Redis Cluster配置

1、理论知识

1、Redis Cluster设计要点

redis cluster在设计的时候，就考虑到了去中心化，去中间件，也就是说，集群中的每个节点都是平等的关系，都是对等的，每个节点都保存各自的数据和整个集群的状态。每个节点都和其他所有节点连接，而且这些连接保持活跃，这样就保证了我们只需要连接集群中的任意一个节点，就可以获取到其他节点的数据。

那么redis 是如何合理分配这些节点和数据的呢？

Redis 集群没有并使用传统的一致性哈希来分配数据，而是采用另外一种叫做哈希槽 (hash slot)的方式来分配的。redis cluster 默认分配了 16384 个slot，当我们set一个key 时，会用CRC16算法来取模得到所属的slot，然后将这个key 分到哈希槽区间的节点上，具体算法就是：CRC16(key) % 16384。

注意的是：必须要3个以上的主节点，否则在创建集群时会失败。

所以，我们假设现在有3个节点已经组成了集群，分别是：A, B, C 三个节点，它们可以是一台机器上的三个端口，也可以是三台不同的服务器。那么，采用哈希槽 (hash slot)的方式来分配16384个slot 的话，它们三个节点分别承担的slot 区间是：

• 节点A覆盖0－5460;
• 节点B覆盖5461－10922;
• 节点C覆盖10923－16383.

那么，现在我想设置一个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。 那么就会把这个key 的存储分配到 A 上了。

同样，当我连接(A,B,C)任何一个节点想获取my_name这个key时，也会这样的算法，然后内部跳转到B节点上获取数据。

这种哈希槽的分配方式有好也有坏，好处就是很清晰，比如我想新增一个节点D，redis cluster的这种做法是从各个节点的前面各拿取一部分slot到D上。大致就会变成这样：

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

同样删除一个节点也是类似，移动完成后就可以删除这个节点了。

所以redis cluster 就是这样的一个形状：

2、Redis Cluster主从模式

redis cluster 为了保证数据的高可用性，加入了主从模式，一个主节点对应一个或多个从节点，主节点提供数据存取，从节点则是从主节点拉取数据备份，当这个主节点挂掉后，就会有这个从节点选取一个来充当主节点，从而保证集群不会挂掉。

上面那个例子里, 集群有ABC三个主节点, 如果这3个节点都没有加入从节点，如果B挂掉了，我们就无法访问整个集群了。A和C的slot也无法访问。

所以我们在集群建立的时候，一定要为每个主节点都添加了从节点, 比如像这样, 集群包含主节点A、B、C, 以及从节点A1、B1、C1, 那么即使B挂掉系统也可以继续正确工作。

B1节点替代了B节点，所以Redis集群将会选择B1节点作为新的主节点，集群将会继续正确地提供服务。 当B重新开启后，它就会变成B1的从节点。

不过需要注意，如果节点B和B1同时挂了，Redis集群就无法继续正确地提供服务了。

2、搭建

1、 redis实例：

192.168.244.128:6379   主
192.168.244.128:6380   从

192.168.244.130:6379   主
192.168.244.130:6380   从

192.168.244.131:6379   主
192.168.244.131:6380   从

2、执行命令创建集群

把cluster-enabled yes 的注释打开

执行命令：./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

新版本已经修改命令为：

./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

注意一个服务器启动多实例时以下配置要不一样：

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

port 6380

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

rdbfile : dbfilenamedump_6380.rdb

3、问题：

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

安装ruby,rubygems 依赖

yum -y install ruby rubygems

2、报错

./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

安装新版ruby

yum remove -y ruby
yum remove -y rubygems

下载ruby-2.6.5.tar.gz

tar –zxvf ruby-2.6.5.tar.gz

cd ruby-2.6.5

./configure

make 

make install

3、重复运行创建集群命令提示：

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、执行命令  . /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、执行命令
./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 的注释打开  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、验证

1、查看集群状态：

./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、登录服务器设置和获取值

[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，设置的值被保存在130服务器

[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"

如上获取值是从130上获取的

以上说明cluster集群配置成功

 

转载自：https://www.cnblogs.com/diegodu/p/9183356.html