小編給大家分享一下Redis Sentinel安裝配置的示例分析，希望大家閱讀完這篇文章之后都有所收獲，下面讓我們一起去探討吧！
Redis Sentinel概述
我們知道Redis類似MySQL數(shù)據(jù)庫自帶主從復(fù)制結(jié)構(gòu)，產(chǎn)品環(huán)境中，如果一旦master發(fā)生crash,我們希望slave可以立即自動提升為主，接替業(yè)務(wù)提供服務(wù)，如何實現(xiàn)這個功能呢？redis sentinel集群可以幫助我們實現(xiàn)這個功能；
Redis Sentinel是Redis官方原生高可用解決方案，Redis Sentinel部署架構(gòu)主要包括兩部分：Redis Sentinel集群和Redis master-slave集群，其中Redis Sentinel集群是由若干Sentinel節(jié)點組成的分布式集群；
可以實現(xiàn)故障發(fā)現(xiàn)、故障轉(zhuǎn)移、配置中心和客戶端通知。Redis Sentinel的節(jié)點數(shù)量要滿足2n+1（n>=1）的奇數(shù)個(官方建議至少3個)。
Redis Sentinel特點
(1)master與slave之間的failover是通過sentinel來監(jiān)控，如果共有5個sentinel，配置參數(shù)中設(shè)置只要有2個sentinel認(rèn)為master crash了，就會進(jìn)行failover,但是進(jìn)行failover的那個sentinel必須先獲得至少3個sentinel的授權(quán)才能實行failover;
(2)sentinel集群不會同一時間多個sentinel并發(fā)執(zhí)行failover,如果第一個進(jìn)行failover的sentinel失敗了，另外一個將會在一定時間內(nèi)重新進(jìn)行failover,以此類推；
(3)當(dāng)failover后，sentinel會獲得master的最新的一個配置版本號，然后在廣播給其他sentinel,所以一個能夠互相通信的sentinel集群最終會采用版本號高且相同的配置；
(4)Redis Sentinel version1開始于Redis2.6, Redis Sentinel version 2 開始于Redis 2.8,建議使用Sentinel 2 ；
(5)Redis-Sentinel是Redis官方推薦的高可用性(HA) 解決方案，Redis-sentinel本身也是一個獨立運行的進(jìn)程，它能監(jiān)控多個master-slave集群，發(fā)現(xiàn)master宕機(jī)后能進(jìn)行自動切換。Sentinel可以監(jiān)視任意多個主服務(wù)器（復(fù)用），以及主服務(wù)器屬下的從服務(wù)器，并在被監(jiān)視的主服務(wù)器下線時，自動執(zhí)行故障轉(zhuǎn)移操作。
SDOWN和ODOWN
SDOWN(主觀宕機(jī))是sentinel自己主觀檢測到master的狀態(tài)是down；
ODOWN(客觀宕機(jī))需要大多數(shù)的sentinel都認(rèn)為master宕機(jī)；
從SDOWN切換到ODOWN不需要任何一致性算法，只需要一個gossip協(xié)議，如果一個sentinel收到了足夠多的sentinel發(fā)來消息告訴它某個master已經(jīng)down掉了，SDOWN狀態(tài)就會變成ODOWN狀態(tài)。如果之后master可用了，這個狀態(tài)就會相應(yīng)地被清理掉。
Sentinel.conf相關(guān)參數(shù)
port 26379
#sentinel的端口號
sentinel monitor mymaster 127.0.0.1 6379 2
#sentinel監(jiān)控的master名稱默認(rèn)是mymaster， 最后數(shù)字2表示如果有兩個sentinel認(rèn)為master掛了，則這個master即認(rèn)為不可用；
注意：我們可以通過配置不同的master名稱，讓一套Sentinel Cluster監(jiān)控多個Redis master-slave集群；
sentinel down-after-milliseconds mymaster 30000
# 默認(rèn)30秒，sentinel會通過ping來判斷master是否存活，如果在30秒內(nèi)master返回pong給sentinel,則認(rèn)為master是好的,否則sentinel認(rèn)為master不可用；
sentinel parallel-syncs mymaster 1
#當(dāng)Sentinel節(jié)點集合對主節(jié)點故障判定達(dá)成一致時，Sentinel領(lǐng)導(dǎo)者節(jié)點會做故障轉(zhuǎn)移操作，選出新的主節(jié)點，原來的從節(jié)點會向新的主節(jié)點發(fā)起復(fù)制操作，限制每次向新的主節(jié)點發(fā)起復(fù)制操作的從節(jié)點個數(shù)為1
sentinel failover-timeout mymaster 180000
# 故障轉(zhuǎn)移超時時間為3min
Redis Sentinel中的身份驗證
當(dāng)一個master配置為需要密碼才能連接時，客戶端和slave在連接時都需要提供密碼；
master通過requirepass設(shè)置自身的密碼，不提供密碼無法連接到這個master；
slave通過masterauth來設(shè)置訪問master時的密碼；
但是當(dāng)使用了sentinel時，由于一個master可能會變成一個slave，一個slave也可能會變成master，所以需要同時設(shè)置上述兩個配置項。
安裝Redis Sentinel
(1)Redis sentinel架構(gòu)圖和節(jié)點環(huán)境
| Roel | Host | IP | Port |
