Redis集群详解

    Redis集群详解

    Redis有三种集群模式,分别是:

    * 主从模式

    * Sentinel模式

    * Cluster模式

    三种集群模式各有特点,关于Redis介绍可以参考这里:NoSQL(二)——Redis

    Redis官网:https://redis.io/ ,最新版本6.0.5

    主从模式

    主从模式介绍
    主从模式是三种模式中最简单的,在主从复制中,数据库分为两类:主数据库(master)和从数据库(slave)。

    其中主从复制有如下特点:

    * 主数据库可以进行读写操作,当读写操作导致数据变化时会自动将数据同步给从数据库

    * 从数据库一般都是只读的,并且接收主数据库同步过来的数据

    * 一个master可以拥有多个slave,但是一个slave只能对应一个master

    * slave挂了不影响其他slave的读和master的读和写,重新启动后会将数据从master同步过来

    * master挂了以后,不影响slave的读,但redis不再提供写服务,master重启后redis将重新对外提供写服务

    * master挂了以后,不会在slave节点中重新选一个master

    工作机制:

    当slave启动后,主动向master发送SYNC命令。master接收到SYNC命令后在后台保存快照(RDB持久化)和缓存保存快照这段时间的命令,然后将保存的快照文件和缓存的命令发送给slave。slave接收到快照文件和命令后加载快照文件和缓存的执行命令。

    复制初始化后,master每次接收到的写命令都会同步发送给slave,保证主从数据一致性。

    安全设置:

    当master节点设置密码后,

    客户端访问master需要密码

    启动slave需要密码,在配置文件中配置即可

    客户端访问slave不需要密码

    缺点:

    从上面可以看出,master节点在主从模式中唯一,若master挂掉,则redis无法对外提供写服务。

    主从模式搭建

    环境准备:

    master节点 192.168.30.128

    slave节点 192.168.30.129

    slave节点 192.168.30.130

    全部下载安装:

    
    # cd /software
    # wget http://download.redis.io/releases/redis-6.0.5.tar.gz
    # tar zxf redis-5.0.4.tar.gz && mv redis-6.0.5/ /usr/local/redis
    # cd /usr/local/redis && make && make install
    # echo $?
    0
    

    全部配置成服务:

    服务文件

    # vim /usr/lib/systemd/system/redis.service

    [Unit]
    Description=Redis persistent key-value database
    After=network.target
    After=network-online.target
    Wants=network-online.target

    [Service]
    ExecStart=/usr/local/bin/redis-server /usr/local/redis/redis.conf –supervised systemd
    ExecStop=/usr/libexec/redis-shutdown
    Type=notify
    User=redis
    Group=redis
    RuntimeDirectory=redis
    RuntimeDirectoryMode=0755

    [Install]
    WantedBy=multi-user.target

    shutdown脚本

    
    # vim /usr/libexec/redis-shutdown
    
    #!/bin/bash
    #
    # Wrapper to close properly redis and sentinel
    test x"$REDIS_DEBUG" != x && set -x
    
    REDIS_CLI=/usr/local/bin/redis-cli
    
    # Retrieve service name
    SERVICE_NAME="$1"
    if [ -z "$SERVICE_NAME" ]; then
      SERVICE_NAME=redis
    fi
    
    # Get the proper config file based on service name
    CONFIG_FILE="/usr/local/redis/$SERVICE_NAME.conf"
    
    # Use awk to retrieve host, port from config file
    HOST=`awk '/^[[:blank:]]*bind/ { print $2 }' $CONFIG_FILE | tail -n1`
    PORT=`awk '/^[[:blank:]]*port/ { print $2 }' $CONFIG_FILE | tail -n1`
    PASS=`awk '/^[[:blank:]]*requirepass/ { print $2 }' $CONFIG_FILE | tail -n1`
    SOCK=`awk '/^[[:blank:]]*unixsocket\s/ { print $2 }' $CONFIG_FILE | tail -n1`
    
    # Just in case, use default host, port
    HOST=${HOST:-127.0.0.1}
    if [ "$SERVICE_NAME" = redis ]; then
      PORT=${PORT:-6379}
    else
      PORT=${PORT:-26739}
    fi
    
    # Setup additional parameters
    # e.g password-protected redis instances
    [ -z "$PASS" ] || ADDITIONAL_PARAMS="-a $PASS"
    
    # shutdown the service properly
    if [ -e "$SOCK" ] ; then
        $REDIS_CLI -s $SOCK $ADDITIONAL_PARAMS shutdown
    else
        $REDIS_CLI -h $HOST -p $PORT $ADDITIONAL_PARAMS shutdown
    fi
    
    # chmod +x /usr/libexec/redis-shutdown
    # useradd -s /sbin/nologin redis
    # chown -R redis:redis /usr/local/redis
    # chown -R reids:redis /data/redis
    # yum install -y bash-completion && source /etc/profile         #命令补全
    
    # systemctl daemon-reload
    # systemctl enable redis
    

    修改配置:

    192.168.30.128

    
    # mkdir -p /data/redis
    
    # vim /usr/local/redis/redis.conf
    
    bind 192.168.30.128        #监听ip,多个ip用空格分隔
    daemonize yes        #允许后台启动
    logfile "/usr/local/redis/redis.log"        #日志路径
    dir /data/redis         #数据库备份文件存放目录
    masterauth 123456        #slave连接master密码,master可省略
    requirepass 123456       #设置master连接密码,slave可省略
    
    appendonly yes         #在/data/redis/目录生成appendonly.aof文件,将每一次写操作请求都追加到appendonly.aof 文件中
    
