redis之master.slave主从复制

时间:2020-02-07 15:37:00 来源:互联网 作者: 神秘的大神 字体:

简介

主机数据更新后根据配置和策略,自动同步到备机的master/slave机制,master以写为主,slave以读为主

从库配置

配置从库,不配主库

配置从库:
    格式: slaveof 主库ip 主库port
    注意: 每次与master断开之后,都需要重新连接,除非配置到redis.conf文件
    
配置文件细节:
    

主从同步一--一主多从(同一台机器上同一个redis运行在三个port上)

1.复制redis配置文件三份

[root@izm5e2q95pbpe1hh0kkwoiz redis-5.0.3]# mkdir test-master-slave

[root@izm5e2q95pbpe1hh0kkwoiz redis-5.0.3]# cp redis.conf test-master-slave/redis6379.conf
[root@izm5e2q95pbpe1hh0kkwoiz redis-5.0.3]# cp redis.conf test-master-slave/redis6380.conf
[root@izm5e2q95pbpe1hh0kkwoiz redis-5.0.3]# cp redis.conf test-master-slave/redis6381.conf

修改另外两份配置文件
    vim redis6379.conf
        daemonize yes
        port 6379
        pidfile /var/run/redis_6379.pid
        logfile "6379.log"
        dbfilename dump6379.rdb
    vim redis6380.conf
        daemonize yes
        port 6380
        pidfile /var/run/redis_6380.pid
        logfile "6380.log"
        dbfilename dump6380.rdb

    vim redis6381.conf
        daemonize yes
        port 6381
        pidfile /var/run/redis_6381.pid
        logfile "6381.log"
        dbfilename dump6381.rdb

2.启动三个redis

[root@izm5e2q95pbpe1hh0kkwoiz test-master-slave]# cd /alidata/redis-5.0.3/bin
[root@izm5e2q95pbpe1hh0kkwoiz bin]# pwd
/alidata/redis-5.0.3/bin
[root@izm5e2q95pbpe1hh0kkwoiz bin]# ps aux | grep redis
root     20603  0.1  0.1 156392  2284 ?        Ssl   2018 681:54 redis-server *:8686
root     21288  0.0  0.0 112680   984 pts/0    R+   10:58   0:00 grep --color=auto redis
[root@izm5e2q95pbpe1hh0kkwoiz bin]# redis-server ../test-master-slave/redis6380.conf 
[root@izm5e2q95pbpe1hh0kkwoiz bin]# ps aux | grep redis
root     20603  0.1  0.1 156392  2284 ?        Ssl   2018 681:54 redis-server *:8686
root     23628  0.0  0.1 153832  2324 ?        Ssl  10:58   0:00 redis-server 127.0.0.1:6380
root     24492  0.0  0.0 112680   980 pts/0    R+   10:58   0:00 grep --color=auto redis
[root@izm5e2q95pbpe1hh0kkwoiz bin]# redis-server ../test-master-slave/redis6381.conf 
[root@izm5e2q95pbpe1hh0kkwoiz bin]# ps aux | grep redis
root     20603  0.1  0.1 156392  2284 ?        Ssl   2018 681:54 redis-server *:8686
root     23628  0.0  0.1 153832  2324 ?        Ssl  10:58   0:00 redis-server 127.0.0.1:6380
root     27142  0.0  0.1 153832  2304 ?        Ssl  10:58   0:00 redis-server 127.0.0.1:6381
root     28470  0.0  0.0 112680   984 pts/0    R+   10:58   0:00 grep --color=auto redis
[root@izm5e2q95pbpe1hh0kkwoiz bin]# redis-server ../test-master-slave/redis6379.conf 
[root@izm5e2q95pbpe1hh0kkwoiz redis-5.0.3]# ps aux | grep redis
root      4705  0.1  0.1 153832  2592 ?        Ssl  11:11   0:00 redis-server 127.0.0.1:6380
root     20603  0.1  0.1 156392  2296 ?        Ssl   2018 681:55 redis-server *:8686
root     22492  0.0  0.1 153832  2296 ?        Ssl  11:14   0:00 redis-server 127.0.0.1:6379
root     23990  0.0  0.0 112680   980 pts/0    R+   11:14   0:00 grep --color=auto redis
root     27142  0.0  0.1 153832  2304 ?        Ssl  10:58   0:00 redis-server 127.0.0.1:6381

3.细节(暂时一主一从)

# 主机器
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:0
master_replid:d9ff48134d9b166cb7f48f4f71a54c9eddc8531c
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:0
second_repl_offset:-1
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0

