redis容災(zāi)部署（哨兵Sentinel）
創(chuàng)新互聯(lián)專業(yè)IDC數(shù)據(jù)服務(wù)器托管提供商，專業(yè)提供成都服務(wù)器托管，服務(wù)器租用，成都服務(wù)器托管，成都服務(wù)器托管，成都多線服務(wù)器托管等服務(wù)器托管服務(wù)。
1、sentinel介紹
Redis Sentinel
Sentinel(哨兵)是用于監(jiān)控redis集群中Master狀態(tài)的工具，其已經(jīng)被集成在redis2.4+的版本中
2、Sentinel作用：
1)：Master狀態(tài)檢測
2)：如果Master異常，則會進行Master-Slave切換，將其中一個Slave作為Master，將之前的Master作為Slave
3)：Master-Slave切換后，master_redis.conf、slave_redis.conf和sentinel.conf的內(nèi)容都會發(fā)生改變，即master_redis.conf中會多一行slaveof的配置，sentinel.conf的監(jiān)控目標會隨之調(diào)換
3、Sentinel工作方式：
1)：每個Sentinel以每秒鐘一次的頻率向它所知的Master，Slave以及其他 Sentinel 實例發(fā)送一個 PING 命令
2)：如果一個實例（instance）距離最后一次有效回復 PING 命令的時間超過 down-after-milliseconds 選項所指定的值， 則這個實例會被 Sentinel 標記為主觀下線。
3)：如果一個Master被標記為主觀下線，則正在監(jiān)視這個Master的所有 Sentinel 要以每秒一次的頻率確認Master的確進入了主觀下線狀態(tài)。
4)：當有足夠數(shù)量的 Sentinel（大于等于配置文件指定的值）在指定的時間范圍內(nèi)確認Master的確進入了主觀下線狀態(tài)， 則Master會被標記為客觀下線
5)：在一般情況下， 每個 Sentinel 會以每 10 秒一次的頻率向它已知的所有Master，Slave發(fā)送 INFO 命令
6)：當Master被 Sentinel 標記為客觀下線時，Sentinel 向下線的 Master 的所有 Slave 發(fā)送 INFO 命令的頻率會從 10 秒一次改為每秒一次
7)：若沒有足夠數(shù)量的 Sentinel 同意 Master 已經(jīng)下線， Master 的客觀下線狀態(tài)就會被移除。
若 Master 重新向 Sentinel 的 PING 命令返回有效回復， Master 的主觀下線狀態(tài)就會被移除。
4、主觀下線和客觀下線
主觀下線：Subjectively Down，簡稱 SDOWN，指的是當前 Sentinel 實例對某個redis服務(wù)器做出的下線判斷。
客觀下線：Objectively Down， 簡稱 ODOWN，指的是多個 Sentinel 實例在對Master Server做出 SDOWN 判斷，并且通過 SENTINEL is-master-down-by-addr 命令互相交流之后，得出的Master Server下線判斷，然后開啟failover.
通俗來講就是：
redis的sentinel系統(tǒng)用來管理多個redis服務(wù)器，可以實現(xiàn)一個功能上實現(xiàn)HA的集群。該系統(tǒng)主要執(zhí)行三個任務(wù)：
1、監(jiān)控（ Monitoring ）： Redis Sentinel實時監(jiān)控主服務(wù)器和從服務(wù)器運行狀態(tài)。
2、提醒（notification）： 當被監(jiān)控的某個 Redis 服務(wù)器出現(xiàn)問題時， Redis Sentinel 可以向系統(tǒng)管理員發(fā)送通知， 也可以通過 API 向其他程序發(fā)送通知
3. 故障遷移（failover發(fā)）：自動主從切換
4. 統(tǒng)一的配置管理：連接者詢問sentinel取得主從的地址
5、Raft分布式算法
1. 主要用途：用于分布式系統(tǒng)，系統(tǒng)容錯，以及選出領(lǐng)頭羊
2. 作者：Diego Ongaro，畢業(yè)于哈佛
3. 目前用到這個算法的項目有：
a. CoreOS : 見下面
b. ectd : a distributed, consistent shared configuration
c. LogCabin : 分布式存儲系統(tǒng)
d. redis sentinel : redis 的監(jiān)控系統(tǒng)
Sentinel使用的Raft算法核心: 原則
1. 所有sentinel都有選舉的領(lǐng)頭羊的權(quán)利
2. 每個sentinel都會要求其他sentinel選舉自己為領(lǐng)頭羊(主要由發(fā)現(xiàn)redis客觀下線的sentinel先發(fā)起選舉)
3. 每個sentinel只有一次選舉的機會
4. 采用先到先得的原則
5. 一旦加入到系統(tǒng)了，則不會自動清除(這一點很重要, why?)
