redis 集群模式使用注意事项
如果使用脚本对key访问，脚本中禁止出现多key访问，只能对一个key访问
集群版会将不同的key hash到不同节点上，如果出现跨节点访问，那么将会出现报错，引用官方的解释如下
Redis Cluster implements all the single key commands available in the non-distributed version of Redis. Commands performing complex multi-key operations like set unions and intersections are implemented for cases where all of the keys involved in the operation hash to the same slot.
Redis Cluster implements a concept called hash tags that can be used to force certain keys to be stored in the same hash slot. However, during manual resharding, multi-key operations may become unavailable for some time while single-key operations are always available.
Redis Cluster does not support multiple databases like the standalone version of Redis. We only support database 0; the SELECT command is not allowed
官网链接
部署集群版redis，具体部署过程参考官网,部署的结果如下，注意使用redis 5.0+版本
.\redis-cli.exe --cluster create 127.0.0.1:7000 127.0.0.1:7001 127.0.0.1:7002 127.0.0.1:7003 127.0.0.1:7004 127.0.0.1:7005 --cluster-replicas 1
>>> Performing hash slots allocation on 6 nodes...
Master[0] -> Slots 0 - 5460
Master[1] -> Slots 5461 - 10922
Master[2] -> Slots 10923 - 16383
Adding replica 127.0.0.1:7004 to 127.0.0.1:7000
Adding replica 127.0.0.1:7005 to 127.0.0.1:7001
Adding replica 127.0.0.1:7003 to 127.0.0.1:7002
>>> Trying to optimize slaves allocation for anti-affinity
[WARNING] Some slaves are in the same host as their master
M: 87c044b9bef0c1ff4195cd97849a4906ff117008 127.0.0.1:7000
slots:[0-10922] (5461 slots) master
M: 20d97ec5b8a129366f7a7496a85404efb8e71371 127.0.0.1:7001
slots:[5461-10922] (5462 slots) master
M: 7a06e73f83922d81356ccd832c24259a99103b2d 127.0.0.1:7002
slots:[10923-16383] (5461 slots) master
S: 7fe11bbc6823aba9a8d94cb256440f17ca1121a0 127.0.0.1:7003
replicates 87c044b9bef0c1ff4195cd97849a4906ff117008
S: 9a8e3e98494d20dfe34d9ec814fd87b5895caf4f 127.0.0.1:7004
replicates 20d97ec5b8a129366f7a7496a85404efb8e71371
S: be03b397995428710aad5ee3248330f4394bc8eb 127.0.0.1:7005
replicates 7a06e73f83922d81356ccd832c24259a99103b2d
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 127.0.0.1:7000)
M: 87c044b9bef0c1ff4195cd97849a4906ff117008 127.0.0.1:7000
slots:[0-10922] (10923 slots) master
2 additional replica(s)
S: 20d97ec5b8a129366f7a7496a85404efb8e71371 127.0.0.1:7001
slots: (0 slots) slave
replicates 87c044b9bef0c1ff4195cd97849a4906ff117008
M: 7a06e73f83922d81356ccd832c24259a99103b2d 127.0.0.1:7002
slots:[10923-16383] (5461 slots) master
1 additional replica(s)
S: be03b397995428710aad5ee3248330f4394bc8eb 127.0.0.1:7005
slots: (0 slots) slave
replicates 7a06e73f83922d81356ccd832c24259a99103b2d
M: 9a8e3e98494d20dfe34d9ec814fd87b5895caf4f 127.0.0.1:7004
slots: (0 slots) master
S: 7fe11bbc6823aba9a8d94cb256440f17ca1121a0 127.0.0.1:7003
slots: (0 slots) slave
replicates 87c044b9bef0c1ff4195cd97849a4906ff117008
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
对两个key设置值
set testkey test
OK
set foo test
-> Redirected to slot [12182] located at 127.0.0.1:7002
OK
当出现Redirected to slot [12182] located at 127.0.0.1:7002说明key foo被分配到其他节点上
执行脚本
eval "local foo = redis.call('get','foo') local test = redis.call('get','testkey') return test" 0
(error) ERR Error running script (call to f_0c156039358148061b8c221e36754272416ca3c4): @user_script:1: @user_script: 1: Lua script attempted to access a non local key in a cluster node
脚本中同时访问了key foo 和 key testkey；出现如下错误(error) ERR Error running script (call to f_0c156039358148061b8c221e36754272416ca3c4): @user_script:1: @user_script: 1: Lua script attempted to access a non local key in a cluster node
所以客户端程序使用脚本时，禁止出现多key访问，开发阶段是单节点，问题暴露不出来，上线后是集群版，当暴露问题再修改会增加成本