docker实现redis集群搭建的方法步骤
导读
目录
一、创建redis docker基础镜像
二、制作redis节点镜像
三、运行redis集群
引用：
摘要：接触docker以来，似乎养成了一种习惯，安装什么应用软件都想往docker方向做，今天就想来尝试下使用docker搭建redis集群。
首先，我们需要理论知识：Redis Cluster是Redis的分布式解决方案，它解决了redis单机中心化的问题，分布式数据库——首要解决把整个数据集按照分区规则映射到多个节点的问题。
这边就需要知道分区规则——哈希分区规则。Redis Cluster 采用哈希分区规则中的虚拟槽分区。所有的键根据哈希函数映射到0 ～ 16383，计算公式：slot = CRC16(key)&16383。每一个节点负责维护一部分槽以及槽所映射的键值数据。
一、创建redis docker基础镜像
下载redis安装包，使用版本为：4.0.1
[root@etcd1 tmp]# mkdir docker_redis_cluster [root@etcd1 tmp]# cd docker_redis_cluster/ [root@etcd2 docker_redis_cluster]# wget http://download.redis.io/releases/redis-4.0.1.tar.gz
解压编译redis
[root@etcd1 docker_redis_cluster]# tar zxvf redis-4.0.1.tar.gz [root@etcd1 docker_redis_cluster]# cd redis-4.0.1/ [root@etcd1 redis-4.0.1]# make
修改redis配置
[root@etcd3 redis-4.0.1]# vi /tmp/docker_redis_cluster/redis-4.0.1/redis.conf
修改bind ip地址
# ~~~ WARNING ~~~ If the computer running Redis is directly exposed to the # internet, binding to all the interfaces is dangerous and will expose the # instance to everybody on the internet. So by default we uncomment the # following bind directive, that will force Redis to listen only into # the IPv4 lookback interface address (this means Redis will be able to # accept connections only from clients running into the same computer it # is running). # # IF YOU ARE SURE YOU WANT YOUR INSTANCE TO LISTEN TO ALL THE INTERFACES # JUST COMMENT THE FOLLOWING LINE. # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #bind 127.0.0.1 bind 0.0.0.0
将守护进程yes改成no
# By default Redis does not run as a daemon. Use 'yes' if you need it. # Note that Redis will write a pid file in /var/run/redis.pid when daemonized. daemonize no
将密码项注释去掉，添加新密码
# Warning: since Redis is pretty fast an outside user can try up to # 150k passwords per second against a good box. This means that you should # use a very strong password otherwise it will be very easy to break. # # requirepass foobared
修改为
# Warning: since Redis is pretty fast an outside user can try up to # 150k passwords per second against a good box. This means that you should # use a very strong password otherwise it will be very easy to break. # requirepass 123456
因为配置了密码，所以，配置中另外一处主从连接也需要配置密码
# If the master is password protected (using the "requirepass" configuration # directive below) it is possible to tell the slave to authenticate before # starting the replication synchronization process, otherwise the master will # refuse the slave request. # # masterauth <master-password>
修改为
# If the master is password protected (using the "requirepass" configuration # directive below) it is possible to tell the slave to authenticate before # starting the replication synchronization process, otherwise the master will # refuse the slave request. # # masterauth <master-password> masterauth 123456
设置日志路径
# Specify the log file name. Also the empty string can be used to force # Redis to log on the standard output. Note that if you use standard # output for logging but daemonize, logs will be sent to /dev/null logfile "/var/log/redis/redis-server.log"
配置集群相关信息，去掉配置项前面的注释