| Sentinel1 | sht-sgmhadoopnn-01 | 172.16.101.54 | 26379 |
| Sentinel2 | sht-sgmhadoopnn-01 | 172.16.101.55 | 26379 |
| Sentinel3 | sht-sgmhadoopnn-02 | 172.16.101.56 | 26379 |
| Master | sht-sgmhadoopdn-01 | 172.16.101.58 | 6379 |
| Slave1 | sht-sgmhadoopdn-02 | 172.16.101.59 | 6379 |
| Slave2 | sht-sgmhadoopdn-03 | 172.16.101.60 | 6379 |
(2)配置Redis主從復(fù)制
[root@sht-sgmhadoopdn-01 redis]# vim redis.conf bind 172.16.101.58 [root@sht-sgmhadoopdn-01 redis]# src/redis-server redis.conf [root@sht-sgmhadoopdn-02 redis]# vim redis.conf bind 172.16.101.59 slaveof 172.16.101.58 6379 [root@sht-sgmhadoopdn-02 redis]# src/redis-server redis.conf [root@sht-sgmhadoopdn-03 redis]# vim redis.conf bind 172.16.101.60 slaveof 172.16.101.58 6379 [root@sht-sgmhadoopdn-03 redis]# src/redis-server redis.conf檢查主從復(fù)制的設(shè)置
[root@sht-sgmhadoopdn-01 redis]# src/redis-cli -h 172.16.101.58 172.16.101.58:6379> client list id=3 addr=172.16.101.59:35718 fd=7 name= age=26 idle=0 flags=S db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=replconf id=4 addr=172.16.101.60:33986 fd=8 name= age=22 idle=0 flags=S db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=replconf id=5 addr=172.16.101.58:38875 fd=9 name= age=4 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=32768 obl=0 oll=0 omem=0 events=r cmd=client172.16.101.58:6379> info replication # Replication role:master connected_slaves:2 slave0:ip=172.16.101.59,port=6379,state=online,offset=57,lag=0 slave1:ip=172.16.101.60,port=6379,state=online,offset=57,lag=0 master_repl_offset:57 repl_backlog_active:1 repl_backlog_size:1048576 repl_backlog_first_byte_offset:2 repl_backlog_histlen:56(3)配置sentinel集群
三個sentinel節(jié)點的sentinel.conf文件配置一樣，如果是在同一個主機(jī)上，則需要使用不同的端口號
[root@sht-sgmhadoopcm-01 redis]# vim sentinel.conf port 26379 daemonize yes protected-mode no logfile "sentinel.log" dir /usr/local/redis sentinel monitor mymaster 172.16.101.58 6379 2 sentinel down-after-milliseconds mymaster 30000 sentinel parallel-syncs mymaster 1sentinel節(jié)點有兩種啟動方法：
src/redis-sentinel sentinel.conf src/redis-server sentinel.conf --sentinel [root@sht-sgmhadoopcm-01 redis]# src/redis-sentinel sentinel.conf [root@sht-sgmhadoopnn-01 redis]# src/redis-sentinel sentinel.conf [root@sht-sgmhadoopnn-02 redis]# src/redis-sentinel sentinel.conf [root@sht-sgmhadoopcm-01 redis]# ps -ef|grep redis|grep -v grep root 7541 1 0 22:33 ? 00:00:00 src/redis-sentinel *:26379 [sentinel](4)檢查整個集群的狀態(tài)