6. 每個sentinel都有唯一的uid，不會因為重啟而變更
7. 達到領(lǐng)頭羊的條件是 N/2 + 1個sentinel選擇了自己
8. 采用配置紀元，如果一次選舉出現(xiàn)腦裂，則配置紀元會遞增，進入下一次選舉，所有sentinel都會處于統(tǒng)一配置紀元，以最新的為標準。
Raft算法核心: 可視圖
Raft Visualization (算法演示)
Raft分布式算法的應(yīng)用
coreos:云計算新星 Docker 正在以火箭般的速度發(fā)展，與它相關(guān)的生態(tài)圈也漸入佳境，CoreOS 就是其中之一。CoreOS 是一個全新的、面向數(shù)據(jù)中心設(shè)計的 Linux 操作系統(tǒng)，在2014年7月發(fā)布了首個穩(wěn)定版本，目前已經(jīng)完成了800萬美元的A輪融資。
一個簡單的主從結(jié)構(gòu)加sentinel集群的架構(gòu)圖如下：
192.168.110.134（master redis，sentinel）----------->192.168.110.135（slave redis，sentinel）
| \ / |
| \ / |
| \ / |
| \ / |
| \ / |
| \ |
| \ |
| / \ |
| / \ |
| / \ |
| / \ |
192.168.110.132(sentinel)----------->192.168.110.133(slave redis，sentinel)
上圖是一主一從節(jié)點，加上兩個部署了sentinel的集群，sentinel集群之間會互相通信，溝通交流redis節(jié)點的狀態(tài)，做出相應(yīng)的判斷并進行處理，這里的主觀下線狀態(tài)和客觀下線狀態(tài)是比較重要的狀態(tài)，它們決定了是否進行故障轉(zhuǎn)移。
可以 通過訂閱指定的頻道信息，當服務(wù)器出現(xiàn)故障得時候通知管理員 客戶端可以將 Sentinel 看作是一個只提供了訂閱功能的 Redis 服務(wù)
器，你不可以使用 PUBLISH 命令向這個服務(wù)器發(fā)送信息，但你可以用 SUBSCRIBE 命令或者 PSUBSCRIBE 命令， 通過訂閱給定的頻道來獲取
相應(yīng)的事件提醒。
6、配置哨兵
1）、配置一個哨兵Sentinel的模式：
把源碼中的sentinel.conf配置文件拷貝到指定目錄
[root@web1 ~]# mkdir /usr/local/sentinel
[root@web1 ~]# cd /usr/local/src/redis-3.2.6/
[root@web1 redis-3.2.6]# cp sentinel.conf /usr/local/sentinel/
[root@web1 redis-3.2.6]# cd /usr/local/sentinel/
[root@web1 sentinel]# vim sentinel.conf
[root@web1 sentinel]# grep -v "^#" sentinel.conf |grep -v "^$"
port 26379
dir /tmp
sentinel monitor mymaster 192.168.110.134 6379 1
sentinel down-after-milliseconds mymaster 30000
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 180000
例子：
#sentinel端口
port 26380
#工作路徑
dir "/usr/local/redis-6380"
# 守護進程模式
daemonize yes
# 指明日志文件名
logfile "./sentinel.log"
#哨兵監(jiān)控的master，主從配置一樣，在進行主從切換時6379會變成當前的master端口，
sentinel monitor mymaster 192.168.137.40 6379 1
# master或slave多長時間（默認30秒）不能使用后標記為s_down狀態(tài)。
sentinel down-after-milliseconds mymaster 5000
#若sentinel在該配置值內(nèi)未能完成failover操作（即故障時master/slave自動切換），則認為本次failover失敗。
sentinel failover-timeout mymaster 18000
#設(shè)置master和slaves驗證密碼
sentinel auth-pass mymaster 123456
#哨兵程序自動添加的部分
# Generated by CONFIG REWRITE
sentinel config-epoch mymaster 0
sentinel leader-epoch mymaster 1
###指明了當前群集的從庫的ip和端口，在主從切換時該值會改變
sentinel known-slave mymaster 192.168.137.40 6380
###除了當前的哨兵還有哪些監(jiān)控的哨兵
sentinel known-sentinel mymaster 192.168.137.40 26379 7a88891a6147e202a53601ca16a3d438e9d55c9d
sentinel current-epoch 1
主要是這一項：
sentinel monitor mymaster 192.168.110.134 6379 2
my mymaster 后跟的是master的ip和端口
最后一個’2’代表我要啟動只要有2個sentinel認為master下線，就認為該master客觀下線，啟動failover并選舉產(chǎn)生新的master。
通常最后一個參數(shù)不能多于啟動的sentinel實例數(shù)。
[root@web2 ~]# mkdir /usr/local/sentinel
[root@web2 ~]# cp /usr/local/src/redis-3.2.6/sentinel.conf /usr/local/sentinel/
[root@web2 ~]# cd /usr/local/sentinel/
[root@web2 sentinel]# vim sentinel.conf
[root@web2 sentinel]# grep -v "^#" sentinel.conf |grep -v "^$"
port 26379
dir /tmp
sentinel monitor mymaster 192.168.110.134 6379 2
sentinel down-after-milliseconds mymaster 30000
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 180000
以后臺啟動模式啟動兩個sentinel（哨兵）:
[root@web1 sentinel]# redis-sentinel /usr/local/sentinel/sentinel.conf &
[1] 18378
[root@web1 sentinel]# 18378:X 16 Dec 15:46:16.732 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 3.2.6 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in sentinel mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 26379
