k8s上面的Redis集群链接不上master的解决办法

• 问题描述

之前在k8s上面部署了一台node，然后创建了6个redis的pod，构建了一个redis的集群，正常运行。

最近添加了一台slave node，然后把其中的几个redis的pod调度到了slave node上面，结果集群就起不来了，看了下log报如下错误：

127.0.0.1:6379> get test
(error) CLUSTERDOWN The cluster is down127.0.0.1:6379> cluster info
cluster_state:fail
cluster_slots_assigned:16384
cluster_slots_ok:0
cluster_slots_pfail:16384
cluster_slots_fail:0
cluster_known_nodes:6
cluster_size:3
cluster_current_epoch:14
cluster_my_epoch:14
cluster_stats_messages_ping_sent:4
cluster_stats_messages_sent:4
cluster_stats_messages_received:0
total_cluster_links_buffer_limit_exceeded:0$ kubectl logs redis-app-5
... ...
1:S 19 Nov 2024 01:58:13.251 * Connecting to MASTER 172.16.43.44:6379
1:S 19 Nov 2024 01:58:13.251 * MASTER <-> REPLICA sync started
1:S 19 Nov 2024 01:58:13.251 * Cluster state changed: ok
1:S 19 Nov 2024 01:58:20.754 # Cluster state changed: fail
1:S 19 Nov 2024 01:59:14.979 # Timeout connecting to the MASTER...
1:S 19 Nov 2024 01:59:14.979 * Reconnecting to MASTER 172.16.43.44:6379 after failure
1:S 19 Nov 2024 01:59:14.979 * MASTER <-> REPLICA sync started
1:S 19 Nov 2024 02:00:15.422 # Timeout connecting to the MASTER...
1:S 19 Nov 2024 02:00:15.422 * Reconnecting to MASTER 172.16.43.44:6379 after failure
1:S 19 Nov 2024 02:00:15.422 * MASTER <-> REPLICA sync started
1:S 19 Nov 2024 02:01:16.357 # Timeout connecting to the MASTER...
1:S 19 Nov 2024 02:01:16.357 * Reconnecting to MASTER 172.16.43.44:6379 after failure
1:S 19 Nov 2024 02:01:16.357 * MASTER <-> REPLICA sync started

• 问题分析

这种情况是redis的pod已经重新启动了，相应的ip地址可能已经变掉了，但是集群部署还是按照重启之前的配置来的，所以导致启动失败。

• 我的解决办法：

1. 首先查看各个redis pod的信息

   $  kubectl describe pod redis-app | grep IPcni.projectcalico.org/podIP: 172.16.178.201/32cni.projectcalico.org/podIPs: 172.16.178.201/32
   IP:               172.16.178.201
   IPs:IP:           172.16.178.201cni.projectcalico.org/podIP: 172.16.178.202/32cni.projectcalico.org/podIPs: 172.16.178.202/32
   IP:               172.16.178.202
   IPs:IP:           172.16.178.202cni.projectcalico.org/podIP: 172.16.43.1/32cni.projectcalico.org/podIPs: 172.16.43.1/32
   IP:               172.16.43.1
   IPs:IP:           172.16.43.1cni.projectcalico.org/podIP: 172.16.178.203/32cni.projectcalico.org/podIPs: 172.16.178.203/32
   IP:               172.16.178.203
   IPs:IP:           172.16.178.203cni.projectcalico.org/podIP: 172.16.43.63/32cni.projectcalico.org/podIPs: 172.16.43.63/32
   IP:               172.16.43.63
   IPs:IP:           172.16.43.63cni.projectcalico.org/podIP: 172.16.178.204/32cni.projectcalico.org/podIPs: 172.16.178.204/32
   IP:               172.16.178.204
   IPs:IP:           172.16.178.204$ kubectl get pods -o wide
   NAME                                 READY   STATUS    RESTARTS         AGE     IP               NODE       NOMINATED NODE   READINESS GATES
   redis-app-0                          1/1     Running   0                2m34s   172.16.178.201   kevin-s1   <none>           <none>
   redis-app-1                          1/1     Running   0                2m32s   172.16.178.202   kevin-s1   <none>           <none>
   redis-app-2                          1/1     Running   0                2m30s   172.16.43.1      kevin-pc   <none>           <none>
   redis-app-3                          1/1     Running   0                2m26s   172.16.178.203   kevin-s1   <none>           <none>
   redis-app-4                          1/1     Running   0                2m24s   172.16.43.63     kevin-pc   <none>           <none>
   redis-app-5                          1/1     Running   0                2m19s   172.16.178.204   kevin-s1   <none>           <none>

