redis演练(7)redisSentinel实现故障转移-创新互联

书接上文.

中仅仅配置了redis主从环境。分别配置了2个主从结构。

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分别是1.有向无环，2星型模型。配置起来非常简单。但是，遗留了一个尾巴，没有阐述。如果master宕掉了怎么办？redis如何实现fail-over故障转移？本文，就重点说一下这块。主要内容

手动实现fail-over效果
sentinel实现自动fail-over效果

手动实现fail-over效果

#有向无环模型（参照redis演练(6) redis主从模式搭建内容）
[root@hadoop2 redis]# ps -ef |grep redis
root      2495     1  2 20:06 ?        00:00:01 bin/redis-server *:6379
root      2503     1  1 20:06 ?        00:00:00 bin/redis-server *:6381
root      2508     1  1 20:06 ?        00:00:00 bin/redis-server *:6380

#Master(有一个从6380)
127.0.0.1:6379> info Replication
# Replication
role:master
connected_slaves:1
slave0:ip=127.0.0.1,port=6380,state=online,offset=99,lag=1
master_repl_offset:99
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:98


#Slave1 连接主6379
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:5
master_sync_in_progress:0
slave_repl_offset:197
slave_priority:100
slave_read_only:1
connected_slaves:1
slave0:ip=127.0.0.1,port=6381,state=online,offset=197,lag=0
master_repl_offset:197
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:196

#6380的从
127.0.0.1:6381> info Replication
# Replication
role:slave
master_host:127.0.0.1
master_port:6380
master_link_status:up
master_last_io_seconds_ago:6
master_sync_in_progress:0
slave_repl_offset:573
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

####################################
模拟6379 宕机
#####################################
[root@hadoop2 redis]# bin/redis-cli shutdown
[root@hadoop2 redis]# bin/redis-cli -p 6379 shutdown
Could not connect to Redis at 127.0.0.1:6379: Connection refused
#观察，发现master_link_status:down，表示主一定宕掉了
127.0.0.1:6380> info  Replication
# Replication
role:slave
master_host:127.0.0.1
master_port:6379
master_link_status:down
master_last_io_seconds_ago:-1
master_sync_in_progress:0
slave_repl_offset:1049
master_link_down_since_seconds:42
slave_priority:100
slave_read_only:1
connected_slaves:1
slave0:ip=127.0.0.1,port=6381,state=online,offset=1105,lag=0
master_repl_offset:1105
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:1104
#开始从主切换(6380 -->6379)
# 只需要简单执行下面两句命令，就将6380主切换为主
127.0.0.1:6380> slaveof no one
OK
127.0.0.1:6380> config set slave-read-only no
OK
127.0.0.1:6380> set title "sentinel"
OK
#连到从服务上，没有问题
127.0.0.1:6381> get title
"sentinel"

日志（6379）

2495:M 05 Sep 20:06:23.615 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
2495:M 05 Sep 20:06:23.615 # Server started, Redis version 3.2.3
2495:M 05 Sep 20:06:23.617 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
2495:M 05 Sep 20:06:24.815 * DB loaded from append only file: 1.199 seconds
2495:M 05 Sep 20:06:24.816 * The server is now ready to accept connections on port 6379
2495:M 05 Sep 20:06:24.816 - DB 0: 20019 keys (0 volatile) in 32768 slots HT.
2495:M 05 Sep 20:06:24.816 - 0 clients connected (0 slaves), 3764336 bytes in use
2495:M 05 Sep 20:06:29.841 - DB 0: 20019 keys (0 volatile) in 32768 slots HT.
2495:M 05 Sep 20:06:29.841 - 0 clients connected (0 slaves), 3764336 bytes in use
2495:M 05 Sep 20:06:34.867 - DB 0: 20019 keys (0 volatile) in 32768 slots HT.
2495:M 05 Sep 20:06:34.875 - 0 clients connected (0 slaves), 3764336 bytes in use
2495:M 05 Sep 20:06:39.919 - DB 0: 20019 keys (0 volatile) in 32768 slots HT.
2495:M 05 Sep 20:06:39.921 - 0 clients connected (0 slaves), 3764336 bytes in use
2495:M 05 Sep 20:06:44.971 - DB 0: 20019 keys (0 volatile) in 32768 slots HT.
2495:M 05 Sep 20:06:44.971 - 0 clients connected (0 slaves), 3764336 bytes in use
2495:M 05 Sep 20:06:50.022 - DB 0: 20019 keys (0 volatile) in 32768 slots HT.
2495:M 05 Sep 20:06:50.022 - 0 clients connected (0 slaves), 3764336 bytes in use
2495:M 05 Sep 20:06:55.134 - DB 0: 20019 keys (0 volatile) in 32768 slots HT.
2495:M 05 Sep 20:06:55.134 - 0 clients connected (0 slaves), 3764336 bytes in use
2495:M 05 Sep 20:06:58.775 - Accepted 127.0.0.1:44408
2495:M 05 Sep 20:06:58.775 * Slave 127.0.0.1:6380 asks for synchronization
2495:M 05 Sep 20:06:58.775 * Full resync requested by slave 127.0.0.1:6380
2495:M 05 Sep 20:06:58.775 * Starting BGSAVE for SYNC with target: disk
2495:M 05 Sep 20:06:58.776 * Background saving started by pid 2511
2511:C 05 Sep 20:06:58.868 * DB saved on disk
2511:C 05 Sep 20:06:58.870 * RDB: 0 MB of memory used by copy-on-write
2495:M 05 Sep 20:06:58.916 * Background saving terminated with success
2495:M 05 Sep 20:06:58.920 * Synchronization with slave 127.0.0.1:6380 succeeded

