我们现在模拟的是主从(1台主机、一台从机)，其主从同步的原理，就是对bin-log二进制文件的同步，将这个文件的内容从主机同步到从机。
一、配置文件的修改
1、主机配置文件修改配置
我们首先需要mysql主机(192.168.254.130)的/etc/my.cnf配置文件，添加如下配置:
#主机唯一ID
server-id=1
#二进制日志
log-bin=mysql-bin
#不需要同步的数据库
binlog-ignore-db=mysql
binlog-ignore-db=information_schema
#同步的数据库名称
binlog-do-db=mycat
#二进制的格式
binlog_format=STATEMENT
我们看下目前整个my.cnf文件
[root@localhost Desktop]# cat /etc/my.cnf
[mysqld]
datadir=/usr/local/mysql/data
basedir=/usr/local/mysql
socket=/usr/local/mysql/data/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
server-id=1
log-bin=mysql-bin
binlog-ignore-db=mysql
binlog-ignore-db=information_schema
binlog-do-db=mycat
binlog_format=STATEMENT
[mysqld_safe]
log-error=/usr/local/mysql/data/mysqld.log
pid-file=/usr/local/mysql/data/mysqld/mysqld.pid
[root@localhost Desktop]#
修改主机的配置文件后，我们需要通过命令重启下服务:
[root@localhost support-files]# ls
magic mysqld_multi.server mysql-log-rotate mysql.server
[root@localhost support-files]# pwd
/usr/local/mysql/support-files
[root@localhost support-files]# ./mysql.server restart
然后我们修改下从机(192.168.254.131)的配置文件。
2、从机的配置
从机的配置修改比较简单：
#从机机器唯一ID
server-id=2
#中继日志
relay-log=mysql-relay
同样修改配置后，我们重启下从机
二、mysql客户端命令操作
下面我们可以通过命令连接到mysql的命令端：
[root@localhost bin]#
[root@localhost bin]# pwd
/usr/local/mysql/bin
[root@localhost bin]# ./mysql -uroot -p
1、主机操作
1）、创建同步用户
首先我们可以在主机创建一个专门用于主从同步用户，通过命令：
GRANT REPLICATION SLAVE ON *.* TO 'SLAVE'@'%' IDENTIFIED BY '123456';
2）、查看同步文件状态
然后我们通过show master status;查看主机的同步内容状态：
mysql> show master status;
+------------------+----------+--------------+--------------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+--------------------------+-------------------+
| mysql-bin.000001 | 154 | mycat | mysql,information_schema | |
+------------------+----------+--------------+--------------------------+-------------------+
1 row in set (0.00 sec)
2、从机操作
1）、设置从机的主机
执行如下命令，这里设置了我们与主机建立同步的相关信息
CHANGE MASTER TO MASTER_HOST='192.168.254.130',
MASTER_USER='SLAVE',
MASTER_PASSWORD='123456',
MASTER_LOG_FILE='mysql-bin.000001',
MASTER_LOG_POS=430;
这里如果提示已经设置了主机配置，可以通过stop slavereset master进行重置。
2）、启动同步
下面我们再通过start slave开启同步：
就可以看到：
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.254.130
Master_User: SLAVE
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 592
Relay_Log_File: mysql-relay.000002
Relay_Log_Pos: 482
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 592
Relay_Log_Space: 685
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 1
Master_UUID: 74397a99-accf-11eb-ae0d-000c2912d302
Master_Info_File: /usr/local/mysql/data/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position: 0
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
1 row in set (0.00 sec)
mysql>
这里我们可以看到Slave_IO_Running、Slave_SQL_Running都为YES，则成功了，如果是下面这种：
*************************** 1. row ***************************
Slave_IO_State: Connecting to master
Master_Host: 192.168.254.130
Master_User: slave
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 430
Relay_Log_File: mysql-relay.000001
Relay_Log_Pos: 4
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Connecting
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 430
Relay_Log_Space: 154
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: NULL
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 1045
Last_IO_Error: error connecting to master 'slave@192.168.254.130:3306' - retry-time: 60 retries: 1
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 0
Master_UUID:
Master_Info_File: /usr/local/mysql/data/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp: 210505 00:18:08
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position: 0
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
1 row in set (0.00 sec)
我们可以看到Last_IO_Error这里有错误，我们就可以去看下日志报的什么问题了，目前我这个是因为同步用户写错了才不能同步，按上面说的先停止同步重置，修改后同步命令，再操作一遍就可以了。