    # echo 'vm.overcommit_memory=1' >> /etc/sysctl.conf
    
    # sysctl -p
    

    192.168.30.129

    
    # mkdir -p /data/redis
    
    # vim /usr/local/redis/redis.conf
    
    bind 192.168.30.129
    daemonize yes
    logfile "/usr/local/redis/redis.log"
    dir /data/redis
    replicaof 192.168.30.128 6379
    masterauth 123456
    requirepass 123456
    appendonly yes
    
    # echo 'vm.overcommit_memory=1' >> /etc/sysctl.conf
    
    # sysctl -p
    

    192.168.30.130

    
    # mkdir -p /data/redis
    
    # vim /usr/local/redis/redis.conf
    
    bind 192.168.30.130
    daemonize yes
    logfile "/usr/local/redis/redis.log"
    dir /data/redis
    replicaof 192.168.30.128 6379
    masterauth 123456
    requirepass 123456
    appendonly yes
    
    # echo 'vm.overcommit_memory=1' >> /etc/sysctl.conf
    
    # sysctl -p
    

    全部启动redis:

    # systemctl start redis

    查看集群状态:

    
    # redis-cli -h 192.168.30.128 -a 123456
    Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
    
    192.168.30.128:6379> info replication
    # Replication
    role:master
    connected_slaves:2
    slave0:ip=192.168.30.129,port=6379,state=online,offset=168,lag=1
    slave1:ip=192.168.30.130,port=6379,state=online,offset=168,lag=1
    master_replid:fb4941e02d5032ad74c6e2383211fc58963dbe90
    master_replid2:0000000000000000000000000000000000000000
    master_repl_offset:168
    second_repl_offset:-1
    repl_backlog_active:1
    repl_backlog_size:1048576
    repl_backlog_first_byte_offset:1
    repl_backlog_histlen:168
    
    
    # redis-cli -h 192.168.30.129 -a 123456 info replication
    
    Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
    # Replication
    role:slave
    master_host:192.168.30.128
    master_port:6379
    master_link_status:up
    master_last_io_seconds_ago:1
    master_sync_in_progress:0
    slave_repl_offset:196
    slave_priority:100
    slave_read_only:1
    connected_slaves:0
    master_replid:fb4941e02d5032ad74c6e2383211fc58963dbe90
    master_replid2:0000000000000000000000000000000000000000
    master_repl_offset:196
    second_repl_offset:-1
    repl_backlog_active:1
    repl_backlog_size:1048576
    repl_backlog_first_byte_offset:1
    repl_backlog_histlen:196
    

    数据演示:

    
    192.168.30.128:6379> keys *
    (empty list or set)
    
    192.168.30.128:6379> set key1 100
    OK
    
    192.168.30.128:6379> set key2 lzx
    OK
    
    192.168.30.128:6379> keys *
    1) "key1"
    2) "key2"
    
    
    # redis-cli -h 192.168.30.129 -a 123456
    Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
    
    192.168.30.129:6379> keys *
    1) "key2"
    2) "key1"
    
    192.168.30.129:6379> CONFIG GET dir
    1) "dir"
    2) "/data/redis"
    
    192.168.30.129:6379> CONFIG GET dbfilename
    1) "dbfilename"
    2) "dump.rdb"
    
    192.168.30.129:6379> get key1
    "100"
    
    192.168.30.129:6379> get key2
    "lzx"
    
    192.168.30.129:6379> set key3 aaa
    (error) READONLY You can't write against a read only replica.
    
    
    # redis-cli -h 192.168.30.130 -a 123456
    Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
    
    192.168.30.130:6379> keys *
    1) "key2"
    2) "key1"
    
    192.168.30.130:6379> CONFIG GET dir
    1) "dir"
    2) "/data/redis"
    
    192.168.30.130:6379> CONFIG GET dbfilename
    1) "dbfilename"
    2) "dump.rdb"
    
    192.168.30.130:6379> get key1
    "100"
    
    192.168.30.130:6379> get key2
    "lzx"
    
    192.168.30.130:6379> set key3 aaa
    (error) READONLY You can't write against a read only replica.
    

    可以看到,在master节点写入的数据,很快就同步到slave节点上,而且在slave节点上无法写入数据。

    Sentinel模式

    Sentinel模式介绍
    主从模式的弊端就是不具备高可用性,当master挂掉以后,Redis将不能再对外提供写入操作,因此sentinel应运而生。

    sentinel中文含义为哨兵,顾名思义,它的作用就是监控redis集群的运行状况,特点如下:

    * sentinel模式是建立在主从模式的基础上,如果只有一个Redis节点,sentinel就没有任何意义

    * 当master挂了以后,sentinel会在slave中选择一个做为master,并修改它们的配置文件,其他slave的配置文件也会被修改,比如slaveof属性会指向新的master

    * 当master重新启动后,它将不再是master而是做为slave接收新的master的同步数据

    * sentinel因为也是一个进程有挂掉的可能,所以sentinel也会启动多个形成一个sentinel集群

    * 多sentinel配置的时候,sentinel之间也会自动监控

    * 当主从模式配置密码时,sentinel也会同步将配置信息修改到配置文件中,不需要担心

    * 一个sentinel或sentinel集群可以管理多个主从Redis,多个sentinel也可以监控同一个redis

    * sentinel最好不要和Redis部署在同一台机器,不然Redis的服务器挂了以后,sentinel也挂了

    工作机制:

