MySQL主库binlog(master-log)与从库relay-log关系代码详解

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

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