# 还没有配置的从机器
127.0.0.1:6380> info replication
# Replication
role:master
connected_slaves:0
master_replid:e06824b502f2bc16c101653a8e36ba954cf35a53
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:0
second_repl_offset:-1
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0

# 配置从redis
127.0.0.1:6380> SLAVEOF 127.0.0.1 6379
OK
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:2
master_sync_in_progress:0
slave_repl_offset:14
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:df2697f1f530565d1fb683f209283e319faea59f
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:14
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:14

# 此时master redis状态
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=127.0.0.1,port=6380,state=online,offset=28,lag=0
master_replid:df2697f1f530565d1fb683f209283e319faea59f
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:28
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:28

redis的master跟slave建立主从关系之后,slave redis会从master的redis获取所有的key

如果master redis down掉,slave redis会继续等待,master redis运行后,slave redis自动连接

如果slave redis down掉之后,slave redis重新启动,不会自动连接master redis,需要重新运行slaveof命令

master redis写入的key,slave redis不能去修改master已经存在的key,在slave中是readonly的

主从同步二--薪火相传

简介

上一个slave可以是下一个slave的master,slave同样可以接受其他slaves的连接和同步请求.
那么该slave作为链条中下一个的master,可以有效减轻master的写压力

中途变更转向:会清除之前的数据,重新建立拷贝最新的.

slaveof 新主库ip 新主库port

细节

# 主master
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=127.0.0.1,port=6380,state=online,offset=28,lag=0
master_replid:df2697f1f530565d1fb683f209283e319faea59f
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:28
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:28

# master6379的slave6380
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:3
master_sync_in_progress:0
slave_repl_offset:2142
slave_priority:100
slave_read_only:1
connected_slaves:1
slave0:ip=127.0.0.1,port=6381,state=online,offset=2142,lag=1
master_replid:df2697f1f530565d1fb683f209283e319faea59f
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:2142
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:2142

# slave6380的slave6381
127.0.0.1:6381> SLAVEOF 127.0.0.1 6380
OK
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:3
master_sync_in_progress:0
slave_repl_offset:2128
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:df2697f1f530565d1fb683f209283e319faea59f
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:2128
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2129
repl_backlog_histlen:0

主从复制三--反客为主

简介

从库运行slaveof no one ,使当前数据库停止与其他数据库的同步,转成主数据库
其他的从库使用"slaveof 新主库ip 新主库port",重新绑定最新的主库

复制原理

slave启动成功,连接到master后会发送一个sync命令

master接到命令启动后台的存盘进程,同时手机所有接收到的用于修改数据命令,

在后台进程执行完毕之后,master将传送整个数据文件到slave,以完成一次完全同步

全量复制: 而slave在接收到数据库文件之后,将其存盘并加载到内存中

增量复制: master继续将新的所有收集到的修改命令依次传递给slave,完成同步

但是只要是重新连接master,一次完全同步(全量复制)将被自动执行

哨兵模式(sentinel)

参考链接: https://redis.io/topics/sentinel

简介

反客为主的自动版,能够后退监控主机是否故障,如果故障了根据投票数自动将从库转换为主库

如何操作

1.调整结构6379带着6380,6381
2.自定义/alidata/redis-5.0.3/test-master-slave目录下新建sentinel.conf文件,名字绝对不能错
3.配置哨兵
    sentinel monitor 被监控数据库名字(自己定义) 被监控数据库ip 被监控数据库port 1
    上面最后一个数字1,表示主机挂掉后slave投票让谁接替成为主机,得票数多少后成为主机
4.启动哨兵
    redis-sentinel /alidata/redis-5.0.3/test-master-slave/sentinel.conf
    如果没有redis-sentinel,则在/alidata/redis-5.0.3/bin目录下使用如下命令:
    redis-server ../test-master-slave/sentinel.conf --sentinel
    
    [root@izm5e2q95pbpe1hh0kkwoiz bin]# redis-server ../test-master-slave/sentinel.conf --sentinel
    16452:X 10 Jan 2020 15:56:54.511 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
    16452:X 10 Jan 2020 15:56:54.511 # Redis version=5.0.3, bits=64, commit=00000000, modified=0, pid=16452, just started
    16452:X 10 Jan 2020 15:56:54.511 # Configuration loaded
                    _._                                                  
               _.-``__ ''-._                                             
          _.-``    `.  `_.  ''-._           Redis 5.0.3 (00000000/0) 64 bit
      .-`` .-```.  ```\/    _.,_ ''-._                                   
     (    '      ,       .-`  | `,    )     Running in sentinel mode
     |`-._`-...-` __...-.``-._|'` _.-'|     Port: 26379
     |    `-._   `._    /     _.-'    |     PID: 16452
      `-._    `-._  `-./  _.-'    _.-'                                   
     |`-._`-._    `-.__.-'    _.-'_.-'|                                  
     |    `-._`-._        _.-'_.-'    |           http://redis.io        
      `-._    `-._`-.__.-'_.-'    _.-'                                   
     |`-._`-._    `-.__.-'    _.-'_.-'|                                  
     |    `-._`-._        _.-'_.-'    |                                  
      `-._    `-._`-.__.-'_.-'    _.-'                                   
          `-._    `-.__.-'    _.-'                                       
              `-._        _.-'                                           
                  `-.__.-'                                               
    
