Redis深刻系列-0x018：Redis同步实践

时间 2019-11-15

标签 redis 深刻系列 0x018 同步实践栏目 Redis 繁體版

原文原文链接

0x001 修改配置

复制两份配置文件，分别命名为redis_6378.conf、redis_6377.conf。他们将在6378、6377两个端口启动

分别修改两个配置：redis

# redis_6378.conf
...
port 6378
slaveof 127.0.0.1 6379
...

# redis_6377.conf
...
port 6377
slaveof 127.0.0.1 6378
...

说明：这里使用监听6379的节点做为主节点，6378做为6379的子节点，6377做为6378的子节点。shell

0x002 同步

启动6379主节点socket

$ redis-server
68931:C 29 May 10:53:54.234 # oO0OoO0OoO0Oo Redis is starting                                 

# 省略部分过程
      _.-``    `.  `_.  ''-._           Redis 4.0.8 (00000000/0) 64 bit
  .-`` .-```.  ```\/    _.,_ ''-._                                   
 (    '      ,       .-`  | `,    )     Running in standalone mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6379
 |    `-._   `._    /     _.-'    |     PID: 68931
# 省略部分过程
68931:M 29 May 10:53:54.237 * Ready to accept connections

启动6378子节点code

$ redis-server ~/Desktop/redis_6378.conf 
# 省略部份内容
                _._                                                  
           _.-``__ ''-._                                             
      _.-``    `.  `_.  ''-._           Redis 4.0.8 (00000000/0) 64 bit
  .-`` .-```.  ```\/    _.,_ ''-._                                   
 (    '      ,       .-`  | `,    )     Running in standalone mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6378
 |    `-._   `._    /     _.-'    |     PID: 69033

# 省略部份内容
# 这里说明启动成功了
69033:S 29 May 10:56:24.581 * Ready to accept connections
# 开始链接主节点
69033:S 29 May 10:56:24.581 * Connecting to MASTER 127.0.0.1:6379
# 开始同步
69033:S 29 May 10:56:24.581 * MASTER <-> SLAVE sync started
69033:S 29 May 10:56:24.581 * Non blocking connect for SYNC fired the event.
69033:S 29 May 10:56:24.581 * Master replied to PING, replication can continue...
# 尝试增量同步
69033:S 29 May 10:56:24.581 * Trying a partial resynchronization (request 87953c7dc97cf1192a243fe5d7708c11acbd0e0f:1).
# 全量同步
69033:S 29 May 10:56:24.582 * Full resync from master: 98a56521a0a958295e499853621029d19ef6b357:0
69033:S 29 May 10:56:24.582 * Discarding previously cached master state.
69033:S 29 May 10:56:24.684 * MASTER <-> SLAVE sync: receiving 826 bytes from master
69033:S 29 May 10:56:24.685 * MASTER <-> SLAVE sync: Flushing old data
69033:S 29 May 10:56:24.685 * MASTER <-> SLAVE sync: Loading DB in memory
69033:S 29 May 10:56:24.685 * MASTER <-> SLAVE sync: Finished with success

此时的6379主节点server

# 省略部份内容
68931:M 29 May 10:53:54.237 * Ready to accept connections
# 上面是以前的状态，下面是`6378`链接进来之后的状态
68931:M 29 May 10:56:24.581 * Slave 127.0.0.1:6378 asks for synchronization
68931:M 29 May 10:56:24.581 * Partial resynchronization not accepted: Replication ID mismatch (Slave asked for '87953c7dc97cf1192a243fe5d7708c11acbd0e0f', my replication IDs are 'dbf6c826156fa5140d891996afcf8cc4f21b61fd' and '0000000000000000000000000000000000000000')
68931:M 29 May 10:56:24.581 * Starting BGSAVE for SYNC with target: disk
68931:M 29 May 10:56:24.582 * Background saving started by pid 69034
69034:C 29 May 10:56:24.584 * DB saved on disk
68931:M 29 May 10:56:24.684 * Background saving terminated with success
# 同步成功
68931:M 29 May 10:56:24.684 * Synchronization with slave 127.0.0.1:6378 succeeded