| `-._ `._ / _.-' | PID: 18378
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
18378:X 16 Dec 15:46:16.734 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
18378:X 16 Dec 15:46:16.734 # Sentinel ID is 28c5f96738e4fe3335088d037a85ef47dfe9ab8f
18378:X 16 Dec 15:46:16.734 # +monitor master mymaster 192.168.110.134 6379 quorum 1
由上圖可以看到：
1、 哨兵已經(jīng)啟動，它的id為236f14b361fc5a0dc0621cf88823ed6e6252b2f3
2、 為master數(shù)據(jù)庫添加了一個監(jiān)控
3、 發(fā)現(xiàn)了2個slave（由此可以看出，哨兵無需配置slave，只需要指定master，哨兵會自動發(fā)現(xiàn)slave）
[root@web1 sentinel]# ps aux|grep redis
root 18357 0.1 1.0 135572 2440 ? Ssl 15:40 0:00 redis-server *:6379
root 18378 0.1 1.0 133528 2572 pts/1 Sl 15:46 0:00 redis-sentinel *:26379 [sentinel]
root 18400 0.0 0.3 103244 864 pts/1 S+ 15:51 0:00 grep redis
6、從Redis宕機測試
把其中一個從redis 的進程 kill掉：
[[root@web1 sentinel]# kill 18357
[root@web1 sentinel]# ps aux|grep redis
root 18378 0.1 1.0 133528 2572 pts/1 Sl 15:46 0:01 redis-sentinel *:26379 [sentinel]
root 18444 0.0 0.3 103244 864 pts/1 S+ 16:00 0:00 grep redis
30秒后哨兵的控制臺輸出：
[root@web1 sentinel]# 18378:X 16 Dec 16:01:16.452 # +sdown master mymaster 192.168.110.134 6379
18378:X 16 Dec 16:01:16.452 # +odown master mymaster 192.168.110.134 6379 #quorum 1/1
18378:X 16 Dec 16:01:16.452 # +new-epoch 9
18378:X 16 Dec 16:01:16.452 # +try-failover master mymaster 192.168.110.134 6379
18378:X 16 Dec 16:01:16.470 # +vote-for-leader 28c5f96738e4fe3335088d037a85ef47dfe9ab8f 9
18378:X 16 Dec 16:01:16.470 # +elected-leader master mymaster 192.168.110.134 6379
18378:X 16 Dec 16:01:16.470 # +failover-state-select-slave master mymaster 192.168.110.134 6379
18378:X 16 Dec 16:01:16.546 # +selected-slave slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
18378:X 16 Dec 16:01:16.546 * +failover-state-send-slaveof-noone slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
18378:X 16 Dec 16:01:16.605 * +failover-state-wait-promotion slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
18378:X 16 Dec 16:01:16.699 # +promoted-slave slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
18378:X 16 Dec 16:01:16.699 # +failover-state-reconf-slaves master mymaster 192.168.110.134 6379
18378:X 16 Dec 16:01:16.759 # +failover-end master mymaster 192.168.110.134 6379
18378:X 16 Dec 16:01:16.759 # +switch-master mymaster 192.168.110.134 6379 192.168.110.135 6379
18378:X 16 Dec 16:01:16.760 * +slave slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
18378:X 16 Dec 16:01:46.858 # +sdown slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
30秒后哨兵的控制臺輸出：
18378:X 16 Dec 16:01:16.759 # +switch-master mymaster 192.168.110.134 6379 192.168.110.135 6379
18378:X 16 Dec 16:01:16.760 * +slave slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
18378:X 16 Dec 16:01:46.858 # +sdown slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
說明已經(jīng)監(jiān)控到剛才我人kill掉的master宕機了
可以看出，slave重新已經(jīng)轉(zhuǎn)換成立主庫 -sdown：說明是恢復服務(wù)。
[root@web2 sentinel]# redis-cli
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
127.0.0.1:6379>
把192.168.110.134恢復：
[root@web1 sentinel]# redis-server /usr/local/redis/etc/redis.conf
[root@web1 sentinel]# 18378:X 16 Dec 16:06:59.825 # -sdown slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
18378:X 16 Dec 16:07:09.806 * +convert-to-slave slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