    16452:X 10 Jan 2020 15:56:54.516 # Sentinel ID is a7d6715b13d229862bd5082e1f0e7734897a1693
    16452:X 10 Jan 2020 15:56:54.516 # +monitor master host6379 127.0.0.1 6379 quorum 1
    16452:X 10 Jan 2020 15:56:54.517 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:56:54.520 * +slave slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6379

    
5.原有的master挂掉之后,自动重新选择master,另外的slave重新挂到新的master下,6379挂掉,投票产生新的master为6381
    16452:X 10 Jan 2020 15:59:43.676 # +odown master host6379 127.0.0.1 6379 #quorum 1/1
    16452:X 10 Jan 2020 15:59:43.676 # +new-epoch 1
    16452:X 10 Jan 2020 15:59:43.676 # +try-failover master host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:59:43.682 # +vote-for-leader a7d6715b13d229862bd5082e1f0e7734897a1693 1
    16452:X 10 Jan 2020 15:59:43.682 # +elected-leader master host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:59:43.682 # +failover-state-select-slave master host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:59:43.745 # +selected-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:59:43.745 * +failover-state-send-slaveof-noone slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:59:43.809 * +failover-state-wait-promotion slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:59:44.588 # +promoted-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:59:44.588 # +failover-state-reconf-slaves master host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:59:44.660 * +slave-reconf-sent slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:59:45.615 * +slave-reconf-inprog slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:59:45.615 * +slave-reconf-done slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6379
    16452:X 10 Jan 2020 15:59:45.691 # +failover-end master host6379 127.0.0.1 6379
    ## 切换到投票出来的新的master之6381
    16452:X 10 Jan 2020 15:59:45.691 # +switch-master host6379 127.0.0.1 6379 127.0.0.1 6381
    16452:X 10 Jan 2020 15:59:45.691 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6381
    16452:X 10 Jan 2020 15:59:45.691 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ host6379 127.0.0.1 6381
    16452:X 10 Jan 2020 16:00:15.768 # +sdown slave 127.0.0.1:6379 127.0.0.1 6379 @ host6379 127.0.0.1 6381

    ## 6381变为新的master,6380为slave,只有6380一个slave
    127.0.0.1:6381> info replication
    # Replication
    role:master
    connected_slaves:1
    slave0:ip=127.0.0.1,port=6380,state=online,offset=23490630,lag=0
    master_replid:9772fad6a5ca29661aeb5e07ca72c013347c5679
    master_replid2:df2697f1f530565d1fb683f209283e319faea59f
    master_repl_offset:23490630
    second_repl_offset:23480570
    repl_backlog_active:1
    repl_backlog_size:1048576
    repl_backlog_first_byte_offset:22442055
    repl_backlog_histlen:1048576
    
    ## 6380是6381的slave
    127.0.0.1:6380> info replication
    # Replication
    role:slave
    master_host:127.0.0.1
    master_port:6381
    master_link_status:up
    master_last_io_seconds_ago:1
    master_sync_in_progress:0
    slave_repl_offset:23491043
    slave_priority:100
    slave_read_only:1
    connected_slaves:0
    master_replid:9772fad6a5ca29661aeb5e07ca72c013347c5679
    master_replid2:df2697f1f530565d1fb683f209283e319faea59f
    master_repl_offset:23491043
    second_repl_offset:23480570
    repl_backlog_active:1
    repl_backlog_size:1048576
    repl_backlog_first_byte_offset:22442468
    repl_backlog_histlen:1048576