# Normal Redis instances can't be part of a Redis Cluster; only nodes that are # started as cluster nodes can. In order to start a Redis instance as a # cluster node enable the cluster support uncommenting the following: # cluster-enabled yes # Every cluster node has a cluster configuration file. This file is not # intended to be edited by hand. It is created and updated by Redis nodes. # Every Redis Cluster node requires a different cluster configuration file. # Make sure that instances running in the same system do not have # overlapping cluster configuration file names. # cluster-config-file nodes-6379.conf # Cluster node timeout is the amount of milliseconds a node must be unreachable # for it to be considered in failure state. # Most other internal time limits are multiple of the node timeout. # cluster-node-timeout 15000
镜像制作
[root@etcd3 docker_redis_cluster]# cd /tmp/docker_redis_cluster [root@etcd3 docker_redis_cluster]# vi Dockerfile # Redis # Version 4.0.1 FROM Centos:7<br> ENV REDIS_HOME /usr/local<br> ADD redis-4.0.1.tar.gz / # 本地的redis源码包复制到镜像的根路径下，ADD命令会在复制过后自动解包。被复制的对象必须处于Dockerfile同一路径，且ADD后面必须使用相对路径 RUN mkdir -p $REDIS_HOME/redis # 创建安装目录 ADD redis-4.0.1/redis.conf $REDIS_HOME/redis/ # 将一开始编译产生并修改后的配置复制到安装目录 RUN yum -y update # 更新yum源 RUN yum install -y gcc make # 安装编译需要的工具 WORKDIR /redis-4.0.1 RUN make RUN mv /redis-4.0.1/src/redis-server $REDIS_HOME/redis/ # 编译后，容器中只需要可执行文件redis-server WORKDIR / RUN rm -rf /redis-4.0.1 # 删除解压文件 RUN yum remove -y gcc make # 安装编译完成之后，可以删除多余的gcc跟make VOLUME ["/var/log/redis"] # 添加数据卷 EXPOSE 6379 # 暴露6379端口，也可以暴露多个端口，这里不需要如此
PS.当前镜像非可执行镜像，所以没有包含ENTRYPOINT和CMD指令
构建镜像
# 切换中国源
[root@etcd3 docker_redis_cluster]# vi /etc/docker/daemon.json
{
"registry-mirrors": ["https://registry.docker-cn.com"]
}
# 编译
[root@etcd3 docker_redis_cluster]# docker build -t hakimdstx/cluster-redis .
...
Complete!
---> 546cb1d34f35
Removing intermediate container 6b6556c5f28d
Step 14/15 : VOLUME /var/log/redis
---> Running in 05a6642e4046
---> e7e2fb8676b2
Removing intermediate container 05a6642e4046
Step 15/15 : EXPOSE 6379
---> Running in 5d7abe1709e2
---> 2d1322475f79
Removing intermediate container 5d7abe1709e2
Successfully built 2d1322475f79镜像制作完成，制作中间可能会报： Public key for glibc-headers-2.17-222.el7.x86_64.rpm is not installed 错误，这时候需要在镜像配置中添加一句命令：
... RUN rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7 RUN yum -y update # 更新yum源 RUN yum install -y gcc make # 安装编译需要的工具
查看镜像：
[root@etcd3 docker_redis_cluster]# docker images REPOSITORY TAG IMAGE ID CREATED SIZE hakimdstx/cluster-redis 4.0.1 1fca5a08a4c7 14 seconds ago 435 MB centos 7 49f7960eb7e4 2 days ago 200 MB
以上，redis 基础镜像就制作完成了
二、制作redis节点镜像
基于此前制作的redis基础镜像创建一个redis节点镜像
[root@etcd3 tmp]# mkdir docker_redis_nodes [root@etcd3 tmp]# cd docker_redis_nodes [root@etcd3 docker_redis_nodes]# vi Dockerfile # Redis Node # Version 4.0.1<br> FROM hakimdstx/cluster-redis:4.0.1 # MAINTAINER_INFO MAINTAINER hakim 1194842583@qq.com ENTRYPOINT ["/usr/local/redis/redis-server", "/usr/local/redis/redis.conf"]
构建redis节点镜像
