硬件环境

本文适用的硬件环境如下

Linux版本：CentOS release 6.7 (Final)Redis版本：3.2.1

Redis已经成功安装，安装路径为/home/idata/yangfan/local/redis-3.2.1。

我们要在单台机器上搭建Redis集群，方式是通过不同的TCP端口启动多个实例，然后组成集群。

 

1、启动Redis多个实例

我们在Redis安装目录下创建目录cluster，并编写7000.conf~7005.conf 6个配置文件，这6个配置文件用来启动6个实例，后面将使用这6个实例组成集群。

以7000.conf为例，配置文件需要填写如下几项。

port  7000                                        //端口7000,7002,7003        bind 10.93.84.53                                     //默认ip为127.0.0.1 需要改为其他节点机器可访问的ip 否则创建集群时无法访问对应的端口，无法创建集群daemonize    yes                               //redis后台运行pidfile  ./redis_7000.pid          //pidfile文件对应7000,7001,7002cluster-enabled  yes                           //开启集群  把注释#去掉cluster-config-file  nodes_7000.conf   //集群的配置  配置文件首次启动自动生成 7000,7001,7002cluster-node-timeout  15000                //请求超时  默认15秒，可自行设置appendonly  yes                           //aof日志开启  有需要就开启，它会每次写操作都记录一条日志　

分别启动6个实例

./bin/redis-server cluster/conf/7000.conf./bin/redis-server cluster/conf/7001.conf ./bin/redis-server cluster/conf/7002.conf ./bin/redis-server cluster/conf/7003.conf ./bin/redis-server cluster/conf/7004.conf ./bin/redis-server cluster/conf/7005.conf

启动成功后，看一下进程

# ps -ef | grep redis | grep clusteridata    15711 22329  0 18:40 pts/10   00:00:00 ./bin/redis-server 10.93.84.53:7000 [cluster]idata    15740 22329  0 18:40 pts/10   00:00:00 ./bin/redis-server 10.93.84.53:7001 [cluster]idata    15810 22329  0 18:40 pts/10   00:00:00 ./bin/redis-server 10.93.84.53:7002 [cluster]idata    17023 22329  0 18:42 pts/10   00:00:00 ./bin/redis-server 10.93.84.53:7003 [cluster]idata    17030 22329  0 18:42 pts/10   00:00:00 ./bin/redis-server 10.93.84.53:7004 [cluster]idata    17035 22329  0 18:42 pts/10   00:00:00 ./bin/redis-server 10.93.84.53:7005 [cluster]

至此，ip=10.93.84.53机器上创建了6个实例，端口号为port=7000~7005。

 

Redis 3.0以上的集群方式是通过Redis安装目录下的bin/redis-trib.rb脚本搭建。

这个脚本是用Ruby编写的，尝试运行，如果打印如下，你可以跳过本文的第二部分。

idata@qa-f1502-xg01.xg01:~/yangfan/local/redis-3.2.1/bin$ ruby redis-trib.rb Usage: redis-trib  
      
      
         create          host1:port1 ... hostN:portN                  --replicas 
       
          check           host:port  info            host:port  fix             host:port                  --timeout 
        
           reshard         host:port                  --from 
         
                            --to 
          
            --slots 
           
             --yes --timeout 
            
              --pipeline 
             
               rebalance host:port --weight 
              
                --auto-weights --use-empty-masters --timeout 
               
                 --simulate --pipeline 
                
                  --threshold 
                 
                   add-node new_host:new_port existing_host:existing_port --slave --master-id 
                  
                    del-node host:port node_id set-timeout host:port milliseconds call host:port command arg arg .. arg import host:port --from 
                   
                     --copy --replace help (show this help)For check, fix, reshard, del-node, set-timeout you can specify the host and port of any working node in the cluster.
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     

如果执行失败，那么不幸的是你的机器没有Ruby运行的环境，那么你需要安装Ruby。进入第二部分。

 

2、安装ruby

下面的过程都是在root权限下完成的。

1）yum安装ruby和依赖的包。

# yum -y install ruby ruby-devel rubygems rpm-build

一般来说，这一步是能正常完成的。

 