    * 每个sentinel以每秒钟一次的频率向它所知的master,slave以及其他sentinel实例发送一个 PING 命令

    * 如果一个实例距离最后一次有效回复 PING 命令的时间超过 down-after-milliseconds 选项所指定的值, 则这个实例会被sentinel标记为主观下线。

    * 如果一个master被标记为主观下线,则正在监视这个master的所有sentinel要以每秒一次的频率确认master的确进入了主观下线状态

    * 当有足够数量的sentinel(大于等于配置文件指定的值)在指定的时间范围内确认master的确进入了主观下线状态, 则master会被标记为客观下线

    * 在一般情况下, 每个sentinel会以每 10 秒一次的频率向它已知的所有master,slave发送 INFO 命令

    * 当master被sentinel标记为客观下线时,sentinel向下线的master的所有slave发送 INFO 命令的频率会从 10 秒一次改为 1 秒一次

    * 若没有足够数量的sentinel同意master已经下线,master的客观下线状态就会被移除;
    若master重新向sentinel的 PING 命令返回有效回复,master的主观下线状态就会被移除

    当使用sentinel模式的时候,客户端就不要直接连接Redis,而是连接sentinel的ip和port,由sentinel来提供具体的可提供服务的Redis实现,这样当master节点挂掉以后,sentinel就会感知并将新的master节点提供给使用者。

    Sentinel模式搭建

    环境准备:

    master节点 192.168.30.128 sentinel端口:26379

    slave节点 192.168.30.129 sentinel端口:26379

    slave节点 192.168.30.130 sentinel端口:26379

    修改配置:

    前面已经下载安装了redis,这里省略,直接修改sentinel配置文件。

    192.168.30.128

    # vim /usr/local/redis/sentinel.conf

    daemonize yes
    logfile “/usr/local/redis/sentinel.log”
    dir “/usr/local/redis/sentinel”                 #sentinel工作目录
    sentinel monitor mymaster 192.168.30.128 6379 2                 #判断master失效至少需要2个sentinel同意,建议设置为n/2+1,n为sentinel个数
    sentinel auth-pass mymaster 123456
    sentinel down-after-milliseconds mymaster 30000                 #判断master主观下线时间,默认30s

    这里需要注意,sentinel auth-pass mymaster 123456需要配置在sentinel monitor mymaster 192.168.30.128 6379 2下面,否则启动报错:

    
    # /usr/local/bin/redis-sentinel /usr/local/redis/sentinel.conf
    
    *** FATAL CONFIG FILE ERROR ***
    Reading the configuration file, at line 104
    >>> 'sentinel auth-pass mymaster 123456'
    No such master with specified name.
    

    全部启动sentinel:

    # mkdir /usr/local/redis/sentinel && chown -R redis:redis /usr/local/redis

    # /usr/local/bin/redis-sentinel /usr/local/redis/sentinel.conf

    任一主机查看日志:

    # tail -f /usr/local/redis/sentinel.log

    21574:X 09 May 2019 15:32:04.298 # Sentinel ID is 30c417116a8edbab09708037366c4a7471beb770
    21574:X 09 May 2019 15:32:04.298 # +monitor master mymaster 192.168.30.128 6379 quorum 2
    21574:X 09 May 2019 15:32:04.299 * +slave slave 192.168.30.129:6379 192.168.30.129 6379 @ mymaster 192.168.30.128 6379
    21574:X 09 May 2019 15:32:04.300 * +slave slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.128 6379
    21574:X 09 May 2019 15:32:16.347 * +sentinel sentinel 79b8d61626afd4d059fb5a6a63393e9a1374e78f 192.168.30.129 26379 @ mymaster 192.168.30.128 6379
    21574:X 09 May 2019 15:32:31.584 * +sentinel sentinel d7b429dcba792103ef0d80827dd0910bd9284d21 192.168.30.130 26379 @ mymaster 192.168.30.128 6379

    Sentinel模式下的几个事件:

    · +reset-master :主服务器已被重置。

    · +slave :一个新的从服务器已经被 Sentinel 识别并关联。

    · +failover-state-reconf-slaves :故障转移状态切换到了 reconf-slaves 状态。

    · +failover-detected :另一个 Sentinel 开始了一次故障转移操作,或者一个从服务器转换成了主服务器。

    · +slave-reconf-sent :领头(leader)的 Sentinel 向实例发送了 [SLAVEOF](/commands/slaveof.html) 命令,为实例设置新的主服务器。

    · +slave-reconf-inprog :实例正在将自己设置为指定主服务器的从服务器,但相应的同步过程仍未完成。

    · +slave-reconf-done :从服务器已经成功完成对新主服务器的同步。

    · -dup-sentinel :对给定主服务器进行监视的一个或多个 Sentinel 已经因为重复出现而被移除 —— 当 Sentinel 实例重启的时候,就会出现这种情况。