6.最先挂掉的master重新运行之后,自动挂载到重新选举出来的master下面,此时最原先的master变为slave
    哨兵检测到后将6379启动,将6379变为6381的slave:
        16452:X 10 Jan 2020 16:04:28.076 * +convert-to-slave slave 127.0.0.1:6379 127.0.0.1 6379 @ host6379 127.0.0.1 6381
    6381下的slave多了6379
        127.0.0.1:6381> info replication
        # Replication
        role:master
        connected_slaves:2
        slave0:ip=127.0.0.1,port=6380,state=online,offset=23501237,lag=2
        slave1:ip=127.0.0.1,port=6379,state=online,offset=23501237,lag=1
        master_replid:9772fad6a5ca29661aeb5e07ca72c013347c5679
        master_replid2:df2697f1f530565d1fb683f209283e319faea59f
        master_repl_offset:23501237
        second_repl_offset:23480570
        repl_backlog_active:1
        repl_backlog_size:1048576
        repl_backlog_first_byte_offset:22452662
        repl_backlog_histlen:1048576
    6379的info replication
        127.0.0.1:6379> info replication
        # Replication
        role:slave
        master_host:127.0.0.1
        master_port:6381
        master_link_status:up
        master_last_io_seconds_ago:1
        master_sync_in_progress:0
        slave_repl_offset:23507614
        slave_priority:100
        slave_read_only:1
        connected_slaves:0
        master_replid:9772fad6a5ca29661aeb5e07ca72c013347c5679
        master_replid2:0000000000000000000000000000000000000000
        master_repl_offset:23507614
        second_repl_offset:-1
        repl_backlog_active:1
        repl_backlog_size:1048576
        repl_backlog_first_byte_offset:23499724
        repl_backlog_histlen:7891

    
7.假如此时投票选举出来的master又挂掉了,此时是什么情况?
    哨兵检测到6381挂掉之后的动作
        16452:X 10 Jan 2020 16:07:53.458 # +sdown master host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:53.458 # +odown master host6379 127.0.0.1 6381 #quorum 1/1
        16452:X 10 Jan 2020 16:07:53.458 # +new-epoch 2
        16452:X 10 Jan 2020 16:07:53.458 # +try-failover master host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:53.463 # +vote-for-leader a7d6715b13d229862bd5082e1f0e7734897a1693 2
        16452:X 10 Jan 2020 16:07:53.463 # +elected-leader master host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:53.463 # +failover-state-select-slave master host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:53.523 # +selected-slave slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:53.523 * +failover-state-send-slaveof-noone slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:53.581 * +failover-state-wait-promotion slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:53.643 # +promoted-slave slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:53.643 # +failover-state-reconf-slaves master host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:53.694 * +slave-reconf-sent slave 127.0.0.1:6379 127.0.0.1 6379 @ host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:54.323 * +slave-reconf-inprog slave 127.0.0.1:6379 127.0.0.1 6379 @ host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:55.333 * +slave-reconf-done slave 127.0.0.1:6379 127.0.0.1 6379 @ host6379 127.0.0.1 6381
        16452:X 10 Jan 2020 16:07:55.386 # +failover-end master host6379 127.0.0.1 6381
        ## 将master从6381切换为6380
        16452:X 10 Jan 2020 16:07:55.386 # +switch-master host6379 127.0.0.1 6381 127.0.0.1 6380
        16452:X 10 Jan 2020 16:07:55.386 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ host6379 127.0.0.1 6380
        16452:X 10 Jan 2020 16:07:55.386 * +slave slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6380
        16452:X 10 Jan 2020 16:08:25.418 # +sdown slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6380
    6380变为master,6379变更为6380的slave:
        127.0.0.1:6380> info replication
        # Replication
        role:master
        connected_slaves:1
        slave0:ip=127.0.0.1,port=6379,state=online,offset=23512243,lag=0
        master_replid:08b69c14d46567b6d0506e84e7c51da49a9661ec
        master_replid2:9772fad6a5ca29661aeb5e07ca72c013347c5679
        master_repl_offset:23512243
        second_repl_offset:23511276
        repl_backlog_active:1
        repl_backlog_size:1048576
        repl_backlog_first_byte_offset:22463668
        repl_backlog_histlen:1048576
    6379变为6380的slave:
        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:23525130
        slave_priority:100
        slave_read_only:1
        connected_slaves:0
        master_replid:08b69c14d46567b6d0506e84e7c51da49a9661ec
        master_replid2:9772fad6a5ca29661aeb5e07ca72c013347c5679
        master_repl_offset:23525130
        second_repl_offset:23511276
        repl_backlog_active:1
        repl_backlog_size:1048576
        repl_backlog_first_byte_offset:23499724
        repl_backlog_histlen:25407

复制缺点

由于所有的写操作都是现在master上操作,然后同步更新到slave上,所以master通不到slave机器有一定的延迟,
当系统很繁忙的时候,延迟问题会更加严重,slave机器数量的增加也会使这个问题更加严重