....

2495:M 05 Sep 20:19:19.471 # User requested shutdown...
2495:M 05 Sep 20:19:19.471 * Calling fsync() on the AOF file.
2495:M 05 Sep 20:19:19.471 * Removing the pid file.
2495:M 05 Sep 20:19:19.472 # Redis is now ready to exit, bye bye...

日志（6380）

2508:S 05 Sep 20:06:58.714 # Server started, Redis version 3.2.3
2508:S 05 Sep 20:06:58.714 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
2508:S 05 Sep 20:06:58.775 * DB loaded from disk: 0.060 seconds
2508:S 05 Sep 20:06:58.775 * The server is now ready to accept connections on port 6380
2508:S 05 Sep 20:06:58.775 * Connecting to MASTER 127.0.0.1:6379
2508:S 05 Sep 20:06:58.775 * MASTER <-> SLAVE sync started
2508:S 05 Sep 20:06:58.775 * Non blocking connect for SYNC fired the event.
2508:S 05 Sep 20:06:58.775 * Master replied to PING, replication can continue...
2508:S 05 Sep 20:06:58.775 * Partial resynchronization not possible (no cached master)
2508:S 05 Sep 20:06:58.802 * Full resync from master: 8d0d86237c36a8d6ace4eed9b5f6e5871b40da29:1
2508:S 05 Sep 20:06:58.917 * MASTER <-> SLAVE sync: receiving 489615 bytes from master
2508:S 05 Sep 20:06:58.922 * MASTER <-> SLAVE sync: Flushing old data
2508:S 05 Sep 20:06:58.938 * MASTER <-> SLAVE sync: Loading DB in memory
2508:S 05 Sep 20:06:58.969 * MASTER <-> SLAVE sync: Finished with success
2508:S 05 Sep 20:06:59.788 * Slave 127.0.0.1:6381 asks for synchronization
2508:S 05 Sep 20:06:59.788 * Full resync requested by slave 127.0.0.1:6381
2508:S 05 Sep 20:06:59.788 * Starting BGSAVE for SYNC with target: disk
2508:S 05 Sep 20:06:59.788 * Background saving started by pid 2512
2512:C 05 Sep 20:06:59.832 * DB saved on disk
2512:C 05 Sep 20:06:59.832 * RDB: 0 MB of memory used by copy-on-write
2508:S 05 Sep 20:06:59.896 * Background saving terminated with success
2508:S 05 Sep 20:06:59.899 * Synchronization with slave 127.0.0.1:6381 succeeded
2508:S 05 Sep 20:10:46.786 * 10000 changes in 60 seconds. Saving...
2508:S 05 Sep 20:10:46.786 * Background saving started by pid 2595
2595:C 05 Sep 20:10:46.800 * DB saved on disk
2595:C 05 Sep 20:10:46.801 * RDB: 0 MB of memory used by copy-on-write
2508:S 05 Sep 20:10:46.887 * Background saving terminated with success
2508:S 05 Sep 20:19:19.472 # Connection with master lost.
2508:S 05 Sep 20:19:19.472 * Caching the disconnected master state.
2508:S 05 Sep 20:19:19.594 * Connecting to MASTER 127.0.0.1:6379
2508:S 05 Sep 20:19:19.595 * MASTER <-> SLAVE sync started
2508:S 05 Sep 20:19:19.595 # Error condition on socket for SYNC: Connection refused
2508:S 05 Sep 20:19:20.619 * Connecting to MASTER 127.0.0.1:6379
2508:S 05 Sep 20:19:20.619 * MASTER <-> SLAVE sync started

...

