feat: allow section-based Surrogate-Key to purge releases and other things without nukiung the whole cache

Author: JacobCoffee

pydotorg/middleware.py

@@ -18,18 +18,45 @@ def __call__(self, request):
 
 class GlobalSurrogateKey:
     """
-    Middleware to insert a Surrogate-Key for purging in Fastly or other caches
+    Middleware to insert a Surrogate-Key for purging in Fastly or other caches.
+
+    Adds both a global key (for full site purges) and section-based keys
+    derived from the URL path (for targeted purges like /downloads/).
     """
 
     def __init__(self, get_response):
         self.get_response = get_response
 
+    def _get_section_key(self, path):
+        """
+        Extract section surrogate key from URL path.
+
+        Examples:
+            /downloads/ -> downloads
+            /downloads/release/python-3141/ -> downloads
+            /events/python-events/ -> events
+            / -> None
+        """
+        parts = path.strip("/").split("/")
+        if parts and parts[0]:
+            return parts[0]
+        return None
+
     def __call__(self, request):
         response = self.get_response(request)
+        keys = []
         if hasattr(settings, "GLOBAL_SURROGATE_KEY"):
-            response["Surrogate-Key"] = " ".join(
-                filter(
-                    None, [settings.GLOBAL_SURROGATE_KEY, response.get("Surrogate-Key")]
-                )
-            )
+            keys.append(settings.GLOBAL_SURROGATE_KEY)
+
+        section_key = self._get_section_key(request.path)
+        if section_key:
+            keys.append(section_key)
+
+        existing = response.get("Surrogate-Key")
+        if existing:
+            keys.append(existing)
+
+        if keys:
+            response["Surrogate-Key"] = " ".join(keys)
+
         return response

pydotorg/tests/test_middleware.py

@@ -1,8 +1,10 @@
-from django.test import TestCase
+from django.test import TestCase, override_settings
 
 from django.contrib.sites.models import Site
 from django.contrib.redirects.models import Redirect
 
+from pydotorg.middleware import GlobalSurrogateKey
+
 
 class MiddlewareTests(TestCase):
 
@@ -25,3 +27,40 @@ def test_redirects(self):
         response = self.client.get(url)
         self.assertEqual(response.status_code, 301)
         self.assertEqual(response['Location'], redirect.new_path)
+
+
+class GlobalSurrogateKeyTests(TestCase):
+
+    def test_get_section_key(self):
+        """Test section key extraction from URL paths."""
+        middleware = GlobalSurrogateKey(lambda r: None)
+
+        self.assertEqual(middleware._get_section_key('/downloads/'), 'downloads')
+        self.assertEqual(middleware._get_section_key('/downloads/release/python-3141/'), 'downloads')
+        self.assertEqual(middleware._get_section_key('/events/'), 'events')
+        self.assertEqual(middleware._get_section_key('/events/python-events/123/'), 'events')
+        self.assertEqual(middleware._get_section_key('/sponsors/'), 'sponsors')
+
+        #  returns None
+        self.assertIsNone(middleware._get_section_key('/'))
+
+        self.assertEqual(middleware._get_section_key('/downloads'), 'downloads')
+        self.assertEqual(middleware._get_section_key('downloads/'), 'downloads')
+
+    @override_settings(GLOBAL_SURROGATE_KEY='pydotorg-app')
+    def test_surrogate_key_header_includes_section(self):
+        """Test that Surrogate-Key header includes both global and section keys."""
+        response = self.client.get('/downloads/')
+        self.assertTrue(response.has_header('Surrogate-Key'))
+        surrogate_key = response['Surrogate-Key']
+
+        self.assertIn('pydotorg-app', surrogate_key)
+        self.assertIn('downloads', surrogate_key)
+
+    @override_settings(GLOBAL_SURROGATE_KEY='pydotorg-app')
+    def test_surrogate_key_header_homepage(self):
+        """Test that homepage only has global surrogate key."""
+        response = self.client.get('/')
+        self.assertTrue(response.has_header('Surrogate-Key'))
+        surrogate_key = response['Surrogate-Key']
+        self.assertIn('pydotorg-app', surrogate_key)