Django multiple databases access example

gistfile1.txt

#!/usr/bin/python
# -*- coding: UTF-8 -*-
# common.db_id3web.py
# 
from __future__ import unicode_literals


import django.db.models as models


class Id3webAdminMixin(object):
    # https://docs.djangoproject.com/en/dev/topics/db/multi-db/#exposing-multiple-databases-in-django-s-admin-interface
    using = 'db_id3web'

    def save_model(self, request, obj, form, change):
        # Tell Django to save objects to the 'other' database.
        obj.save(using=self.using)

    def delete_model(self, request, obj):
        # Tell Django to delete objects from the 'other' database
        obj.delete(using=self.using)

    def get_queryset(self, request):
        # Tell Django to look for objects on the 'other' database.
        return super(MultiDBModelAdmin, self).get_queryset(request).using(self.using)

    def formfield_for_foreignkey(self, db_field, request, **kwargs):
        # Tell Django to populate ForeignKey widgets using a query
        # on the 'other' database.
        return super(MultiDBModelAdmin, self).formfield_for_foreignkey(db_field, request, using=self.using, **kwargs)

    def formfield_for_manytomany(self, db_field, request, **kwargs):
        # Tell Django to populate ManyToMany widgets using a query
        # on the 'other' database.
        return super(MultiDBModelAdmin, self).formfield_for_manytomany(db_field, request, using=self.using, **kwargs)


class Id3WebRouterMixin(object):
    """
    A router to control all database operations on models in the
    id3web application.
    """
    list_id3_applications = [
        'clients',
        'licences',
    ]
        
    def db_for_read(self, model, **hints):
        """
        Attempts to read licences models go to db_id3web.
        """
        if model._meta.app_label in Id3WebRouterMixin.list_id3_applications:
            return 'db_id3web'
        return None

    def db_for_write(self, model, **hints):
        """
        Attempts to write licences models go to db_id3web.
        """
        if model._meta.app_label in Id3WebRouterMixin.list_id3_applications:
            return 'db_id3web'
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """
        Allow relations if a model in the licences app is involved.
        """
        if ((obj1._meta.app_label in Id3WebRouterMixin.list_id3_applications) or 
            (obj2._meta.app_label in Id3WebRouterMixin.list_id3_applications)):
           return True
        return None

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """
        Make sure the licences app only appears in the 'db_id3web'
        database.
        """
        if app_label in Id3WebRouterMixin.list_id3_applications:
            return db == 'db_id3web'
        return None
        
        
        

gistfile2.txt

#!/usr/bin/python
# -*- coding: UTF-8 -*-
# clients.routers.py

# http://python-future.org/imports.html
# To write a Python 2/3 compatible codebase, the first step is to add this line 
# to the top of each module:

from common.db_id3web import Id3WebRouterMixin

class ClientRouter(Id3WebRouterMixin):
    """
    A router to control all database operations on models in the
    licences application.
    """
    pass
                
               

gistfile3.txt

# settings.base.py


# Database
# https://docs.djangoproject.com/en/dev/ref/settings/#databases
# https://docs.djangoproject.com/en/dev/topics/db/multi-db/
# https://github.com/joke2k/django-environ
#================================================================
DATABASES = {
    'default': env.db('DATABASE_DJANGO'),
    'db_id3web': env.db('DATABASE_MASTER_ID3WEB')
}

# https://docs.djangoproject.com/en/dev/topics/db/multi-db/#topics-db-multi-db-routing
DATABASE_ROUTERS = [
    'clients.routers.ClientRouter',
    'licences.routers.LicenceRouter',
]