一: mysql主从复制大体流程

1. master会将变动记录到二进制日志里面

2. master有一个i/o将二进制日志发送到slave

3. slave有一个i/o线程把master发送来的二进制写入到relay日志里面

4. slave有一个SQL线程, 按照relay日志处理slave的数据

二: 主库和从库的配置

注意: 主库和从库的版本要一样

1. 主库配置

[mysqld]

character-set-server=utf8

collation-server=utf8_general_ci

server-id=100log-bin=mysql-bin

[client]

default-character-set=utf8

[mysql]

default-character-set=utf8

2. 从库配置

[mysqld]

character-set-server=utf8

collation-server=utf8_general_ci

server-id=101log-bin=mysql-slave-bin

relay_log=edu-mysql-relay-bin

[client]

default-character-set=utf8

[mysql]

default-character-set=utf8

三: 操作步骤

四: Python代码的实现(读写分离)

1. 实现读写分离的准备

settings.py配置

DATABASES ={

'default': {'ENGINE': 'django.db.backends.mysql','NAME': 'test','USER': 'root','PASSWORD': '123456','HOST': '39.105.40.122','PORT': 33307,

},'slave': {'ENGINE': 'django.db.backends.mysql','NAME': 'test','USER': 'root','PASSWORD': '123456','HOST': '39.105.40.122','PORT': 33306,

}

}

DATABASE_ROUTERS= ['router.Router1',]

views.py

from django.shortcuts importrender,HttpResponse#Create your views here.

from app01.models importBookdefindex(request):#Book.objects.using("default").create(title="xx",price=10)

#ret=Book.objects.all().using("slave")

#using 是queryset对象的方法

#print(ret)

#Book.objects.create(title="yyy", price=100)

ret =Book.objects.all()print(ret)return HttpResponse('ok')

创建router.py文件

classRouter1:

# 只读数据库def db_for_read(self, model, **hints):"""Attempts to read auth models go to auth_db."""

return 'slave'

# 只写数据库

def db_for_write(self, model, **hints):"""Attempts to write auth models go to auth_db."""

return 'default'

# 数据库进行迁移的时候进行约束(但不会报错)

def allow_migrate(self, db, app_label, model_name=None, **hints):#print("zzzz")

if db == 'slave' and app_label=="app01":return False

2. 实现读写分离(手动和自动操作)

2.1 共同操作

python manage.py makemigrations#python manage.py migrate app名字 --database=配置文件数据库名称 注意: 写数据库

python manage.py migrate app01 --database=default

2.2 手动操作(一般不使用)

#用using说明你要往哪个库写还是读

models.UserType.objects.using('default').create(title='普通用户')

result= models.UserType.objects.all().using('slave')

2.3自动操作

创建router.py文件(在里面写入如上面的router.py文件)

问题: (分库)

app01中的表在default数据库创建

app02中的表在db1数据库创建

如何解决不同的应用使用不同的数据库?

实现步骤:(settings配置如上)

1.

python manage.py makemigrations

2.

#app01中的表在default数据库创建

python manage.py migrate app01 --database=default

3.

#app02中的表在db1数据库创建

python manage.py migrate app02 --database=db1

手动操作

m1.UserType.objects.using('default').create(title='VVIP')

m2.Users.objects.using('db1').create(name='VVIP',email='xxx')

自动操作

classRouter1:def db_for_read(self, model, **hints):"""Attempts to read auth models go to auth_db."""

if model._meta.app_label == 'app01':return 'default'

else:return 'db1'

def db_for_write(self, model, **hints):"""Attempts to write auth models go to auth_db."""

if model._meta.app_label == 'app01':return 'default'

else:return 'db1'DATABASE_ROUTERS= ['db_router.Router1', ]

#使用：

m1.UserType.objects.using('default').create(title='VVIP')

m2.Users.objects.using('db1').create(name='VVIP', email='xxx')#其他：

classRouter1:#数据库迁移时进行约束：

def allow_migrate(self, db, app_label, model_name=None, **hints):"""All non-auth models end up in this pool."""

if db == 'db1' and app_label == 'app02':returnTrueelif db == 'default' and app_label == 'app01':returnTrueelse:returnFalse#如果返回None，那么表示交给后续的router，如果后续没有router，则相当于返回True

def db_for_read(self, model, **hints):"""Attempts to read auth models go to auth_db."""

if model._meta.app_label == 'app01':return 'default'

else:return 'db1'

def db_for_write(self, model, **hints):"""Attempts to write auth models go to auth_db."""

if model._meta.app_label == 'app01':return 'default'

else:return 'db1'