1.环境说明

系统：CentOS-7-x86_64
ip：192.168.18.236
REDIS_HOME:/opt/redis-4.0.1
redis节点：
    192.168.18.236：6379 master
    192.168.18.236：6380 slave
    192.168.18.236：6381 slave

2.修改配置

cd /opt/redis-4.0.1
cp redis.conf redis_6380.conf
cp redis.conf redis_6381.conf

#修改port、pidfile、slaveof
vi redis_6380.conf
    port 6380
    pidfile /var/run/redis_6380.pid
    slaveof 127.0.0.1 6379

vi redis_6381.conf
    port 6381
    pidfile /var/run/redis_6381.pid
    slaveof 127.0.0.1 6379

3.启动测试

cd /opt/redis-4.0.1

#启动master和2个slave
./src/redis-server redis.conf 
./src/redis-server redis_6380.conf 
./src/redis-server redis_6381.conf 

#打开3个shell窗口，登录3个客户端
./src/redis-cli -p 6379
./src/redis-cli -p 6380
./src/redis-cli -p 6381

#查看6379复制系统中的信息
127.0.0.1:6379> INFO replication
    # Replication
    role:master
    connected_slaves:2
    slave0:ip=127.0.0.1,port=6380,state=online,offset=1246,lag=1
    slave1:ip=127.0.0.1,port=6381,state=online,offset=1246,lag=1
    master_replid:8bb4c076d0ce5179282dac083bf526173d8ef33b
    master_replid2:0000000000000000000000000000000000000000
    master_repl_offset:1246
    second_repl_offset:-1
    repl_backlog_active:1
    repl_backlog_size:1048576
    repl_backlog_first_byte_offset:1
    repl_backlog_histlen:1246

#查看6380复制系统中的信息
127.0.0.1:6380> INFO replication
    # Replication
    role:slave
    master_host:127.0.0.1
    master_port:6379
    master_link_status:up
    master_last_io_seconds_ago:3
    master_sync_in_progress:0
    slave_repl_offset:1442
    slave_priority:100
    slave_read_only:1
    connected_slaves:0
    master_replid:8bb4c076d0ce5179282dac083bf526173d8ef33b
    master_replid2:0000000000000000000000000000000000000000
    master_repl_offset:1442
    second_repl_offset:-1
    repl_backlog_active:1
    repl_backlog_size:1048576
    repl_backlog_first_byte_offset:1
    repl_backlog_histlen:1442

4.sentinel配置

sentinel介绍

1. Redis-Sentinel是Redis官方推荐的高可用性(HA)解决方案

2. 当用Redis做Master-slave的高可用方案时，假如master宕机了，Redis本身(包括它的很多客户端)都没有实现自动进行主备切换

3. 而Redis-sentinel本身也是一个独立运行的进程，它能监控多个master-slave集群，发现master宕机后能进行自懂切换。
   它的主要功能有以下几点:

   • 不时地监控redis是否按照预期良好地运行;
   • 如果发现某个redis节点运行出现状况，能够通知另外一个进程(例如它的客户端);
   • 能够进行自动切换。当一个master节点不可用时，能够选举出master的多个slave(如果有超过一个slave的话)中的一个来作为新的master,其它的slave节点会将它所追随的master的地址改为被提升为master的slave的新地址。

4. Sentinel支持集群
   很显然，只使用单个sentinel进程来监控redis集群是不可靠的，当sentinel进程宕掉后(sentinel本身也有单点问题，single-point-of-failure)整个集群系统将无法按照预期的方式运行。所以有必要将sentinel集群

搭建2个sentinel节点

cd /opt/redis-4.0.1

cp sentinel.conf  sentinel_26380.conf 
vi sentinel.conf
    #后端启动   
    daemonize yes
    logfile "/var/log/sentinel.log"
    sentinel monitor mymaster 127.0.0.1 6379 2
vi sentinel_26380.conf
    port 26380
    #后端启动
    daemonize yes
    logfile "/var/log/sentinel_26380.log"
    sentinel monitor mymaster 127.0.0.1 6379 2