启动6377子节点get

redis-server ~/Desktop/redis_6377.conf 
# 省略部份内容
                _._                                                  
           _.-``__ ''-._                                             
      _.-``    `.  `_.  ''-._           Redis 4.0.8 (00000000/0) 64 bit
  .-`` .-```.  ```\/    _.,_ ''-._                                   
 (    '      ,       .-`  | `,    )     Running in standalone mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6377
 |    `-._   `._    /     _.-'    |     PID: 69207

# 启动完成
69207:S 29 May 11:02:22.569 * Ready to accept connections
# 链接上一级节点
69207:S 29 May 11:02:22.569 * Connecting to MASTER 127.0.0.1:6378
69207:S 29 May 11:02:22.570 * MASTER <-> SLAVE sync started
69207:S 29 May 11:02:22.570 * Non blocking connect for SYNC fired the event.
69207:S 29 May 11:02:22.570 * Master replied to PING, replication can continue...
69207:S 29 May 11:02:22.570 * Trying a partial resynchronization (request 98a56521a0a958295e499853621029d19ef6b357:1).
69207:S 29 May 11:02:22.570 * Successful partial resynchronization with master.
69207:S 29 May 11:02:22.570 * MASTER <-> SLAVE sync: Master accepted a Partial Resynchronization.

0x003数据写入

使用redis-cli向6379主节点写入数据同步

$ redis-cli -h 127.0.0.1 -p 6379
127.0.0.1:6379> set name redis
OK
127.0.0.1:6379> get name
"redis"

使用redis-cli链接6378子节点并读取在主节点写入的数据it
```
$ redis-cli -h 127.0.0.1 -p 6378
127.0.0.1:6378> get name
"redis"
```
使用redis-cli链接637 7子节点并读去在主节点写入的数据io
```
$ redis-cli -h 127.0.0.1 -p 6377
127.0.0.1:6377> get name
"redis"
```

使用redis-cli链接6378子节点并尝试写入数据event

127.0.0.1:6378> set name redis-cli
(error) READONLY You can't write against a read only slave.

说明：子节点能够读取到主节点写入的数据，说明同步成功了，子节点没法写入数据，由于子节点是默认只读的，修改配置能够作到子节点可读写

0x004 断开链接

关闭6378子节点

$ redis-cli -h 127.0.0.1 -p 6378
127.0.0.1:6378> shutdown
not connected>

此时的6378

# 上面是以前的状态，下面是`6378`关机时候的状态
9033:S 29 May 11:09:54.587 # User requested shutdown...
69033:S 29 May 11:09:54.587 * Saving the final RDB snapshot before exiting.
69033:S 29 May 11:09:54.588 * DB saved on disk
69033:S 29 May 11:09:54.588 * Removing the pid file.
69033:S 29 May 11:09:54.589 # Redis is now ready to exit, bye bye...

此时的6379

# 上面是以前的状态，下面是`6378`关机以后的状态
68931:M 29 May 11:09:54.589 # Connection with slave 127.0.0.1:6378 lost.

此时的6377

...
# 6377 会一直尝试从新链接`6378`
69219:S 29 May 11:12:07.132 * Connecting to MASTER 127.0.0.1:6378
69219:S 29 May 11:12:07.132 * MASTER <-> SLAVE sync started
69219:S 29 May 11:12:07.132 # Error condition on socket for SYNC: Connection refused
69219:S 29 May 11:12:07.132 * Connecting to MASTER 127.0.0.1:6378
69219:S 29 May 11:12:07.132 * MASTER <-> SLAVE sync started
69219:S 29 May 11:12:07.132 # Error condition on socket for SYNC: Connection refused
...

0x005 子节点可读

修改配置
```
# redis_6378.conf
slave-read-only no
```

从新启动6378，并向6378写入数据

$ redis-cli -h 127.0.0.1 -p 6378
# 此时配置子节点不是只读的，因此能够写入
127.0.0.1:6378> set name redis-cli
OK
127.0.0.1:6378> get name 
"redis-cli"

链接6377并读取6378写入的key

$ redis-cli -h 127.0.0.1 -p 6377
127.0.0.1:6377> get name
"redis"

链接6379并读取6378写入的key

$ redis-cli -h 127.0.0.1 -p 6379
127.0.0.1:6379> GET name
"redis"

说明：虽然此时的6378子节点是可读的，可是并不会传播到其余子节点或者主节点，而且在下次同步的时候，将会被删除。