[root@web1 sentinel]#
[root@web1 sentinel]#
[root@web1 sentinel]# ps aux|grep redis
root 18378 0.2 1.0 133528 2636 pts/1 Sl 15:46 0:02 redis-sentinel *:26379 [sentinel]
root 18487 0.1 1.0 135572 2564 ? Ssl 16:06 0:00 redis-server *:6379
root 18491 0.0 0.3 103244 864 pts/1 S+ 16:08 0:00 grep redis
192.168.110.134是作為從庫加入到復制中的（主庫不會切換過來）：
測試下：
[root@web2 sentinel]# redis-cli
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=192.168.110.134,port=6379,state=online,offset=2835,lag=1
master_repl_offset:2835
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:2834
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=192.168.110.134,port=6379,state=online,offset=9687,lag=0
master_repl_offset:9832
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:9831
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=192.168.110.134,port=6379,state=online,offset=36450,lag=0
master_repl_offset:36595
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:36594
127.0.0.1:6379> set name2 lisi
OK
127.0.0.1:6379> set age2 22
OK
127.0.0.1:6379> get name2
"lisi"
127.0.0.1:6379> get age2
"22"
127.0.0.1:6379>
[root@web1 sentinel]# redis-cli
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:192.168.110.135
master_port:6379
master_link_status:up
master_last_io_seconds_ago:0
master_sync_in_progress:0
slave_repl_offset:73863
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
127.0.0.1:6379> get name2
"lisi"
127.0.0.1:6379> get set2
(nil)
127.0.0.1:6379> get age2
"22"
127.0.0.1:6379>
效果不錯：
把主庫切換回192.168.110.134
[root@web2 sentinel]# ps aux|grep redis
root 7063 0.1 1.2 135572 3116 ? Ssl 14:35 0:13 redis-server *:6379
root 7649 0.0 0.3 103244 864 pts/1 S+ 16:48 0:00 grep redis
[root@web2 sentinel]# kill 7063
[root@web1 sentinel]# 18522:X 16 Dec 16:49:05.725 # +sdown master mymaster 192.168.110.135 6379
18522:X 16 Dec 16:49:05.725 # +odown master mymaster 192.168.110.135 6379 #quorum 1/1
18522:X 16 Dec 16:49:05.725 # +new-epoch 10
18522:X 16 Dec 16:49:05.725 # +try-failover master mymaster 192.168.110.135 6379
18522:X 16 Dec 16:49:05.736 # +vote-for-leader 28c5f96738e4fe3335088d037a85ef47dfe9ab8f 10
18522:X 16 Dec 16:49:05.736 # +elected-leader master mymaster 192.168.110.135 6379
18522:X 16 Dec 16:49:05.736 # +failover-state-select-slave master mymaster 192.168.110.135 6379
18522:X 16 Dec 16:49:05.791 # +selected-slave slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
18522:X 16 Dec 16:49:05.791 * +failover-state-send-slaveof-noone slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
18522:X 16 Dec 16:49:05.875 * +failover-state-wait-promotion slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
18522:X 16 Dec 16:49:06.233 # +promoted-slave slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
18522:X 16 Dec 16:49:06.233 # +failover-state-reconf-slaves master mymaster 192.168.110.135 6379
18522:X 16 Dec 16:49:06.331 # +failover-end master mymaster 192.168.110.135 6379
18522:X 16 Dec 16:49:06.331 # +switch-master mymaster 192.168.110.135 6379 192.168.110.134 6379
18522:X 16 Dec 16:49:06.331 * +slave slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
18522:X 16 Dec 16:49:36.394 # +sdown slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
切換成功
[root@web1 sentinel]# redis-cli
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
127.0.0.1:6379>
恢復192.168.110.135的redis：
