高可用问题，如何保证redis的持续高可用性。
容量问题，单实例redis内存没法无限扩充，达到32G后就进入了64位世界，性能降低。
并发性能问题，redis号称单实例10万并发，但也是有尽头的。
哈希槽的概念
Redis 集群中内置了 16384 个哈希槽，当须要在 Redis 集群中放置一个 key-value 时，redis 先对 key 使用 crc16 算法算出一个结果，而后把结果对 16384 求余数， 这样每一个 key 都会对应一个编号在 0-16383 之间的哈希槽，redis 会根据节点数量大 致均等的将哈希槽映射到不一样的节点。 Redis 集群没有使用一致性hash, 而是引入了哈希槽的概念。 Redis 集群有16384个哈希槽,每一个key经过CRC16校验后对16384取模来决定放置哪一个槽.集群的每一个节点负责一部分hash槽。这种结构很容易添加或者删除节点，而且不管是添加删除或者修改某一个节点，都不会形成集群不可用的状态。 使用哈希槽的好处就在于能够方便的添加或移除节点。 当须要增长节点时，只须要把其余节点的某些哈希槽挪到新节点就能够了； 当须要移除节点时，只须要把移除节点上的哈希槽挪到其余节点就好了； 这样之后新增或移除节点的时候不用先停掉全部的 redis 服务而继续运行.
redis-cluster的优点
官方推荐，毋庸置疑。
去中心化，集群最大可增长1000个节点，性能随节点增长而线性扩展。
管理方便，后续可自行增长或摘除节点，移动分槽等等。
简单，易上手。
一.Redis集群配置参数
cluster-enabled <yes/no>: 若是是yes，表示启用集群，不然以单例模式启动
cluster-config-file < filename> : 可选，这不是一个用户可编辑的配置文件，这个文件是Redis集群节点自动持久化每次配置的改变，为了在启动的时候从新读取它。
cluster-node-timeout < milliseconds>: 超时时间，集群节点不可用的最大时间。若是一个master节点不可到达超过了指定时间，则认为它失败了。注意，每个在指定时间内不能到达大多数master节点的节点将中止接受查询请求。
cluster-slave-validity-factor < factor>: 若是设置为0，则一个slave将老是尝试故障转移一个master。若是设置为一个正数，那么最大失去链接的时间是node timeout乘以这个factor。
cluster-migration-barrier < count>: 一个master和slave保持链接的最小数量（即：最少与多少个slave保持链接），也就是说至少与其它多少slave保持链接的slave才有资格成为master。
cluster-require-full-coverage < yes/no>: 若是设置为yes，这也是默认值，若是key space没有达到百分之多少时中止接受写请求。若是设置为no，将仍然接受查询请求，即便它只是请求部分key。node
二. 建立Redis节点
(1) 建立不一样配置文件节点
在redis目录下面建立8000到8005不一样的5个节点,每一个节点下面新建各类的redis.conf配置文件redis
cd redis
mkdir 8000 8001 8002 8003 8004 8005
复制redis下的redis.conf到redis/8000/下面,其余端口号的依次执行
cd redis
cp redis.conf /redis/8000/
(2) redis.conf配置文件
以端口号8000为例,其余节点的只是改下端口号算法
protected-mode no
port 8000
cluster-enabled yes
cluster-config-file nodes-8000.conf
cluster-node-timeout 5000
daemonize yes
pidfile /var/run/redis_8000.pid
logfile "8000.log"
dir /redis/data
bind 127.0.0.1ruby
(3)依次启动各端口实例
cd redis
cd 8000/redis-server redis.conf
其余端口依次执行
执行后查看端口号
[root@localhost 8005]# ps -ef|grep redis
[root@localhost 8005]# ps -ef|grep redis
root 3140 1 0 18:11 ? 00:00:00 redis-server 127.0.0.1:8000 [cluster]
root 3153 1 0 18:12 ? 00:00:00 redis-server 127.0.0.1:8001 [cluster]
root 3158 1 0 18:12 ? 00:00:00 redis-server 127.0.0.1:8002 [cluster]
root 3163 1 0 18:12 ? 00:00:00 redis-server 127.0.0.1:8003 [cluster]
root 3168 1 0 18:12 ? 00:00:00 redis-server 127.0.0.1:8004 [cluster]
root 3173 1 0 18:12 ? 00:00:00 redis-server 127.0.0.1:8005 [cluster]
root 3178 2043 0 18:12 pts/0 00:00:00 grep --color=auto redisbash
三.搭建集群
(1) 安装ruby
比较简单的是用redis-trib工具，它在src目录下。它是一个ruby程序，因此须要先安装ruby并发
yum install ruby
yum install rubygems
gem install redisapp
执行最后一条命令可能出现问题以下:curl
[root@localhost /]# gem install redis
Fetching: redis-4.0.3.gem (100%)
ERROR: Error installing redis:
redis requires Ruby version >= 2.2.2.