2）使用gem这个命令来安装redis接口

gem是ruby的一个工具包

# gem install redis

安装过程出错

郁闷，看样子要升级ruby版本。

 

3）升级Ruby的版本

安装rvm，我不知道这是个什么东西，但是感觉像是Ruby的一个包管理器。

# curl -L get.rvm.io | bash -s stable

WTF，又出问题了

气急败坏的照着他说的做

# gpg2 --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3gpg: keyring `/root/.gnupg/secring.gpg' createdgpg: requesting key D39DC0E3 from hkp server keys.gnupg.netgpg: /root/.gnupg/trustdb.gpg: trustdb createdgpg: key D39DC0E3: public key "Michal Papis (RVM signing) 
     
      " importedgpg: no ultimately trusted keys foundgpg: Total number processed: 1gpg:               imported: 1  (RSA: 1)
     

然后重新下载rvm安装，成功了。

# curl -L get.rvm.io | bash -s stable   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current                                 Dload  Upload   Total   Spent    Left  Speed100 24090  100 24090    0     0  18023      0  0:00:01  0:00:01 --:--:--  129kDownloading https://github.com/rvm/rvm/archive/1.29.3.tar.gzDownloading https://github.com/rvm/rvm/releases/download/1.29.3/1.29.3.tar.gz.ascgpg: Signature made Mon 11 Sep 2017 04:59:21 AM CST using RSA key ID BF04FF17gpg: Good signature from "Michal Papis (RVM signing) 
     
      "gpg:                 aka "Michal Papis 
      
       "gpg:                 aka "[jpeg image of size 5015]"gpg: WARNING: This key is not certified with a trusted signature!gpg:          There is no indication that the signature belongs to the owner.Primary key fingerprint: 409B 6B17 96C2 7546 2A17  0311 3804 BB82 D39D C0E3     Subkey fingerprint: 62C9 E5F4 DA30 0D94 AC36  166B E206 C29F BF04 FF17GPG verified '/usr/local/rvm/archives/rvm-1.29.3.tgz'Creating group 'rvm'Installing RVM to /usr/local/rvm/Installation of RVM in /usr/local/rvm/ is almost complete:  * First you need to add all users that will be using rvm to 'rvm' group,    and logout - login again, anyone using rvm will be operating with `umask u=rwx,g=rwx,o=rx`.  * To start using RVM you need to run `source /etc/profile.d/rvm.sh`    in all your open shell windows, in rare cases you need to reopen all shell windows.
      
     

接着，source环境，让rvm可用。

# source /usr/local/rvm/scripts/rvm

查看Ruby可用版本

# rvm list known# MRI Rubies[ruby-]1.8.6[-p420][ruby-]1.8.7[-head] # security released on head[ruby-]1.9.1[-p431][ruby-]1.9.2[-p330][ruby-]1.9.3[-p551][ruby-]2.0.0[-p648][ruby-]2.1[.10][ruby-]2.2[.7][ruby-]2.3[.4][ruby-]2.4[.1]