[root@web2 sentinel]# redis-server /etc/redis.conf
127.0.0.1:6379> 18522:X 16 Dec 16:52:32.351 # -sdown slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
18522:X 16 Dec 16:52:42.305 * +convert-to-slave slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
127.0.0.1:6379>
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=192.168.110.135,port=6379,state=online,offset=13653,lag=1
master_repl_offset:13667
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:13666
127.0.0.1:6379>
1
[root@web2 sentinel]# redis-cli
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:192.168.110.134
master_port:6379
master_link_status:up
master_last_io_seconds_ago:2
master_sync_in_progress:0
slave_repl_offset:16502
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
127.0.0.1:6379>
2）、配置兩個哨兵Sentinel的模式：
[root@web1 sentinel]# grep -v "^$" /usr/local/sentinel/sentinel.conf |grep -v "^#"
port 26379
dir "/tmp"
sentinel myid 28c5f96738e4fe3335088d037a85ef47dfe9ab8f
sentinel monitor mymaster 192.168.110.134 6379 2
sentinel config-epoch mymaster 10
sentinel leader-epoch mymaster 10
sentinel known-slave mymaster 192.168.110.135 6379
sentinel known-sentinel mymaster 192.168.110.135 26379 16286f52de2675345d1b11bc8946adc5d3f0c360
sentinel current-epoch 10
[root@web2 sentinel]# grep -v "^$" /usr/local/sentinel/sentinel.conf |grep -v "^#"
port 26379
dir "/tmp"
sentinel myid 16286f52de2675345d1b11bc8946adc5d3f0c360
sentinel monitor mymaster 192.168.110.134 6379 2
sentinel config-epoch mymaster 0
sentinel leader-epoch mymaster 6
sentinel known-slave mymaster 192.168.110.135 6379
sentinel known-sentinel mymaster 192.168.110.134 26379 28c5f96738e4fe3335088d037a85ef47dfe9ab8f
sentinel current-epoch 10
主要是這一項：
sentinel monitor mymaster 192.168.110.134 6379 2
最后一個’2’代表我要啟動只要有2個sentinel認為master下線，就認為該master客觀下線，啟動failover并選舉產(chǎn)生新的master。
通常最后一個參數(shù)不能多于啟動的sentinel實例數(shù)。
[root@web1 sentinel]# redis-sentinel /usr/local/sentinel/sentinel.conf &
[1] 18747
[root@web1 sentinel]# 18747:X 16 Dec 17:04:30.597 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 3.2.6 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in sentinel mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 26379
| `-._ `._ / _.-' | PID: 18747
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
18747:X 16 Dec 17:04:30.599 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
18747:X 16 Dec 17:04:30.599 # Sentinel ID is 28c5f96738e4fe3335088d037a85ef47dfe9ab8f
18747:X 16 Dec 17:04:30.599 # +monitor master mymaster 192.168.110.134 6379 quorum 2
18747:X 16 Dec 17:05:00.659 # +sdown sentinel 16286f52de2675345d1b11bc8946adc5d3f0c360 192.168.110.135 26379 @ mymaster 192.168.110.134 6379
[root@web2 sentinel]# redis-sentinel /usr/local/sentinel/sentinel.conf &
[1] 7726
You have new mail in /var/spool/mail/root
[root@web2 sentinel]# 7726:X 16 Dec 17:04:33.835 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 3.2.6 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in sentinel mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 26379
| `-._ `._ / _.-' | PID: 7726
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
7726:X 16 Dec 17:04:33.836 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
7726:X 16 Dec 17:04:33.836 # Sentinel ID is 16286f52de2675345d1b11bc8946adc5d3f0c360
7726:X 16 Dec 17:04:33.836 # +monitor master mymaster 192.168.110.134 6379 quorum 2
