是什么 ：
也就是我們所說的主從復制，主機數據更新后根據配置和策略，自動同步到備機的master/slaver機制，Master以寫為主，Slave以讀為主
能干嘛：
讀寫分離，容災恢復
怎么玩：
1.配從(庫)不配主(庫)
2.從庫配置：slaveof 主庫IP 主庫端口
每次與master斷開之后，都需要重新連接，除非你配置進redis.conf文件
Info replication
3.修改配置文件細節操作
拷貝多個redis.conf文件
開啟daemonize yes
Pid文件名字
指定端口
Log文件名字
Dump.rdb名字
4.常用3招：
一主二仆
薪火相傳
反客為主
在同一台機器的不同端口演示，類似於多台機器
拷貝多份配置文件
[root@node1 myredis]# cp redis.conf redis6379.conf
[root@node1 myredis]# cp redis.conf redis6380.conf
[root@node1 myredis]# cp redis.conf redis6381.conf
[root@node1 myredis]#
分別修改對應的配置文件
[root@node1 myredis]# vim redis6379.conf
[root@node1 myredis]# vim redis6380.conf
[root@node1 myredis]# vim redis6381.conf
[root@node1 myredis]#
info replication
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>
127.0.0.1:6380> 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:0 127.0.0.1:6380>
127.0.0.1:6381> 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:0 127.0.0.1:6381>
一仆二主：
127.0.0.1:6379> set k1 v1
OK
127.0.0.1:6379> set k2 v2
OK
127.0.0.1:6379> set k3 v3
OK
127.0.0.1:6379> keys *
1) "k3"
2) "k2"
3) "k1"
127.0.0.1:6380> SLAVEOF 127.0.0.1 6379
OK
127.0.0.1:6380> get k4
"v4"
127.0.0.1:6380>
127.0.0.1:6381> slaveof 127.0.0.1 6379
OK
127.0.0.1:6381> get k1
"v1"
127.0.0.1:6381>
再次輸入info replication
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:2
slave0:ip=127.0.0.1,port=6380,state=online,offset=291,lag=1
slave1:ip=127.0.0.1,port=6381,state=online,offset=291,lag=0
master_repl_offset:291
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:290
127.0.0.1:6379>
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:9
master_sync_in_progress:0
slave_repl_offset:333
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
127.0.0.1:6380>
讀寫分離：
slave節點不能寫入
127.0.0.1:6380> set k6 v6
(error) READONLY You can't write against a read only slave.
127.0.0.1:6380>
主機掛掉時：
127.0.0.1:6379> SHUTDOWN
not connected> exit
You have new mail in /var/spool/mail/root
[root@node1 ~]#
slave節點狀態：
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:753
master_link_down_since_seconds:17
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
127.0.0.1:6380>
主機修復后：
[root@node1 ~]# redis-server /myredis/redis6379.conf
[root@node1 ~]# redis-cli -p 6379
127.0.0.1:6379> set k7 v7
OK
127.0.0.1:6379>
slave節點：
127.0.0.1:6380> get k7
"v7"
127.0.0.1:6380>
在當前這種狀體下，主機掛掉后從機不會改變狀態，會原地待命
從機down掉之后會需要與主機從新連接，除非寫進conf配置文件
127.0.0.1:6380> slaveof 127.0.0.1 6379
OK
127.0.0.1:6380> get k7
"v7"
127.0.0.1:6380>
薪火相傳：
配置6381的主節點為6380
127.0.0.1:6381> SLAVEOF 127.0.0.1 6380
OK
127.0.0.1:6381>
則此時節點狀態為
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=127.0.0.1,port=6380,state=online,offset=1957,lag=1
master_repl_offset:1957
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:1956
127.0.0.1:6379>
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:4
master_sync_in_progress:0
slave_repl_offset:2027
slave_priority:100
slave_read_only:1
connected_slaves:1
slave0:ip=127.0.0.1,port=6381,state=online,offset=71,lag=1
master_repl_offset:71
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:70
127.0.0.1:6380>
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:10
master_sync_in_progress:0
slave_repl_offset:99
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
127.0.0.1:6381>
反客為主：
SLAVEOF no one：使當前數據庫停止與其他數據庫的同步，轉成主數據庫
127.0.0.1:6380> SLAVEOF no one
OK
127.0.0.1:6380> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=127.0.0.1,port=6381,state=online,offset=267,lag=0
master_repl_offset:267
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:266
127.0.0.1:6380>
復制原理：
Slave啟動成功連接到master后會發送一個sync命令
Master接到命令啟動后台的存盤進程，同時收集所有接收到的用於修改數據集命令，在后台進程執行完畢后，master將傳送整個數據文件到slave，以完成一次完全同步
全量復制：slave服務在接收到數據庫文件數據后，將其存盤並加載到內存中。
增量復制：Master繼續將新的所有收集到的修改命令依次傳給slave，完成同步，但是只要是重新連接master，一次完全同步(全量復制)將被自動執行
哨兵模式（sentinel）：
是什么：
反客為主的自動版，能夠后台監控主機是否故障，如果故障了根據投票數自動將從庫轉換為主庫。
怎么玩：
調整結構，6379帶着80,81
127.0.0.1:6380> SLAVEOF 127.0.0.1 6379 OK 127.0.0.1:6380> info repication 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:7 master_sync_in_progress:0 slave_repl_offset:3833 slave_priority:100 slave_read_only:1 connected_slaves:0 master_repl_offset:225 repl_backlog_active:1 repl_backlog_size:1048576 repl_backlog_first_byte_offset:2 repl_backlog_histlen:224 127.0.0.1:6380>
127.0.0.1:6381> slaveof 127.0.0.1 6379 OK 127.0.0.1:6381> 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:3861 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:0 127.0.0.1:6381>
