Redis Cluster配置

1、理論知識

1、Redis Cluster設計要點

redis cluster在設計的時候，就考慮到了去中心化，去中間件，也就是說，集群中的每個節點都是平等的關系，都是對等的，每個節點都保存各自的數據和整個集群的狀態。每個節點都和其他所有節點連接，而且這些連接保持活躍，這樣就保證了我們只需要連接集群中的任意一個節點，就可以獲取到其他節點的數據。

那么redis 是如何合理分配這些節點和數據的呢？

Redis 集群沒有並使用傳統的一致性哈希來分配數據，而是采用另外一種叫做哈希槽 (hash slot)的方式來分配的。redis cluster 默認分配了 16384 個slot，當我們set一個key 時，會用CRC16算法來取模得到所屬的slot，然后將這個key 分到哈希槽區間的節點上，具體算法就是：CRC16(key) % 16384。

注意的是：必須要3個以上的主節點，否則在創建集群時會失敗。

所以，我們假設現在有3個節點已經組成了集群，分別是：A, B, C 三個節點，它們可以是一台機器上的三個端口，也可以是三台不同的服務器。那么，采用哈希槽 (hash slot)的方式來分配16384個slot 的話，它們三個節點分別承擔的slot 區間是：

• 節點A覆蓋0－5460;
• 節點B覆蓋5461－10922;
• 節點C覆蓋10923－16383.

那么，現在我想設置一個key ,比如叫my_name:

set my_name yangyi

按照redis cluster的哈希槽算法：CRC16('my_name')%16384 = 2412。 那么就會把這個key 的存儲分配到 A 上了。

同樣，當我連接(A,B,C)任何一個節點想獲取my_name這個key時，也會這樣的算法，然后內部跳轉到B節點上獲取數據。

這種哈希槽的分配方式有好也有壞，好處就是很清晰，比如我想新增一個節點D，redis cluster的這種做法是從各個節點的前面各拿取一部分slot到D上。大致就會變成這樣：

• 節點A覆蓋1365-5460
• 節點B覆蓋6827-10922
• 節點C覆蓋12288-16383
• 節點D覆蓋0-1364,5461-6826,10923-12287

同樣刪除一個節點也是類似，移動完成后就可以刪除這個節點了。

所以redis cluster 就是這樣的一個形狀：

2、Redis Cluster主從模式

redis cluster 為了保證數據的高可用性，加入了主從模式，一個主節點對應一個或多個從節點，主節點提供數據存取，從節點則是從主節點拉取數據備份，當這個主節點掛掉后，就會有這個從節點選取一個來充當主節點，從而保證集群不會掛掉。

上面那個例子里, 集群有ABC三個主節點, 如果這3個節點都沒有加入從節點，如果B掛掉了，我們就無法訪問整個集群了。A和C的slot也無法訪問。

所以我們在集群建立的時候，一定要為每個主節點都添加了從節點, 比如像這樣, 集群包含主節點A、B、C, 以及從節點A1、B1、C1, 那么即使B掛掉系統也可以繼續正確工作。

B1節點替代了B節點，所以Redis集群將會選擇B1節點作為新的主節點，集群將會繼續正確地提供服務。 當B重新開啟后，它就會變成B1的從節點。

不過需要注意，如果節點B和B1同時掛了，Redis集群就無法繼續正確地提供服務了。

2、搭建

1、 redis實例：

192.168.244.128:6379   主
192.168.244.128:6380   從

192.168.244.130:6379   主
192.168.244.130:6380   從

192.168.244.131:6379   主
192.168.244.131:6380   從

2、執行命令創建集群

把cluster-enabled yes 的注釋打開

執行命令：./redis-trib.rb create --replicas 1 192.168.244.128:6379 192.168.244.128:6380 192.168.244.130:6379 192.168.244.130:6380 192.168.244.131:6379 192.168.244.131:6380

