How to achieve read and write separation in mysql master-slave based on docker and django

1. Master-slave construction

The process or principle of slave synchronization:

• 1) The master will record the changes in the binary log ;

• 2) The master has an I/O thread to send the binary log to the slave;

• 3) The slave has an I/O thread Write the binary sent by the master into the relay log;

• 4) The slave has a SQL thread and processes the slave data according to the relay log.

Practical operation

Create two folders:

mkdir  /home/mysql/data/
touch /home/mysql/conf.d
touch /home/mysql/my.cnf
 
mkdir  /home/mysql2/data/
touch /home/mysql/conf.d
touch /home/mysql/my.cnf

Modify the configuration file:

Configuration file of the main library, server-id and enable binlog log

[mysqld]
user=mysql
character-set-server=utf8
default_authentication_plugin=mysql_native_password
secure_file_priv=/var/lib/mysql
expire_logs_days=7
sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
max_connections=1000
server-id=100  
log-bin=mysql-bin
[client]
default-character-set=utf8
[mysql]
default-character-set=utf8

Configuration of the slave library:

The following two lines are added

log-bin=mysql-slave-bin #Specify log
relay_log=edu-mysql-relay-bin Specify relay log

[mysqld]
user=mysql
character-set-server=utf8
default_authentication_plugin=mysql_native_password
secure_file_priv=/var/lib/mysql
expire_logs_days=7
sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
max_connections=1000
server-id=101 
log-bin=mysql-slave-bin
relay_log=edu-mysql-relay-bin
[client]
default-character-set=utf8
[mysql]
default-character-set=utf8

Pull up two A mysql container:

#启动主库容器（挂载外部目录，端口映射成33307，密码设置为123456）
docker run  -di -v /home/mysql/data/:/var/lib/mysql -v /home/mysql/conf.d:/etc/mysql/conf.d -v /home/mysql/my.cnf:/etc/mysql/my.cnf -p 33307:3306 --name mysql-master -e MYSQL_ROOT_PASSWORD=123456 mysql:5.7
#启动从库容器（挂载外部目录，端口映射成33306，密码设置为123456）
docker run  -di -v /home/mysql2/data/:/var/lib/mysql -v /home/mysql2/conf.d:/etc/mysql/conf.d -v /home/mysql2/my.cnf:/etc/mysql/my.cnf -p 33306:3306 --name mysql-slave -e MYSQL_ROOT_PASSWORD=123456 mysql:5.7

Create the test user and authorize

#在主库创建用户并授权
##创建test用户
create user 'test'@'%' identified by '123';
##授权用户
grant all privileges on *.* to 'test'@'%' ;
###刷新权限
flush privileges;
#查看主服务器状态(显示如下图)
show master status;
# 可以看到日志文件的名字，和现在处在哪个位置

to connect to the slave library and configure the connection to the main library

Use the command "show slave status\G" to check whether the master_log_file is the same

#连接从库
mysql -h 172.16.209.100 -P 33306 -u root -p123456
#配置详解
/*
change master to 
master_host='MySQL主服务器IP地址', 
master_user='之前在MySQL主服务器上面创建的用户名'， 
master_password='之前创建的密码', 
master_log_file='MySQL主服务器状态中的二进制文件名', 
master_log_pos='MySQL主服务器状态中的position值';
*/
# 输入命令如下
change master to master_host='101.133.225.166',master_port=33307,master_user='test',master_password='123',master_log_file='mysql-bin.000003',master_log_pos=0;
# 启用从库
start slave;
# 查看从库状态（如下图）
show slave status\G;
####这两个是yes表示配成功 ####
   Slave_IO_Running: Yes
   Slave_SQL_Running: Yes

Test:

#在主库上创建数据库test1
create database test1;
use test1;
#创建表
create table tom (id int not null,name varchar(100)not null ,age tinyint);
#插入数据
insert tom (id,name,age) values(1,'xxx',20),(2,'yyy',7),(3,'zzz',23);

2.django implements read and write separation

settings.py configuration

#1  在setting中配置
DATABASES = {
    # 主库
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'lqz1',
        'USER': 'root',
        'PASSWORD': '123456',
        'HOST': '101.133.225.166',
        'PORT': 33307,
    },
    # 从库
    'db1': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'lqz1',
        'USER': 'root',
        'PASSWORD': '123456',
        'HOST': '101.133.225.166',
        'PORT': 33306,
    },
}

Manually specify read-write separation

####手动来做
    # 向default库写，主库
    res=models.Book.objects.using('default').create(name='金瓶梅',price=33.4)
    # 去从库查
    res=models.Book.objects.using('db1').all().first()
    print(res.name)

Automatically specify (write router and configure setting)

Create a db_router.py# in the root directory ##

class Router1:
    def db_for_read(self, model, **hints):
        return 'db1'
    def db_for_write(self, model, **hints):
        return 'default'

Register in setting

# 注册一下 # 4 以后只要是写操作，就会用default，只要是读操作自动去db1
	DATABASE_ROUTERS = ['db_router.Router1',]

More fine-grained (required when sub-database and table sub-database)

class Router1:
    def db_for_read(self, model, **hints):
        if model._meta.model_name == 'book':
            return 'db1'
        else:
            return 'default'
 
    def db_for_write(self, model, **hints):
        return 'default'

When migrating the database, you can specify which app’s table structure to migrate to Which library

# django默认是default
python manage.py migrate app01 --database=default

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