[root@etcd3 docker_redis_nodes]# docker build -t hakimdstx/nodes-redis:4.0.1 . Sending build context to Docker daemon 2.048 kB Step 1/3 : FROM hakimdstx/cluster-redis:4.0.1 ---> 1fca5a08a4c7 Step 2/3 : MAINTAINER hakim 1194842583@qq.com ---> Running in cc6e07eb2c36 ---> 55769d3bfacb Removing intermediate container cc6e07eb2c36 Step 3/3 : ENTRYPOINT /usr/local/redis/redis-server /usr/local/redis/redis.conf ---> Running in f5dedf88f6f6 ---> da64da483559 Removing intermediate container f5dedf88f6f6 Successfully built da64da483559
查看镜像
[root@etcd3 docker_redis_nodes]# docker images REPOSITORY TAG IMAGE ID CREATED SIZE hakimdstx/nodes-redis 4.0.1 da64da483559 51 seconds ago 435 MB hakimdstx/cluster-redis 4.0.1 1fca5a08a4c7 9 minutes ago 435 MB centos 7 49f7960eb7e4 2 days ago 200 MB
三、运行redis集群
运行redis容器
[root@etcd3 docker_redis_nodes]# docker run -d --name redis-6379 -p 6379:6379 hakimdstx/nodes-redis:4.0.1 1673a7d859ea83257d5bf14d82ebf717fb31405c185ce96a05f597d8f855aa7d [root@etcd3 docker_redis_nodes]# docker run -d --name redis-6380 -p 6380:6379 hakimdstx/nodes-redis:4.0.1 df6ebce6f12a6f3620d5a29adcfbfa7024e906c3af48f21fa7e1fa524a361362 [root@etcd3 docker_redis_nodes]# docker run -d --name redis-6381 -p 6381:6379 hakimdstx/nodes-redis:4.0.1 396e174a1d9235228b3c5f0266785a12fb1ea49efc7ac755c9e7590e17aa1a79 [root@etcd3 docker_redis_nodes]# docker run -d --name redis-6382 -p 6382:6379 hakimdstx/nodes-redis:4.0.1 d9a71dd3f969094205ffa7596c4a04255575cdd3acca2d47fe8ef7171a3be528 [root@etcd3 docker_redis_nodes]# docker run -d --name redis-6383 -p 6383:6379 hakimdstx/nodes-redis:4.0.1 73e4f843d8cb28595456e21b04f97d18ce1cdf8dc56d1150844ba258a3781933 [root@etcd3 docker_redis_nodes]# docker run -d --name redis-6384 -p 6384:6379 hakimdstx/nodes-redis:4.0.1 10c62aafa4dac47220daf5bf3cec84406f086d5261599b54ec6c56bb7da97d6d
查看容器信息
[root@etcd3 redis]# docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 10c62aafa4da hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 3 seconds ago Up 2 seconds 0.0.0.0:6384->6379/tcp redis-6384 73e4f843d8cb hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 12 seconds ago Up 10 seconds 0.0.0.0:6383->6379/tcp redis-6383 d9a71dd3f969 hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 20 seconds ago Up 18 seconds 0.0.0.0:6382->6379/tcp redis-6382 396e174a1d92 hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 3 days ago Up 3 days 0.0.0.0:6381->6379/tcp redis-6381 df6ebce6f12a hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 3 days ago Up 3 days 0.0.0.0:6380->6379/tcp redis-6380 1673a7d859ea hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 3 days ago Up 3 days 0.0.0.0:6379->6379/tcp redis-6379
运行 redis 集群容器
通过远程连接，查看redis info replication 信息
[root@etcd2 ~]# redis-cli -h 192.168.10.52 -p 6379 192.168.10.52:6379> info replication NOAUTH Authentication required. 192.168.10.52:6379> auth 123456 OK 192.168.10.52:6379> info replication # Replication role:master connected_slaves:0 master_replid:2f0a7b50aed699fa50a79f3f7f9751a070c50ee9 master_replid2:0000000000000000000000000000000000000000 master_repl_offset:0 second_repl_offset:-1 repl_backlog_active:0 repl_backlog_size:1048576 repl_backlog_first_byte_offset:0 repl_backlog_histlen:0 192.168.10.52:6379> # 其余基本信息同上
