Middleware

The RLSContextMiddleware is responsible for setting PostgreSQL session variables that your RLS policies use for filtering.

How It Works

1. Extracts user and tenant information from the request
2. Sets PostgreSQL session variables using SET LOCAL
3. These variables are available to RLS policies during the request
4. Clears the context after the request completes

Basic Setup

Add the middleware after Django's authentication middleware:

MIDDLEWARE = [
    # ... other middleware
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django_rls.middleware.RLSContextMiddleware',  # Must be after auth
    # ... other middleware
]

Default Behavior

By default, the middleware sets:

• rls.user_id: The ID of the authenticated user
• rls.tenant_id: Extracted from the request (if available)

Context Processors (Recommended)

The easiest way to inject custom context variables is using Context Processors. This avoids the need to subclass the middleware entirely.

1. Define a Processor

Create a function that accepts a request and returns a dictionary of variables to set.

# myapp/context.py
def user_info(request):
    if not request.user.is_authenticated:
        return {}

    return {
        'user_email': request.user.email,
        'user_is_staff': request.user.is_staff
    }

2. Register in Settings

Add the path to your function in settings.py:

RLS_CONTEXT_PROCESSORS = [
    'myapp.context.user_info',
    # 'myapp.context.other_info',
]

The middleware will automatically execute these functions and set the returned key-value pairs as session variables (e.g., rls.user_email, rls.user_is_staff).

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Customizing Context Extraction (Advanced)

If you need deeper control (e.g., extracting tenant from a subdomain), you can subclass the middleware.

Custom Tenant Detection

The middleware looks for tenant information in this order:

1. request.tenant (set by other middleware)
2. request.user.profile.tenant_id
3. request.session['tenant_id']

You can customize this by subclassing:

from django_rls.middleware import RLSContextMiddleware

class CustomRLSMiddleware(RLSContextMiddleware):
    def _get_tenant_id(self, request):
        # Custom logic to extract tenant
        if hasattr(request, 'organization'):
            return request.organization.id

        # From subdomain
        host = request.get_host()
        subdomain = host.split('.')[0]
        try:
            from myapp.models import Tenant
            tenant = Tenant.objects.get(subdomain=subdomain)
            return tenant.id
        except Tenant.DoesNotExist:
            return None

Adding Custom Context Variables

from django_rls.middleware import RLSContextMiddleware
from django_rls.db.functions import set_rls_context

class ExtendedRLSMiddleware(RLSContextMiddleware):
    def _set_rls_context(self, request):
        # Call parent to set user_id and tenant_id
        super()._set_rls_context(request)

        # Add custom context
        if hasattr(request.user, 'profile'):
            profile = request.user.profile
            set_rls_context('department', profile.department)
            set_rls_context('role', profile.role)
            set_rls_context('region', profile.region)

Context Variables in Policies

Use the context variables in your policies:

class RegionalData(RLSModel):
    region = models.CharField(max_length=50)

    class Meta:
        rls_policies = [
            CustomPolicy(
                'region_policy',
                expression="region = current_setting('rls.region', true)"
            ),
        ]

Handling Anonymous Users

The middleware handles anonymous users gracefully:

class PublicRLSMiddleware(RLSContextMiddleware):
    def _set_rls_context(self, request):
        if request.user.is_authenticated:
            super()._set_rls_context(request)
        else:
            # Set a special context for anonymous users
            set_rls_context('user_id', '-1')
            set_rls_context('is_anonymous', 'true')

Performance Considerations

1. Minimize Context Calls: Set all context variables at once
2. Cache Lookups: Cache tenant lookups if they're expensive
3. Use Connection Pooling: RLS context is per-connection

Example with caching:

from django.core.cache import cache

class CachedTenantMiddleware(RLSContextMiddleware):
    def _get_tenant_id(self, request):
        if not request.user.is_authenticated:
            return None

        cache_key = f'user_tenant_{request.user.id}'
        tenant_id = cache.get(cache_key)

        if tenant_id is None:
            tenant_id = request.user.profile.tenant_id
            cache.set(cache_key, tenant_id, 300)  # Cache for 5 minutes

        return tenant_id

Testing with Middleware

When testing, you can set context manually:

from django.test import TestCase
from django_rls.db.functions import set_rls_context

class MyTestCase(TestCase):
    def setUp(self):
        self.user = User.objects.create_user('testuser')
        self.tenant = Tenant.objects.create(name='Test Tenant')

    def test_with_context(self):
        # Manually set context for tests
        set_rls_context('user_id', self.user.id)
        set_rls_context('tenant_id', self.tenant.id)

        # Your test code here
        documents = Document.objects.all()
        # ...

Debugging Middleware

Enable debug logging to see what context is being set:

# settings.py
LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'console': {
            'class': 'logging.StreamHandler',
        },
    },
    'loggers': {
        'django_rls': {
            'handlers': ['console'],
            'level': 'DEBUG',
        },
    },
}

Common Patterns

Multi-Database Setup

class MultiDBRLSMiddleware(RLSContextMiddleware):
    def _set_rls_context(self, request):
        # Set context for each database
        for db_alias in ['default', 'tenant_db']:
            with connections[db_alias].cursor() as cursor:
                cursor.execute(
                    "SELECT set_config('rls.user_id', %s, true)",
                    [str(request.user.id)]
                )

API Authentication

class APIRLSMiddleware(RLSContextMiddleware):
    def _set_rls_context(self, request):
        # Handle both session and token auth
        if hasattr(request, 'auth'):
            # DRF token authentication
            set_rls_context('user_id', request.user.id)
            set_rls_context('api_key', request.auth.key)
        else:
            # Regular session auth
            super()._set_rls_context(request)