461 slots) master
M: 4367e4a45e557406a3112e7b79f82a44d4ce485e 10.168.235.239:6379
slots:[5461-10922] (5462 slots) master
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.登入後複製
注意上面的master節點，會產生對應節點id：bcae187137a9b30d7dab8fe0d8ed4a46c6e39638、#adab8fe0d8ed4a46c6e39638、#ab8 729 、4367e4a45e557406a3112e7b79f82a44d4ce485e，用於建立slave節點。
# 为每个master节点添加slave节点
# 10.168.235.196:6379的位置可以是任意一个master节点,一般我们用第一个master节点即redis-0的ip地址
# --cluster-master-id参数指定该salve节点对应的master节点的id
# -a参数指定redis的密码
# redis-0的master节点，添加redis-1为slave节点
redis-cli --cluster add-node 10.168.235.225:6379 10.168.235.196:6379 --cluster-slave --cluster-master-id bcae187137a9b30d7dab8fe0d8ed4a46c6e39638 -a jxbd
# redis-2的master节点，添加redis-3为slave节点
redis-cli --cluster add-node 10.168.235.198:6379 10.168.235.239:6379 --cluster-slave --cluster-master-id a2cec159bbe2efa11a8f60287b90927bcb214729 -a jxbd
# redis-4的master节点，添加redis-5为slave节点
redis-cli --cluster add-node 10.168.233.238:6379 10.168.235.222:6379 --cluster-slave --cluster-master-id 4367e4a45e557406a3112e7b79f82a44d4ce485e -a jxbd
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顯示以下訊息，即為新增成功：
[OK] All nodes agree about slots configuration.
[OK] All 16384 slots covered.
[OK] New node added correctly.
#坑：
一開始是想用headless的網域創建redis叢集的，這樣節點重啟後就不需要更新ip，但是redis不支援使用域名，所以只能繞了一圈又回到固定ip的方法，跟容器環境很不協調。
1.2redis叢集狀態驗證（可選）
# 进入到redis客户端，集群需要带上-c，有密码需要带上-a
redis-cli -c -a jxbd
# 查看redis集群信息
127.0.0.1:6379> cluster info
cluster_state:ok
cluster_slots_assigned:16384
cluster_slots_ok:16384
cluster_slots_pfail:0
cluster_slots_fail:0
cluster_known_nodes:6
cluster_size:3
cluster_current_epoch:3
cluster_my_epoch:1
cluster_stats_messages_ping_sent:7996
cluster_stats_messages_pong_sent:7713
cluster_stats_messages_sent:15709
cluster_stats_messages_ping_received:7710
cluster_stats_messages_pong_received:7996
cluster_stats_messages_meet_received:3
cluster_stats_messages_received:15709
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注意：
現在進入叢集中的任一個Pod中都可以存取Redis服務，前面我們建立了一個headless類型的Service，kubernetes叢集會為此服務指派一個DNS記錄，格式為:$(pod.name).$(headless server.name).${namespace}.svc.cluster.local，每次存取該服務名稱時，將會直接進入到redis的節點上。 svc.cluster.local可省略。例如：
redis-cli -c -a jxbd -h redis-0.redis-hs.jxbp -p 6379
# 查看redis集群状态
127.0.0.1:6379> cluster nodes
70220b45e978d0cb3df19b07e55d883b49f4127d 10.168.235.238:6379@16379 slave 4367e4a45e557406a3112e7b79f82a44d4ce485e 0 1670306292673 2 connected
122b89a51a9bf005e3d47b6d721c65621d2e9a75 10.168.235.225:6379@16379 slave bcae187137a9b30d7dab8fe0d8ed4a46c6e39638 0 1670306290558 1 connected
c2afcb9e83038a47d04bf328ead8033788548234 10.168.235.198:6379@16379 slave a2cec159bbe2efa11a8f60287b90927bcb214729 0 1670306291162 3 connected
4367e4a45e557406a3112e7b79f82a44d4ce485e 10.168.235.239:6379@16379 master - 0 1670306291561 2 connected 5461-10922
bcae187137a9b30d7dab8fe0d8ed4a46c6e39638 10.168.235.196:6379@16379 myself,master - 0 1670306291000 1 connected 0-5460
a2cec159bbe2efa11a8f60287b90927bcb214729 10.168.235.222:6379@16379 master - 0 1670306292166 3 connected 10923-16383
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可以看到3個master，3個slave節點，都是connected狀態。
# 会找到对应的槽进行set操作，去到10.168.235.222节点
set name1 llsydn
-> Redirected to slot [12933] located at 10.168.235.222:6379
OK
# set name1成功
10.168.235.222:6379> set name1 llsydn
OK
# get name1成功
10.168.235.222:6379> get name1
"llsydn"
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master節點進行set操作，slave節點複製。主從複製
1.3重啟pod,驗證集群（可選）
# redis-1未重启之前
10.168.235.239:6379> cluster nodes
4367e4a45e557406a3112e7b79f82a44d4ce485e 10.168.235.239:6379@16379 myself,master - 0 1670307319000 2 connected 5461-10922
bcae187137a9b30d7dab8fe0d8ed4a46c6e39638 10.168.235.196:6379@16379 master - 0 1670307319575 1 connected 0-5460
70220b45e978d0cb3df19b07e55d883b49f4127d 10.168.235.238:6379@16379 slave 4367e4a45e557406a3112e7b79f82a44d4ce485e 0 1670307318000 2 connected