可以看到，客户连接之后，因为之前设置了密码，所以需要先输入密码认证，否则就无法通过。以上信息，我们知道所有的redis都是master角色 role:master ，这显然不是我们所希望的。
在配置之前我们需要查看所有容器当前的IP地址
[root@etcd3 redis]# docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 10c62aafa4da hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 3 seconds ago Up 2 seconds 0.0.0.0:6384->6379/tcp redis-6384 73e4f843d8cb hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 12 seconds ago Up 10 seconds 0.0.0.0:6383->6379/tcp redis-6383 d9a71dd3f969 hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 20 seconds ago Up 18 seconds 0.0.0.0:6382->6379/tcp redis-6382 396e174a1d92 hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 3 days ago Up 3 days 0.0.0.0:6381->6379/tcp redis-6381 df6ebce6f12a hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 3 days ago Up 3 days 0.0.0.0:6380->6379/tcp redis-6380 1673a7d859ea hakimdstx/nodes-redis:4.0.1 "/usr/local/redis/..." 3 days ago Up 3 days 0.0.0.0:6379->6379/tcp redis-6379 [root@etcd3 redis]# [root@etcd3 redis]# docker inspect 10c62aafa4da 73e4f843d8cb d9a71dd3f969 396e174a1d92 df6ebce6f12a 1673a7d859ea | grep IPA "SecondaryIPAddresses": null, "IPAddress": "172.17.0.7", "IPAMConfig": null, "IPAddress": "172.17.0.7", "SecondaryIPAddresses": null, "IPAddress": "172.17.0.6", "IPAMConfig": null, "IPAddress": "172.17.0.6", "SecondaryIPAddresses": null, "IPAddress": "172.17.0.5", "IPAMConfig": null, "IPAddress": "172.17.0.5", "SecondaryIPAddresses": null, "IPAddress": "172.17.0.4", "IPAMConfig": null, "IPAddress": "172.17.0.4", "SecondaryIPAddresses": null, "IPAddress": "172.17.0.3", "IPAMConfig": null, "IPAddress": "172.17.0.3", "SecondaryIPAddresses": null, "IPAddress": "172.17.0.2", "IPAMConfig": null, "IPAddress": "172.17.0.2",
可以知道： redis-6379：172.17.0.2，redis-6380：172.17.0.3，redis-6381：172.17.0.4，redis-6382：172.17.0.5，redis-6383：172.17.0.6，redis-6384：172.17.0.7
配置redis
ert
Redis Cluster 的集群感知操作
//集群(cluster) CLUSTER INFO 打印集群的信息 CLUSTER NODES 列出集群当前已知的所有节点（node），以及这些节点的相关信息。 //节点(node) CLUSTER MEET <ip> <port> 将 ip 和 port 所指定的节点添加到集群当中，让它成为集群的一份子。 CLUSTER FORGET <node_id> 从集群中移除 node_id 指定的节点。 CLUSTER REPLICATE <node_id> 将当前节点设置为 node_id 指定的节点的从节点。 CLUSTER SAVECONFIG 将节点的配置文件保存到硬盘里面。 //槽(slot) CLUSTER ADDSLOTS <slot> [slot ...] 将一个或多个槽（slot）指派（assign）给当前节点。 CLUSTER DELSLOTS <slot> [slot ...] 移除一个或多个槽对当前节点的指派。 CLUSTER FLUSHSLOTS 移除指派给当前节点的所有槽，让当前节点变成一个没有指派任何槽的节点。 CLUSTER SETSLOT <slot> NODE <node_id> 将槽 slot 指派给 node_id 指定的节点，如果槽已经指派给另一个节点，那么先让另一个节点删除该槽>，然后再进行指派。 CLUSTER SETSLOT <slot> MIGRATING <node_id> 将本节点的槽 slot 迁移到 node_id 指定的节点中。 CLUSTER SETSLOT <slot> IMPORTING <node_id> 从 node_id 指定的节点中导入槽 slot 到本节点。 CLUSTER SETSLOT <slot> STABLE 取消对槽 slot 的导入（import）或者迁移（migrate）。 //键 (key) CLUSTER KEYSLOT <key> 计算键 key 应该被放置在哪个槽上。 CLUSTER COUNTKEYSINSLOT <slot> 返回槽 slot 目前包含的键值对数量。 CLUSTER GETKEYSINSLOT <slot> <count> 返回 count 个 slot 槽中的键。
redis 集群感知：节点握手——是指一批运行在集群模式的节点通过Gossip协议彼此通信，达到感知对方的过程。