[root@sht-sgmhadoopcm-01 redis]# src/redis-cli -h 172.16.101.54 -p 26379 172.16.101.54:26379> client list id=3 addr=172.16.101.55:43182 fd=13 name=sentinel-ab45fe6c-cmd age=138 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=ping id=4 addr=172.16.101.56:60016 fd=15 name=sentinel-e32f20c0-cmd age=136 idle=1 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=ping id=5 addr=172.16.101.54:35342 fd=17 name= age=26 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=32768 obl=0 oll=0 omem=0 events=r cmd=client 172.16.101.54:26379> info sentinel # Sentinel sentinel_masters:1 sentinel_tilt:0 sentinel_running_scripts:0 sentinel_scripts_queue_length:0 sentinel_simulate_failure_flags:0 master0:name=mymaster,status=ok,address=172.16.101.58:6379,slaves=2,sentinels=3 [root@sht-sgmhadoopdn-01 redis]# src/redis-cli -h 172.16.101.58 -p 6379 172.16.101.58:6379> client list id=16 addr=172.16.101.54:56510 fd=10 name=sentinel-30393e76-pubsub age=326 idle=0 flags=N db=0 sub=1 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=subscribe id=17 addr=172.16.101.54:56508 fd=11 name=sentinel-30393e76-cmd age=326 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=ping id=18 addr=172.16.101.55:57444 fd=12 name=sentinel-ab45fe6c-cmd age=177 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=publish id=19 addr=172.16.101.55:57446 fd=13 name=sentinel-ab45fe6c-pubsub age=177 idle=0 flags=N db=0 sub=1 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=subscribe id=3 addr=172.16.101.59:35718 fd=7 name= age=3936 idle=0 flags=S db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=replconf id=4 addr=172.16.101.60:33986 fd=8 name= age=3932 idle=0 flags=S db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=32768 obl=0 oll=0 omem=0 events=r cmd=replconf id=20 addr=172.16.101.56:55648 fd=14 name=sentinel-e32f20c0-cmd age=173 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=ping id=21 addr=172.16.101.56:55650 fd=15 name=sentinel-e32f20c0-pubsub age=173 idle=0 flags=N db=0 sub=1 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=subscribe id=5 addr=172.16.101.58:38875 fd=9 name= age=3914 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=32768 obl=0 oll=0 omem=0 events=r cmd=client當(dāng)我們啟動主從節(jié)點和sentinel節(jié)點后，sentinel.conf配置文件會自動添加或修改參數(shù)
[root@sht-sgmhadoopcm-01 redis]# cat sentinel.conf sentinel myid 30393e76e002cb64db92fb8bcb88d79f2d85a82b sentinel config-epoch mymaster 0 sentinel leader-epoch mymaster 0 # Generated by CONFIG REWRITE sentinel known-slave mymaster 172.16.101.60 6379 sentinel known-slave mymaster 172.16.101.59 6379 sentinel known-sentinel mymaster 172.16.101.55 26379 ab45fe6c0f010473ce3b7b4d2120e1a83776b736 sentinel known-sentinel mymaster 172.16.101.56 26379 e32f20c0f315e712c9921371f15729246f3816a0 sentinel current-epoch 0 [root@sht-sgmhadoopnn-01 redis]# cat sentinel.conf sentinel myid ab45fe6c0f010473ce3b7b4d2120e1a83776b736 sentinel config-epoch mymaster 0 sentinel leader-epoch mymaster 0 # Generated by