(2).升级ruby
(1) 安装curl
sudo yum install curl
(2) 秘钥key
gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB
(3) 下载rvm
curl -sSL https://get.rvm.io | bash -s stable
(4) 查找配置文件
find / -name rvm.sh
(5) 配置文件生效
source /etc/profile.d/rvm.sh
(6) 下载rvm依赖
rvm requirements
(7) 查看rvm库ruby版本
rvm list known
(8) 安装ruby指定版本
rvm install ruby-2.4.4
(9) 使用ruby版本默认
rvm use 2.4.4 default
(10) 安装
gem install redis
3.其余相关操做
(1) 卸载rubygems
若是安装shibai,须要卸载,能够执行
yum remove rubygems -y
(2) 卸载ruby的redis扩展包
gem uninstall redis --version 3.3.3
(3) 查看redis路径
find / -name “redis”
(4) 查看gem的镜像地址
$ gem sources -l
*** CURRENT SOURCES ***
https://rubygems.org/
(5) 移动该镜像,并添加新镜像
删除原gem源
gem sources --remove https://rubygems.org/
添加国内源
gem sources -a https://gems.ruby-china.com
(3) 建立集群
Redis5.0集群管理工具redis-trib.rb已经被废弃，因此不用安装ruby啥的了，上面安装ruby的方法针对于redis5.0如下使用,当时redis-trib.rb的功能，如今已经集成到了redis-cli中，而且能够在有认证的状况执行了，能够经过./redis-cli --cluster help查看使用方式。
redis-cli 集群命令帮助文档
[root@localhost src]# redis-cli --cluster help
Cluster Manager Commands:
create host1:port1 ... hostN:portN
--cluster-replicas <arg>
check host:port
info host:port
fix host:port
reshard host:port
--cluster-from <arg>
--cluster-to <arg>
--cluster-slots <arg>
--cluster-yes
--cluster-timeout <arg>
--cluster-pipeline <arg>
rebalance host:port
--cluster-weight <node1=w1...nodeN=wN>
--cluster-use-empty-masters
--cluster-timeout <arg>
--cluster-simulate
--cluster-pipeline <arg>
--cluster-threshold <arg>
add-node new_host:new_port existing_host:existing_port
--cluster-slave
--cluster-master-id <arg>
del-node host:port node_id
call host:port command arg arg .. arg
set-timeout host:port milliseconds
import host:port
--cluster-from <arg>
--cluster-copy
--cluster-replace
help
建立集群以下:
redis-cli --cluster create 127.0.0.1:8000 127.0.0.1:8001 127.0.0.1:8002 127.0.0.1:8003 127.0.0.1:8004 127.0.0.1:8005 --cluster-replicas 1
若是出现问题
[ERR] Node 127.0.0.1:8000 is not empty. Either the node already knows other nodes (check with CLUSTE
删除生成的配置文件nodes.conf，若是不行则说明如今建立的结点包括了旧集群的结点信息，须要删除redis的持久化文件后再重启redis，好比：appendonly.aof、dump.rdb
而后继续
[root@localhost 8005]# redis-cli --cluster create 127.0.0.1:8000 127.0.0.1:8001 127.0.0.1:8002 127.0.0.1:8003 127.0.0.1:8004 127.0.0.1:8005 --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 127.0.0.1:8003 to 127.0.0.1:8000
Adding replica 127.0.0.1:8004 to 127.0.0.1:8001
Adding replica 127.0.0.1:8005 to 127.0.0.1:8002
>>> Trying to optimize slaves allocation for anti-affinity
[WARNING] Some slaves are in the same host as their master
M: f70c555de0ab6863247271b03570dcb017748a1d 127.0.0.1:8000
slots:[0-5460] (5461 slots) master
M: 1c2dd486c7f885f86501932c144da131c68fdcad 127.0.0.1:8001
slots:[5461-10922] (5462 slots) master
M: 9f103d9ecc5506b095919154dfb80bc8cfbb414e 127.0.0.1:8002