192.168.10.52:6379> CLUSTER MEET 172.17.0.3 6379 OK 192.168.10.52:6379> CLUSTER MEET 172.17.0.4 6379 OK 192.168.10.52:6379> CLUSTER MEET 172.17.0.5 6379 OK 192.168.10.52:6379> CLUSTER MEET 172.17.0.6 6379 OK 192.168.10.52:6379> CLUSTER MEET 172.17.0.7 6379 OK 192.168.10.52:6379> CLUSTER NODES 54cb5c2eb8e5f5aed2d2f7843f75a9284ef6785c 172.17.0.3:6379@16379 master - 0 1528697195600 1 connected f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 172.17.0.4:6379@16379 master - 0 1528697195600 0 connected ae86224a3bc29c4854719c83979cb7506f37787a 172.17.0.7:6379@16379 master - 0 1528697195600 5 connected 98aebcfe42d8aaa8a3375e4a16707107dc9da683 172.17.0.6:6379@16379 master - 0 1528697194000 4 connected 0bbdc4176884ef0e3bb9b2e7d03d91b0e7e11f44 172.17.0.5:6379@16379 master - 0 1528697194995 3 connected 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 172.17.0.2:6379@16379 myself,master - 0 1528697195000 2 connected
当前已经使这六个节点组成集群，但是现在还无法工作，因为集群节点还没有分配槽（slot）。
分配槽信息
查看172.17.0.2:6379 的槽个数
192.168.10.52:6379> CLUSTER INFO cluster_state:fail cluster_slots_assigned:0 # 被分配槽的个数为0 cluster_slots_ok:0 cluster_slots_pfail:0 cluster_slots_fail:0 cluster_known_nodes:6 cluster_size:0 cluster_current_epoch:5 cluster_my_epoch:2 cluster_stats_messages_ping_sent:260418 cluster_stats_messages_pong_sent:260087 cluster_stats_messages_meet_sent:10 cluster_stats_messages_sent:520515 cluster_stats_messages_ping_received:260086 cluster_stats_messages_pong_received:260328 cluster_stats_messages_meet_received:1 cluster_stats_messages_received:520415
上面看到集群状态是失败的，原因是槽位没有分配，而且需要一次性把16384个槽位完全分配了，集群才可用。
分配槽位
分配槽位： CLUSTER ADDSLOTS 槽位，一个槽位只能分配一个节点，16384个槽位必须分配完，不同节点不能冲突。
所以通过脚本进行分配 addslots.sh：
#!/bin/bash # node1 192.168.10.52 172.17.0.2 n=0 for ((i=n;i<=5461;i++)) do /usr/local/bin/redis-cli -h 192.168.10.52 -p 6379 -a 123456 CLUSTER ADDSLOTS $i done # node2 192.168.10.52 172.17.0.3 n=5462 for ((i=n;i<=10922;i++)) do /usr/local/bin/redis-cli -h 192.168.10.52 -p 6380 -a 123456 CLUSTER ADDSLOTS $i done # node3 192.168.10.52 172.17.0.4 n=10923 for ((i=n;i<=16383;i++)) do /usr/local/bin/redis-cli -h 192.168.10.52 -p 6381 -a 123456 CLUSTER ADDSLOTS $i done
其中， -a 123456 表示需要输入的密码。
192.168.10.52:6379> CLUSTER INFO cluster_state:fail # 集群状态为失败 cluster_slots_assigned:16101 # 没有完全分配结束 cluster_slots_ok:16101 cluster_slots_pfail:0 cluster_slots_fail:0 cluster_known_nodes:6 cluster_size:3 cluster_current_epoch:5 cluster_my_epoch:2 cluster_stats_messages_ping_sent:266756 cluster_stats_messages_pong_sent:266528 cluster_stats_messages_meet_sent:10 cluster_stats_messages_sent:533294 cluster_stats_messages_ping_received:266527 cluster_stats_messages_pong_received:266666 cluster_stats_messages_meet_received:1 cluster_stats_messages_received:533194<br> 192.168.10.52:6379> CLUSTER INFO cluster_state:ok # 集群状态为成功 cluster_slots_assigned:16384 # 已经全部分配完成 cluster_slots_ok:16384 cluster_slots_pfail:0 cluster_slots_fail:0 cluster_known_nodes:6 cluster_size:3 cluster_current_epoch:5 cluster_my_epoch:2 cluster_stats_messages_ping_sent:266757 cluster_stats_messages_pong_sent:266531 cluster_stats_messages_meet_sent:10 cluster_stats_messages_sent:533298 cluster_stats_messages_ping_received:266530 cluster_stats_messages_pong_received:266667 cluster_stats_messages_meet_received:1 cluster_stats_messages_received:533198
综上可知，当全部槽位分配完成之后，集群还是可行的，如果我们手欠，移除一个槽位，那么集群就立马那不行了，自己去试试吧 ——CLUSTER DELSLOTS 0 。
