ORM - DB Router

settings.py

1. 配置DATABASES

   DATABASES = {
       'default': {
           'ENGINE': 'django.db.backends.mysql',
           'HOST': os.environ.get('FLOW_HOST', '101.251.234.164'),
           'PORT': 3306,
           'NAME': os.environ.get('FLOW_DB_NAME', 'flow_snmp'),
           'USER': os.environ.get('FLOW_DB_USER', 'root'),
           'PASSWORD': os.environ.get('FLOW_DB_PASSWORD', '4CbPsJJo'),
           'CHARSET': 'utf-8'
       },
       'cloud': {
           'ENGINE': 'django.db.backends.mysql',
           'HOST': os.environ.get('CLOUD_HOST', '101.251.234.164'),
           'USER': os.environ.get('CLOUD_DB_USER', 'root'),
           'PASSWORD': os.environ.get('CLOUD_DB_PASSWORD', '4CbPsJJo'),
           'NAME': os.environ.get('CLOUD_DB_NAME', 'cdscp_trunk'),
           'PORT': 3306,
           'CHARSET': 'utf-8',
       }
   }
   

   default必须配置，如果不需要可以配成：'default': {}

   但是，为了避免调试错误（莫名原因），尽量给default设置值。

2. 配置数据库路由

   # 该变量必须配，指明router类
   DATABASE_ROUTERS = ["db.db_routers.DatabaseRouter"]
   # 下面的变量用在model的Meta子类下的app_label，非必需
   DB_LABEL_FLOW = 'flow'
   DB_LABEL_CLOUD = 'cloud'
   # 用在router类中映射app_label->db name关系
   DATABASE_MAPPING = {
       # 'app_name': 'database_name'
       'flow': 'default',
       'cloud': 'cloud'
   }
   

配置路由类

from django.conf import settings

DATABASE_MAPPING = settings.DATABASE_MAPPING


class DatabaseRouter(object):
    """
    配置数据库路由
    """
    def db_for_read(self, model, **hints):
        """
        Attempts to read flow_app models go to flow DB.
        :param model:
        :param hints:
        :return: settings配置的database节点名称，并非db name
        """
        if model._meta.app_label in DATABASE_MAPPING:
            return DATABASE_MAPPING[model._meta.app_label]
        return None

    def db_for_write(self, model, **hints):
        """
        Attempts to write flow_app models go to flow DB.
        :param model:
        :param hints:
        :return:
        """
        if model._meta.app_label in DATABASE_MAPPING:
            return DATABASE_MAPPING[model._meta.app_label]
        return None

    # def allow_relation(self, obj1, obj2, **hints):
    #     pass

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """Make sure that apps only appear in the related database."""
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(app_label) == db
        elif app_label in DATABASE_MAPPING:
            return False
        return None

    # def allow_syncdb(self, db, model):
    #     return False