MySQL's binlog log

First, what is binlog

binlogIt is a binary file format for recording user database updated SQL statement information, such as changing the database tables and change the contents of the SQL statement will be recorded in the binlog, but the library table and other contents of the query will not be recorded .

By default, the binloglog is in binary format can not be used to view text tool commands (for example, cat, vi, etc.) to view, and use mysqlbinloganalytic view.

Two, binlog role

Primary database for replication and recovery from an incremental data.

Three, binlog three modes

3.1 Row Level mode (RBR)

不记录每条sql语句的上下文信息，只需记录哪条数据被修改了，修改成什么样了。

advantage:

准确性强，能准确复制数据的变更

Disadvantages:

会产生大量的日志,导致较大的网络IO和磁盘IO

3.2 Statement Level Mode (SBR)

每一条修改数据的 sql 都会记录到 master 的 bin_log 中，slave 在复制的时候 sql 进程会解析成 master 端执行过的相同的 sql 在 slave 库上再次执行。

advantage:

不需要记录每一条sql语句和每一行的数据变化，减少了binlog日志量，节约IO，提高性能。

Disadvantages:

在某些情况下会导致 master-slave 中的数据不一致(如sleep()函数， last_insert_id()，以及user-defined functions(udf)等会出现问题)

3.3 MIXED mode (MBR)

以上两种模式的混合使用，一般的复制使用 STATEMENT 模式保存 binlog，对于 STATEMENT 模式无法复制的操作使用 ROW 模式保存 binlog，MySQL会根据执行的 SQL 语句选择日志保存方式。

advantage:

准确性强，文件大小适中

Disadvantages:

有可能发生主从不一致问题

Select 3.4 binlog mode

1. 不用存储过程、触发器、函数，选择默认的 Statement level
2. 用到MySQL的特殊功能（存储过程、触发器、函数）选择Mixed模式
3. 用到MySQL的特殊功能（存储过程、触发器、函数），又希望数据最大化一直则选择Row模式

Four, binlog common parameters

parameter name	meaning
log_bin = {on | off | base_name}	Specifies whether to enable recording binary log or specify a log path
sql_log_bin ={ on | off }	Specifies whether to record the binary log enabled
expire_logs_days	Specified time automatically deleted binary log that logs the expiration time
log_bin_index	Specifies the path to the file mysql-bin.index
binlog_format = { mixed | row | statement }	Specifies the binary log records based on what mode
max_binlog_size	Specifies the maximum binary log file
binlog_cache_size	Specify transaction log buffer size
max_binlog_cache_size	Specifies the maximum size for binary log cache
sync_binlog = { 0 | n }	Specify how many times the write buffer, brush plate

Fifth, practice

5.1 binlog check function is turned on

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

We can see binlogthe function is disabled by default.

5.2 open binlog function

Create a binlogstorage path and empowerment

[root@VM_0_15_centos log]# mkdir -p /var/log/mysql
[root@VM_0_15_centos log]# chown -R mysql.mysql /var/log/mysql

Edit my.cnfProfile

[root@VM_0_15_centos log]# vim /etc/my.cnf

In the [mysqld]Edit under the following labels:

# binlog 存放路径
log_bin=/var/log/mysql/mysql-bin
# 服务Id,保持唯一
server_id=1

Restart MySQL service

[root@VM_0_15_centos log]# systemctl restart mysqld

Re-examine whether to open the log function

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

5.3 binlog View mode

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

You can see the MySQL 5.7version of the default binlogmode ROW.

5.4 modify binlog mode

Edit my.cnfProfile

[root@VM_0_15_centos log]# vim /etc/my.cnf

In the [mysqld]Edit under the following labels:

binlog_format=mixed 

Restart Service

[root@VM_0_15_centos log]# systemctl restart mysqld

View binlogmode

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

5.5 View binlog file

View statementschema file:

mysqlbinlog 文件名

View rowschema file

mysqlbinlog -vv 文件名

5.6 Delete binlog file

method one:

reset master

Note: This command will delete all the logs and let the log file restarts from 000001.

Method Two:

PURGE { BINARY | MASTER } LOGS { TO 'log_name' | BEFORE datetime_expr }

Example:

purge master logs to "binlog_name.00000X" 

It will clear 00000Xall log files before.

Method three: Modify the my.cnfConfiguration

expire_logs_days = 3             #保留最近3天的binlog;默认值是0,表示不自动删除.