自定義的/myredis目錄下新建sentinel.conf文件，名字覺不能錯
[root@node1 myredis]# touch sentinel.conf
sentinel.conf 文件的內容：（末尾的1表示誰的票數多余1票，誰就是新的領導）
sentinel monitor host6379 127.0.0.1 6379 1
啟動哨兵：
使用 redis-sentinel /myredis/sentinel.conf 啟動
[root@node1 myredis]# redis-sentinel /myredis/sentinel.conf 9871:X 30 Nov 09:22:52.073 * Increased maximum number of open files to 10032 (it was originally set to 1024). _._ _.-``__ ''-._ _.-`` `. `_. ''-._ Redis 3.0.4 (00000000/0) 64 bit .-`` .-```. ```\/ _.,_ ''-._ ( ' , .-` | `, ) Running in sentinel mode |`-._`-...-` __...-.``-._|'` _.-'| Port: 26379 | `-._ `._ / _.-' | PID: 9871 `-._ `-._ `-./ _.-' _.-' |`-._`-._ `-.__.-' _.-'_.-'| | `-._`-._ _.-'_.-' | http://redis.io `-._ `-._`-.__.-'_.-' _.-' |`-._`-._ `-.__.-' _.-'_.-'| | `-._`-._ _.-'_.-' | `-._ `-._`-.__.-'_.-' _.-' `-._ `-.__.-' _.-' `-._ _.-' `-.__.-' 9871:X 30 Nov 09:22:52.077 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128. 9871:X 30 Nov 09:22:52.077 # Sentinel runid is 07858ebd94d326270f4a56e0501afefe82e444b1 9871:X 30 Nov 09:22:52.079 # +monitor master host6379 127.0.0.1 6379 quorum 1 9871:X 30 Nov 09:22:53.077 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6379 9871:X 30 Nov 09:22:53.091 * +slave slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6379
原有的master掛了：
哨兵的監視窗口增加新的內容：
9895:X 30 Nov 09:42:54.522 # +sdown master host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:54.522 # +odown master host6379 127.0.0.1 6379 #quorum 1/1 9895:X 30 Nov 09:42:54.522 # +new-epoch 1 9895:X 30 Nov 09:42:54.522 # +try-failover master host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:54.648 # +vote-for-leader ccc2dc958a8ae1e16294b81567126ec4031bf192 1 9895:X 30 Nov 09:42:54.648 # +elected-leader master host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:54.648 # +failover-state-select-slave master host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:54.725 # +selected-slave slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:54.725 * +failover-state-send-slaveof-noone slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:54.778 * +failover-state-wait-promotion slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:55.704 # +promoted-slave slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:55.704 # +failover-state-reconf-slaves master host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:55.752 * +slave-reconf-sent slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:56.778 * +slave-reconf-inprog slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:56.778 * +slave-reconf-done slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:56.877 # +failover-end master host6379 127.0.0.1 6379 9895:X 30 Nov 09:42:56.877 # +switch-master host6379 127.0.0.1 6379 127.0.0.1 6380 9895:X 30 Nov 09:42:56.878 * +slave slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6380 9895:X 30 Nov 09:42:56.878 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ host6379 127.0.0.1 6380
6380變為了新的master
127.0.0.1:6380> info replication # Replication role:master connected_slaves:1 slave0:ip=127.0.0.1,port=6381,state=online,offset=123955,lag=0 master_repl_offset:123955 repl_backlog_active:1 repl_backlog_size:1048576 repl_backlog_first_byte_offset:2 repl_backlog_histlen:123954 127.0.0.1:6380>
此時6381的狀態
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:1 master_sync_in_progress:0 slave_repl_offset:125992 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:0 127.0.0.1:6381>
問題：如果之前的master重啟回來，會不會雙master沖突
啟動掛掉的6379后
哨兵監控打印：
9895:X 30 Nov 09:43:26.931 # +sdown slave 127.0.0.1:6379 127.0.0.1 6379 @ host6379 127.0.0.1 6380 9895:X 30 Nov 09:45:51.015 # -sdown slave 127.0.0.1:6379 127.0.0.1 6379 @ host6379 127.0.0.1 6380 9895:X 30 Nov 09:46:00.994 * +convert-to-slave slave 127.0.0.1:6379 127.0.0.1 6379 @ host6379 127.0.0.1 6380
啟動后，6379的狀態：
成為了當前master的salve節點
127.0.0.1:6379> info replication # Replication role:slave master_host:127.0.0.1 master_port:6380 master_link_status:up master_last_io_seconds_ago:1 master_sync_in_progress:0 slave_repl_offset:132805 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> keys * 1) "k7" 127.0.0.1:6379>
復制的缺點：
復制延時：由於所有的寫操作都是閑在Master上操作，然后同步更新到salve上，所以從Master同步到Slave機器有一定的延遲，當系統很繁忙的時候，延遲問題會更加嚴重，Slave機器數量的增加也會使這個問題更加嚴重。