如何变成高可用性
以上我们已经搭建了一套完整的可运行的redis cluster，但是每个节点都是单点，这样子可能出现，一个节点挂掉，整个集群因为槽位分配不完全而崩溃，因此，我们需要为每个节点配置副本备用节点。
前面我们已经提前创建了6个备用节点，搭建集群花了三个，因此还有剩下三个直接可以用来做备用副本。
192.168.10.52:6379> 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 # 总共6个节点 cluster_size:3 # 集群为 3 个节点 cluster_current_epoch:5 cluster_my_epoch:2 cluster_stats_messages_ping_sent:270127 cluster_stats_messages_pong_sent:269893 cluster_stats_messages_meet_sent:10 cluster_stats_messages_sent:540030 cluster_stats_messages_ping_received:269892 cluster_stats_messages_pong_received:270037 cluster_stats_messages_meet_received:1 cluster_stats_messages_received:539930
查看所有节点的id
192.168.10.52:6379> CLUSTER NODES 54cb5c2eb8e5f5aed2d2f7843f75a9284ef6785c 172.17.0.3:6379@16379 master - 0 1528704114535 1 connected 5462-10922 f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 172.17.0.4:6379@16379 master - 0 1528704114000 0 connected 10923-16383 ae86224a3bc29c4854719c83979cb7506f37787a 172.17.0.7:6379@16379 master - 0 1528704114023 5 connected 98aebcfe42d8aaa8a3375e4a16707107dc9da683 172.17.0.6:6379@16379 master - 0 1528704115544 4 connected 0bbdc4176884ef0e3bb9b2e7d03d91b0e7e11f44 172.17.0.5:6379@16379 master - 0 1528704114836 3 connected 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 172.17.0.2:6379@16379 myself,master - 0 1528704115000 2 connected 0-5461
编写脚本，添加副本节点
[root@etcd2 tmp]# vi addSlaveNodes.sh #!/bin/bash /usr/local/bin/redis-cli -h 192.168.10.52 -p 6382 -a 123456 CLUSTER REPLICATE 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 /usr/local/bin/redis-cli -h 192.168.10.52 -p 6383 -a 123456 CLUSTER REPLICATE 54cb5c2eb8e5f5aed2d2f7843f75a9284ef6785c /usr/local/bin/redis-cli -h 192.168.10.52 -p 6384 -a 123456 CLUSTER REPLICATE f45f9109f2297a83b1ac36f9e1db5e70bbc174ab
注意：1、作为备用的节点，必须是未分配槽位的，否者会操作失败 (error) ERR To set a master the node must be empty and without assigned slots 。
2、需要从需要添加的节点上面执行操作，CLUSTER REPLICATE [node_id] ，使当前节点成为 node_id 的副本节点。
3、添加从节点（集群复制）： 复制的原理和单机的Redis复制原理一样，区别是：集群下的从节点也需要运行在cluster模式下，要先添加到集群里面，再做复制。
查看所有节点信息：
192.168.10.52:6379> CLUSTER NODES 54cb5c2eb8e5f5aed2d2f7843f75a9284ef6785c 172.17.0.3:6379@16379 master - 0 1528705604149 1 connected 5462-10922 f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 172.17.0.4:6379@16379 master - 0 1528705603545 0 connected 10923-16383 ae86224a3bc29c4854719c83979cb7506f37787a 172.17.0.7:6379@16379 slave f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 0 1528705603144 5 connected 98aebcfe42d8aaa8a3375e4a16707107dc9da683 172.17.0.6:6379@16379 slave 54cb5c2eb8e5f5aed2d2f7843f75a9284ef6785c 0 1528705603000 4 connected 0bbdc4176884ef0e3bb9b2e7d03d91b0e7e11f44 172.17.0.5:6379@16379 slave 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 0 1528705603000 3 connected 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 172.17.0.2:6379@16379 myself,master - 0 1528705602000 2 connected 0-5461
可以看到我们现在实现了三主三从的一个高可用集群。
高可用测试——故障转移
查看当前运行状态：