2508:S 05 Sep 20:20:49.783 # Error condition on socket for SYNC: Connection refused
2508:M 05 Sep 20:20:50.283 * Discarding previously cached master state.
2508:M 05 Sep 20:20:50.283 * MASTER MODE enabled (user request from 'id=6 addr=127.0.0.1:54717 fd=8 name= age=696 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=slaveof')
2508:M 05 Sep 20:25:47.073 * 1 changes in 900 seconds. Saving...
2508:M 05 Sep 20:25:47.074 * Background saving started by pid 2722
2722:C 05 Sep 20:25:47.087 * DB saved on disk
2722:C 05 Sep 20:25:47.088 * RDB: 0 MB of memory used by copy-on-write
2508:M 05 Sep 20:25:47.176 * Background saving terminated with success
2508:M 05 Sep 20:40:48.064 * 1 changes in 900 seconds. Saving...
2508:M 05 Sep 20:40:48.064 * Background saving started by pid 2813
2813:C 05 Sep 20:40:48.075 * DB saved on disk
2813:C 05 Sep 20:40:48.075 * RDB: 0 MB of memory used by copy-on-write
2508:M 05 Sep 20:40:48.165 * Background saving terminated with success

6381日志

2503:S 05 Sep 20:06:54.667 * DB loaded from disk: 0.087 seconds
2503:S 05 Sep 20:06:54.667 * The server is now ready to accept connections on port 6381
2503:S 05 Sep 20:06:54.667 * Connecting to MASTER 127.0.0.1:6380
2503:S 05 Sep 20:06:54.667 * MASTER <-> SLAVE sync started
2503:S 05 Sep 20:06:54.667 # Error condition on socket for SYNC: Connection refused
2503:S 05 Sep 20:06:55.691 * Connecting to MASTER 127.0.0.1:6380
2503:S 05 Sep 20:06:55.692 * MASTER <-> SLAVE sync started
2503:S 05 Sep 20:06:55.692 # Error condition on socket for SYNC: Connection refused
2503:S 05 Sep 20:06:56.716 * Connecting to MASTER 127.0.0.1:6380
2503:S 05 Sep 20:06:56.717 * MASTER <-> SLAVE sync started
2503:S 05 Sep 20:06:56.717 # Error condition on socket for SYNC: Connection refused
2503:S 05 Sep 20:06:57.741 * Connecting to MASTER 127.0.0.1:6380
2503:S 05 Sep 20:06:57.742 * MASTER <-> SLAVE sync started
2503:S 05 Sep 20:06:57.742 # Error condition on socket for SYNC: Connection refused
2503:S 05 Sep 20:06:58.764 * Connecting to MASTER 127.0.0.1:6380
2503:S 05 Sep 20:06:58.764 * MASTER <-> SLAVE sync started
2503:S 05 Sep 20:06:58.764 * Non blocking connect for SYNC fired the event.
2503:S 05 Sep 20:06:58.775 * Master replied to PING, replication can continue...
2503:S 05 Sep 20:06:58.775 * Partial resynchronization not possible (no cached master)
2503:S 05 Sep 20:06:58.776 * Master does not support PSYNC or is in error state (reply: -ERR Can't SYNC while not connected with my master)
2503:S 05 Sep 20:06:58.776 * Retrying with SYNC...
2503:S 05 Sep 20:06:58.803 # MASTER aborted replication with an error: ERR Can't SYNC while not connected with my master
2503:S 05 Sep 20:06:59.786 * Connecting to MASTER 127.0.0.1:6380
2503:S 05 Sep 20:06:59.787 * MASTER <-> SLAVE sync started
2503:S 05 Sep 20:06:59.787 * Non blocking connect for SYNC fired the event.
2503:S 05 Sep 20:06:59.787 * Master replied to PING, replication can continue...
2503:S 05 Sep 20:06:59.787 * Partial resynchronization not possible (no cached master)
2503:S 05 Sep 20:06:59.788 * Full resync from master: e1bfca531c87795977333fca30c7a75eea64a1de:1
2503:S 05 Sep 20:06:59.897 * MASTER <-> SLAVE sync: receiving 489615 bytes from master
2503:S 05 Sep 20:06:59.900 * MASTER <-> SLAVE sync: Flushing old data
2503:S 05 Sep 20:06:59.917 * MASTER <-> SLAVE sync: Loading DB in memory
2503:S 05 Sep 20:06:59.969 * MASTER <-> SLAVE sync: Finished with success

