Django 数据库路由：精通多数据库配置

            DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'mydatabase',
        'USER': 'mydatabaseuser',
        'PASSWORD': 'mypassword',
        'HOST': '127.0.0.1',
        'PORT': '5432',
    },
    'users': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'user_database',
        'USER': 'user_db_user',
        'PASSWORD': 'user_db_password',
        'HOST': 'db.example.com',
        'PORT': '3306',
    },
    'analytics': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': 'analytics.db',
    },
}

            

              
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            # routers.py

class UserRouter:
    """
    A router to control all database operations on models in the
    users application.
    """
    route_app_labels = {'users'}

    def db_for_read(self, model, **hints):
        """
        Attempts to read users models go to users_db.
        """
        if model._meta.app_label in self.route_app_labels:
            return 'users'
        return None

    def db_for_write(self, model, **hints):
        """
        Attempts to write users models go to users_db.
        """
        if model._meta.app_label in self.route_app_labels:
            return 'users'
        return 'default'

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

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """
        Make sure the users app only appears in the 'users' database.
        """
        if app_label in self.route_app_labels:
            return db == 'users'
        return True

            

              
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            DATABASE_ROUTERS = ['your_project.routers.UserRouter']

            

              
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            class ReadReplicaRouter:
    """
    Routes read operations for specific models to a read replica.
    """
    read_replica_models = ['myapp.MyModel', 'anotherapp.AnotherModel']

    def db_for_read(self, model, **hints):
        if f'{model._meta.app_label}.{model._meta.model_name.capitalize()}' in self.read_replica_models:
            return 'read_replica'
        return None

    def db_for_write(self, model, **hints):
        return 'default'

    def allow_relation(self, obj1, obj2, **hints):
        return True

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        return True

            

              
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            # views.py

from django.db import connections
from myapp.models import MyModel

def my_view(request):
    # Force reads from the 'users' database
    instance = MyModel.objects.using('users').get(pk=1)
    # Create a new object using 'analytics' database
    new_instance = MyModel(name='New Object')
    new_instance.save(using='analytics')
    return HttpResponse("Success!")

            

              
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            # routers.py

from django.contrib.auth import get_user_model

class UserTypeRouter:
    """
    Routes database operations based on user type.
    """

    def db_for_read(self, model, **hints):
        user = hints.get('instance')  # Attempt to extract user instance
        if user and user.is_superuser:
            return 'admin_db'
        return 'default'

    def db_for_write(self, model, **hints):
        user = hints.get('instance')  # Attempt to extract user instance
        if user and user.is_superuser:
            return 'admin_db'
        return 'default'

    def allow_relation(self, obj1, obj2, **hints):
        return True

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        return True

            

              
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            # views.py

from myapp.models import MyModel

def my_view(request):
    user = request.user
    instance = MyModel.objects.using('default').get(pk=1)

    # Pass the user instance as a hint during save
    new_instance = MyModel(name='New Object')
    new_instance.save(using='default', update_fields=['name'], instance=user)  # Pass user as instance
    return HttpResponse("Success!")

            

              
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            python manage.py migrate --database=users

            

              
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            # tests.py

from django.test import TestCase
from myapp.models import MyModel
from django.db import connections

class DatabaseRoutingTest(TestCase):
    def test_data_is_written_to_correct_database(self):
        # Create an object
        instance = MyModel.objects.create(name='Test Object')

        # Check which database the object was saved to
        db = connections[instance._state.db]
        self.assertEqual(instance._state.db, 'default') # Replace 'default' with expected database

        # Retrieve object from specific database
        instance_from_other_db = MyModel.objects.using('users').get(pk=instance.pk)

        # Make sure there are no errors, and that everything is working as expected
        self.assertEqual(instance_from_other_db.name, "Test Object")


            

              
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