2. 然后通过inem0o/redis-trib根据pods的最新ip重新创建集群

   $ sudo docker run --rm -ti inem0o/redis-trib create --replicas 1 172.16.178.201:6379 172.16.178.202:6379 172.16.43.1:6379 172.16.43.63:6379 172.16.178.204:6379 172.16.178.203:6379

3. 在创建集群的过程中可能会遇到下面这个错误

$ sudo docker run --rm -ti inem0o/redis-trib create --replicas 1 172.16.178.201:6379 172.16.178.202:6379 172.16.43.1:6379 172.16.43.63:6379 172.16.178.204:6379 172.16.178.203:6379
>>> Creating cluster
[ERR] Node 172.16.178.201:6379 is not empty. Either the node already knows other nodes (check with CLUSTER NODES) or contains some key in database 0.

 这种情况是因为redis的pod没有被重置，需要登录出问题的pod然后用redis-cii重置集群

$ kubectl exec -it redis-app-0 -- redis-cli -h 172.16.178.201 -p 6379
172.16.178.201:6379> CLUSTER RESET
OK

出问题的pod全部重置完之后再执行上面的命令，集群重新构建成功

$ sudo docker run --rm -ti inem0o/redis-trib create --replicas 1 172.16.178.201:6379 172.16.178.202:6379 172.16.43.1:6379 172.16.43.63:6379 172.16.178.204:6379 172.16.178.203:6379
>>> Creating cluster
>>> Performing hash slots allocation on 6 nodes...
Using 3 masters:
172.16.178.201:6379
172.16.178.202:6379
172.16.43.1:6379
Adding replica 172.16.43.63:6379 to 172.16.178.201:6379
Adding replica 172.16.178.204:6379 to 172.16.178.202:6379
Adding replica 172.16.178.203:6379 to 172.16.43.1:6379
M: 57d9f345d23e7bf7dd2f331e14d9d7143aa9617f 172.16.178.201:6379slots:0-5460 (5461 slots) master
M: f5d617c0ed655dd6afa32c5d4ec6260713668639 172.16.178.202:6379slots:5461-10922 (5462 slots) master
M: 808de7e00f10fe17a5582cd76a533159a25006d8 172.16.43.1:6379slots:10923-16383 (5461 slots) master
S: 44ac042b99b9b73051b05d1be3d98cf475f67f0a 172.16.43.63:6379replicates 57d9f345d23e7bf7dd2f331e14d9d7143aa9617f
S: 8db8f89b7b28d0ce098de275340e3c4679fd342d 172.16.178.204:6379replicates f5d617c0ed655dd6afa32c5d4ec6260713668639
S: 2f5860e62f03ea17d398bbe447a6f1d428ae8698 172.16.178.203:6379replicates 808de7e00f10fe17a5582cd76a533159a25006d8
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 172.16.178.201:6379)
M: 57d9f345d23e7bf7dd2f331e14d9d7143aa9617f 172.16.178.201:6379slots:0-5460 (5461 slots) master1 additional replica(s)
S: 44ac042b99b9b73051b05d1be3d98cf475f67f0a 172.16.43.63:6379@16379slots: (0 slots) slavereplicates 57d9f345d23e7bf7dd2f331e14d9d7143aa9617f
M: f5d617c0ed655dd6afa32c5d4ec6260713668639 172.16.178.202:6379@16379slots:5461-10922 (5462 slots) master1 additional replica(s)
S: 8db8f89b7b28d0ce098de275340e3c4679fd342d 172.16.178.204:6379@16379slots: (0 slots) slavereplicates f5d617c0ed655dd6afa32c5d4ec6260713668639
S: 2f5860e62f03ea17d398bbe447a6f1d428ae8698 172.16.178.203:6379@16379slots: (0 slots) slavereplicates 808de7e00f10fe17a5582cd76a533159a25006d8
M: 808de7e00f10fe17a5582cd76a533159a25006d8 172.16.43.1:6379@16379slots:10923-16383 (5461 slots) master1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