CONFIG REWRITE sentinel known-slave mymaster 172.16.101.60 6379 sentinel known-slave mymaster 172.16.101.59 6379 sentinel known-sentinel mymaster 172.16.101.56 26379 e32f20c0f315e712c9921371f15729246f3816a0 sentinel known-sentinel mymaster 172.16.101.54 26379 30393e76e002cb64db92fb8bcb88d79f2d85a82b sentinel current-epoch 0 [root@sht-sgmhadoopnn-02 redis]# cat sentinel.conf sentinel myid e32f20c0f315e712c9921371f15729246f3816a0 sentinel config-epoch mymaster 0 sentinel leader-epoch mymaster 0 # Generated by CONFIG REWRITE sentinel known-slave mymaster 172.16.101.60 6379 sentinel known-slave mymaster 172.16.101.59 6379 sentinel known-sentinel mymaster 172.16.101.54 26379 30393e76e002cb64db92fb8bcb88d79f2d85a82b sentinel known-sentinel mymaster 172.16.101.55 26379 ab45fe6c0f010473ce3b7b4d2120e1a83776b736 sentinel current-epoch 0測試自動failover
[root@sht-sgmhadoopdn-01 redis]# ps -ef|grep redis root 15128 1 0 21:17 ? 00:00:05 src/redis-server 172.16.101.58:6379 [root@sht-sgmhadoopdn-01 redis]# kill -9 15128 [root@sht-sgmhadoopcm-01 redis]# tail -f sentinel.log 7541:X 05 Aug 22:55:48.052 # +sdown master mymaster 172.16.101.58 6379 #sentinel主觀認(rèn)為master crash; 7541:X 05 Aug 22:55:48.143 # +odown master mymaster 172.16.101.58 6379 #quorum 2/2 #只要有兩個sentinel節(jié)點認(rèn)為master crash,則客觀認(rèn)為master crash 7541:X 05 Aug 22:55:48.143 # +new-epoch 1 7541:X 05 Aug 22:55:48.143 # +try-failover master mymaster 172.16.101.58 6379 7541:X 05 Aug 22:55:48.165 # +vote-for-leader 30393e76e002cb64db92fb8bcb88d79f2d85a82b 1 7541:X 05 Aug 22:55:48.166 # ab45fe6c0f010473ce3b7b4d2120e1a83776b736 voted for ab45fe6c0f010473ce3b7b4d2120e1a83776b736 1 7541:X 05 Aug 22:55:48.173 # e32f20c0f315e712c9921371f15729246f3816a0 voted for ab45fe6c0f010473ce3b7b4d2120e1a83776b736 1 7541:X 05 Aug 22:55:48.544 # +config-update-from sentinel ab45fe6c0f010473ce3b7b4d2120e1a83776b736 172.16.101.55 26379 @ mymaster 172.16.101.58 6379 7541:X 05 Aug 22:55:48.544 # +switch-master mymaster 172.16.101.58 6379 172.16.101.60 6379 7541:X 05 Aug 22:55:48.545 * +slave slave 172.16.101.59:6379 172.16.101.59 6379 @ mymaster 172.16.101.60 6379 7541:X 05 Aug 22:55:48.545 * +slave slave 172.16.101.58:6379 172.16.101.58 6379 @ mymaster 172.16.101.60 6379 #從這一步到下一步執(zhí)行failover成功之間需要等待30s，這是由于參數(shù)sentinel down-after-milliseconds mymaster控制，master 30s之內(nèi)沒有響應(yīng)sentinel才會真正的failover; 7541:X 05 Aug 22:56:18.562 # +sdown slave 172.16.101.58:6379 172.16.101.58 6379 @ mymaster 172.16.101.60 6379master和slave發(fā)生了變化，IP60成為新的master,IP58成為slave
