一、了解Binary Log结构
1.1、High-Level Binary Log Structure and Contents
• Binlog包括binary log files和index file
• 每个binary log文件的前4字节是Magic Number，紧接着是一组描述数据修改的Events
• The magic number bytes are 0xfe 0x62 0x69 0x6e = 0xfe ‘b‘‘i‘‘n‘
• 每个Event包括header bytes和data bytes
header bytes：Event类型，什么时候，由哪个server生成等信息
data bytes：特定的数据修改
• 第一个Event是Description Event，描述文件的格式版本
• 其他Events按照binlog_version(1、3、4)进行记录
• 最后一个Event是Log-rotation Event，指定下一个binary log的文件名称
• index文件里面是当前binary log的一个列表
1.2、Binary Log结构示意图
# Binary Log结构示意图(binlog_version=4) |<----------------------------------Events---------------------------------->| |<---------Fisrt Event--------->|<------Mid Events----->|<---Final Event---->| +--------------+-------------------------------+--------+-----+--------+--------------------+ | Magic Number | FDE(Format Description Event) | Event1 | ... | EventN | Log-rotation Event | +--------------+-------------------------------+--------+-----+--------+--------------------+ |<-event header->|<-event data->|
上图是binlog_version=4(MySQL 5.0 and up)的示意图
二、index file添加一行不存在的binary log记录
查看当前binary log
# 查看当前binary log [root@ZST1 logs]# ll total 20 -rw-r-----. 1 mysql mysql 201 Jan 12 11:32 mysql-bin.000004 -rw-r-----. 1 mysql mysql 201 Jan 12 11:32 mysql-bin.000005 -rw-r-----. 1 mysql mysql 177 Jan 12 11:34 mysql-bin.000006 -rw-r-----. 1 mysql mysql 177 Jan 12 11:37 mysql-bin.000007 -rw-r-----. 1 mysql mysql 220 Jan 12 11:34 mysql-bin.index [root@ZST1 logs]# cat mysql-bin.index /data/mysql/mysql3308/logs/mysql-bin.000004 /data/mysql/mysql3308/logs/mysql-bin.000005 /data/mysql/mysql3308/logs/mysql-bin.000006 /data/mysql/mysql3308/logs/mysql-bin.000007 [root@ZST1 logs]#
mysql-bin.index 添加一行已经删除的记录/data/mysql/mysql3308/logs/mysql-bin.000001，重新启动数据库服务
# 查看error log [root@ZST1 ~]# more /data/mysql/mysql3308/data/error.log ... 2018-01-12T03:34:33.467474Z 0 [Note] InnoDB: Loading buffer pool(s) from /data/mysql/mysql3308/data/ib_buffer_pool mysqld: File ‘/data/mysql/mysql3308/logs/mysql-bin.000001‘ not found (Errcode: 2 - No such file or directory) 2018-01-12T03:34:33.546276Z 0 [ERROR] Failed to open log (file ‘/data/mysql/mysql3308/logs/mysql-bin.000001‘, errno 2) 2018-01-12T03:34:33.546294Z 0 [ERROR] Could not open log file 2018-01-12T03:34:33.563485Z 0 [Warning] Failed to set up SSL because of the following SSL library error: SSL context is not usable without certificate and private key 2018-01-12T03:34:33.563528Z 0 [Note] Server hostname (bind-address): ‘*‘; port: 3308 数据库服务最终启动起来
mysql-bin.index 添加一行未来的记录/data/mysql/mysql3308/logs/mysql-bin.000017，重新启动数据库服务
# 查看error log [root@ZST1 ~]# more /data/mysql/mysql3308/data/error.log ... 2018-01-12T03:44:45.921370Z 0 [Note] InnoDB: Loading buffer pool(s) from /data/mysql/mysql3308/data/ib_buffer_pool mysqld: File ‘/data/mysql/mysql3308/logs/mysql-bin.000017‘ not found (Errcode: 2 - No such file or directory) 2018-01-12T03:44:46.017490Z 0 [ERROR] Failed to open log (file ‘/data/mysql/mysql3308/logs/mysql-bin.000017‘, errno 2) 2018-01-12T03:44:46.017509Z 0 [ERROR] Could not open log file 2018-01-12T03:44:46.017532Z 0 [ERROR] Can not init tc log 2018-01-12T03:44:46.017545Z 0 [ERROR] Aborting 数据库服务最终退出
启动过程会读取index file中的第一条和最后一条记录，然后检查对应的文件是否存在。如果第一条不存在，error log中会有报错，但服务正常启动；如果最后一条不存在，error log中会有报错，服务退出。即使你打乱index file中列表顺序，或者写入其他信息，它始终只验证index file的第一条和最后一条~
三、手动创建一个binary log，但不添加到index file
如果touch_seq < max(exists_seq)，正常启动，最新的new_seq=max(exists_seq)+1
如果max(exists_seq) < touch_seq < pow(2,31)-1，正常启动，最新的new_seq=touch_seq+1，当new_seq > pow(2,31)-1001 时会往error log中写入警告
如果touch_seq = pow(2,31)-1，mysqld退出