    · +sentinel :一个监视给定主服务器的新 Sentinel 已经被识别并添加。

    · +sdown :给定的实例现在处于主观下线状态。

    · -sdown :给定的实例已经不再处于主观下线状态。

    · +odown :给定的实例现在处于客观下线状态。

    · -odown :给定的实例已经不再处于客观下线状态。

    · +new-epoch :当前的纪元(epoch)已经被更新。

    · +try-failover :一个新的故障迁移操作正在执行中,等待被大多数 Sentinel 选中(waiting to be elected by the majority)。

    · +elected-leader :赢得指定纪元的选举,可以进行故障迁移操作了。

    · +failover-state-select-slave :故障转移操作现在处于 select-slave 状态 —— Sentinel 正在寻找可以升级为主服务器的从服务器。

    · no-good-slave :Sentinel 操作未能找到适合进行升级的从服务器。Sentinel 会在一段时间之后再次尝试寻找合适的从服务器来进行升级,又或者直接放弃执行故障转移操作。

    · selected-slave :Sentinel 顺利找到适合进行升级的从服务器。

    · failover-state-send-slaveof-noone :Sentinel 正在将指定的从服务器升级为主服务器,等待升级功能完成。

    · failover-end-for-timeout :故障转移因为超时而中止,不过最终所有从服务器都会开始复制新的主服务器(slaves will eventually be configured to replicate with the new master anyway)。

    · failover-end :故障转移操作顺利完成。所有从服务器都开始复制新的主服务器了。

    · +switch-master :配置变更,主服务器的 IP 和地址已经改变。 这是绝大多数外部用户都关心的信息。

    · +tilt :进入 tilt 模式。

    · -tilt :退出 tilt 模式。

    master宕机演示:

    192.168.30.128

    # systemctl stop redis

    # tail -f /usr/local/redis/sentinel.log

    22428:X 09 May 2019 15:51:29.287 # +sdown master mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:29.371 # +odown master mymaster 192.168.30.128 6379 #quorum 2/2
    22428:X 09 May 2019 15:51:29.371 # +new-epoch 1
    22428:X 09 May 2019 15:51:29.371 # +try-failover master mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:29.385 # +vote-for-leader 30c417116a8edbab09708037366c4a7471beb770 1
    22428:X 09 May 2019 15:51:29.403 # d7b429dcba792103ef0d80827dd0910bd9284d21 voted for 30c417116a8edbab09708037366c4a7471beb770 1
    22428:X 09 May 2019 15:51:29.408 # 79b8d61626afd4d059fb5a6a63393e9a1374e78f voted for 30c417116a8edbab09708037366c4a7471beb770 1
    22428:X 09 May 2019 15:51:29.451 # +elected-leader master mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:29.451 # +failover-state-select-slave master mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:29.528 # +selected-slave slave 192.168.30.129:6379 192.168.30.129 6379 @ mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:29.528 * +failover-state-send-slaveof-noone slave 192.168.30.129:6379 192.168.30.129 6379 @ mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:29.594 * +failover-state-wait-promotion slave 192.168.30.129:6379 192.168.30.129 6379 @ mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:30.190 # +promoted-slave slave 192.168.30.129:6379 192.168.30.129 6379 @ mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:30.190 # +failover-state-reconf-slaves master mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:30.258 * +slave-reconf-sent slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:30.511 # -odown master mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:31.233 * +slave-reconf-inprog slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:31.233 * +slave-reconf-done slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:31.297 # +failover-end master mymaster 192.168.30.128 6379
    22428:X 09 May 2019 15:51:31.297 # +switch-master mymaster 192.168.30.128 6379 192.168.30.129 6379
    22428:X 09 May 2019 15:51:31.298 * +slave slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.129 6379
    22428:X 09 May 2019 15:51:31.298 * +slave slave 192.168.30.128:6379 192.168.30.128 6379 @ mymaster 192.168.30.129 6379
    22428:X 09 May 2019 15:52:31.307 # +sdown slave 192.168.30.128:6379 192.168.30.128 6379 @ mymaster 192.168.30.129 6379

    从日志中可以看到,master已经从192.168.30.128转移到192.168.30.129上

    192.168.30.129上查看集群信息

    
    # /usr/local/bin/redis-cli -h 192.168.30.129 -p 6379 -a 123456
    Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
    
    192.168.30.129:6379> info replication
    # Replication
    role:master
    connected_slaves:1
    slave0:ip=192.168.30.130,port=6379,state=online,offset=291039,lag=1
    master_replid:757aff269236ed2707ba584a86a40716c1c76d74
    master_replid2:47a862fc0ff20362be29096ecdcca6d432070ee9
    master_repl_offset:291182
    second_repl_offset:248123
    repl_backlog_active:1
    repl_backlog_size:1048576
    repl_backlog_first_byte_offset:1
    repl_backlog_histlen:291182
    
    192.168.30.129:6379> set key4 linux
    OK
    

    当前集群中只有一个slave——192.168.30.130,master是192.168.30.129,且192.168.30.129具有写权限。

    192.168.30.130上查看redis的配置文件也可以看到replicaof 192.168.30.129 6379,这是sentinel在选举master是做的修改。