[root@sht-sgmhadoopcm-01 redis]# src/redis-cli -h 172.16.101.54 -p 26379 172.16.101.54:26379> sentinel masters 1) 1) "name" 2) "mymaster" 3) "ip" 4) "172.16.101.60" ...... 172.16.101.54:26379> sentinel slaves mymaster 1) 1) "name" 2) "172.16.101.58:6379" 3) "ip" 4) "172.16.101.58" 9) "flags" 10) "s_down,slave,disconnected" 2) 1) "name" 2) "172.16.101.59:6379" 3) "ip" 4) "172.16.101.59" 9) "flags" 10) "slave"重啟修復(fù)好的舊master之后，會自動成為新master的從庫
[root@sht-sgmhadoopdn-01 redis]# src/redis-server redis.conf [root@sht-sgmhadoopcm-01 redis]# tail -f sentinel.log 7541:X 05 Aug 23:11:10.556 # -sdown slave 172.16.101.58:6379 172.16.101.58 6379 @ mymaster 172.16.101.60 6379 7541:X 05 Aug 23:11:20.518 * +convert-to-slave slave 172.16.101.58:6379 172.16.101.58 6379 @ mymaster 172.16.101.60 6379Failover過程分析：
Each Sentinel detects the master is down with an +sdown event.
This event is later escalated to +odown, which means that multiple Sentinels agree about the fact the master is not reachable.
Sentinels vote a Sentinel that will start the first failover attempt.
The failover happens.
sentinel節(jié)點會定期通過ping檢測redis的master是否存活，一旦master crash,
首先sentinel自己會主觀認(rèn)為master crash,然后三個sentinel之間彼此通信，只要有兩個sentinel節(jié)點認(rèn)為master crash,則客觀認(rèn)為master crash，
接著三個sentinel節(jié)點會投票，得到兩票的一個sentinel會去執(zhí)行failover,
最后master 30s之內(nèi)沒有響應(yīng)sentinel才會真正的failover;
一旦掛掉的舊master修復(fù)，重新啟動后，會作為新master的從庫存在；
FAQ
Error1:
[root@sht-sgmhadoopcm-01 redis]# src/redis-cli -h 172.16.101.54 -p 26379 172.16.101.54:26379> ping (error) DENIED Redis is running in protected mode because protected mode is enabled, no bind address was specified, no authentication password is requested to clients. In this mode connections are only accepted from the loopback interface. If you want to connect from external computers to Redis you may adopt one of the following solutions: 1) Just disable protected mode sending the command 'CONFIG SET protected-mode no' from the loopback interface by connecting to Redis from the same host the server is running, however MAKE SURE Redis is not publicly accessible from internet if you do so. Use CONFIG REWRITE to make this change permanent. 2) Alternatively you can just disable the protected mode by editing the Redis configuration file, and setting the protected mode option to 'no', and then restarting the server. 3) If you started the server manually just for testing, restart it with the '--protected-mode no' option. 4) Setup a bind address or an authentication password. NOTE: You only need to do one of the above things in order for the server to start accepting connections from the outside. 解決方法： [root@sht-sgmhadoopcm-01 redis]# vim sentinel.conf protected-mode no看完了這篇文章，相信你對“Redis Sentinel安裝配置的示例分析”有了一定的了解，如果想了解更多相關(guān)知識，歡迎關(guān)注創(chuàng)新互聯(lián)行業(yè)資訊頻道，感謝各位的閱讀！
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