192.168.10.52:6379> CLUSTER NODES 54cb5c2eb8e5f5aed2d2f7843f75a9284ef6785c 172.17.0.3:6379@16379 master - 0 1528705604149 1 connected 5462-10922 f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 172.17.0.4:6379@16379 master - 0 1528705603545 0 connected 10923-16383 ae86224a3bc29c4854719c83979cb7506f37787a 172.17.0.7:6379@16379 slave f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 0 1528705603144 5 connected 98aebcfe42d8aaa8a3375e4a16707107dc9da683 172.17.0.6:6379@16379 slave 54cb5c2eb8e5f5aed2d2f7843f75a9284ef6785c 0 1528705603000 4 connected 0bbdc4176884ef0e3bb9b2e7d03d91b0e7e11f44 172.17.0.5:6379@16379 slave 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 0 1528705603000 3 connected 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 172.17.0.2:6379@16379 myself,master - 0 1528705602000 2 connected 0-5461
以上，运行正常
尝试关闭一个master，选择端口为6380的容器，停掉之后：
192.168.10.52:6379> CLUSTER NODES 54cb5c2eb8e5f5aed2d2f7843f75a9284ef6785c 172.17.0.3:6379@16379 master,fail - 1528706408935 1528706408000 1 connected 5462-10922 f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 172.17.0.4:6379@16379 master - 0 1528706463000 0 connected 10923-16383 ae86224a3bc29c4854719c83979cb7506f37787a 172.17.0.7:6379@16379 slave f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 0 1528706462980 5 connected 98aebcfe42d8aaa8a3375e4a16707107dc9da683 172.17.0.6:6379@16379 slave 54cb5c2eb8e5f5aed2d2f7843f75a9284ef6785c 0 1528706463000 4 connected 0bbdc4176884ef0e3bb9b2e7d03d91b0e7e11f44 172.17.0.5:6379@16379 slave 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 0 1528706463985 3 connected 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 172.17.0.2:6379@16379 myself,master - 0 1528706462000 2 connected 0-5461 192.168.10.52:6379> 192.168.10.52:6379> CLUSTER INFO cluster_state:fail cluster_slots_assigned:16384 cluster_slots_ok:10923 cluster_slots_pfail:0 cluster_slots_fail:5461 cluster_known_nodes:6 cluster_size:3 cluster_current_epoch:5 cluster_my_epoch:2 cluster_stats_messages_ping_sent:275112 cluster_stats_messages_pong_sent:274819 cluster_stats_messages_meet_sent:10 cluster_stats_messages_fail_sent:5 cluster_stats_messages_sent:549946 cluster_stats_messages_ping_received:274818 cluster_stats_messages_pong_received:275004 cluster_stats_messages_meet_received:1 cluster_stats_messages_fail_received:1 cluster_stats_messages_received:549824
以上，发现整个集群都失败了，从节点没有自动升级为主节点，怎么回事？？
重启停掉的容器，经排查日志信息 [root@df6ebce6f12a /]# tail -f /var/log/redis/redis-server.log ：
1:S 11 Jun 09:57:46.712 # Cluster state changed: ok 1:S 11 Jun 09:57:46.718 * (Non critical) Master does not understand REPLCONF listening-port: -NOAUTH Authentication required. 1:S 11 Jun 09:57:46.718 * (Non critical) Master does not understand REPLCONF capa: -NOAUTH Authentication required. 1:S 11 Jun 09:57:46.719 * Partial resynchronization not possible (no cached master) 1:S 11 Jun 09:57:46.719 # Unexpected reply to PSYNC from master: -NOAUTH Authentication required. 1:S 11 Jun 09:57:46.719 * Retrying with SYNC... 1:S 11 Jun 09:57:46.719 # MASTER aborted replication with an error: NOAUTH Authentication required. 1:S 11 Jun 09:57:46.782 * Connecting to MASTER 172.17.0.6:6379 1:S 11 Jun 09:57:46.782 * MASTER <-> SLAVE sync started 1:S 11 Jun 09:57:46.782 * Non blocking connect for SYNC fired the event.
