1. 背景

   * MySQL Replication默认都是异步（asynchronous），当主库在执行完一些事务后，是不会管备库的进度的。如果备库不幸落后，而更不幸的是主库此时又出现Crash（例如宕机），这时备库中的数据就是不完整的。简而言之，在主库发生故障的时候，我们无法使用备库来继续提供数据一致的服务了。

   * Semi sync Replication(半同步复制)是在master上提交完成后，再传送到slave等待ack应答，仅仅在一定情况下事务的已经传递到一个slave上，但是并不确保已经在备库上执行完成，会造成最后一次events的主备不一致。

   * lossless replication(无损复制)是在master提前过程中，传送到slave中等待应答。当至少一个slave request bilog后写入到relay-log并flush disk，就返回ack

2. lossless replication传输过程

3. 环境

   * master 实例环境

mysql> system cat /etc/redhat-release
CentOS release 6.8 (Final)

mysql> system ifconfig eth0  | sed -rn '2s#^.*addr:(.*)  Bca.*$#\1#gp'
172.18.0.1

mysql> show variables like 'version';
+---------------+------------+
| Variable_name | Value      |
+---------------+------------+
| version       | 5.7.18-log |
+---------------+------------+
1 row in set (0.00 sec)

   * slave 实例环境

mysql> system cat /etc/redhat-release
CentOS release 6.8 (Final)

mysql> system ifconfig eth0  | sed -rn '2s#^.*addr:(.*)  Bca.*$#\1#gp'
172.18.4.1

mysql> show variables like 'version';
+---------------+------------+
| Variable_name | Value      |
+---------------+------------+
| version       | 5.7.18-log |
+---------------+------------+
1 row in set (0.00 sec)

   * master 实例my.cnf文件

[mysqld]
########basic settings########
# 主从server-id一定要设置不同
server-id = 110
port = 3306
user = mysql
bind_address = 0.0.0.0    
character_set_server=utf8mb4
skip_name_resolve = 1
datadir = /data/mysql_data
log_error = error.log
#######replication settings########
master_info_repository = TABLE
relay_log_info_repository = TABLE
# MySQL复制是基于binlog日志的
log_bin = bin.log
sync_binlog = 1
log_slave_updates
# MySQL binlog格式搭建主从时必须设置为row
binlog_format = row
relay_log = relay.log
relay_log_recovery = 1
slave_skip_errors = ddl_exist_errors
######semi sync replication settings########
# 设置插件目录路径
plugin_dir=/usr/local/mysql/lib/plugin
# 加载插件
plugin_load = "rpl_semi_sync_master=semisync_master.so;rpl_semi_sync_slave=semisync_slave.so"
# 开启master semi sync replication
rpl_semi_sync_master_enabled = 1
# 开启slave semi sync replication
rpl_semi_sync_slave_enabled = 1
# 等待5秒无ack应答自动切换为异步模式
rpl_semi_sync_master_timeout = 5000
# 开启lossless replication
rpl_semi_sync_master_wait_point= AFTER_SYNC
# 至少有1个slave接收到日志
rpl_semi_sync_master_wait_for_slave_count = 1

   * slave 实例my.cnf文件

[mysqld]
########basic settings########
server-id = 210
port = 3306
user = mysql
bind_address = 0.0.0.0
character_set_server=utf8mb4
skip_name_resolve = 1
datadir = /data/mysql_data
log_error = error.log
# slave上开启只读，避免应用误写导致主从数据不一致
read_only = on
super_read_only = on
#######replication settings########
master_info_repository = TABLE
relay_log_info_repository = TABLE
log_bin = bin.log
sync_binlog = 1
log_slave_updates
binlog_format = row
relay_log = relay.log
relay_log_recovery = 1
binlog_gtid_simple_recovery = 1
slave_skip_errors = ddl_exist_errors
######semi sync replication settings########
plugin_dir=/usr/local/mysql/lib/plugin
plugin_load = "rpl_semi_sync_master=semisync_master.so;rpl_semi_sync_slave=semisync_slave.so"
loose_rpl_semi_sync_master_enabled = 1
loose_rpl_semi_sync_slave_enabled = 1
loose_rpl_semi_sync_master_timeout = 5000
rpl_semi_sync_master_wait_point = AFTER_SYNC
rpl_semi_sync_master_wait_for_slave_count = 1

4. 搭建无数据基于无损全复制主从 [ master原来无数据 ]

