MySQL主库binlog(master-log)与从库relay-log关系代码详解
作者：遥望青春
这篇文章主要介绍了MySQL主库binlog与从库relay-log关系的相关内容，涉及部分代码，需要的朋友可以参考。
主库binlog:
# at 2420
#170809 17:16:20 server id 1882073306 end_log_pos 2451 CRC32 0x58f2db87 Xid = 32880
COMMIT/*!*/;
# at 2451
#170814 11:07:18 server id 1882073306 end_log_pos 2528 CRC32 0x40774a4b Query thread_id=92 exec_time=0 error_code=0
SET TIMESTAMP=1502680038/*!*/;
BEGIN
/*!*/;
# at 2528
# at 2560
#170814 11:07:18 server id 1882073306 end_log_pos 2560 CRC32 0x7bdf274b Intvar
SET INSERT_ID=107/*!*/;
#170814 11:07:18 server id 1882073306 end_log_pos 2669 CRC32 0x68e441c8 Query thread_id=92 exec_time=0 error_code=0
SET TIMESTAMP=1502680038/*!*/;
insert into t2 (name) values ('a100')
/*!*/;
# at 2669
# at 2701
#170814 11:07:27 server id 1882073306 end_log_pos 2701 CRC32 0xcf89b910 Intvar
SET INSERT_ID=108/*!*/;
#170814 11:07:27 server id 1882073306 end_log_pos 2810 CRC32 0x78466d7b Query thread_id=92 exec_time=0 error_code=0
SET TIMESTAMP=1502680047/*!*/;
insert into t2 (name) values ('a200')
/*!*/;
# at 2810
# at 2842
#170814 11:07:30 server id 1882073306 end_log_pos 2842 CRC32 0x1e5a0847 Intvar
SET INSERT_ID=109/*!*/;
#170814 11:07:30 server id 1882073306 end_log_pos 2951 CRC32 0xebeb947c Query thread_id=92 exec_time=0 error_code=0
SET TIMESTAMP=1502680050/*!*/;
insert into t2 (name) values ('a300')
/*!*/;
# at 2951
#170814 11:07:34 server id 1882073306 end_log_pos 2982 CRC32 0x6436ad60 Xid = 32934
COMMIT/*!*/;
从库relay-log:
/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/;
/*!40019 SET @@session.max_insert_delayed_threads=0*/;
/*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/;
DELIMITER /*!*/;
# at 4
#170809 17:17:24 server id 1882083306 end_log_pos 120 CRC32 0x5df4221c Start: binlog v 4, server v 5.6.23-72.1-log created 170809 17:17:24
# at 120
#700101 8:00:00 server id 1882073306 end_log_pos 0 CRC32 0x0b8a412f Rotate to test-mysql-bin.000116 pos: 2451
# at 172
#170809 16:28:12 server id 1882073306 end_log_pos 0 CRC32 0xd0d3bf30 Start: binlog v 4, server v 5.6.23-72.1-log created 170809 16:28:12
# at 288
#170814 11:07:18 server id 1882073306 end_log_pos 2528 CRC32 0x40774a4b Query thread_id=92 exec_time=0 error_code=0
SET TIMESTAMP=1502680038/*!*/;
SET @@session.pseudo_thread_id=92/*!*/;
SET @@session.foreign_key_checks=1, @@session.sql_auto_is_null=0, @@session.unique_checks=1, @@session.autocommit=1/*!*/;
SET @@session.sql_mode=1073741824/*!*/;
SET @@session.auto_increment_increment=1, @@session.auto_increment_offset=1/*!*/;
/*!\C utf8 *//*!*/;
SET @@session.character_set_client=33,@@session.collation_connection=33,@@session.collation_server=33/*!*/;
SET @@session.lc_time_names=0/*!*/;
SET @@session.collation_database=DEFAULT/*!*/;
BEGIN
/*!*/;
# at 365
# at 397
#170814 11:07:18 server id 1882073306 end_log_pos 2560 CRC32 0x7bdf274b Intvar
SET INSERT_ID=107/*!*/;
#170814 11:07:18 server id 1882073306 end_log_pos 2669 CRC32 0x68e441c8 Query thread_id=92 exec_time=0 error_code=0
use `db1`/*!*/;
SET TIMESTAMP=1502680038/*!*/;
insert into t2 (name) values ('a100')
/*!*/;
# at 506
# at 538
#170814 11:07:27 server id 1882073306 end_log_pos 2701 CRC32 0xcf89b910 Intvar
SET INSERT_ID=108/*!*/;
#170814 11:07:27 server id 1882073306 end_log_pos 2810 CRC32 0x78466d7b Query thread_id=92 exec_time=0 error_code=0
SET TIMESTAMP=1502680047/*!*/;
insert into t2 (name) values ('a200')
/*!*/;
# at 647
# at 679
#170814 11:07:30 server id 1882073306 end_log_pos 2842 CRC32 0x1e5a0847 Intvar
SET INSERT_ID=109/*!*/;
#170814 11:07:30 server id 1882073306 end_log_pos 2951 CRC32 0xebeb947c Query thread_id=92 exec_time=0 error_code=0
SET TIMESTAMP=1502680050/*!*/;
insert into t2 (name) values ('a300')
/*!*/;
# at 788
#170814 11:07:34 server id 1882073306 end_log_pos 2982 CRC32 0x6436ad60 Xid = 32934
COMMIT/*!*/;
注意relay log的这一行：
#700101 8:00:00 server id 1882073306 end_log_pos 0 CRC32 0x0b8a412f Rotate to test-mysql-bin.000116 pos: 2451
说明此relay log保存的是主库 test-mysql-bin.000116 的信息，从position 2451 开始。
看一个具体的对应关系：
主库的binlog如下：
# at 2560
#170814 11:07:18 server id 1882073306 end_log_pos 2560 CRC32 0x7bdf274b Intvar
SET INSERT_ID=107/*!*/;
#170814 11:07:18 server id 1882073306 end_log_pos 2669 CRC32 0x68e441c8 Query thread_id=92 exec_time=0 error_code=0
SET TIMESTAMP=1502680038/*!*/;
insert into t2 (name) values ('a100')
/*!*/;
# at 2669
对应从库relay-log如下几行：
# at 397
#170814 11:07:18 server id 1882073306 end_log_pos 2560 CRC32 0x7bdf274b Intvar
SET INSERT_ID=107/*!*/;
#170814 11:07:18 server id 1882073306 end_log_pos 2669 CRC32 0x68e441c8 Query thread_id=92 exec_time=0 error_code=0
use `db1`/*!*/;
SET TIMESTAMP=1502680038/*!*/;
insert into t2 (name) values ('a100')
/*!*/;
# at 506
另外注意show slave status\G的以下几行的关系：
Master_Log_File: test-mysql-bin.000117 Read_Master_Log_Pos: 774
上面二行代表IO线程,相对于主库
Relay_Log_File: relay-log.000038 Relay_Log_Pos: 723
上面二行代表了sql线程,相对于从库
Relay_Master_Log_File: test-mysql-bin.000117 Exec_Master_Log_Pos: 555
上面二行代表了sql线程,相对主库
其中Relay_Log_Pos: 723 和 Exec_Master_Log_Pos: 555 对应的sql语句一致。
总结
以上就是本文关于MySQL主库binlog与从库relay-log关系代码详解的全部内容，希望对大家有所帮助。感兴趣的朋友可以参阅：mysql中binlog_format模式与配置详细分析、几个比较重要的MySQL变量、MySQL prepare原理详解等，有什么问题可以随时留言，欢迎大家交流讨论。