查看集群状态：

$ kubectl exec -it redis-app-3 -- redis-cli
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:14
cluster_my_epoch:3
cluster_stats_messages_ping_sent:39
cluster_stats_messages_pong_sent:40
cluster_stats_messages_meet_sent:1
cluster_stats_messages_sent:80
cluster_stats_messages_ping_received:40
cluster_stats_messages_pong_received:36
cluster_stats_messages_received:76
total_cluster_links_buffer_limit_exceeded:0

至此问题解决。

=========================================================================

2024.11.20更新

=========================================================================

因为重启node之后，node上面的pod也会被重启，而redis pod 的IP地址是启动时候随机分配的，所以重启node可能会导致集群再次down掉，另一种解决办法就是在构建集群的时候，使用各个redis pod的DNS名称构造，DNS名称的格式是：

<statefulset-name>-<ordinal>.<service-name>.<namespace>.svc.cluster.local

其中的<statefulset-name><service-name>和<namespace>可以从redis-stateful.yaml里面获取到

-<ordinal>就是instance的编号

例如下面这个redis-stateful.yaml

$ cat redis-stateful.yaml
apiVersion: apps/v1
kind: StatefulSet
metadata:name: redis-app
spec:serviceName: redis-servicereplicas: 6selector:matchLabels:app: redisappCluster: redis-clustertemplate:metadata:labels:app: redisappCluster: redis-clusterspec:containers:- name: redisimage: redisimagePullPolicy: IfNotPresentcommand: ["/bin/bash", "-ce", "tail -f /dev/null"]command: ["redis-server"]args:- "/etc/redis/redis.conf"- "--protected-mode"- "no"ports:- name: rediscontainerPort: 6379protocol: "TCP"- name: clustercontainerPort: 16379protocol: "TCP"volumeMounts:- name: "redis-conf"mountPath: "/etc/redis"- name: "redis-data"mountPath: "/var/lib/redis"volumes:- name: "redis-conf"configMap:name: "redis-conf"items:- key: "redis.conf"path: "redis.conf"volumeClaimTemplates:- metadata:name: redis-dataspec:accessModes: [ "ReadWriteMany" ]storageClassName: "redis"resources:requests:storage: 1Gi

其中

<statefulset-name>是redis-app

<service-name>是redis-service

<namespace>默认为default （你可以配置自己的namespace）

因为起了6个节点，所以<ordinal>是0~5

有了以上信息，那么构造集群的命令就是

$ kubectl exec -it redis-app-0 -n default -- redis-cli --cluster create 
redis-app-1.redis-service.default.svc.cluster.local:6379 
redis-app-2.redis-service.default.svc.cluster.local:6379 
redis-app-3.redis-service.default.svc.cluster.local:6379 
redis-app-4.redis-service.default.svc.cluster.local:6379 
redis-app-5.redis-service.default.svc.cluster.local:6379 
redis-app-0.redis-service.default.svc.cluster.local:6379 --cluster-replicas 1

至此redis集群构造成功，重启node之后，集群的节点还是可以通过DNS name连接成功。

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:15
cluster_my_epoch:15
cluster_stats_messages_ping_sent:1204
cluster_stats_messages_pong_sent:1195
cluster_stats_messages_meet_sent:1
cluster_stats_messages_sent:2400
cluster_stats_messages_ping_received:1195
cluster_stats_messages_pong_received:1200
cluster_stats_messages_received:2395
total_cluster_links_buffer_limit_exceeded:0