可以看到最新的版本是2.4.1，那么我们装最新的吧。

# rvm install 2.4.1Searching for binary rubies, this might take some time.No binary rubies available for: centos/6/x86_64/ruby-2.4.1.Continuing with compilation. Please read 'rvm help mount' to get more information on binary rubies.Checking requirements for centos.Installing requirements for centos.Installing required packages: libffi-devel, libyaml-devel......Requirements installation successful.Installing Ruby from source to: /usr/local/rvm/rubies/ruby-2.4.1, this may take a while depending on your cpu(s)...ruby-2.4.1 - #downloading ruby-2.4.1, this may take a while depending on your connection...curl: (35) SSL connect errorThere was an error(35).Checking fallback: https://ftp.ruby-lang.org/pub/ruby/2.4/ruby-2.4.1.tar.bz2  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current                                 Dload  Upload   Total   Spent    Left  Speed100 11.9M  100 11.9M    0     0  1753k      0  0:00:07  0:00:07 --:--:-- 2919kruby-2.4.1 - #extracting ruby-2.4.1 to /usr/local/rvm/src/ruby-2.4.1....ruby-2.4.1 - #applying patch /usr/local/rvm/patches/ruby/2.4.1/random_c_using_NR_prefix.patch.ruby-2.4.1 - #configuring..................................................................ruby-2.4.1 - #post-configuration..ruby-2.4.1 - #compiling..............................................................................................ruby-2.4.1 - #installing.........................ruby-2.4.1 - #making binaries executable..ruby-2.4.1 - #downloading rubygems-2.6.14  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current                                 Dload  Upload   Total   Spent    Left  Speed100  751k  100  751k    0     0   443k      0  0:00:01  0:00:01 --:--:--  628kNo checksum for downloaded archive, recording checksum in user configuration.ruby-2.4.1 - #extracting rubygems-2.6.14....ruby-2.4.1 - #removing old rubygems.........ruby-2.4.1 - #installing rubygems-2.6.14...........................ruby-2.4.1 - #gemset created /usr/local/rvm/gems/ruby-2.4.1@globalruby-2.4.1 - #importing gemset /usr/local/rvm/gemsets/global.gems...............................................ruby-2.4.1 - #generating global wrappers........ruby-2.4.1 - #gemset created /usr/local/rvm/gems/ruby-2.4.1ruby-2.4.1 - #importing gemsetfile /usr/local/rvm/gemsets/default.gems evaluated to empty gem listruby-2.4.1 - #generating default wrappers........ruby-2.4.1 - #adjusting #shebangs for (gem irb erb ri rdoc testrb rake).Install of ruby-2.4.1 - #complete Ruby was built without documentation, to build it run: rvm docs generate-ri

至此，我们升级了Ruby的版本。

 

4）安装gem redis接口，成功！

gem install redisFetching: redis-4.0.1.gem (100%)Successfully installed redis-4.0.1Parsing documentation for redis-4.0.1Installing ri documentation for redis-4.0.1Done installing documentation for redis after 0 seconds1 gem installed

 

5）安装rubygems，成功！

# yum install -y rubygemsLoaded plugins: fastestmirror, securitySetting up Install ProcessLoading mirror speeds from cached hostfilebase                                                                                                                                                   | 3.7 kB     00:00     didi_jenkins_enable                                                                                                                                    | 1.5 kB     00:00     didi_op_toa_enable                                                                                                                                     | 1.5 kB     00:00     didi_txjenkins_enable                                                                                                                                  | 1.5 kB     00:00     didi_update                                                                                                                                            | 1.5 kB     00:00     epel                                                                                                                                                   | 4.3 kB     00:00     extras                                                                                                                                                 | 3.4 kB     00:00     tmprepo                                                                                                                                                | 1.5 kB     00:00     updates                                                                                                                                                | 3.4 kB     00:00     Package rubygems-1.3.7-5.el6.noarch already installed and latest versionNothing to do

至此，我们的Ruby和运行redis-trib.rb需要的环境安装完成了。 

 

3、Redis集群搭建

有了Ruby执行环境，可以开始将之前的6个实例组建成集群了。

命令方式：

ruby ./bin/redis-trib.rb create --replicas 1 10.93.84.53:7000 10.93.84.53:7001 10.93.84.53:7002 10.93.84.53:7003 10.93.84.53:7004 10.93.84.53:7005

--replicas 1表示为集群的master节点创建1个副本。那么6个实例里，有三个master，有三个是slave。 后面跟上6个实例就好了，形式就是ip:port