   * Master 创建复制所使用的用户 [ 此处ip设置为slave服务IP或者% ]

mysql> grant replication slave on *.* to 'rpl'@'172.18.4.1' identified by '123';
Query OK, 0 rows affected, 1 warning (0.00 sec)

   * master服务器上查看binlog文件名和日志位置

mysql> show master status;
+------------+----------+--------------+------------------+-------------------+
| File       | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------+----------+--------------+------------------+-------------------+
| bin.000002 |      689 |              |                  |                   |
+------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

   * slave服务器上设置master信息

           未开启slave服务时，Slave_IO_Running与Slave_SQL_Running状态成No

           master_log_file 设置开始复制文件, master_log_pos 开始文件复制点

mysql> show slave status;          # 未开启复制功能时，slave状态是空的
Empty set (0.00 sec)

mysql> change master to master_host='172.18.0.1',master_user='rpl',master_password='123',master_log_file='bin.000002',master_log_pos=689;
Query OK, 0 rows affected, 2 warnings (0.03 sec)

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: 
                  Master_Host: 172.18.0.1
                  Master_User: rpl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: bin.000002
          Read_Master_Log_Pos: 689
               Relay_Log_File: relay.000001
                Relay_Log_Pos: 4
        Relay_Master_Log_File: bin.000002
             Slave_IO_Running: No
            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: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 689
              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: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 0
                  Master_UUID: 
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: 
           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)

   * 开启slave服务，并查看状态

     正常开启slave服务后，Slave_IO_Running与Slave_SQL_Running状态成Yes

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 172.18.0.1
                  Master_User: rpl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: bin.000002
          Read_Master_Log_Pos: 689
               Relay_Log_File: relay.000002
                Relay_Log_Pos: 314
        Relay_Master_Log_File: bin.000002
             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: 689
              Relay_Log_Space: 511
              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: 110
                  Master_UUID: d7d5a01b-6ea0-11e7-9773-00163e0432c5
             Master_Info_File: mysql.slave_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)

   * Master上查看Slave连接信息

mysql> show slave hosts;
+-----------+------+------+-----------+--------------------------------------+
| Server_id | Host | Port | Master_id | Slave_UUID                           |
+-----------+------+------+-----------+--------------------------------------+
|       210 |      | 3306 |       110 | 499ecfb3-6ea2-11e7-aec1-00163e028c02 |
+-----------+------+------+-----------+--------------------------------------+
1 row in set (0.00 sec)

   * Master上操作创建数据库与表，并插入数据

mysql> create database mytest character set utf8mb4;
Query OK, 1 row affected (0.01 sec)

mysql> use mytest;
Database changed
mysql> create table users(
    -> id BIGINT NOT NULL AUTO_INCREMENT,
    -> name VARCHAR(255) NOT NULL,
    -> sex ENUM('M', 'F') NOT NULL DEFAULT 'M',
    -> age INT SIGNED NOT NULL DEFAULT '0',
    -> PRIMARY KEY (id)
    -> )ENGINE=INNODB DEFAULT CHARSET=utf8mb4;
Query OK, 0 rows affected (0.02 sec)

mysql> insert into users values(null, 'tom', 'M', 24), (null, 'jak', 'F', 32), (null, 'sea', 'M', 35), (null, 'lisea', 'M', 29);
Query OK, 4 rows affected (0.01 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> select * from users;
+----+-------+-----+-----+
| id | name  | sex | age |
+----+-------+-----+-----+
|  1 | tom   | M   |  24 |
|  2 | jak   | F   |  32 |
|  3 | sea   | M   |  35 |
|  4 | lisea | M   |  29 |
+----+-------+-----+-----+
4 rows in set (0.00 sec)

   * Slave上查看

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| mytest             |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> use mytest;
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_mytest |
+------------------+
| users            |
+------------------+
1 row in set (0.00 sec)

mysql> select * from users;
+----+-------+-----+-----+
| id | name  | sex | age |
+----+-------+-----+-----+
|  1 | tom   | M   |  24 |
|  2 | jak   | F   |  32 |
|  3 | sea   | M   |  35 |
|  4 | lisea | M   |  29 |
+----+-------+-----+-----+
4 rows in set (0.00 sec)

5. 搭建有数据基于无损全复制主从 [ master原来有数据 ]