7726:X 16 Dec 17:04:34.668 # +new-epoch 10
7726:X 16 Dec 17:05:03.836 # +sdown sentinel 28c5f96738e4fe3335088d037a85ef47dfe9ab8f 192.168.110.134 26379 @ mymaster 192.168.110.134 6379
上面是有問題的：原因是bind 默認是僅僅監(jiān)控本機和 192.168.1.1這兩個IP地址
# bind 127.0.0.1 192.168.1.1
添加： bind 0.0.0.0
就沒問題了
配置文件：
[root@web1 ~]# grep -v "^$" /usr/local/sentinel/sentinel.conf |grep -v "^#"
bind 0.0.0.0
port 26379
dir "/tmp"
sentinel myid 28c5f96738e4fe3335088d037a85ef47dfe9ab8f
sentinel monitor mymaster 192.168.110.135 6379 2
sentinel config-epoch mymaster 14
sentinel leader-epoch mymaster 14
sentinel known-slave mymaster 192.168.110.134 6379
sentinel known-sentinel mymaster 192.168.110.135 26379 16286f52de2675345d1b11bc8946adc5d3f0c360
sentinel current-epoch 14
主要是下面兩項：
bind 0.0.0.0
sentinel monitor mymaster 192.168.110.135 6379 2
如果設(shè)置了密碼則添加下面一項：
# sentinel auth-pass
sentinel auth-pass def_master 012_345^678-90
[root@web1 ~]# redis-sentinel /usr/local/sentinel/sentinel.conf &
[1] 1963
[root@web1 ~]# 1963:X 19 Dec 11:55:29.670 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 3.2.6 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in sentinel mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 26379
| `-._ `._ / _.-' | PID: 1963
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
1963:X 19 Dec 11:55:29.671 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
1963:X 19 Dec 11:55:29.671 # Sentinel ID is 28c5f96738e4fe3335088d037a85ef47dfe9ab8f
1963:X 19 Dec 11:55:29.672 # +monitor master mymaster 192.168.110.134 6379 quorum 2
上面表示啟動沒問題的：
kill掉一個從redis，觀察sentinel控制臺輸出信息：
[root@web1 ~]# kill 1912
[root@web1 ~]# ps aux|grep redis
root 1963 0.2 1.0 133528 2588 pts/0 Sl 11:55 0:00 redis-sentinel 0.0.0.0:26379 [sentinel]
root 1992 0.0 0.3 103244 864 pts/0 S+ 11:58 0:00 grep redis
[root@web1 ~]# 1963:X 19 Dec 11:59:06.906 # +sdown master mymaster 192.168.110.134 6379
1963:X 19 Dec 11:59:06.963 # +odown master mymaster 192.168.110.134 6379 #quorum 2/2
1963:X 19 Dec 11:59:06.963 # +new-epoch 14
1963:X 19 Dec 11:59:06.963 # +try-failover master mymaster 192.168.110.134 6379
1963:X 19 Dec 11:59:06.972 # +vote-for-leader 28c5f96738e4fe3335088d037a85ef47dfe9ab8f 14
1963:X 19 Dec 11:59:06.992 # 16286f52de2675345d1b11bc8946adc5d3f0c360 voted for 28c5f96738e4fe3335088d037a85ef47dfe9ab8f 14
1963:X 19 Dec 11:59:07.035 # +elected-leader master mymaster 192.168.110.134 6379
1963:X 19 Dec 11:59:07.035 # +failover-state-select-slave master mymaster 192.168.110.134 6379
1963:X 19 Dec 11:59:07.136 # +selected-slave slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
1963:X 19 Dec 11:59:07.136 * +failover-state-send-slaveof-noone slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
1963:X 19 Dec 11:59:07.199 * +failover-state-wait-promotion slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
1963:X 19 Dec 11:59:08.171 # +promoted-slave slave 192.168.110.135:6379 192.168.110.135 6379 @ mymaster 192.168.110.134 6379
1963:X 19 Dec 11:59:08.171 # +failover-state-reconf-slaves master mymaster 192.168.110.134 6379
1963:X 19 Dec 11:59:08.260 # +failover-end master mymaster 192.168.110.134 6379
1963:X 19 Dec 11:59:08.260 # +switch-master mymaster 192.168.110.134 6379 192.168.110.135 6379
1963:X 19 Dec 11:59:08.260 * +slave slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