slots:[10923-16383] (5461 slots) master
S: 298c94aa55f1cdcf53918fd9301f617b6dca37f7 127.0.0.1:8003
replicates 9f103d9ecc5506b095919154dfb80bc8cfbb414e
S: e57e483ae48a85d95e1374bf4ba486e7a4df256b 127.0.0.1:8004
replicates f70c555de0ab6863247271b03570dcb017748a1d
S: 4c61c720fa60a3d507fe355ae27218b0ac096f8a 127.0.0.1:8005
replicates 1c2dd486c7f885f86501932c144da131c68fdcad
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 127.0.0.1:8000)
M: f70c555de0ab6863247271b03570dcb017748a1d 127.0.0.1:8000
slots:[0-5460] (5461 slots) master
1 additional replica(s)
S: e57e483ae48a85d95e1374bf4ba486e7a4df256b 127.0.0.1:8004
slots: (0 slots) slave
replicates f70c555de0ab6863247271b03570dcb017748a1d
M: 1c2dd486c7f885f86501932c144da131c68fdcad 127.0.0.1:8001
slots:[5461-10922] (5462 slots) master
1 additional replica(s)
S: 298c94aa55f1cdcf53918fd9301f617b6dca37f7 127.0.0.1:8003
slots: (0 slots) slave
replicates 9f103d9ecc5506b095919154dfb80bc8cfbb414e
M: 9f103d9ecc5506b095919154dfb80bc8cfbb414e 127.0.0.1:8002
slots:[10923-16383] (5461 slots) master
1 additional replica(s)
S: 4c61c720fa60a3d507fe355ae27218b0ac096f8a 127.0.0.1:8005
slots: (0 slots) slave
replicates 1c2dd486c7f885f86501932c144da131c68fdcad
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
[root@localhost 8005]#
四. 集群操做
(1)查看集群信息与集群节点信息
查看集群信息工具
127.0.0.1:8000> cluster info
cluster_state:ok
cluster_slots_assigned:16384
cluster_slots_ok:16384
cluster_slots_pfail:0
cluster_slots_fail:0
cluster_known_nodes:6
cluster_size:3
cluster_current_epoch:6
cluster_my_epoch:1
cluster_stats_messages_ping_sent:2902
cluster_stats_messages_pong_sent:1422
cluster_stats_messages_fail_sent:4
cluster_stats_messages_sent:4328
cluster_stats_messages_ping_received:1422
cluster_stats_messages_pong_received:1446
cluster_stats_messages_fail_received:7
cluster_stats_messages_received:2875
查看节点信息
127.0.0.1:8002> cluster nodes
298c94aa55f1cdcf53918fd9301f617b6dca37f7 127.0.0.1:8003@18003 slave 9f103d9ecc5506b095919154dfb80bc8cfbb414e 0 1544402618000 4 connected
1c2dd486c7f885f86501932c144da131c68fdcad 127.0.0.1:8001@18001 master - 0 1544402617072 2 connected 5461-10922
9f103d9ecc5506b095919154dfb80bc8cfbb414e 127.0.0.1:8002@18002 myself,master - 0 1544402616000 3 connected 10923-16383
e57e483ae48a85d95e1374bf4ba486e7a4df256b 127.0.0.1:8004@18004 master - 0 1544402618478 7 connected 0-5460
4c61c720fa60a3d507fe355ae27218b0ac096f8a 127.0.0.1:8005@18005 slave 1c2dd486c7f885f86501932c144da131c68fdcad 0 1544402617473 6 connected
f70c555de0ab6863247271b03570dcb017748a1d 127.0.0.1:8000@18000 slave e57e483ae48a85d95e1374bf4ba486e7a4df256b 0 1544402617000 7 connected
(2) 查看节点信息
如查看节点8001端口号的集群信息性能
[root@localhost src]# redis-cli --cluster check 127.0.0.1:8001
127.0.0.1:8001 (1c2dd486...) -> 1 keys | 5462 slots | 1 slaves.