    重新把192.168.30.128上进程启动

    # systemctl start redis

    # tail -f /usr/local/redis/sentinel.log

    22428:X 09 May 2019 15:51:31.297 # +switch-master mymaster 192.168.30.128 6379 192.168.30.129 6379
    22428:X 09 May 2019 15:51:31.298 * +slave slave 192.168.30.130:6379 192.168.30.130 6379 @ mymaster 192.168.30.129 6379
    22428:X 09 May 2019 15:51:31.298 * +slave slave 192.168.30.128:6379 192.168.30.128 6379 @ mymaster 192.168.30.129 6379
    22428:X 09 May 2019 15:52:31.307 # +sdown slave 192.168.30.128:6379 192.168.30.128 6379 @ mymaster 192.168.30.129 6379
    22428:X 09 May 2019 16:01:24.872 # -sdown slave 192.168.30.128:6379 192.168.30.128 6379 @ mymaster 192.168.30.129 6379

    查看集群信息

    
    # /usr/local/bin/redis-cli -h 192.168.30.128 -p 6379 -a 123456
    Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
    
    192.168.30.128:6379> info replication
    # Replication
    role:slave
    master_host:192.168.30.129
    master_port:6379
    master_link_status:up
    master_last_io_seconds_ago:0
    master_sync_in_progress:0
    slave_repl_offset:514774
    slave_priority:100
    slave_read_only:1
    connected_slaves:0
    master_replid:757aff269236ed2707ba584a86a40716c1c76d74
    master_replid2:0000000000000000000000000000000000000000
    master_repl_offset:514774
    second_repl_offset:-1
    repl_backlog_active:1
    repl_backlog_size:1048576
    repl_backlog_first_byte_offset:376528
    repl_backlog_histlen:138247
    
    192.168.30.128:6379> get key4
    "linux"
    
    192.168.30.128:6379> set key5
    (error) ERR wrong number of arguments for 'set' command
    

    即使192.168.30.128重新启动redis服务,也是作为slave加入redis集群,192.168.30.129仍然是master。

    Cluster模式

    Cluster模式介绍
    sentinel模式基本可以满足一般生产的需求,具备高可用性。但是当数据量过大到一台服务器存放不下的情况时,主从模式或sentinel模式就不能满足需求了,这个时候需要对存储的数据进行分片,将数据存储到多个Redis实例中。cluster模式的出现就是为了解决单机Redis容量有限的问题,将Redis的数据根据一定的规则分配到多台机器。

    cluster可以说是sentinel和主从模式的结合体,通过cluster可以实现主从和master重选功能,所以如果配置两个副本三个分片的话,就需要六个Redis实例。因为Redis的数据是根据一定规则分配到cluster的不同机器的,当数据量过大时,可以新增机器进行扩容。

    使用集群,只需要将redis配置文件中的cluster-enable配置打开即可。每个集群中至少需要三个主数据库才能正常运行,新增节点非常方便。

    cluster集群特点:

    * 多个redis节点网络互联,数据共享

    * 所有的节点都是一主一从(也可以是一主多从),其中从不提供服务,仅作为备用

    * 不支持同时处理多个key(如MSET/MGET),因为redis需要把key均匀分布在各个节点上,
    并发量很高的情况下同时创建key-value会降低性能并导致不可预测的行为

    * 支持在线增加、删除节点

    * 客户端可以连接任何一个主节点进行读写

    Cluster模式搭建

    环境准备:

    三台机器,分别开启两个redis服务(端口)

    192.168.30.128 端口:7001,7002

    192.168.30.129 端口:7003,7004

    192.168.30.130 端口:7005,7006

    修改配置文件:

    192.168.30.128

    # mkdir /usr/local/redis/cluster

    # cp /usr/local/redis/redis.conf /usr/local/redis/cluster/redis_7001.conf

    # cp /usr/local/redis/redis.conf /usr/local/redis/cluster/redis_7002.conf

    # chown -R redis:redis /usr/local/redis

    # mkdir -p /data/redis/cluster/{redis_7001,redis_7002} && chown -R redis:redis /data/redis

    
    # vim /usr/local/redis/cluster/redis_7001.conf
    
    bind 192.168.30.128
    port 7001
    daemonize yes
    pidfile "/var/run/redis_7001.pid"
    logfile "/usr/local/redis/cluster/redis_7001.log"
    dir "/data/redis/cluster/redis_7001"
    #replicaof 192.168.30.129 6379
    masterauth 123456
    requirepass 123456
    appendonly yes
    cluster-enabled yes
    cluster-config-file nodes_7001.conf
    cluster-node-timeout 15000
    
    
    # vim /usr/local/redis/cluster/redis_7002.conf
    
    bind 192.168.30.128
    port 7002
    daemonize yes
    pidfile "/var/run/redis_7002.pid"
    logfile "/usr/local/redis/cluster/redis_7002.log"
    dir "/data/redis/cluster/redis_7002"
    #replicaof 192.168.30.129 6379
    masterauth "123456"
    requirepass "123456"
    appendonly yes
    cluster-enabled yes
    cluster-config-file nodes_7002.conf
    cluster-node-timeout 15000
    

    其它两台机器配置与192.168.30.128一致,此处省略

    启动redis服务:

    # redis-server /usr/local/redis/cluster/redis_7001.conf

    # tail -f /usr/local/redis/cluster/redis_7001.log

    # redis-server /usr/local/redis/cluster/redis_7002.conf

    # tail -f /usr/local/redis/cluster/redis_7002.log

    其它两台机器启动与192.168.30.128一致,此处省略

    安装ruby并创建集群(低版本):
    如果redis版本比较低,则需要安装ruby。任选一台机器安装ruby即可

    
    # yum -y groupinstall "Development Tools"
    
    # yum install -y gdbm-devel libdb4-devel libffi-devel libyaml libyaml-devel ncurses-devel openssl-devel readline-devel tcl-devel
    
