redis主從搭建（超簡單）
redis是非關係型資料庫，原理一搜一大把，這裡就不再贅述了，只介紹簡單的搭建方法
達到目的：用sentinel嗅探主伺服器狀態，如果down了，十秒鐘內完成切換，將slave升為master，當master再次啟動時，變成slave狀態
主伺服器：192.168.1.11
從伺服器：192.168.1.12
主伺服器操作：
1、關閉防火牆和Selinux
2、yum -y install gcc //編譯時需要用到gcc
3、wget http://download.redis.io/releases/redis-3.2.8.tar.gz //下載安裝包
4、tar zxf redis-3.2.8.tar.gz -C /usr/src/ //解壓檔案
5、cd /usr/src/redis-3.2.8/ && make && make install //編譯安裝
6、mkdir -p /usr/local/redis/etc //建立配置檔案及日誌所存放的目錄
mkdir /usr/local/redis/log
7、cp /usr/src/redis-3.2.8/redis.conf /usr/local/redis/etc/ //複製redis和sentinel的配置檔案到
cp /usr/src/redis-3.2.8/sentinel.conf /usr/local/redis/etc/sentinel.bak --/usr/local/redis/etc下便於管理
8、vi/usr/local/redis/etc/redis.conf
修改：bind 0.0.0.0 //允許所有網段的IP與master連線
daemonize yes//在後臺啟動
9、grep -Ev ^# /usr/local/redis/etc/sentinel.bak | grep -v ^$ > sentinel.conf //將註釋和空白行刪除
10、vi /usr/local/redis/etc/sentinel.conf
daemonize yes//新增，使其可以在後臺執行
logfile "/usr/local/redis/log/sentinel.log" //新增sentinel.log的位置
sentinel monitor mymaster 127.0.0.1 6379 1
11、redis-server /usr/local/redis/etc/redis.conf //啟動redis
redis-sentinel /usr/local/redis/etc/sentinel.conf //啟動sentinel
slave伺服器操作（和master基本差不多）：
1、關閉防火牆和Selinux
2、yum -y install gcc //編譯時需要用到gcc
3、wget http://download.redis.io/releases/redis-3.2.8.tar.gz //下載安裝包
4、tar zxf redis-3.2.8.tar.gz -C /usr/src/ //解壓檔案
5、cd /usr/src/redis-3.2.8/ && make && make install //編譯安裝
6、mkdir -p /usr/local/redis/etc //建立配置檔案所存放的目錄
7、cp /usr/src/redis-3.2.8/redis.conf /usr/local/redis/etc/ //複製redis的配置檔案到/usr/local/redis/etc/下
8、vi /usr/local/redis/etc/redis.conf
修改：bind 0.0.0.0//允許所有網段的IP與master連線
daemonize yes //在後臺啟動
slaveof 192.168.1.11 6379 //指定主伺服器的IP地址和埠
9、redis-server /usr/local/redis/etc/redis.conf //啟動redis
到此redis就安裝並啟動成功了，接下來進行驗證：
Master：
redis-cli -c -p 6379 --啟動客戶端
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=192.168.1.12,port=6379,state=online,offset=3006,lag=1
master_repl_offset:3006
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:3005
Slave：
redis-cli -c -p 6379 --啟動客戶端
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:192.168.1.11
master_port:6379
master_link_status:up
master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_repl_offset:7759
slave_priority:100
slave_read_only:1
connected_slaves:0
master_repl_offset:0
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0
檢視主的sentinel日誌：tail -f /usr/local/redis/log/sentinel.log
6570:X 24 Jan 22:27:50.467 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 3.2.8 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in sentinel mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 26379
| `-._ `._ / _.-' | PID: 6570
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
6570:X 24 Jan 22:27:50.477 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
6570:X 24 Jan 22:27:50.489 # Sentinel ID is 93e3d0398f60b58e9ba788a8da0faf0187d9ff72
6570:X 24 Jan 22:27:50.489 # +monitor master mymaster 127.0.0.1 6379 quorum 1
6570:X 24 Jan 22:28:10.638 * +slave slave 192.168.1.12:6379 192.168.1.12 6379 @ mymaster 127.0.0.1 6379
當master down掉以後，在30秒內會有日誌輸出
5810:X 25 Jan 00:17:43.383 # +sdown master mymaster 127.0.0.1 6379
5810:X 25 Jan 00:17:43.383 # +odown master mymaster 127.0.0.1 6379 #quorum 1/1
5810:X 25 Jan 00:17:43.383 # +new-epoch 2
5810:X 25 Jan 00:17:43.383 # +try-failover master mymaster 127.0.0.1 6379
5810:X 25 Jan 00:17:43.396 # +vote-for-leader 2aff889c03041c04168c5d07db0988213f05cb49 2
5810:X 25 Jan 00:17:43.396 # +elected-leader master mymaster 127.0.0.1 6379
5810:X 25 Jan 00:17:43.396 # +failover-state-select-slave master mymaster 127.0.0.1 6379
5810:X 25 Jan 00:17:43.481 # +selected-slave slave 192.168.1.12:6379 192.168.1.12 6379 @ mymaster 127.0.0.1 6379
5810:X 25 Jan 00:17:43.481 * +failover-state-send-slaveof-noone slave 192.168.1.12:6379 192.168.1.12 6379 @ mymaster 127.0.0.1 6379
5810:X 25 Jan 00:17:43.572 * +failover-state-wait-promotion slave 192.168.1.12:6379 192.168.1.12 6379 @ mymaster 127.0.0.1 6379
5810:X 25 Jan 00:17:43.883 # +promoted-slave slave 192.168.1.12:6379 192.168.1.12 6379 @ mymaster 127.0.0.1 6379
5810:X 25 Jan 00:17:43.883 # +failover-state-reconf-slaves master mymaster 127.0.0.1 6379
5810:X 25 Jan 00:17:43.972 # +failover-end master mymaster 127.0.0.1 6379
5810:X 25 Jan 00:17:43.973 # +switch-master mymaster 127.0.0.1 6379 192.168.1.12 6379
5810:X 25 Jan 00:17:43.974 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 192.168.1.12 6379
檢視192.168.1.12（原來的slave）的資訊
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:0
master_repl_offset:0
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0
可以清楚的看到當master down掉以後，會將master自動切換到slave上，使slave成為新的master，到此就結束了，
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