127.0.0.1:8002 (9f103d9e...) -> 1 keys | 5461 slots | 1 slaves.
127.0.0.1:8004 (e57e483a...) -> 0 keys | 5461 slots | 0 slaves.
[OK] 2 keys in 3 masters.
0.00 keys per slot on average.
>>> Performing Cluster Check (using node 127.0.0.1:8001)
M: 1c2dd486c7f885f86501932c144da131c68fdcad 127.0.0.1:8001
slots:[5461-10922] (5462 slots) master
1 additional replica(s)
M: 9f103d9ecc5506b095919154dfb80bc8cfbb414e 127.0.0.1:8002
slots:[10923-16383] (5461 slots) master
1 additional replica(s)
M: e57e483ae48a85d95e1374bf4ba486e7a4df256b 127.0.0.1:8004
slots:[0-5460] (5461 slots) master
S: 298c94aa55f1cdcf53918fd9301f617b6dca37f7 127.0.0.1:8003
slots: (0 slots) slave
replicates 9f103d9ecc5506b095919154dfb80bc8cfbb414e
S: 4c61c720fa60a3d507fe355ae27218b0ac096f8a 127.0.0.1:8005
slots: (0 slots) slave
replicates 1c2dd486c7f885f86501932c144da131c68fdcad
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
查看集群正常
(3) 客户端操做集群
redis-cli -p 8001
[root@localhost src]# redis-cli -p 8001
127.0.0.1:8001> get a
(error) MOVED 15495 127.0.0.1:8002
127.0.0.1:8001>
这边提示MOVED命令,则用以下:
[root@localhost src]# redis-cli -c -p 8001
127.0.0.1:8001> get a
-> Redirected to slot [15495] located at 127.0.0.1:8002
"aaaa"
127.0.0.1:8002>
能够看到，客户端链接加-c选项的时候，存储和提取key的时候不断在8001和8002之间跳转，这个称为客户端重定向。之因此发生客户端重定向，是由于Redis Cluster中的每一个Master节点都会负责一部分的槽(slot)，存取的时候都会进行键值空间计算定位key映射在哪一个槽(slot)上，若是映射的槽(slot)正好是当前Master节点负责则直接存取，不然就跳转到其余Master节点负的槽(slot)中存取，这个过程对客户端是透明的。继续看下文的集群分区原理。
(4) 删除节点
删除端口号8000的节点:redis-cli --cluster del-node 127.0.0.1:8000
[root@localhost src]# redis-cli --cluster del-node 127.0.0.1:8000 f70c555de0ab6863247271b03570dcb017748a1d
>>> Removing node f70c555de0ab6863247271b03570dcb017748a1d from cluster 127.0.0.1:8000
>>> Sending CLUSTER FORGET messages to the cluster...
>>> SHUTDOWN the node.