1963:X 19 Dec 11:59:38.290 # +sdown slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
另一臺：
[root@web2 ~]# redis-sentinel /usr/local/sentinel/sentinel.conf &
[1] 1809
[root@web2 ~]# 1809:X 19 Dec 11:55:35.698 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 3.2.6 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in sentinel mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 26379
| `-._ `._ / _.-' | PID: 1809
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
1809:X 19 Dec 11:55:35.700 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
1809:X 19 Dec 11:55:35.700 # Sentinel ID is 16286f52de2675345d1b11bc8946adc5d3f0c360
1809:X 19 Dec 11:55:35.700 # +monitor master mymaster 192.168.110.134 6379 quorum 2
1809:X 19 Dec 11:59:06.895 # +sdown master mymaster 192.168.110.134 6379
1809:X 19 Dec 11:59:06.999 # +new-epoch 14
1809:X 19 Dec 11:59:07.001 # +vote-for-leader 28c5f96738e4fe3335088d037a85ef47dfe9ab8f 14
1809:X 19 Dec 11:59:08.020 # +odown master mymaster 192.168.110.134 6379 #quorum 2/2
1809:X 19 Dec 11:59:08.020 # Next failover delay: I will not start a failover before Mon Dec 19 12:05:07 2016
1809:X 19 Dec 11:59:08.284 # +config-update-from sentinel 28c5f96738e4fe3335088d037a85ef47dfe9ab8f 192.168.110.134 26379 @ mymaster 192.168.110.134 6379
1809:X 19 Dec 11:59:08.284 # +switch-master mymaster 192.168.110.134 6379 192.168.110.135 6379
1809:X 19 Dec 11:59:08.284 * +slave slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
1809:X 19 Dec 11:59:38.344 # +sdown slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
[root@web2 ~]# redis-cli
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
127.0.0.1:6379>
恢復192.168.110.134：
[root@web1 ~]# redis-server /usr/local/redis/etc/redis.conf
[root@web1 ~]# 1963:X 19 Dec 12:14:24.393 # -sdown slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
[root@web1 ~]# redis-cli
127.0.0.1:6379> info replication
# Replication
role:slave
master_host:192.168.110.135
master_port:6379
master_link_status:up
master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_repl_offset:38769
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
127.0.0.1:6379>
135上的顯示：
repl_backlog_histlen:0
127.0.0.1:6379> 1809:X 19 Dec 12:14:24.105 # -sdown slave 192.168.110.134:6379 192.168.110.134 6379 @ mymaster 192.168.110.135 6379
127.0.0.1:6379>
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=192.168.110.134,port=6379,state=online,offset=2404,lag=1
master_repl_offset:2404
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:2403
也是僅僅作為從。
2）、配置三個哨兵Sentinel的模式：
[root@web2 ~]# scp redis-3.2.6.tar.gz 192.168.110.133:/root
The authenticity of host '192.168.110.133 (192.168.110.133)' can't be established.
RSA key fingerprint is 60:6c:0d:f4:3b:f8:42:b1:c9:7e:ab:c4:bc:83:d1:09.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.110.133' (RSA) to the list of known hosts.
root@192.168.110.133's password:
redis-3.2.6.tar.gz 100% 1509KB 1.5MB/s 00:00
[root@node2 ~]# iptables -I INPUT 6 -m state --state NEW -p tcp --dport 6379 -j ACCEPT
[root@node2 ~]# iptables -I INPUT 7 -m state --state NEW -p tcp --dport 26379 -j ACCEPT
[root@node2 ~]# tar -zxvf redis-3.2.6.tar.gz -C /usr/local/src/
[root@node2 ~]# cd /usr/local/src/redis-3.2.6/
[root@node2 redis-3.2.6]# make
[root@node2 redis-3.2.6]# make install
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