2.sentinel实现fail-over自动切换

从源文件中复制sentinel.conf
cp /usr/local/src/redis-3.2.3/sentinel.conf  /usr/local/redis/
#修改确认如下参数
sentinel monitor mymaster 127.0.0.1 6379 1
sentinel down-after-milliseconds mymaster 5000
sentinel failover-timeout mymaster 180000
sentinel parallel-syncs mymaster 1

参照
http://www.redis.cn/topics/sentinel.html

 bin/redis-server redis.conf  
 bin/redis-server redis6380.conf  
 bin/redis-server redis6381.conf 
 bin/redis-server sentinel.conf  --sentinel

端口	标志
6379	Master
6380	Slave
6381	Slave

使用sentinel 监控(正常初始化状态，使用sentinel监控如下）

2.1 Master状态

127.0.0.1:26379> sentinel masters
1) 1) "name"
   2) "mymaster"
   3) "ip"
   4) "127.0.0.1"
   5) "port"
   6) "6379"
   7) "runid"
   8) "4d2b8e087e297f5d6347e1599a37c4998ad056d6"
   9) "flags"
  10) "master"
  11) "link-pending-commands"
  12) "0"
  13) "link-refcount"
  14) "1"
  15) "last-ping-sent"
  16) "0"
  17) "last-ok-ping-reply"
  18) "410"
  19) "last-ping-reply"
  20) "410"
  21) "down-after-milliseconds"
  22) "5000"
  23) "info-refresh"
  24) "7817"
  25) "role-reported"
  26) "master"
  27) "role-reported-time"
  28) "58045"
  29) "config-epoch"
  30) "0"
  31) "num-slaves"
  32) "2"
  33) "num-other-sentinels"
  34) "0"
  35) "quorum"
  36) "1"
  37) "failover-timeout"
  38) "180000"
  39) "parallel-syncs"
  40) "1"

可以知道Master的端口，备节点等信息。

2.2 查看初始的Slave信息

127.0.0.1:26379> sentinel slaves mymaster
1) 1) "name"
   2) "127.0.0.1:6380"
   3) "ip"
   4) "127.0.0.1"
   5) "port"
   6) "6380"
   7) "runid"
   8) "c344769d6d1cfd814437034b39f04b17851dca66"
   9) "flags"
  10) "slave"
  11) "link-pending-commands"
  12) "0"
  13) "link-refcount"
  14) "1"
  15) "last-ping-sent"
  16) "0"
  17) "last-ok-ping-reply"
  18) "693"
  19) "last-ping-reply"
  20) "693"
  21) "down-after-milliseconds"
  22) "5000"
  23) "info-refresh"
  24) "6445"
  25) "role-reported"
  26) "slave"
  27) "role-reported-time"
  28) "96788"
  29) "master-link-down-time"
  30) "0"
  31) "master-link-status"
  32) "ok"
  33) "master-host"
  34) "127.0.0.1"
  35) "master-port"
  36) "6379"
  37) "slave-priority"
  38) "100"
  39) "slave-repl-offset"
  40) "6058"
2) 1) "name"
   2) "127.0.0.1:6381"
   3) "ip"
   4) "127.0.0.1"
   5) "port"
   6) "6381"
   7) "runid"
   8) "9f8666ce6e7b30d01449f6fb10d8556030a96186"
   9) "flags"
  10) "slave"
  11) "link-pending-commands"
  12) "0"
  13) "link-refcount"
  14) "1"
  15) "last-ping-sent"
  16) "0"
  17) "last-ok-ping-reply"
  18) "693"
  19) "last-ping-reply"
  20) "693"
  21) "down-after-milliseconds"
  22) "5000"
  23) "info-refresh"
  24) "6444"
  25) "role-reported"
  26) "slave"
  27) "role-reported-time"
  28) "96788"
  29) "master-link-down-time"
  30) "0"
  31) "master-link-status"
  32) "ok"
  33) "master-host"
  34) "127.0.0.1"
  35) "master-port"
  36) "6379"
  37) "slave-priority"
  38) "100"
  39) "slave-repl-offset"
  40) "6058"

