mysql binlog初步介绍

binlog 即二进制日志,它记录了数据库上的所有改变，并以二进制的形式保存在磁盘中； 它可以用来查看数据库的变更历史、数据库增量备份和恢复、Mysql的复制（主从数据库的复制）。

mysql binlog解析

binlog有三种格式:

• Statement 基于SQL语句的复制(statement-based replication,SBR)，
• Row 基于行的复制(row-based replication,RBR)，
• Mixed 混合模式复制(mixed-based replication,MBR)。

在我这边mysql 5.7.20版本中默认是使用Row的, 而且默认情况下没有开启binlog

mysql> select version();
+-----------+
| version() |
+-----------+
| 5.7.20    |
+-----------+
1 row in set (0.00 sec)

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

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

mac环境下开启mysql的binlog

编辑my.cnf文件，对于我来说就是/usr/local/etc/my.cnf文件，在其中增加下面的内容：

log-bin = /Users/rollenholt/Downloads/mysql/binlog
binlog-format = ROW
server_id = 1

然后brew services restart mysql重启mysql，接下来我们就可以验证mysql的binlog已经开启了：

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

mysql>
mysql> show binary logs;
+---------------+-----------+
| Log_name      | File_size |
+---------------+-----------+
| binlog.000001 |       177 |
| binlog.000002 |       177 |
| binlog.000003 |       177 |
| binlog.000004 |       154 |
+---------------+-----------+
4 rows in set (0.00 sec)

mysql> show master status;
+---------------+----------+--------------+------------------+-------------------+
| File          | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+---------------+----------+--------------+------------------+-------------------+
| binlog.000004 |      154 |              |                  |                   |
+---------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

mysql> show master logs;
+---------------+-----------+
| Log_name      | File_size |
+---------------+-----------+
| binlog.000001 |       177 |
| binlog.000002 |       177 |
| binlog.000003 |       177 |
| binlog.000004 |       154 |
+---------------+-----------+
4 rows in set (0.00 sec)

同时查看我们配置的log-bin属性对于的目录下：

~/Downloads/mysql » ls
binlog.000001 binlog.000002 binlog.000003 binlog.000004 binlog.index
------------------------------------------------------------
~/Downloads/mysql » cat binlog.index
/Users/rollenholt/Downloads/mysql/binlog.000001
/Users/rollenholt/Downloads/mysql/binlog.000002
/Users/rollenholt/Downloads/mysql/binlog.000003
/Users/rollenholt/Downloads/mysql/binlog.000004
------------------------------------------------------------
~/Downloads/mysql » cat binlog.000001
_binR �[w{5.7.20-logR �[8


**4SVѶR �[#��_]�hu �[����%                                                                        ------------------------------------------------------------
~/Downloads/mysql »

binlog相关的基本命令：

• 查看是否开启binlog show variables like 'log_bin'
• 获取binlog文件列表 show binary logs
• 查看master上的binlog show master logs
• 只查看第一个binlog文件的内容

mysql> show binlog events;
+---------------+-----+----------------+-----------+-------------+---------------------------------------+
| Log_name      | Pos | Event_type     | Server_id | End_log_pos | Info                                  |
+---------------+-----+----------------+-----------+-------------+---------------------------------------+
| binlog.000001 |   4 | Format_desc    |         1 |         123 | Server ver: 5.7.20-log, Binlog ver: 4 |
| binlog.000001 | 123 | Previous_gtids |         1 |         154 |                                       |
| binlog.000001 | 154 | Stop           |         1 |         177 |                                       |
+---------------+-----+----------------+-----------+-------------+---------------------------------------+
3 rows in set (0.01 sec)

• 查看指定binlog文件的内容 show binlog events in 'binlog.000001'
• 删除binlog
  • 使用linux命令删除binlog文件
  • 设置binlog的过期时间 使用variable expire_logs_days
  • 手动删除binlog
    • reset master;//删除master的binlog
    • reset slave; //删除slave的中继日志
    • purge master logs before '2012-03-30 17:20:00'; //删除指定日期以前的日志索引中binlog日志文件
    • purge master logs to 'mysql-bin.000002'; //删除指定日志文件的日志索引中binlog日志文件

mysql> show variables like '%expire_logs_days%';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| expire_logs_days | 0     |
+------------------+-------+
1 row in set (0.00 sec)

• flush logs 刷新日志
  • 当停止或重启服务器时，服务器会把日志文件记入下一个日志文件，Mysql会在重启时生成一个新的日志文件，文件序号递增；此外，如果日志文件超过max_binlog_size（默认值1G）系统变量配置的上限时，也会生成新的日志文件（在这里需要注意的是，如果你正使用大的事务，二进制日志还会超过max_binlog_size，不会生成新的日志文件，事务全写入一个二进制日志中,这种情况主要是为了保证事务的完整性）；日志被刷新时，新生成一个日志文件。

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