Django project to connect multiple database configuration

1, the database connection settings

pip install PyMySQL

2, the project of the same name in the directory myproject/myprojectunder __init__.pyadd the following code

import pymysql
pymysql.install_as_MySQLdb()

3, modify settings.pythe default database default

= DATABASES {
     ' default ' : {
         ' ENGINE ' : ' django.db.backends.mysql ' , # Database Engine 
          ' NAME ' : ' pythondms ' ,                        # database name 
          ' the USER ' : ' the root ' ,                        # username 
          ' PASSWORD ' : ' ' ,                    # password 
          ' HOST ': ' 36.103.245.29 ' ,                            # database host, the default is localhost 
          ' PORT ' : ' 3306 ' ,                            # database port, MySQL default is 3306 
          ' the OPTIONS ' : {
              ' the autocommit ' : True, 
         } 
    } 
}

4, a multi-connection configuration database

# Database configuration 
DATABASES = {
    ' default ' : {
           ' ENGINE ' : ' django.db.backends.mysql ' , # Database Engine 
          ' NAME ' : ' pythondms ' ,                        # database name 
          ' the USER ' : ' the root ' ,                        # username 
          ' pASSWORD ' : ' ' ,                    # password 
          'HOST' : ' 36.103.245.29 ' ,                            # database host, the default is localhost 
          ' PORT ' : ' 3306 ' ,                            # database port, MySQL default is 3306 
          ' the OPTIONS ' : {
              ' the autocommit ' : True, 
         } 
    }, 
    ' of default1 ' : {
           ' eNGINE ' : ' django.db.backends.mysql ' , # database engine 
          'NAME': ' Pythondms ' ,                        # database name 
          ' the USER ' : ' root ' ,                        # username 
          ' PASSWORD ' : ' ' ,                    # password 
          ' HOST ' : ' 39.107.35.95 ' ,                            # database host, the default is localhost 
          ' PORT ' : ' 3306 ' ,                           # Database port, MySQL defaults to 3306
          'OPTIONS': {
             'autocommit': True,
         }
    }
}
DATABASE_ROUTERS = ['dms.database_router.DatabaseAppsRouter']
DATABASE_APPS_MAPPING = {
    'userctrl': 'default',
    'app02': 'default1',
}

Here it is configured with a routing database dms.database_router.DatabaseAppsRouter, and then specify the app specified database 'userctrl': 'default', 'app02': 'default',. Now we need alas project of the same name in the directory myproject/myprojectto create a new case database_router.pyto implement routing database.

# database_router.py

from django.conf import settings

DATABASE_MAPPING = settings.DATABASE_APPS_MAPPING


class DatabaseAppsRouter(object):
    """
    A router to control all database operations on models for different
    databases.

    In case an app is not set in settings.DATABASE_APPS_MAPPING, the router
    will fallback to the `default` database.

    Settings example:

    DATABASE_APPS_MAPPING = {'app1': 'db1', 'app2': 'db2'}
    """

    def db_for_read(self, model, **hints):
        """"Point all read operations to the specific database."""
        if model._meta.app_label in DATABASE_MAPPING:
            return DATABASE_MAPPING[model._meta.app_label]
        return None

    def db_for_write(self, model, **hints):
        """Point all write operations to the specific database."""
        if model._meta.app_label in DATABASE_MAPPING:
            return DATABASE_MAPPING[model._meta.app_label]
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """Allow any relation between apps that use the same database."""
        db_obj1= DATABASE_MAPPING.get(obj1._meta.app_label)
        db_obj2 = DATABASE_MAPPING.get(obj2._meta.app_label)
        if db_obj1 and db_obj2:
            if db_obj1 == db_obj2:
                return True
            else:
                return False
        return None

    def allow_syncdb(self, db, model):
        """Make sure that apps only appear in the related database."""

        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(model._meta.app_label) == db
        elif model._meta.app_label in DATABASE_MAPPING:
            return False
        return None

    def allow_migrate(self, db, app_label, model=None, **hints):
        """
        Make sure the auth app only appears in the 'auth_db'
        database.
        """
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(app_label) == db
        elif app_label in DATABASE_MAPPING:
            return False
        return None

    # for Django 1.4 - Django 1.6
    def allow_syncdb(self, db, model):
        """Make sure that apps only appear in the related database."""
 
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(model._meta.app_label) == db
        elif model._meta.app_label in DATABASE_MAPPING:
            return False
        return None
 
    # Django 1.7 - Django 1.11
    def allow_migrate(self, db, app_label, model_name=None, **hints):
        # print db, app_label, model_name, hints
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(app_label) == db
        elif app_label in DATABASE_MAPPING:
            return False
        return None
            

So that we achieve a different database using a different app, we can use the python manage.py migrate --database=mysql02command to achieve database synchronization (creating tables)