三、主从同步测试
1、主机创建库
我们先在主机创建我们前面设置的要同步的数据库mycat：
mysql> create database mycat;
Query OK, 1 row affected (0.00 sec)
mysql> use mycat;
Database changed
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mycat |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
mysql>
2、从机查看库
然后我们就能在从机看到这个库了
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mycat |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
3、表数据的初始
下面我们进行表数据的测试
1）、主机
首先我们再主机建立表并插入数据
mysql> use mycat;
Database changed
mysql>
mysql> create table `test1`(
-> id int auto_increment not null primary key,
-> name varchar(10) default null
-> );
Query OK, 0 rows affected (0.03 sec)
mysql> insert into test1(`id`,`name`) value(1,"petty");
Query OK, 1 row affected (0.16 sec)
mysql> select * from test1;
+----+-------+
| id | name |
+----+-------+
| 1 | petty |
+----+-------+
1 row in set (0.00 sec)
mysql>
2）、从机
下面我们在从机查看看有没有成功同步：
mysql> use mycat;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show tables;
+-----------------+
| Tables_in_mycat |
+-----------------+
| test1 |
+-----------------+
1 row in set (0.00 sec)
mysql> select * from test1;
+----+-------+
| id | name |
+----+-------+
| 1 | petty |
+----+-------+
1 row in set (0.00 sec)
mysql>
可以看到我们的主从配置已经成功了。
四、多主多从
我们还可以多主多从，例如我们一个主从序列是编号1位主机、编号2为从机，然后编号3为主机、编号4为从机，同时编号1主机与编号3主机相互为主从，这样就是其中主机一台有问题，整个mysql集群还是能正常工作。
由于目前只有3台机，只使用三台来写demo(一台windows，两台linux)。
1、编号1主机(192.168.254.30)
1）、修改配置
我们首先需要修改其原来的etc/my.cnf文件，添加：
# 作为从机也修改其bin-log日志
log-slave-updates
#自增长的幅度
auto-increment-increment=2
#自增长的开始位置
auto-increment-offset=1
整个文件的信息
[root@localhost Desktop]# cat /etc/my.cnf
[mysqld]
datadir=/usr/local/mysql/data
basedir=/usr/local/mysql
socket=/usr/local/mysql/data/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
server-id=1
log-bin=mysql-bin
binlog-ignore-db=mysql
binlog-ignore-db=information_schema
binlog-do-db=mycat
binlog_format=STATEMENT
log-slave-updates
auto-increment-increment=2
auto-increment-offset=1
[mysqld_safe]
log-error=/usr/local/mysql/data/mysqld.log
pid-file=/usr/local/mysql/data/mysqld/mysqld.pid
[root@localhost Desktop]#
修改这个文件后我们需要重启机器
2、编号2从机（192.168.254.31）
这台原来已经配置其连接30机器了，所以这次不用修改
3、编号3主机(192.168.254.1)
1）、修改配置文件
由于这台机器是windows，所以我们需要修改其的my.ini文件，在其最后面添加
server-id=3
log-bin=mysql-bin
binlog-ignore-db=mysql
binlog-ignore-db=information_schema
binlog-do-db=mycat
binlog_format=STATEMENT
log-slave-updates
auto-increment-increment=2
auto-increment-offset=2
注意我们上面改了server-id，同时也改了其的增长开始点auto-increment-offset=2。同时再重启服务。
2）、创建同步用户
首先我们可以在主机创建一个专门用于主从同步用户，通过命令：
GRANT REPLICATION SLAVE ON *.* TO 'SLAVE'@'%' IDENTIFIED BY '123456';
3）、查看状态
mysql> show master status;
+------------------+----------+--------------+--------------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+--------------------------+-------------------+
| mysql-bin.000001 | 154 | mycat | mysql,information_schema | |
+------------------+----------+--------------+--------------------------+-------------------+
1 row in set (0.00 sec)
mysql>
4）、设置同步的状态
下面我们运行其连接的主机(30)信息
CHANGE MASTER TO MASTER_HOST='192.168.254.130',
MASTER_USER='SLAVE',
MASTER_PASSWORD='123456',
MASTER_LOG_FILE='mysql-bin.000001',
MASTER_LOG_POS=430;
5）、编号1主机同步(192.168.254.30)
我们需要设置其去同步编号3主机(192.168.254.1)，即我们前面查看的编号3的(master status)：
CHANGE MASTER TO MASTER_HOST='192.168.254.1',
MASTER_USER='SLAVE',
MASTER_PASSWORD='123456',
MASTER_LOG_FILE='mysql-bin.000001',
MASTER_LOG_POS=154;
然后我们在编号1主机执行同步start slave;，也在编号3主机执行同步start slave;。
4、测试查看
1）、可能的问题(可略过)
现在我们测试，然后分别查看这两台的master状态show master status;。
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.254.1
Master_User: SLAVE
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 154
Relay_Log_File: localhost-relay-bin.000002
Relay_Log_Pos: 320
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
........