新版本已經修改命令為：

./redis-cli --cluster create 192.168.244.128:6379 192.168.244.128:6380 192.168.244.130:6379 192.168.244.130:6380 192.168.244.131:6379 192.168.244.131:6380 --cluster-replicas 1 -a zjl123

 

注意一個服務器啟動多實例時以下配置要不一樣：

pidfile : pidfile/var/run/redis/redis_6380.pid

port 6380

logfile : logfile/var/log/redis/redis_6380.log

rdbfile : dbfilenamedump_6380.rdb

 

3、問題：

1、報錯：/usr/bin/env: ruby: No such file or directory

安裝ruby,rubygems 依賴

yum -y install ruby rubygems

 

2、報錯

./redis-trib.rb:6: odd number list for Hash
         white: 29,
               ^
./redis-trib.rb:6: syntax error, unexpected ':', expecting '}'
         white: 29,
               ^
./redis-trib.rb:7: syntax error, unexpected ',', expecting kEND

 

安裝新版ruby

yum remove -y ruby
yum remove -y rubygems

下載ruby-2.6.5.tar.gz

tar –zxvf ruby-2.6.5.tar.gz

cd ruby-2.6.5

./configure

make 

make install

3、重復運行創建集群命令提示：

You should use redis-cli instead.

All commands and features belonging to redis-trib.rb have been moved
 to redis-cli.
In order to use them you should call redis-cli with the --cluster
 option followed by the subcommand name, arguments and options.

Use the following syntax:
redis-cli --cluster SUBCOMMAND [ARGUMENTS] [OPTIONS]

Example:
redis-cli --cluster create 192.168.244.128:6379 192.168.244.128:6380 192.168.244.130:6379 192.168.244.130:6380 192.168.244.131:6379 192.168.244.131:6380 --cluster-replicas 1

To get help about all subcommands, type:
redis-cli --cluster help

[root@zjltest3 src]# redis-cli --cluster create 192.168.244.128:6379 192.168.244.128:6380 192.168.244.130:6379 192.168.244.130:6380 192.168.244.131:6379 192.168.244.131:6380 --cluster-replicas 1
-bash: redis-cli: command not foun

4、執行命令  . /redis-cli --cluster create 192.168.244.128:6379 192.168.244.128:6380 192.168.244.130:6379 192.168.244.130:6380 192.168.244.131:6379 192.168.244.131:6380 --cluster-replicas 1

[ERR] Node 192.168.244.128:6379 NOAUTH Authentication required.

5、執行命令
./redis-cli --cluster create 192.168.244.128:6379 192.168.244.128:6380 192.168.244.130:6379 192.168.244.130:6380 192.168.244.131:6379 192.168.244.131:6380 --cluster-replicas 1 -a zjl123

Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
 [ERR] Node 192.168.244.128:6379 is not configured as a cluster node.