   * 查看mytest库内容

Database changed
mysql> show tables;
+------------------+
| Tables_in_mytest |
+------------------+
| users            |
+------------------+
1 row in set (0.00 sec)

mysql> select * from users;
+----+-------+-----+-----+
| id | name  | sex | age |
+----+-------+-----+-----+
|  1 | tom   | M   |  24 |
|  2 | jak   | F   |  32 |
|  3 | sea   | M   |  35 |
|  4 | lisea | M   |  29 |
+----+-------+-----+-----+
4 rows in set (0.00 sec)

   * 使用mysqldump原子导出master库数据，并记录binlog [ 测试只有mytest库 ]

     如果有多个库，-B参数后逗号分隔。

[root@master ~]# mysqldump --single-transaction --master-data -B mytest -uroot -p > mytest.sql
Enter password:

   * 将导出的备份文件mytest.sql传输到slave

[root@master ~]# scp ./mytest.sql root@172.18.4.1:/root

   * slave创建相同的数据库，并将备份导入

mysql> create database mytest character set utf8mb4;
Query OK, 1 row affected (0.01 sec)

[root@slave ~]# mysql -uroot -p mytest < mytest.sql 
Enter password:

   * Master 创建复制所使用的用户 [ 此处ip设置为slave服务IP或者% ]

mysql> grant replication slave on *.* to 'rpl'@'172.18.4.1' identified by '123';
Query OK, 0 rows affected, 1 warning (5.01 sec)

   * 查看备份文件mytest.sql查看binlog文件名和日志位置

[root@slave ~]# grep 'CHANGE MASTER TO' mytest.sql 
CHANGE MASTER TO MASTER_LOG_FILE='bin.000002', MASTER_LOG_POS=1575;

   * slave服务器上设置master信息

           未开启slave服务时，Slave_IO_Running与Slave_SQL_Running状态成No

mysql> show slave status;        # 未开启复制功能时，slave状态是空的
Empty set (0.00 sec)

mysql> change master to master_host='172.18.0.1',master_user='rpl',master_password='123',master_log_file='bin.000002',master_log_pos=1575;
Query OK, 0 rows affected, 2 warnings (0.02 sec)

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: 
                  Master_Host: 172.18.0.1
                  Master_User: rpl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: bin.000002
          Read_Master_Log_Pos: 1575
               Relay_Log_File: relay.000001
                Relay_Log_Pos: 4
        Relay_Master_Log_File: bin.000002
             Slave_IO_Running: No
            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: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 1575
              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: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 0
                  Master_UUID: 
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: 
           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)

   * 开启slave服务，并查看状态

mysql> start slave;
Query OK, 0 rows affected (0.01 sec)

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 172.18.0.1
                  Master_User: rpl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: bin.000002
          Read_Master_Log_Pos: 1872
               Relay_Log_File: relay.000002
                Relay_Log_Pos: 611
        Relay_Master_Log_File: bin.000002
             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: 1872
              Relay_Log_Space: 808
              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: 110
                  Master_UUID: d7d5a01b-6ea0-11e7-9773-00163e0432c5
             Master_Info_File: mysql.slave_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)

   * master上mytest库数据操作

mysql> select * from mytest.users;
+----+-------+-----+-----+
| id | name  | sex | age |
+----+-------+-----+-----+
|  1 | tom   | M   |  24 |
|  2 | jak   | F   |  32 |
|  3 | sea   | M   |  35 |
|  4 | lisea | M   |  29 |
+----+-------+-----+-----+
4 rows in set (0.00 sec)

mysql> insert into mytest.users select null, 'test', 'M', 42;
Query OK, 1 row affected (0.01 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> update mytest.users set name='seasea'  where id = 3;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from mytest.users;
+----+--------+-----+-----+
| id | name   | sex | age |
+----+--------+-----+-----+
|  1 | tom    | M   |  24 |
|  2 | jak    | F   |  32 |
|  3 | seasea | M   |  35 |
|  4 | lisea  | M   |  29 |
|  5 | test   | M   |  42 |
+----+--------+-----+-----+
5 rows in set (0.00 sec)

   * slave上查看

mysql> select * from mytest.users;
+----+--------+-----+-----+
| id | name   | sex | age |
+----+--------+-----+-----+
|  1 | tom    | M   |  24 |
|  2 | jak    | F   |  32 |
|  3 | seasea | M   |  35 |
|  4 | lisea  | M   |  29 |
|  5 | test   | M   |  42 |
+----+--------+-----+-----+
5 rows in set (0.00 sec)

6. 总结

以需求驱动技术，技术本身没有优略之分，只有业务之分。