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.254.130
Master_User: SLAVE
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000002
Read_Master_Log_Pos: 462
Relay_Log_File: LAPTOP-QR83QEC0-relay-bin.000003
Relay_Log_Pos: 675
Relay_Master_Log_File: mysql-bin.000002
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
.........
可以看到它们的同步都是yes。这里可能有问题，我们需要自己解决，例如我在编号1机器修改配置，然后在查看其的状态，
mysql> show master status;
+------------------+----------+--------------+--------------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+--------------------------+-------------------+
| mysql-bin.000002 | 462 | mycat | mysql,information_schema | |
+------------------+----------+--------------+--------------------------+-------------------+
1 row in set (0.00 sec)
mysql>
我如果以这个消息去让编号3机器同步编号1，就会报(因为我又运行了一条新的插入语句)，但建表语句是在日志mysql-bin.000001，而这里我因为重启了，其有有新的mysql-bin.000002，所以有修改回了原来编号2的同步信息。
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.254.130
Master_User: SLAVE
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000002
Read_Master_Log_Pos: 462
Relay_Log_File: LAPTOP-QR83QEC0-relay-bin.000002
Relay_Log_Pos: 320
Relay_Master_Log_File: mysql-bin.000002
Slave_IO_Running: Yes
Slave_SQL_Running: No
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 1146
Last_Error: Error 'Table 'mycat.test1' doesn't exist' on query. Default database: 'mycat'. Query: 'insert into test1(`id`,`name`) value(2,"TOm")'
2）、在编号3插入数据
下面我们再编号3插入数据，看编号1、2能不能看到
在编号3操作：
mysql> insert into test1(`id`,`name`) value(3,"kitt");
Query OK, 1 row affected (0.01 sec)
mysql> select * from test1;
+----+-------+
| id | name |
+----+-------+
| 1 | petty |
| 2 | TOm |
| 3 | kitt |
+----+-------+
3 rows in set (0.00 sec)
mysql>
在编号1查看
mysql> select * from test1;
+----+-------+
| id | name |
+----+-------+
| 1 | petty |
| 2 | TOm |
| 3 | kitt |
+----+-------+
3 rows in set (0.00 sec)
mysql>
在编号2查看
mysql> select * from test1;
+----+-------+
| id | name |
+----+-------+
| 1 | petty |
| 2 | TOm |
| 3 | kitt |
+----+-------+
3 rows in set (0.00 sec)
mysql>
可以看到目前我们已经同步成功了，在编号1中能查看到主机编号3的插入信息。
3）、编号1处理数据
下面我们在编号1操作查看
编号1：
mysql> insert into test1(`id`,`name`) value(4,"lisa");
Query OK, 1 row affected (0.00 sec)
mysql> select * from test1;
+----+-------+
| id | name |
+----+-------+
| 1 | petty |
| 2 | TOm |
| 3 | kitt |
| 4 | lisa |
+----+-------+
4 rows in set (0.00 sec)
mysql>
编号3：
mysql> select * from test1;
+----+-------+
| id | name |
+----+-------+
| 1 | petty |
| 2 | TOm |
| 3 | kitt |
| 4 | lisa |
+----+-------+
4 rows in set (0.00 sec)
mysql>
可以看到其是相互同步的。
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