? ??redis 终于推出正式的集群解决方案,最新稳定版本v3.0.2。集群实现目的将不同的key分散到不同的节点上,传统哈希算法hash(key)%n,不适用于添加和删除节点场景,会导致大量的key无法命中,扩展比较困难。redis 没有采用一致性hash,而采用哈希槽( hash slot ) 方式来实现数据共享。
? ? 具体算法:crc16( key )%16384,从而将 16384 个槽分配至不同的节点上。?
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环境准备:
192.168.5.8 ? ? 三个redis服务,分别监听 7000 70001 70002 ?端口
192.168.5.14 ? 三个redis服务,分别监听 7003 70004 70005 ?端口 ?
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一. 配置
class="conf" name="code">#redis.conf port 7000 #监听端口,集群间通信端口为 10000+7000 cluster-enabled yes #启用集群 cluster-config-file nodes-7000.conf #指定节点配置文件,由redis自动生成管理 cluster-node-timeout 5000 #节点间通信最大超时时间 appendonly yes #启动aof持久化模式? ??
二. 运行
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192.168.5.8 上启动三个redis实例,分别监听7000,7001,7002 三个端口。192.168.5.14启动实例监听7003,7004,7005三个端口。?
mkdir cluster-test cd cluster-test mkdir 7000 7001 7002 mkdir 7003 7004 7005 cd 7000 ./redis-server redis.conf
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三. 集群
cd $REDIS_SRC/src ./redis-trib.rb create --replicas 1 192.168.5.14:7000 192.168.5.14:7001 192.168.5.14:7002 192.168.5.8:7003 192.168.5.8:7004 192.168.5.8:7005
? ?选项 --replicas 1 为每个主机创建一个相应的备机
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运行该脚本报错,没有配置ruby环境。
./redis-trib.rb:24:in `require': no such file to load -- rubygems (LoadError)
from ./redis-trib.rb:24
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方法一:用yum安装
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#yum源安装ruby yum install -y ruby yum install -y rubygems # 安装redis库 gem install redis ERROR: could not find gem redis locally or in a repository #又被墙了,可恶 #下载redis库并安装 wget https://rubygems.org/downloads/redis-3.2.1.gem gem source gem source -a http://rubygems.org/ gem install redis-3.2.1.gem?? ?运行上述命令,报错:[ERR] Sorry, can't connect to node 192.168.5.14:7000,ruby 1.8.5 (2006-08-25) [i386-linux]。运行客户端 ./redis-cli -p 7000 能正常交互,搜索发现是redis官方需要较高的ruby版本。
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方法二:源码安装
既然用yum不能安装最新版本,还是老老实实用源码安装?
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#源码安装ruby wget http://cache.ruby-lang.org/pub/ruby/2.2/ruby-2.2.2.tar.gz tar -xvf ruby-2.2.2.tar.gz ./configure --prefix=/usr/local/ruby-2.2.2 make && make install gem install redis?? ?运行上述命令正常,发现 7000,7001,7003 变成主机,7002,7004,7005成为备机。
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[root@pclient redis]# ./redis-trib.rb create --replicas 1 192.168.5.14:7000 192.168.5.14:7001 192.168.5.14:7002 192.168.5.8:7003 192.168.5.8:7004 192.168.5.8:7005 >>> Creating cluster Connecting to node 192.168.5.14:7000: OK Connecting to node 192.168.5.14:7001: OK Connecting to node 192.168.5.14:7002: OK Connecting to node 192.168.5.8:7003: OK Connecting to node 192.168.5.8:7004: OK Connecting to node 192.168.5.8:7005: OK >>> Performing hash slots allocation on 6 nodes... ...... [OK] All nodes agree about slots configuration. >>> Check for open slots... >>> Check slots coverage... [OK] All 16384 slots covered.
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测试:
$ redis-cli -c -p 7000#集群交互必须加上-c选项,否则执行出错。
redis 127.0.0.1:7000> set foo bar -> Redirected to slot [12182] located at 127.0.0.1:7002 OK redis 127.0.0.1:7002> set hello world -> Redirected to slot [866] located at 127.0.0.1:7000 OK redis 127.0.0.1:7000> get foo -> Redirected to slot [12182] located at 127.0.0.1:7002 "bar" redis 127.0.0.1:7000> get hello -> Redirected to slot [866] located at 127.0.0.1:7000 "world"
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参考资料:
http://redis.io/topics/cluster-tutorial
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