122b89a51a9bf005e3d47b6d721c65621d2e9a75 10.168.235.225:6379@16379 slave bcae187137a9b30d7dab8fe0d8ed4a46c6e39638 0 1670307319781 1 connected
c2afcb9e83038a47d04bf328ead8033788548234 10.168.235.198:6379@16379 slave a2cec159bbe2efa11a8f60287b90927bcb214729 0 1670307319071 3 connected
a2cec159bbe2efa11a8f60287b90927bcb214729 10.168.235.222:6379@16379 master - 0 1670307318000 3 connected 10923-16383
# 重启redis-1
kubectl delete pod redis-1 -n jxbp
pod "redis-1" deleted
# redis-1重启之后
10.168.235.239:6379> cluster nodes
4367e4a45e557406a3112e7b79f82a44d4ce485e 10.168.235.239:6379@16379 myself,master - 0 1670307349000 2 connected 5461-10922
bcae187137a9b30d7dab8fe0d8ed4a46c6e39638 10.168.235.196:6379@16379 master - 0 1670307349988 1 connected 0-5460
70220b45e978d0cb3df19b07e55d883b49f4127d 10.168.235.238:6379@16379 slave 4367e4a45e557406a3112e7b79f82a44d4ce485e 0 1670307349000 2 connected
122b89a51a9bf005e3d47b6d721c65621d2e9a75 10.168.235.232:6379@16379 slave bcae187137a9b30d7dab8fe0d8ed4a46c6e39638 0 1670307350089 1 connected
c2afcb9e83038a47d04bf328ead8033788548234 10.168.235.198:6379@16379 slave a2cec159bbe2efa11a8f60287b90927bcb214729 0 1670307350000 3 connected
a2cec159bbe2efa11a8f60287b90927bcb214729 10.168.235.222:6379@16379 master - 0 1670307348000 3 connected 10923-16383
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可以看到重啟後的，redis-1節點，雖然ip變了，但是redis集群，還是可以識別到新的ip，叢集還是正常的。
10.168.235.225 ---> 10.168.235.232
1.4建立Service服務
#在前面我們建立了用於實作StatefulSet的Headless Service，但該Service沒有Cluster Ip，因此不能用於外界訪問。因此，我們需要建立一個專門為Redis叢集提供存取和負載平衡的Service。
這裡可以使用ClusterIP，NodePort。這裡，我使用的是NodePort。
vi redis-ss.yaml
---
apiVersion: v1
kind: Service
metadata:
labels:
k8s.kuboard.cn/layer: db
k8s.kuboard.cn/name: redis
name: redis-ss
namespace: jxbp
spec:
ports:
- name: imdgss
port: 6379
protocol: TCP
targetPort: 6379
nodePort: 6379
selector:
k8s.kuboard.cn/layer: db
k8s.kuboard.cn/name: redis
type: NodePort登入後複製
建立名稱為：redis-ss的服務。
在K8S叢集中暴露6379端口，並且會對labels name為k8s.kuboard.cn/name: redis的pod進行負載平衡。
然後在K8S叢集中，就可以透過redis-ss:6379，對redis叢集進行存取。
kubectl get service -n jxbp
>NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
redis-hs ClusterIP None <none> 6379/TCP 76m
redis-ss NodePort 10.96.54.201 <none> 6379:6379/TCP 2s
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1.5 Springboot專案配置
spring.redis.cluster.nodes=redis-ss:6379
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1.6相關疑問分析
至此，大家可能會疑惑，那為什麼沒有使用穩定的標誌，Redis Pod也能正常進行故障轉移呢？這涉及了Redis本身的機制。因為，Redis叢集中每個節點都有自己的NodeId（保存在自動產生的nodes.conf中），而該NodeId不會隨著IP的變化和變化，這其實也是固定的網路標誌。換句話說，即使某位Redis Pod因重新啟動而重新啟動，該Pod仍將使用已儲存的NodeId來維持其身分。可以透過NFS查看redis-0節點設定檔nodes.conf
vi /opt/nfs/pv1/nodes.conf
> f6d4993467a4ab1f3fa806f1122edd39f6466394 10.168.235.228:6379@16379 slave ebed24c8fca9ebc16ceaaee0c2bc2e3e09f7b2c0 0 1670316449064 2 connected
ebed24c8fca9ebc16ceaaee0c2bc2e3e09f7b2c0 10.168.235.240:6379@16379 myself,master - 0 1670316450000 2 connected 5461-10922
955e1236652c2fcb11f47c20a43149dcd1f1f92b 10.168.235.255:6379@16379 master - 0 1670316449565 1 connected 0-5460
574c40485bb8f6cfaf8618d482efb06f3e323f88 10.168.235.224:6379@16379 slave 955e1236652c2fcb11f47c20a43149dcd1f1f92b 0 1670316449000 1 connected
91bd3dc859ce51f1ed0e7cbd07b13786297bd05b 10.168.235.237:6379@16379 slave fe0b74c5e461aa22d4d782f891b78ddc4306eed4 0 1670316450672 3 connected
fe0b74c5e461aa22d4d782f891b78ddc4306eed4 10.168.235.253:6379@16379 master - 0 1670316450068 3 connected 10923-16383
vars currentEpoch 3 lastVoteEpoch 0
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如上，第一列為NodeId，穩定不變；第二列為IP和連接埠信息，可能會改變。
這裡，我們介紹NodeId的兩種使用場景：
當某個Slave Pod斷線重連後IP改變，但是Master發現其NodeId依舊， 就認為該Slave還是之前的Slave。
如果某個 Master Pod 斷線，集群中的其他 Slave 會進行選舉選出新的 Master。如果舊的Master上線後，叢集發現它的NodeId仍然相同，那麼它會成為新Master的從屬節點。
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