此时，sentinel日志风平浪静

2847:X 07 Sep 21:01:27.567 # Sentinel ID is 1b9d1d720b11ecf5568c3dc0194305e86c47ed9a
2847:X 07 Sep 21:01:27.567 # +monitor master mymaster 127.0.0.1 6379 quorum 1

2.3 模拟Master6379宕机）

127.0.0.1:6379> debug sleep 100
OK

2.4 sentinel自动进行failover切换

观看sentinel日志(sentinel具体工作详情)

2847:X 07 Sep 21:01:27.567 # +monitor master mymaster 127.0.0.1 6379 quorum 1
2847:X 07 Sep 21:03:49.117 # +sdown master mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:49.117 # +odown master mymaster 127.0.0.1 6379 #quorum 1/1
2847:X 07 Sep 21:03:49.117 # +new-epoch 4
2847:X 07 Sep 21:03:49.117 # +try-failover master mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:49.128 # +vote-for-leader 1b9d1d720b11ecf5568c3dc0194305e86c47ed9a 4
2847:X 07 Sep 21:03:49.129 # +elected-leader master mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:49.129 # +failover-state-select-slave master mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:49.185 # +selected-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:49.185 * +failover-state-send-slaveof-noone slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:49.252 * +failover-state-wait-promotion slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:50.262 # +promoted-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:50.262 # +failover-state-reconf-slaves master mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:50.315 * +slave-reconf-sent slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:51.308 * +slave-reconf-inprog slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:51.308 * +slave-reconf-done slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:51.365 # +failover-end master mymaster 127.0.0.1 6379
2847:X 07 Sep 21:03:51.365 # +switch-master mymaster 127.0.0.1 6379 127.0.0.1 6381
2847:X 07 Sep 21:03:51.365 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381
2847:X 07 Sep 21:03:51.365 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381
2847:X 07 Sep 21:03:56.399 # +sdown slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381
2847:X 07 Sep 21:05:23.708 # -sdown slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381
2847:X 07 Sep 21:05:33.730 * +convert-to-slave slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381

2.6 failover切换后监控信息

127.0.0.1:26379> sentinel masters
1) 1) "name"
   2) "mymaster"
   3) "ip"
   4) "127.0.0.1"
   5) "port"
   6) "6381" （这儿变成了6381）
   7) "runid"
   8) "9f8666ce6e7b30d01449f6fb10d8556030a96186"
   9) "flags"
  10) "master"
  11) "link-pending-commands"
  12) "0"
  13) "link-refcount"
  14) "1"
  15) "last-ping-sent"
  16) "0"
  17) "last-ok-ping-reply"
  18) "190"
  19) "last-ping-reply"
  20) "190"
  21) "down-after-milliseconds"
  22) "5000"
  23) "info-refresh"
  24) "1905"
  25) "role-reported"
  26) "master"
  27) "role-reported-time"
  28) "42128"
  29) "config-epoch"
  30) "4"
  31) "num-slaves"
  32) "2"
  33) "num-other-sentinels"
  34) "0"
  35) "quorum"
  36) "1"
  37) "failover-timeout"
  38) "180000"
  39) "parallel-syncs"
  40) "1"