6、把cluster-enabled yes 的注釋打開  成功：

Master[0] -> Slots 0 - 5460
Master[1] -> Slots 5461 - 10922
Master[2] -> Slots 10923 - 16383
Adding replica 192.168.244.130:6380 to 192.168.244.128:6379
Adding replica 192.168.244.131:6380 to 192.168.244.130:6379
Adding replica 192.168.244.128:6380 to 192.168.244.131:6379
M: 0f6f4aabd05f0ef3a214a3e67b139ce52c8d5ca4 192.168.244.128:6379
   slots:[0-5460],[5634],[8157] (5461 slots) master
S: 1d6b7a10046a75b3ab5461a8d29f411837a3c0d8 192.168.244.128:6380
   replicates 0f30ac78eba3be20aa307ea64c09b5025de165af
M: d34845ed63f35645e820946cc0dc24460621a386 192.168.244.130:6379
   slots:[5461-10922] (5462 slots) master
S: 1332da24115473f73e04dfe8b67cd1e595a34a11 192.168.244.130:6380
   replicates 0f6f4aabd05f0ef3a214a3e67b139ce52c8d5ca4
M: 0f30ac78eba3be20aa307ea64c09b5025de165af 192.168.244.131:6379
   slots:[10923-16383] (5461 slots) master
S: 1a57a63faa17e5fda4025a5f088fc70055990a07 192.168.244.131:6380
   replicates d34845ed63f35645e820946cc0dc24460621a386
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 192.168.244.128:6379)
M: 0f6f4aabd05f0ef3a214a3e67b139ce52c8d5ca4 192.168.244.128:6379
   slots:[0-5460] (5461 slots) master
   1 additional replica(s)
S: 1d6b7a10046a75b3ab5461a8d29f411837a3c0d8 192.168.244.128:6380
   slots: (0 slots) slave
   replicates 0f30ac78eba3be20aa307ea64c09b5025de165af
M: d34845ed63f35645e820946cc0dc24460621a386 192.168.244.130:6379
   slots:[5461-10922] (5462 slots) master
   1 additional replica(s)
S: 1a57a63faa17e5fda4025a5f088fc70055990a07 192.168.244.131:6380
   slots: (0 slots) slave
   replicates d34845ed63f35645e820946cc0dc24460621a386
S: 1332da24115473f73e04dfe8b67cd1e595a34a11 192.168.244.130:6380
   slots: (0 slots) slave
   replicates 0f6f4aabd05f0ef3a214a3e67b139ce52c8d5ca4
M: 0f30ac78eba3be20aa307ea64c09b5025de165af 192.168.244.131:6379
   slots:[10923-16383] (5461 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.

 

3、驗證

1、查看集群狀態：

./redis-cli --cluster check 192.168.244.128:6379

Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
192.168.244.128:6379 (0f6f4aab...) -> 0 keys | 5461 slots | 1 slaves.
192.168.244.130:6379 (d34845ed...) -> 0 keys | 5462 slots | 1 slaves.
192.168.244.131:6379 (0f30ac78...) -> 0 keys | 5461 slots | 1 slaves.
[OK] 0 keys in 3 masters.
0.00 keys per slot on average.
>>> Performing Cluster Check (using node 192.168.244.128:6379)
M: 0f6f4aabd05f0ef3a214a3e67b139ce52c8d5ca4 192.168.244.128:6379
   slots:[0-5460] (5461 slots) master
   1 additional replica(s)
S: 1d6b7a10046a75b3ab5461a8d29f411837a3c0d8 192.168.244.128:6380
   slots: (0 slots) slave
   replicates 0f30ac78eba3be20aa307ea64c09b5025de165af
M: d34845ed63f35645e820946cc0dc24460621a386 192.168.244.130:6379
   slots:[5461-10922] (5462 slots) master
   1 additional replica(s)
S: 1a57a63faa17e5fda4025a5f088fc70055990a07 192.168.244.131:6380
   slots: (0 slots) slave
   replicates d34845ed63f35645e820946cc0dc24460621a386
S: 1332da24115473f73e04dfe8b67cd1e595a34a11 192.168.244.130:6380
   slots: (0 slots) slave
   replicates 0f6f4aabd05f0ef3a214a3e67b139ce52c8d5ca4
M: 0f30ac78eba3be20aa307ea64c09b5025de165af 192.168.244.131:6379
   slots:[10923-16383] (5461 slots) master
   1 additional replica(s)
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

2、登錄服務器設置和獲取值

[root@zjltest3 src]# ./redis-cli -c -h 192.168.244.128 -p 6379 -a zjl123               
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
192.168.244.128:6379> set zjl 123
-> Redirected to slot [5634] located at 192.168.244.130:6379
OK
192.168.244.130:6379>

如上，設置的值被保存在130服務器

[root@zjltest2 redis]# src/redis-cli -c -h 192.168.244.128 -p 6379 -a zjl123    
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
192.168.244.128:6379> get zjl
-> Redirected to slot [5634] located at 192.168.244.130:6379
"123"

如上獲取值是從130上獲取的

 

以上說明cluster集群配置成功

 

轉載自：https://www.cnblogs.com/diegodu/p/9183356.html