#启动两个sentinel服务
./src/redis-sentinel  sentinel.conf 
./src/redis-sentinel  sentinel_26380.conf 

5.测试sentinel

1）.把6379 master节点关闭

ps aux | grep redis-server
#把6379的服务kill掉
kill -9 3584

2）.查看sentinel log

cat /var/log/sentinel.log 
    4323:X 21 Sep 10:15:57.638 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
    4323:X 21 Sep 10:15:57.638 # Redis version=4.0.1, bits=64, commit=00000000, modified=0, pid=4323, just started
    4323:X 21 Sep 10:15:57.638 # Configuration loaded
    4324:X 21 Sep 10:15:57.641 * Increased maximum number of open files to 10032 (it was originally set to 1024).
    4324:X 21 Sep 10:15:57.643 * Running mode=sentinel, port=26379.
    4324:X 21 Sep 10:15:57.643 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
    4324:X 21 Sep 10:15:57.643 # Sentinel ID is 8ad4ea46a01c2176d7665b64fad69e08080bf9a8
    4324:X 21 Sep 10:15:57.643 # +monitor master mymaster 127.0.0.1 6379 quorum 2
    4324:X 21 Sep 10:16:05.756 * +sentinel sentinel 1e3e9ae7f00507f5153ee3cef0ba2dc2a97c2ff1 127.0.0.1 26380 @ mymaster 127.0.0.1 6379
    4324:X 21 Sep 10:18:56.619 # +sdown master mymaster 127.0.0.1 6379
    4324:X 21 Sep 10:18:56.753 # +new-epoch 1
    4324:X 21 Sep 10:18:56.754 # +vote-for-leader 1e3e9ae7f00507f5153ee3cef0ba2dc2a97c2ff1 1
    4324:X 21 Sep 10:18:57.189 # +config-update-from sentinel 1e3e9ae7f00507f5153ee3cef0ba2dc2a97c2ff1 127.0.0.1 26380 @ mymaster 127.0.0.1 6379
    4324:X 21 Sep 10:18:57.189 # +switch-master mymaster 127.0.0.1 6379 127.0.0.1 6381
    4324:X 21 Sep 10:18:57.189 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381
    4324:X 21 Sep 10:18:57.189 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381
    4324:X 21 Sep 10:19:27.248 # +sdown slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381

发现自动将master切换到6381上

3）.cat sentinel.conf

#发现自动改为6381
sentinel monitor mymaster 127.0.0.1 6381 2

4）.登录6381客户端,查看是否为master

./src/redis-cli -p 6381
#查看复制系统信息，role已经改为master
127.0.0.1:6381> INFO replication
    # Replication
    role:master
    connected_slaves:1
    slave0:ip=127.0.0.1,port=6380,state=online,offset=52458,lag=0
    master_replid:9d438d265f580c023e1b08e73f0ea5edda5b8a8f
    master_replid2:0000000000000000000000000000000000000000
    master_repl_offset:52591
    second_repl_offset:-1
    repl_backlog_active:1
    repl_backlog_size:1048576
    repl_backlog_first_byte_offset:25409
    repl_backlog_histlen:27183

5）.再重新启动6379节点

./src/redis-server redis.conf
./src/redis-cli -p 6379
#发现role为slave
127.0.0.1:6379> INFO replication
    # Replication
    role:slave
    master_host:127.0.0.1
    master_port:6381
    master_link_status:up
    master_last_io_seconds_ago:0
    master_sync_in_progress:0
    slave_repl_offset:83939
    slave_priority:100
    slave_read_only:1
    connected_slaves:0
    master_replid:9d438d265f580c023e1b08e73f0ea5edda5b8a8f
    master_replid2:0000000000000000000000000000000000000000
    master_repl_offset:83939
    second_repl_offset:-1
    repl_backlog_active:1
    repl_backlog_size:1048576
    repl_backlog_first_byte_offset:77064
    repl_backlog_histlen:6876