    # mkdir -p ~/rpmbuild/{BUILD,BUILDROOT,RPMS,SOURCES,SPECS,SRPMS}
    
    # wget http://cache.ruby-lang.org/pub/ruby/2.2/ruby-2.2.3.tar.gz -P ~/rpmbuild/SOURCES
    
    # wget http://raw.githubusercontent.com/tjinjin/automate-ruby-rpm/master/ruby22x.spec -P ~/rpmbuild/SPECS
    
    # rpmbuild -bb ~/rpmbuild/SPECS/ruby22x.spec
    
    # rpm -ivh ~/rpmbuild/RPMS/x86_64/ruby-2.2.3-1.el7.x86_64.rpm
    
    # gem install redis         #目的是安装这个,用于配置集群
    

    # cp /usr/local/redis/src/redis-trib.rb /usr/bin/

    # redis-trib.rb create –replicas 1 192.168.30.128:7001 192.168.30.128:7002 192.168.30.129:7003 192.168.30.129:7004 192.168.30.130:7005 192.168.30.130:7006

    创建集群:

    我这里是redis6.0.5,所以不需要安装ruby,直接创建集群即可

    
    # redis-cli -a 123456 --cluster create 192.168.30.128:7001 192.168.30.128:7002 192.168.30.129:7003 192.168.30.129:7004 192.168.30.130:7005 192.168.30.130:7006 --cluster-replicas 1
    
    Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
    >>> Performing hash slots allocation on 6 nodes...
    Master[0] -> Slots 0 - 5460
    Master[1] -> Slots 5461 - 10922
    Master[2] -> Slots 10923 - 16383
    Adding replica 192.168.30.129:7004 to 192.168.30.128:7001
    Adding replica 192.168.30.130:7006 to 192.168.30.129:7003
    Adding replica 192.168.30.128:7002 to 192.168.30.130:7005
    M: 80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001
      slots:[0-5460] (5461 slots) master
    S: b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002
      replicates 6788453ee9a8d7f72b1d45a9093838efd0e501f1
    M: 4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003
      slots:[5461-10922] (5462 slots) master
    S: b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004
      replicates 80c80a3f3e33872c047a8328ad579b9bea001ad8
    M: 6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005
      slots:[10923-16383] (5461 slots) master
    S: 277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006
      replicates 4d74ec66e898bf09006dac86d4928f9fad81f373
    Can I set the above configuration? (type 'yes' to accept): yes         #输入yes,接受上面配置
    >>> Nodes configuration updated
    >>> Assign a different config epoch to each node
    >>> Sending CLUSTER MEET messages to join the cluster
    

    可以看到,

    192.168.30.128:7001是master,它的slave是192.168.30.129:7004;

    192.168.30.129:7003是master,它的slave是192.168.30.130:7006;

    192.168.30.130:7005是master,它的slave是192.168.30.128:7002

    自动生成nodes.conf文件:

    
    # ls /data/redis/cluster/redis_7001/
    appendonly.aof dump.rdb nodes-7001.conf
    
    # vim /data/redis/cluster/redis_7001/nodes-7001.conf 
    
    6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557454406312 5 connected 10923-16383
    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557454407000 6 connected
    b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557454408371 5 connected
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 myself,master - 0 1557454406000 1 connected 0-5460
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557454407366 4 connected
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557454407000 3 connected 5461-10922
    vars currentEpoch 6 lastVoteEpoch 0
    

    集群操作

    登录集群:

    # redis-cli -c -h 192.168.30.128 -p 7001 -a 123456 # -c,使用集群方式登录

    查看集群信息:

    192.168.30.128:7001> CLUSTER INFO #集群状态

    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:580
    cluster_stats_messages_pong_sent:551
    cluster_stats_messages_sent:1131
    cluster_stats_messages_ping_received:546
    cluster_stats_messages_pong_received:580
    cluster_stats_messages_meet_received:5
    cluster_stats_messages_received:1131

    列出节点信息:

    
    192.168.30.128:7001> CLUSTER NODES         #列出节点信息
    
    6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557455176000 5 connected 10923-16383
    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557455174000 6 connected
    b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557455175000 5 connected
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 myself,master - 0 1557455175000 1 connected 0-5460
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557455174989 4 connected
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557455175995 3 connected 5461-10922
    

    这里与nodes.conf文件内容相同

    写入数据:

    
    192.168.30.128:7001> set key111 aaa
    -> Redirected to slot [13680] located at 192.168.30.130:7005        #说明数据到了192.168.30.130:7005上
    OK
    
    192.168.30.130:7005> set key222 bbb
    -> Redirected to slot [2320] located at 192.168.30.128:7001         #说明数据到了192.168.30.128:7001上
    OK
    
    192.168.30.128:7001> set key333 ccc
    -> Redirected to slot [7472] located at 192.168.30.129:7003         #说明数据到了192.168.30.129:7003上
    OK
    
    192.168.30.129:7003> get key111
    -> Redirected to slot [13680] located at 192.168.30.130:7005
    "aaa"
    
    192.168.30.130:7005> get key333
    -> Redirected to slot [7472] located at 192.168.30.129:7003
    "ccc"
    