如果touch_seq > pow(2,31)-1，正常启动，会往error log中写入警告
3.1、MySQL binlog后面的编号最大是多大
最大编号参考文章：MySQL binlog后面的编号最大是多大
原文结论：
1、MySQL binlog的最大sequence是：pow(2,31)-1 = 2147483647
2、当 pow(2,31)-1001 < sequence < pow(2,31)-1 会往error log中写入警告
3、binlog的sequence达到最大值(2147483647)时，不管有没有mysql-bin.000001类似这样的文件，mysqld都是退出
4、在MySQL产生binlog时会读取当前日件文目录下的log-bin的base name获取下一个日志文件的后面的Seq。所以日志目录下文件太多，会影响MySQL的启动及日志切换。这里也有一个大的隐患，运行中给放一个较大的日志文件，在下次日志文件切换时有可能很快就接近于最大值，造成mysqld crash退出
5、一定要监控error log的输出，并足够重视
查看源码
# 源码信息 sql/binlog.cc #define MAX_LOG_UNIQUE_FN_EXT 0x7FFFFFFF #define LOG_WARN_UNIQUE_FN_EXT_LEFT 1000 /* check if reached the maximum possible extension number */ if (max_found == MAX_LOG_UNIQUE_FN_EXT) { sql_print_error("Log filename extension number exhausted: %06lu. \ Please fix this by archiving old logs and updating the index files.", max_found); error= 1; goto end; } /* print warning if reaching the end of available extensions. */ if ((next > (MAX_LOG_UNIQUE_FN_EXT - LOG_WARN_UNIQUE_FN_EXT_LEFT))) sql_print_warning("Next log extension: %lu. \ Remaining log filename extensions: %lu. Please consider archiving some logs.", next, (MAX_LOG_UNIQUE_FN_EXT - next)); mysql> select conv(‘7FFFFFFF‘,16,10); +------------------------+ | conv(‘7FFFFFFF‘,16,10) | +------------------------+ | 2147483647 | +------------------------+
源码逻辑正是上面的结论1、2、3。如果我们的binlog的sequence疯涨到2147483647，那很不幸mysqld会退出。。。但如果我们在正常情况下，touch一个大于2147483647的binary log的文件会出现什么情况呢？
3.2、MySQL binlog后面的编号最大到底是多大
首先我们从2147483648开始
# reset master mydba@192.168.85.132,3308 [replcrash]> reset master; Query OK, 0 rows affected (0.01 sec) # 查看binary log mydba@192.168.85.132,3308 [replcrash]> show binary logs; +------------------+-----------+ | Log_name | File_size | +------------------+-----------+ | mysql-bin.000001 | 154 | +------------------+-----------+ row in set (0.00 sec) # touch 2^31 [root@ZST1 logs]# touch mysql-bin.2147483648 [root@ZST1 logs]# chown -R mysql:mysql * # flush执行5次 mydba@192.168.85.132,3308 [replcrash]> flush binary logs; Query OK, 0 rows affected (0.01 sec) # 查看binary log mydba@192.168.85.132,3308 [replcrash]> show binary logs; +----------------------+-----------+ | Log_name | File_size | +----------------------+-----------+ | mysql-bin.000001 | 205 | | mysql-bin.2147483649 | 205 | | mysql-bin.2147483650 | 205 | | mysql-bin.2147483651 | 205 | | mysql-bin.2147483652 | 205 | | mysql-bin.2147483653 | 154 | +----------------------+-----------+ rows in set (0.00 sec) # 查看error log [root@ZST1 data]# cat error.log 2018-01-08T09:09:06.235149Z 3 [Warning] Next log extension: 2147483649. Remaining log filename extensions: 18446744073709551614. Please consider archiving some logs. 2018-01-08T09:09:23.868883Z 3 [Warning] Next log extension: 2147483650. Remaining log filename extensions: 18446744073709551613. Please consider archiving some logs. 2018-01-08T09:10:29.670811Z 3 [Warning] Next log extension: 2147483651. Remaining log filename extensions: 18446744073709551612. Please consider archiving some logs. 2018-01-08T09:10:30.401541Z 3 [Warning] Next log extension: 2147483652. Remaining log filename extensions: 18446744073709551611. Please consider archiving some logs. 2018-01-08T09:10:31.075702Z 3 [Warning] Next log extension: 2147483653. Remaining log filename extensions: 18446744073709551610. Please consider archiving some logs. [root@ZST1 logs]# # 再次reset master mydba@192.168.85.132,3308 [replcrash]> reset master; Query OK, 0 rows affected (0.02 sec) # 查看binary log mydba@192.168.85.132,3308 [replcrash]> show binary logs; +----------------------+-----------+ | Log_name | File_size | +----------------------+-----------+ | mysql-bin.2147483649 | 154 | +----------------------+-----------+ row in set (0.00 sec)
可以看到，执行flush binary logs后，sequence一直往后+1(next)。error log中会有警告日志，next > (MAX_LOG_UNIQUE_FN_EXT - LOG_WARN_UNIQUE_FN_EXT_LEFT)恒成立；Remaining log filename extensions后面的数值看着有点怪异~
