Move header_control from common to openedx/core

openedx/core/djangoapps/contentserver/middleware.py

@@ -10,12 +10,12 @@ from django.http import (
     HttpResponseBadRequest, HttpResponseNotFound, HttpResponsePermanentRedirect)
 from student.models import CourseEnrollment
 
-from header_control import force_header_for_response
 from xmodule.assetstore.assetmgr import AssetManager
 from xmodule.contentstore.content import StaticContent, XASSET_LOCATION_TAG
 from xmodule.modulestore import InvalidLocationError
 from opaque_keys import InvalidKeyError
 from opaque_keys.edx.locator import AssetLocator
+from openedx.core.djangoapps.header_control import force_header_for_response
 from .caching import get_cached_content, set_cached_content
 from xmodule.modulestore.exceptions import ItemNotFoundError
 from xmodule.exceptions import NotFoundError

openedx/core/djangoapps/header_control/__init__.py

@@ -0,0 +1,22 @@
+"""
+This middleware is used for adjusting the headers in a response before it is sent to the end user.
+
+This middleware is intended to sit as close as possible to the top of the middleare list as possible,
+so that it is one of the last pieces of middleware to touch the response, and thus can most accurately
+adjust/control the headers of the response.
+"""
+
+
+def remove_headers_from_response(response, *headers):
+    """Removes the given headers from the response using the header_control middleware."""
+    response.remove_headers = headers
+
+
+def force_header_for_response(response, header, value):
+    """Forces the given header for the given response using the header_control middleware."""
+    force_headers = {}
+    if hasattr(response, 'force_headers'):
+        force_headers = response.force_headers
+    force_headers[header] = value
+
+    response.force_headers = force_headers

openedx/core/djangoapps/header_control/decorators.py

@@ -0,0 +1,68 @@
+"""
+Middleware decorator for removing headers.
+"""
+
+from functools import wraps
+from openedx.core.djangoapps.header_control import remove_headers_from_response, force_header_for_response
+
+
+def remove_headers(*headers):
+    """
+    Decorator that removes specific headers from the response.
+    Usage:
+        @remove_headers("Vary")
+        def myview(request):
+            ...
+
+    The HeaderControlMiddleware must be used and placed as closely as possible to the top
+    of the middleware chain, ideally after any caching middleware but before everything else.
+
+    This decorator is not safe for multiple uses: each call will overwrite any previously set values.
+    """
+    def _decorator(func):
+        """
+        Decorates the given function.
+        """
+        @wraps(func)
+        def _inner(*args, **kwargs):
+            """
+            Alters the response.
+            """
+            response = func(*args, **kwargs)
+            remove_headers_from_response(response, *headers)
+            return response
+
+        return _inner
+
+    return _decorator
+
+
+def force_header(header, value):
+    """
+    Decorator that forces a header in the response to have a specific value.
+    Usage:
+        @force_header("Vary", "Origin")
+        def myview(request):
+            ...
+
+    The HeaderControlMiddleware must be used and placed as closely as possible to the top
+    of the middleware chain, ideally after any caching middleware but before everything else.
+
+    This decorator is not safe for multiple uses: each call will overwrite any previously set values.
+    """
+    def _decorator(func):
+        """
+        Decorates the given function.
+        """
+        @wraps(func)
+        def _inner(*args, **kwargs):
+            """
+            Alters the response.
+            """
+            response = func(*args, **kwargs)
+            force_header_for_response(response, header, value)
+            return response
+
+        return _inner
+
+    return _decorator

openedx/core/djangoapps/header_control/middleware.py

@@ -0,0 +1,24 @@
+"""
+Middleware used for adjusting headers in a response before it is sent to the end user.
+"""
+
+
+class HeaderControlMiddleware(object):
+    """
+    Middleware that can modify/remove headers in a response.
+
+    This can be used, for example, to remove headers i.e. drop any Vary headers to improve cache performance.
+    """
+
+    def process_response(self, _request, response):
+        """
+        Processes the given response, potentially remove or modifying headers.
+        """
+
+        for header in getattr(response, 'remove_headers', []):
+            del response[header]
+
+        for header, value in getattr(response, 'force_headers', {}).iteritems():
+            response[header] = value
+
+        return response