执行情况：

# ruby ./bin/redis-trib.rb create --replicas 1 10.93.84.53:7000 10.93.84.53:7001 10.93.84.53:7002 10.93.84.53:7003 10.93.84.53:7004 10.93.84.53:7005>>> Creating cluster>>> Performing hash slots allocation on 6 nodes...Using 3 masters:10.93.84.53:700010.93.84.53:700110.93.84.53:7002Adding replica 10.93.84.53:7003 to 10.93.84.53:7000Adding replica 10.93.84.53:7004 to 10.93.84.53:7001Adding replica 10.93.84.53:7005 to 10.93.84.53:7002M: 6346ae8c7af7949658619fcf4021cc7aca454819 10.93.84.53:7000   slots:0-5460 (5461 slots) masterM: 5ac973bceab0d486c497345fe884ff54d1bb225a 10.93.84.53:7001   slots:5461-10922 (5462 slots) masterM: cc46a4a1c0ec3f621b6b5405c6c10b7cffe73932 10.93.84.53:7002   slots:10923-16383 (5461 slots) masterS: 92f62ec93a0550d962f81213ca7e9b3c9c996afd 10.93.84.53:7003   replicates 6346ae8c7af7949658619fcf4021cc7aca454819S: 942c9f97dc68198c39f425d13df0d8e3c40c5a58 10.93.84.53:7004   replicates 5ac973bceab0d486c497345fe884ff54d1bb225aS: a92a81532b63652bbd862be6f19a9bd8832e5e05 10.93.84.53:7005   replicates cc46a4a1c0ec3f621b6b5405c6c10b7cffe73932Can 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 clusterWaiting for the cluster to join...>>> Performing Cluster Check (using node 10.93.84.53:7000)M: 6346ae8c7af7949658619fcf4021cc7aca454819 10.93.84.53:7000   slots:0-5460 (5461 slots) master   1 additional replica(s)S: a92a81532b63652bbd862be6f19a9bd8832e5e05 10.93.84.53:7005   slots: (0 slots) slave   replicates cc46a4a1c0ec3f621b6b5405c6c10b7cffe73932M: 5ac973bceab0d486c497345fe884ff54d1bb225a 10.93.84.53:7001   slots:5461-10922 (5462 slots) master   1 additional replica(s)S: 942c9f97dc68198c39f425d13df0d8e3c40c5a58 10.93.84.53:7004   slots: (0 slots) slave   replicates 5ac973bceab0d486c497345fe884ff54d1bb225aS: 92f62ec93a0550d962f81213ca7e9b3c9c996afd 10.93.84.53:7003   slots: (0 slots) slave   replicates 6346ae8c7af7949658619fcf4021cc7aca454819M: cc46a4a1c0ec3f621b6b5405c6c10b7cffe73932 10.93.84.53:7002   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.

 可以看到16384个slot都已经创建完成，并且建立了3个master和对应的replica:

Using 3 masters:10.93.84.53:700010.93.84.53:700110.93.84.53:7002Adding replica 10.93.84.53:7003 to 10.93.84.53:7000Adding replica 10.93.84.53:7004 to 10.93.84.53:7001Adding replica 10.93.84.53:7005 to 10.93.84.53:7002 。。。

[OK] All 16384 slots covered.

 

 

4、验证集群状态

登录集群客户端，-c标识以集群方式登录

./bin/redis-cli -h 10.93.84.53 -p 7000 -c

查看集群状态

10.93.84.53:7000> cluster infocluster_state:okcluster_slots_assigned:16384cluster_slots_ok:16384cluster_slots_pfail:0cluster_slots_fail:0cluster_known_nodes:6cluster_size:3cluster_current_epoch:8cluster_my_epoch:8cluster_stats_messages_sent:215cluster_stats_messages_received:21510.93.84.53:7000> cluster nodes942c9f97dc68198c39f425d13df0d8e3c40c5a58 10.93.84.53:7004 slave 5ac973bceab0d486c497345fe884ff54d1bb225a 0 1507806791940 5 connected5ac973bceab0d486c497345fe884ff54d1bb225a 10.93.84.53:7001 master - 0 1507806788937 2 connected 5461-10922a92a81532b63652bbd862be6f19a9bd8832e5e05 10.93.84.53:7005 slave cc46a4a1c0ec3f621b6b5405c6c10b7cffe73932 0 1507806790939 6 connectedcc46a4a1c0ec3f621b6b5405c6c10b7cffe73932 10.93.84.53:7002 master - 0 1507806789937 3 connected 10923-163836346ae8c7af7949658619fcf4021cc7aca454819 10.93.84.53:7000 myself,slave 92f62ec93a0550d962f81213ca7e9b3c9c996afd 0 0 1 connected92f62ec93a0550d962f81213ca7e9b3c9c996afd 10.93.84.53:7003 master - 0 1507806792941 8 connected 0-5460