备库信息

127.0.0.1:26379> sentinel slaves mymaster
1) 1) "name"
   2) "127.0.0.1:6379"
   3) "ip"
   4) "127.0.0.1"
   5) "port"
   6) "6379"
   7) "runid"
   8) ""
   9) "flags"
  10) "s_down,slave"（此时6379 还处在sleep状态，过了休眠时间会更新该状态）
  11) "link-pending-commands"
  12) "44"
  13) "link-refcount"
  14) "1"
  15) "last-ping-sent"
  16) "48488"
  17) "last-ok-ping-reply"
  18) "48488"
  19) "last-ping-reply"
  20) "48488"
  21) "s-down-time"
  22) "43454"
  23) "down-after-milliseconds"
  24) "5000"
  25) "info-refresh"
  26) "1473253479853"
  27) "role-reported"
  28) "slave"
  29) "role-reported-time"
  30) "48488"
  31) "master-link-down-time"
  32) "0"
  33) "master-link-status"
  34) "err"
  35) "master-host"
  36) "?"
  37) "master-port"
  38) "0"
  39) "slave-priority"
  40) "100"
  41) "slave-repl-offset"
  42) "0"
2) 1) "name"
   2) "127.0.0.1:6380"
   3) "ip"
   4) "127.0.0.1"
   5) "port"
   6) "6380"
   7) "runid"
   8) "c344769d6d1cfd814437034b39f04b17851dca66"
   9) "flags"
  10) "slave"
  11) "link-pending-commands"
  12) "0"
  13) "link-refcount"
  14) "1"
  15) "last-ping-sent"
  16) "0"
  17) "last-ok-ping-reply"
  18) "308"
  19) "last-ping-reply"
  20) "308"
  21) "down-after-milliseconds"
  22) "5000"
  23) "info-refresh"
  24) "8265"
  25) "role-reported"
  26) "slave"
  27) "role-reported-time"
  28) "48488"
  29) "master-link-down-time"
  30) "0"
  31) "master-link-status"
  32) "ok"
  33) "master-host"
  34) "127.0.0.1"
  35) "master-port"
  36) "6381"
  37) "slave-priority"
  38) "100"
  39) "slave-repl-offset"
  40) "11780"

127.0.0.1:26379> sentinel slaves mymaster
1) 1) "name"
   2) "127.0.0.1:6379"
   3) "ip"
   4) "127.0.0.1"
   5) "port"
   6) "6379"
   7) "runid"
   8) "4d2b8e087e297f5d6347e1599a37c4998ad056d6"
   9) "flags"
  10) "slave" s_down没有了
  11) "link-pending-commands"
  12) "0"
  13) "link-refcount"
  14) "1"
  15) "last-ping-sent"
  16) "0"
  17) "last-ok-ping-reply"
  18) "869"
  19) "last-ping-reply"
  20) "869"
  21) "down-after-milliseconds"
  22) "5000"
  23) "info-refresh"
  24) "3426"
  25) "role-reported"
  26) "slave"
  27) "role-reported-time"
  28) "3426"
  29) "master-link-down-time"
  30) "0"
  31) "master-link-status"
  32) "ok"
  33) "master-host"
  34) "127.0.0.1"
  35) "master-port"
  36) "6381"
  37) "slave-priority"
  38) "100"
  39) "slave-repl-offset"
  40) "16556"
...

手动切换failover

127.0.0.1:26379> SENTINEL failover mymaster
OK
#切换为6379
127.0.0.1:26379> SENTINEL get-master-addr-by-name mymaster
1) "127.0.0.1"
2) "6379"

2847:X 07 Sep 21:46:46.793 # +switch-master mymaster 127.0.0.1 6381 127.0.0.1 6379
2847:X 07 Sep 21:46:46.794 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6379
2847:X 07 Sep 21:46:46.794 * +slave slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6379
2847:X 07 Sep 21:46:56.910 * +convert-to-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6379

sentinel 发生failover，会更新对应主备库的redis.conf文件。
6379对应的配置文件，添加了slaveof参数
[root@hadoop2 redis]# cat redis.conf | grep slaveof
# Master-Slave replication. Use slaveof to make a Redis instance a copy of
# slaveof
slaveof 127.0.0.1 6381
6380对应的配置文件，修改了slaveof参数
[root@hadoop2 redis]# cat redis6380.conf | grep slaveof
# Master-Slave replication. Use slaveof to make a Redis instance a copy of
slaveof 127.0.0.1 6381

至此演练结束

3其他

3.1 重要的quorum参数。

演练设置quorum=1，纯粹为了简单，线上环境不能重要。

http://redis.io/topics/sentinel 中提供了讨论了4个场景，在以后慢慢演练讨论下。

复制sentinel.conf时，需要处理sentinel生成的信息如
sentinel myid 575cb680ff3d3cbad55cdb978c1d6b5962abe7ac
否则，sentinel之间通信存在问题

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