第二次reset后的sequence从2147483649开始，并不是从000001开始，不知道什么原因。
我们继续加大sequence，直到接近9223372036854775808
# touch 2^63-2 [root@ZST1 logs]# touch mysql-bin.9223372036854775806 [root@ZST1 logs]# chown -R mysql:mysql * # flush执行5次 mydba@192.168.85.132,3308 [replcrash]> flush binary logs; Query OK, 0 rows affected (0.01 sec) # 查看binary log mydba@192.168.85.132,3308 [replcrash]> show binary logs; +-------------------------------+-----------+ | Log_name | File_size | +-------------------------------+-----------+ | mysql-bin.000001 | 214 | | mysql-bin.9223372036854775807 | 214 | | mysql-bin.9223372036854775808 | 154 | | mysql-bin.9223372036854775808 | 154 | | mysql-bin.9223372036854775808 | 154 | | mysql-bin.9223372036854775808 | 154 | +-------------------------------+-----------+ rows in set (0.00 sec) # 查看error log [root@ZST1 data]# cat error.log 2018-01-08T09:35:20.879612Z 3 [Warning] Next log extension: 9223372036854775807. Remaining log filename extensions: 9223372039002259456. Please consider archiving some logs. 2018-01-08T09:35:22.082530Z 3 [Warning] Next log extension: 9223372036854775808. Remaining log filename extensions: 9223372039002259455. Please consider archiving some logs. 2018-01-08T09:35:22.934636Z 3 [Warning] Next log extension: 9223372036854775808. Remaining log filename extensions: 9223372039002259455. Please consider archiving some logs. 2018-01-08T09:35:23.544604Z 3 [Warning] Next log extension: 9223372036854775808. Remaining log filename extensions: 9223372039002259455. Please consider archiving some logs. 2018-01-08T09:35:24.134664Z 3 [Warning] Next log extension: 9223372036854775808. Remaining log filename extensions: 9223372039002259455. Please consider archiving some logs. [root@ZST1 logs]#
当sequence达到9223372036854775808后，再flush binary log，看不出产生新binary log~
[root@ZST1 logs]# mysqlbinlog -v --base64-output=decode-rows mysql-bin.9223372036854775808 /*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/; /*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/; DELIMITER /*!*/; # at 4 #180112 15:57:18 server id 1323308 end_log_pos 123 CRC32 0x798b200f Start: binlog v 4, server v 5.7.19-log created 180112 15:57:18 # Warning: this binlog is either in use or was not closed properly. # at 123 #180112 15:57:18 server id 1323308 end_log_pos 154 CRC32 0xf3252c32 Previous-GTIDs # [empty] # at 154 #180112 15:57:18 server id 1323308 end_log_pos 214 CRC32 0x6054f256 Rotate to mysql-bin.9223372036854775808 pos: 4 SET @@SESSION.GTID_NEXT= ‘AUTOMATIC‘ /* added by mysqlbinlog */ /*!*/; DELIMITER ; # End of log file /*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/; /*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=0*/; [root@ZST1 logs]#
解析binlog可以在末尾看到Rotate to mysql-bin.9223372036854775808 pos: 4
也就是说再怎么切，也只能切到9223372036854775808，这个文件感觉有点不太正常，不受max_binlog_size限制，解析出的日志莫名不完整~
恢复原始：手工删除 mysql-bin.2147483647 这类大文件，然后修改 mysql-bin.index；或者直接清空logs文件夹，再重新启动数据库服务
四、参考文档
MySQL binlog后面的编号最大是多大：http://wubx.net/mysql-binlog-max-sequence/
High-Level Binary Log Structure and Contents：https://dev.mysql.com/doc/internals/en/binary-log-structure-and-contents.html
Binary Log Versions：https://dev.mysql.com/doc/internals/en/binary-log-versions.html
Event Structure：https://dev.mysql.com/doc/internals/en/event-structure.html