    192.168.30.129:7003> 
    

    可以看出redis cluster集群是去中心化的,每个节点都是平等的,连接哪个节点都可以获取和设置数据。

    当然,平等指的是master节点,因为slave节点根本不提供服务,只是作为对应master节点的一个备份。

    增加节点:

    192.168.30.129上增加一节点:

    
    # cp /usr/local/redis/cluster/redis_7003.conf /usr/local/redis/cluster/redis_7007.conf
    
    # vim /usr/local/redis/cluster/redis_7007.conf
    
    bind 192.168.30.129
    port 7007
    daemonize yes
    pidfile "/var/run/redis_7007.pid"
    logfile "/usr/local/redis/cluster/redis_7007.log"
    dir "/data/redis/cluster/redis_7007"
    #replicaof 192.168.30.129 6379
    masterauth "123456"
    requirepass "123456"
    appendonly yes
    cluster-enabled yes
    cluster-config-file nodes_7007.conf
    cluster-node-timeout 15000
    
    # mkdir /data/redis/cluster/redis_7007
    
    # chown -R redis:redis /usr/local/redis && chown -R redis:redis /data/redis
    
    # redis-server /usr/local/redis/cluster/redis_7007.conf 
    

    192.168.30.130上增加一节点:

    
    # cp /usr/local/redis/cluster/redis_7005.conf /usr/local/redis/cluster/redis_7008.conf
    
    # vim /usr/local/redis/cluster/redis_7007.conf
    
    bind 192.168.30.130
    port 7008
    daemonize yes
    pidfile "/var/run/redis_7008.pid"
    logfile "/usr/local/redis/cluster/redis_7008.log"
    dir "/data/redis/cluster/redis_7008"
    #replicaof 192.168.30.130 6379
    masterauth "123456"
    requirepass "123456"
    appendonly yes
    cluster-enabled yes
    cluster-config-file nodes_7008.conf
    cluster-node-timeout 15000
    
    # mkdir /data/redis/cluster/redis_7008
    
    # chown -R redis:redis /usr/local/redis && chown -R redis:redis /data/redis
    
    # redis-server /usr/local/redis/cluster/redis_7008.conf 
    

    集群中增加节点:

    
    192.168.30.129:7003> CLUSTER MEET 192.168.30.129 7007
    OK
    
    192.168.30.129:7003> CLUSTER NODES
    
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 myself,master - 0 1557457361000 3 connected 5461-10922
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master - 0 1557457364746 1 connected 0-5460
    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557457362000 6 connected
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557457363000 4 connected
    b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557457362000 5 connected
    e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557457362729 0 connected
    6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557457363739 5 connected 10923-16383
    
    
    192.168.30.129:7003> CLUSTER MEET 192.168.30.130 7008
    OK
    
    192.168.30.129:7003> CLUSTER NODES
    
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 myself,master - 0 1557457489000 3 connected 5461-10922
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master - 0 1557457489000 1 connected 0-5460
    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557457489000 6 connected
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557457488000 4 connected
    b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557457489472 5 connected
    1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 master - 0 1557457489259 0 connected
    e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557457489000 0 connected
    6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557457490475 5 connected 10923-16383
    

    可以看到,新增的节点都是以master身份加入集群的

    更换节点身份:

    将新增的192.168.30.130:7008节点身份改为192.168.30.129:7007的slave

    # redis-cli -c -h 192.168.30.130 -p 7008 -a 123456 cluster replicate e51ab166bc0f33026887bcf8eba0dff3d5b0bf14

    cluster replicate后面跟node_id,更改对应节点身份。也可以登入集群更改

    
    # redis-cli -c -h 192.168.30.130 -p 7008 -a 123456
    
    192.168.30.130:7008> CLUSTER REPLICATE e51ab166bc0f33026887bcf8eba0dff3d5b0bf14
    OK
    
    192.168.30.130:7008> CLUSTER NODES
    
    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557458316881 3 connected
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master - 0 1557458314864 1 connected 0-5460
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557458316000 3 connected 5461-10922
    6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557458315872 5 connected 10923-16383
    b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557458317890 5 connected
    1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557458315000 7 connected
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557458315000 1 connected
    e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557458314000 0 connected
    

    查看相应的nodes.conf文件,可以发现有更改,它记录当前集群的节点信息

    # cat /data/redis/cluster/redis_7001/nodes-7001.conf

    1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557458236169 7 connected
    6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master – 0 1557458235000 5 connected 10923-16383
    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557458234103 6 connected
    b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557458235129 5 connected
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 myself,master – 0 1557458234000 1 connected 0-5460
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557458236000 4 connected
    e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master – 0 1557458236000 0 connected
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master – 0 1557458233089 3 connected 5461-10922
    vars currentEpoch 7 lastVoteEpoch 0

    删除节点:

    192.168.30.130:7008> CLUSTER FORGET 1a1c7f02fce87530bd5abdfc98df1cffce4f1767
    (error) ERR I tried hard but I can’t forget myself… #无法删除登录节点

    192.168.30.130:7008> CLUSTER FORGET e51ab166bc0f33026887bcf8eba0dff3d5b0bf14
    (error) ERR Can’t forget my master! #不能删除自己的master节点

    192.168.30.130:7008> CLUSTER FORGET 6788453ee9a8d7f72b1d45a9093838efd0e501f1
    OK #可以删除其它的master节点