openedx/core/djangoapps/header_control/tests/test_decorators.py

@@ -0,0 +1,33 @@
+"""Tests for remove_headers and force_header decorator. """
+from django.http import HttpResponse, HttpRequest
+from django.test import TestCase
+
+from openedx.core.djangoapps.header_control.decorators import remove_headers, force_header
+
+
+def fake_view(_request):
+    """Fake view that returns an empty response."""
+    return HttpResponse()
+
+
+class TestRemoveHeaders(TestCase):
+    """Test the `remove_headers` decorator."""
+
+    def test_remove_headers(self):
+        request = HttpRequest()
+        wrapper = remove_headers('Vary', 'Accept-Encoding')
+        wrapped_view = wrapper(fake_view)
+        response = wrapped_view(request)
+        self.assertEqual(len(response.remove_headers), 2)
+
+
+class TestForceHeader(TestCase):
+    """Test the `force_header` decorator."""
+
+    def test_force_header(self):
+        request = HttpRequest()
+        wrapper = force_header('Vary', 'Origin')
+        wrapped_view = wrapper(fake_view)
+        response = wrapped_view(request)
+        self.assertEqual(len(response.force_headers), 1)
+        self.assertEqual(response.force_headers['Vary'], 'Origin')

openedx/core/djangoapps/header_control/tests/test_middleware.py

@@ -0,0 +1,71 @@
+"""Tests for header_control middleware."""
+from django.http import HttpResponse, HttpRequest
+from django.test import TestCase
+
+from openedx.core.djangoapps.header_control import remove_headers_from_response, force_header_for_response
+from openedx.core.djangoapps.header_control.middleware import HeaderControlMiddleware
+
+
+class TestHeaderControlMiddlewareProcessResponse(TestCase):
+    """Test the `header_control` middleware. """
+    def setUp(self):
+        super(TestHeaderControlMiddlewareProcessResponse, self).setUp()
+        self.middleware = HeaderControlMiddleware()
+
+    def test_doesnt_barf_if_not_modifying_anything(self):
+        fake_request = HttpRequest()
+
+        fake_response = HttpResponse()
+        fake_response['Vary'] = 'Cookie'
+        fake_response['Accept-Encoding'] = 'gzip'
+
+        result = self.middleware.process_response(fake_request, fake_response)
+        self.assertEquals('Cookie', result['Vary'])
+        self.assertEquals('gzip', result['Accept-Encoding'])
+
+    def test_doesnt_barf_removing_nonexistent_headers(self):
+        fake_request = HttpRequest()
+
+        fake_response = HttpResponse()
+        fake_response['Vary'] = 'Cookie'
+        fake_response['Accept-Encoding'] = 'gzip'
+        remove_headers_from_response(fake_response, 'Vary', 'FakeHeaderWeeee')
+
+        result = self.middleware.process_response(fake_request, fake_response)
+        self.assertNotIn('Vary', result)
+        self.assertEquals('gzip', result['Accept-Encoding'])
+
+    def test_removes_intended_headers(self):
+        fake_request = HttpRequest()
+
+        fake_response = HttpResponse()
+        fake_response['Vary'] = 'Cookie'
+        fake_response['Accept-Encoding'] = 'gzip'
+        remove_headers_from_response(fake_response, 'Vary')
+
+        result = self.middleware.process_response(fake_request, fake_response)
+        self.assertNotIn('Vary', result)
+        self.assertEquals('gzip', result['Accept-Encoding'])
+
+    def test_forces_intended_header(self):
+        fake_request = HttpRequest()
+
+        fake_response = HttpResponse()
+        fake_response['Vary'] = 'Cookie'
+        fake_response['Accept-Encoding'] = 'gzip'
+        force_header_for_response(fake_response, 'Vary', 'Origin')
+
+        result = self.middleware.process_response(fake_request, fake_response)
+        self.assertEquals('Origin', result['Vary'])
+        self.assertEquals('gzip', result['Accept-Encoding'])
+
+    def test_does_not_mangle_undecorated_response(self):
+        fake_request = HttpRequest()
+
+        fake_response = HttpResponse()
+        fake_response['Vary'] = 'Cookie'
+        fake_response['Accept-Encoding'] = 'gzip'
+
+        result = self.middleware.process_response(fake_request, fake_response)
+        self.assertEquals('Cookie', result['Vary'])
+        self.assertEquals('gzip', result['Accept-Encoding'])