 一些原理

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。

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，一致性哈希对向集群中新增和删除实例的支持很好，但是哈希槽对向集群新增实例或者删除实例的话，需要额外的操作，需要手动的将slot重新平均的分配到新集群的实例中。

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。

Redis 集群会把数据存在一个master节点，然后在这个master和其对应的salve之间进行数据同步。当读取数据时，也根据一致性哈希算法到对应的master节点获取数据。只有当一个master 挂掉之后，才会启动一个对应的salve节点，充当master。

需要注意的是：必须要3个或以上的主节点，否则在创建集群时会失败，并且当存活的主节点数小于总节点数的一半时，整个集群就无法提供服务了。

 

5、python集群客户端

以Python Redis Cluster集群的使用方式为例，简单说明一下如何使用，让大家更直观的了解一下Redis集群。

Redis集群方式与单机方式在python客户端实现上是有很大不同的。

• 包不同，单机依赖包redis-py，集群依赖包redis-py-cluster
• 对同时操作多个keys的命令(mset, mget, sinter, ...)，redis-py-cluster重写StriceRedis(单机Redis操作类)了其方法，而这些方法丧失了命令的原子性。
• Pipelines在集群中的表现也不同了。在单机版中，pipeline是批量batch提交redis批量执行的，但是在集群版中，是one by one提交redis执行完成直接返回，在客户端重新组合成一个列表返回。所以集群中只是看起来像是批量执行。
• 一些命令是会Fanout(扇形)发送到集群中各个shard中执行并汇总的，如ping，keys等。一些命令是不提倡使用(blocked)，如watch，unwatch等。

我只是简单翻译了官网的一些内容，相信信息大家可以参考：

 

1）安装redis-py-cluster 

简单的通过pip安装redis-py-cluster包。如果安装失败，可以自助下载安装。

# pip install redis-py-cluster     Collecting redis-py-cluster  Downloading redis_py_cluster-1.3.4-py2.py3-none-any.whlRequirement already satisfied: redis>=2.10.2 in /home/idata/pythonEnv/idataPlatEnv/lib/python2.7/site-packages/redis-2.10.5-py2.7.egg (from redis-py-cluster)Installing collected packages: redis-py-clusterSuccessfully installed redis-py-cluster-1.3.4

 

2）一个简单的demo

封装了RedisCluster操作类，实现了一些方法，其实就是做了一层封装。

封装的意义是：我喜欢对这些封装增加一些装饰器，控制异常和重试等逻辑。

# -*- coding:utf-8 -*-from rediscluster import StrictRedisClusterredis_nodes = [        {'host': '10.93.84.53', 'port': 7000},        {'host': '10.93.84.53', 'port': 7001},        {'host': '10.93.84.53', 'port': 7002},        {'host': '10.93.84.53', 'port': 7003},        {'host': '10.93.84.53', 'port': 7004},        {'host': '10.93.84.53', 'port': 7005},    ]class RedisCluster(object):    def __init__(self, redis_nodes):        self.cluster = StrictRedisCluster(startup_nodes=redis_nodes)    # 无差别的方法    def set(self, name, value, ex=None, px=None, nx=False, xx=False):        return self.cluster.set(name, value, ex, px, nx, xx)        # 无差别的方法    def get(self, name):        return self.cluster.get(name)        # 扇形发送的命令    def cluster_info(self):        return self.cluster.cluster_info()    # 重写StrictRedis的方法    def mset(self, *args, **kwargs):        return self.cluster.mset(args, kwargs)        # 重写StrictRedis的方法    def mget(self, keys, *args):        return self.cluster.mget(keys, args)        cluster = RedisCluster(redis_nodes)cluster.cluster_info()