    192.168.30.130:7008> CLUSTER NODES

    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557458887328 3 connected
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master – 0 1557458887000 1 connected 0-5460
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master – 0 1557458886000 3 connected 5461-10922
    b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave – 0 1557458888351 5 connected
    1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557458885000 7 connected
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557458883289 1 connected
    e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master – 0 1557458885310 0 connected

    192.168.30.130:7008> CLUSTER FORGET b4d3eb411a7355d4767c6c23b4df69fa183ef8bc
    OK #可以删除其它的slave节点

    192.168.30.130:7008> CLUSTER NODES

    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557459031397 3 connected
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master – 0 1557459032407 1 connected 0-5460
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master – 0 1557459035434 3 connected 5461-10922
    6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master – 0 1557459034000 5 connected 10923-16383
    1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557459032000 7 connected
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557459034000 1 connected
    e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master – 0 1557459034427 0 connected

    保存配置:

    192.168.30.130:7008> CLUSTER SAVECONFIG #将节点配置信息保存到硬盘
    OK

    # cat /data/redis/cluster/redis_7001/nodes-7001.conf

    1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557458236169 7 connected
    6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master – 0 1557458235000 5 connected 10923-16383
    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557458234103 6 connected
    b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557458235129 5 connected
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 myself,master – 0 1557458234000 1 connected 0-5460
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557458236000 4 connected
    e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master – 0 1557458236000 0 connected
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master – 0 1557458233089 3 connected 5461-10922
    vars currentEpoch 7 lastVoteEpoch 0

    # redis-cli -c -h 192.168.30.130 -p 7008 -a 123456
    Warning: Using a password with ‘-a’ or ‘-u’ option on the command line interface may not be safe.

    192.168.30.130:7008> CLUSTER NODES
    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557459500741 3 connected
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master – 0 1557459500000 1 connected 0-5460
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master – 0 1557459501000 3 connected 5461-10922
    6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master – 0 1557459500000 5 connected 10923-16383
    b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557459499737 5 connected
    1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557459499000 7 connected
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 slave 80c80a3f3e33872c047a8328ad579b9bea001ad8 0 1557459501750 1 connected
    e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master – 0 1557459498000 0 connected

    可以看到,之前删除的节点又恢复了,这是因为对应的配置文件没有删除,执行CLUSTER SAVECONFIG恢复。

    模拟master节点挂掉:

    192.168.30.128

    
    # netstat -lntp |grep 7001
    tcp    0   0 192.168.30.128:17001  0.0.0.0:*        LISTEN   6701/redis-server 1 
    tcp    0   0 192.168.30.128:7001   0.0.0.0:*        LISTEN   6701/redis-server 1 
    
    # kill 6701
    

    192.168.30.130:7008> CLUSTER NODES

    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557461178000 3 connected
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 master,fail – 1557460950483 1557460947145 1 disconnected
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master – 0 1557461174922 3 connected 5461-10922
    6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master – 0 1557461181003 5 connected 10923-16383
    b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557461179993 5 connected
    1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557461176000 7 connected
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 master – 0 1557461178981 8 connected 0-5460
    e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master – 0 1557461179000 0 connected

    对应7001的一行可以看到,master fail,状态为disconnected;而对应7004的一行,slave已经变成master。

    重新启动7001节点:

    
    # redis-server /usr/local/redis/cluster/redis_7001.conf
    
    192.168.30.130:7008> CLUSTER NODES
    
    277daeb8660d5273b7c3e05c263f861ed5f17b92 192.168.30.130:7006@17006 slave 4d74ec66e898bf09006dac86d4928f9fad81f373 0 1557461307000 3 connected
    80c80a3f3e33872c047a8328ad579b9bea001ad8 192.168.30.128:7001@17001 slave b6331cbc986794237c83ed2d5c30777c1551546e 0 1557461305441 8 connected
    4d74ec66e898bf09006dac86d4928f9fad81f373 192.168.30.129:7003@17003 master - 0 1557461307962 3 connected 5461-10922
    6788453ee9a8d7f72b1d45a9093838efd0e501f1 192.168.30.130:7005@17005 master - 0 1557461304935 5 connected 10923-16383
    b4d3eb411a7355d4767c6c23b4df69fa183ef8bc 192.168.30.128:7002@17002 slave 6788453ee9a8d7f72b1d45a9093838efd0e501f1 0 1557461306000 5 connected
    1a1c7f02fce87530bd5abdfc98df1cffce4f1767 192.168.30.130:7008@17008 myself,slave e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 0 1557461305000 7 connected
    b6331cbc986794237c83ed2d5c30777c1551546e 192.168.30.129:7004@17004 master - 0 1557461308972 8 connected 0-5460
    e51ab166bc0f33026887bcf8eba0dff3d5b0bf14 192.168.30.129:7007@17007 master - 0 1557461307000 0 connected
    

    可以看到,7001节点启动后为slave节点,并且是7004的slave节点。即master节点如果挂掉,它的slave节点变为新master节点继续对外提供服务,而原来的master节点如果重启,则变为新master节点的slave节点。

    另外,如果这里是拿7007节点做测试的话,会发现7008节点并不会切换,这是因为7007节点上根本没数据。集群数据被分为三份,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7004覆盖0-5460
    节点7003覆盖5461-10922
    节点7005覆盖10923-16383

    更多参考:

    Redis集群常用命令

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