可以看到，主从之间访问需要auth，之前忘记了配置 redis.conf 中的 # masterauth <master-password> ，所以导致主从之间无法通讯。修改配置之后，自动故障转移正常。
有时候需要实施人工故障转移：
登录6380端口的从节点：6383，执行 CLUSTER FAILOVER 命令：
192.168.10.52:6383> CLUSTER FAILOVER (error) ERR Master is down or failed, please use CLUSTER FAILOVER FORCE
发现因为master已经down了，所以我们需要执行强制转移
192.168.10.52:6383> CLUSTER FAILOVER FORCE OK
查看当前 cluster node 情况：
192.168.10.52:6383> CLUSTER NODES 0bbdc4176884ef0e3bb9b2e7d03d91b0e7e11f44 172.17.0.5:6379@16379 slave 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 0 1528707535332 3 connected ae86224a3bc29c4854719c83979cb7506f37787a 172.17.0.7:6379@16379 slave f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 0 1528707534829 5 connected f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 172.17.0.4:6379@16379 master - 0 1528707534527 0 connected 10923-16383 98aebcfe42d8aaa8a3375e4a16707107dc9da683 172.17.0.6:6379@16379 myself,master - 0 1528707535000 6 connected 5462-10922 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 172.17.0.2:6379@16379 master - 0 1528707535834 2 connected 0-5461 54cb5c2eb8e5f5aed2d2f7843f75a9284ef6785c 172.17.0.3:6379@16379 master,fail - 1528707472833 1528707472000 1 connected
从节点已经升级为master节点。这时候，我们尝试重启了，6380节点的redis（其实是重新启动停掉的容器）：
192.168.10.52:6383> CLUSTER NODES 0bbdc4176884ef0e3bb9b2e7d03d91b0e7e11f44 172.17.0.5:6379@16379 slave 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 0 1528707556044 3 connected ae86224a3bc29c4854719c83979cb7506f37787a 172.17.0.7:6379@16379 slave f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 0 1528707555000 5 connected f45f9109f2297a83b1ac36f9e1db5e70bbc174ab 172.17.0.4:6379@16379 master - 0 1528707556000 0 connected 10923-16383 98aebcfe42d8aaa8a3375e4a16707107dc9da683 172.17.0.6:6379@16379 myself,master - 0 1528707556000 6 connected 5462-10922 760e4d0039c5ac13d04aa4791c9e6dc28544d7c7 172.17.0.2:6379@16379 master - 0 1528707556000 2 connected 0-5461 54cb5c2eb8e5f5aed2d2f7843f75a9284ef6785c 172.17.0.3:6379@16379 slave 98aebcfe42d8aaa8a3375e4a16707107dc9da683 0 1528707556547 6 connected
我们发现，6380节点反而变成了 6383节点的从节点。
现在集群应该是完整的了，所以，集群状态应该已经恢复了，我们查看下：
192.168.10.52:6383> 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:6 cluster_stats_messages_ping_sent:19419 cluster_stats_messages_pong_sent:19443 cluster_stats_messages_meet_sent:1 cluster_stats_messages_auth-req_sent:5 cluster_stats_messages_update_sent:1 cluster_stats_messages_sent:38869 cluster_stats_messages_ping_received:19433 cluster_stats_messages_pong_received:19187 cluster_stats_messages_meet_received:5 cluster_stats_messages_fail_received:4 cluster_stats_messages_auth-ack_received:2 cluster_stats_messages_received:38631
OK，没有问题。
集群访问
客户端在初始化的时候只需要知道一个节点的地址即可，客户端会先尝试向这个节点执行命令，比如 get key ，如果key所在的slot刚好在该节点上，则能够直接执行成功。如果slot不在该节点，则节点会返回MOVED错误，同时把该slot对应的节点告诉客户端，客户端可以去该节点执行命令
192.168.10.52:6383> get hello (error) MOVED 866 172.17.0.2:6379 192.168.10.52:6379> set number 20004 (error) MOVED 7743 172.17.0.3:6379
另外，redis集群版只使用db0，select命令虽然能够支持select 0。其他的db都会返回错误。
192.168.10.52:6383> select 0 OK 192.168.10.52:6383> select 1 (error) ERR SELECT is not allowed in cluster mode
近期，有网友询问docker redis集群连接报错的问题，具体报错如下：
初步认为是，node节点没有全部添加进去，添加之后，依然有上述问题。想到是跨主机访问，应该是路由寻址不了导致的。当初写上述教程的时候，docker是以默认的网络模式bridge模式运行的，毕竟当初是以学习整理文档为主，主要是单机访问。但是，实际应用化场景中，多是公网跨主机访问，问题明朗了，想着集群这东西最好还是设置成共享主机公网ip比较好，于是解决如下：
在docker运行时，执行网络模式为：host。 端口冲突解决，毕竟host模式下，容器会占用宿主机的端口，于是，我们就从配置下手，在宿主机上生成配置redis-60001.conf,redis-60002.conf,redis-60003.conf...，有多少端口建多少个文件，最终运行一个容器，挂载一个配置到容器中用于覆盖主机中的配置。
最终的运行方式如下：
docker run -d --name redis-6380 --net host -v /tmp/redis.conf:/usr/local/redis/redis.conf hakimdstx/nodes-redis:4.0.1
至此，网络问题得到解决。
PS.生产环境需要注意防火墙问题，不然也是会报错的。
引用：
1、Redis Cluster部署、管理和测试
2、Docker下redis的主从、持久化配置
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