MYSQL双击热备(主-从),同步的触发机制

从服务器上有个IO线程负责抓取主服务器二进制日志，并将主服务器的二进制日志内容放到从服务器上的中继日志里。

然后从服务器上还有个SQL线程，负责将中继日志里的内容在从服务器上执行，也就是在从服务器执行同步。

综上，你所说的“同步负载”是由从服务器负担的，这个过程对主服务器有所影响的就是网络开销，因为需要把主服务器上的二进制日志通过网络传到从服务器。

1、将SQL语句直接嵌入到shell脚本文件中

复制代码 代码如下:

--演示环境

[root@SZDB ~]# more /etc/issue

CentOS release 5.9 (Final)

Kernel \r on an \m

root@localhost[(none)]>show variables like 'version'

+---------------+------------+

| Variable_name | Value |

+---------------+------------+

| version | 5.6.12-log |

+---------------+------------+

[root@SZDB ~]# more shell_call_sql1.sh

#!/bin/bash

# Define log

TIMESTAMP=`date +%Y%m%d%H%M%S`

LOG=call_sql_${TIMESTAMP}.log

echo "Start execute sql statement at `date`." >>${LOG}

# execute sql stat

mysql -uroot -p123456 -e "

tee /tmp/temp.log

drop database if exists tempdb

create database tempdb

use tempdb

create table if not exists tb_tmp(id smallint,val varchar(20))

insert into tb_tmp values (1,'jack'),(2,'robin'),(3,'mark')

select * from tb_tmp

notee

quit"

echo -e "\n">>${LOG}

echo "below is output result.">>${LOG}

cat /tmp/temp.log>>${LOG}

echo "script executed successful.">>${LOG}

exit

[root@SZDB ~]# ./shell_call_sql1.sh

Logging to file '/tmp/temp.log'

+------+-------+

| id | val |

+------+-------+

|1 | jack |

|2 | robin |

|3 | mark |

+------+-------+

Outfile disabled.

2、命令行调用单独的SQL文件

复制代码 代码如下:

[root@SZDB ~]# more temp.sql

tee /tmp/temp.log

drop database if exists tempdb

create database tempdb

use tempdb

create table if not exists tb_tmp(id smallint,val varchar(20))

insert into tb_tmp values (1,'jack'),(2,'robin'),(3,'mark')

select * from tb_tmp

notee

[root@SZDB ~]# mysql -uroot -p123456 -e "source /root/temp.sql"

Logging to file '/tmp/temp.log'

+------+-------+

| id | val |

+------+-------+

|1 | jack |

|2 | robin |

|3 | mark |

+------+-------+

Outfile disabled.

3、使用管道符调用SQL文件

复制代码 代码如下:

[root@SZDB ~]# mysql -uroot -p123456 </root/temp.sql

Logging to file '/tmp/temp.log'

id val

1 jack

2 robin

3 mark

Outfile disabled.

#使用管道符调用SQL文件以及输出日志

[root@SZDB ~]# mysql -uroot -p123456 </root/temp.sql >/tmp/temp.log

[root@SZDB ~]# more /tmp/temp.log

Logging to file '/tmp/temp.log'

id val

1 jack

2 robin

3 mark

Outfile disabled.

4、shell脚本中MySQL提示符下调用SQL

复制代码 代码如下:

[root@SZDB ~]# more shell_call_sql2.sh

#!/bin/bash

mysql -uroot -p123456 <<EOF

source /root/temp.sql

select current_date()

delete from tempdb.tb_tmp where id=3

select * from tempdb.tb_tmp where id=2

EOF

exit

[root@SZDB ~]# ./shell_call_sql2.sh

Logging to file '/tmp/temp.log'

id val

1 jack

2 robin

3 mark

Outfile disabled.

current_date()

2014-10-14

id val

2 robin

5、shell脚本中变量输入与输出

复制代码 代码如下:

[root@SZDB ~]# more shell_call_sql3.sh

#!/bin/bash

cmd="select count(*) from tempdb.tb_tmp"

cnt=$(mysql -uroot -p123456 -s -e "${cmd}")

echo "Current count is : ${cnt}"

exit

[root@SZDB ~]# ./shell_call_sql3.sh

Warning: Using a password on the command line interface can be insecure.

Current count is : 3

[root@SZDB ~]# echo "select count(*) from tempdb.tb_tmp"|mysql -uroot -p123456 -s

3

[root@SZDB ~]# more shell_call_sql4.sh

#!/bin/bash

id=1

cmd="select count(*) from tempdb.tb_tmp where id=${id}"

cnt=$(mysql -uroot -p123456 -s -e "${cmd}")

echo "Current count is : ${cnt}"

exit

[root@SZDB ~]# ./shell_call_sql4.sh

Current count is : 1

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