删除后再次查看下节点信息
127.0.0.1:8001> cluster nodes
9f103d9ecc5506b095919154dfb80bc8cfbb414e 127.0.0.1:8002@18002 master - 0 1544406706289 3 connected 10923-16383
1c2dd486c7f885f86501932c144da131c68fdcad 127.0.0.1:8001@18001 myself,master - 0 1544406705000 2 connected 5461-10922
e57e483ae48a85d95e1374bf4ba486e7a4df256b 127.0.0.1:8004@18004 master - 0 1544406705000 7 connected 0-5460
298c94aa55f1cdcf53918fd9301f617b6dca37f7 127.0.0.1:8003@18003 slave 9f103d9ecc5506b095919154dfb80bc8cfbb414e 0 1544406705284 4 connected
4c61c720fa60a3d507fe355ae27218b0ac096f8a 127.0.0.1:8005@18005 slave 1c2dd486c7f885f86501932c144da131c68fdcad 0 1544406706000 6 connected
发现端口号8000的节点已不存在
(5) 添加节点
将刚才删除的端口8000的节点添加到集群中的8001的主节点
[root@localhost 8005]# redis-cli --cluster add-node 127.0.0.1:8000 127.0.0.1:8001
>>> Adding node 127.0.0.1:8000 to cluster 127.0.0.1:8001
>>> Performing Cluster Check (using node 127.0.0.1:8001)
M: 1c2dd486c7f885f86501932c144da131c68fdcad 127.0.0.1:8001
slots:[5461-10922] (5462 slots) master
1 additional replica(s)
M: e57e483ae48a85d95e1374bf4ba486e7a4df256b 127.0.0.1:8004
slots:[0-5460] (5461 slots) master
M: 9f103d9ecc5506b095919154dfb80bc8cfbb414e 127.0.0.1:8002
slots:[10923-16383] (5461 slots) master
1 additional replica(s)
S: 4c61c720fa60a3d507fe355ae27218b0ac096f8a 127.0.0.1:8005
slots: (0 slots) slave
replicates 1c2dd486c7f885f86501932c144da131c68fdcad
S: 298c94aa55f1cdcf53918fd9301f617b6dca37f7 127.0.0.1:8003
slots: (0 slots) slave
replicates 9f103d9ecc5506b095919154dfb80bc8cfbb414e
[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.
>>> Send CLUSTER MEET to node 127.0.0.1:8000 to make it join the cluster.
[OK] New node added correctly.
[root@localhost 8005]# redis-cli -c -p 8000
127.0.0.1:8000> cluster nodes
298c94aa55f1cdcf53918fd9301f617b6dca37f7 127.0.0.1:8003@18003 slave 9f103d9ecc5506b095919154dfb80bc8cfbb414e 0 1544411418529 3 connected
e57e483ae48a85d95e1374bf4ba486e7a4df256b 127.0.0.1:8004@18004 master - 0 1544411418000 7 connected 0-5460
ef3394bfe7574d617960422a9f3b7009cd2923eb 127.0.0.1:8000@18000 myself,master - 0 1544411417000 0 connected
1c2dd486c7f885f86501932c144da131c68fdcad 127.0.0.1:8001@18001 master - 0 1544411416519 2 connected 5461-10922
9f103d9ecc5506b095919154dfb80bc8cfbb414e 127.0.0.1:8002@18002 master - 0 1544411418328 3 connected 10923-16383
4c61c720fa60a3d507fe355ae27218b0ac096f8a 127.0.0.1:8005@18005 slave 1c2dd486c7f885f86501932c144da131c68fdcad 0 1544411416820 2 connected
127.0.0.1:8000>
查询下节点信息,已经添加成功
(6) 平衡各节点槽数量 [root@localhost 8005]# redis-cli --cluster rebalance --cluster-threshold 1 127.0.0.1:8000 >>> Performing Cluster Check (using node 127.0.0.1:8000) [OK] All nodes agree about slots configuration. >>> Check for open slots... >>> Check slots coverage... [OK] All 16384 slots covered. *** No rebalancing needed! All nodes are within the 1.00% threshold.