Support an async middleware for the toolbar.

extract redudant code in _postprocess

disable non async capable panels

add middleware sync and async compatible test case

rename file

add panel async compatibility tests/

added panel async compatibility tests/

marked erreneous panels as non async

refactor panel test

Add function docstrings

update async panel compatibility tests

revert middleware back to __call__ and __acall__ approach

update architecture.rst documentation

fix typo in docs

remove ASGI keyword from docs

Author: salty-ivy

debug_toolbar/middleware.py

@@ -6,6 +6,7 @@
 import socket
 from functools import lru_cache
 
+from asgiref.sync import iscoroutinefunction, markcoroutinefunction
 from django.conf import settings
 from django.utils.module_loading import import_string
 
@@ -62,14 +63,50 @@ class DebugToolbarMiddleware:
     on outgoing response.
     """
 
+    sync_capable = True
+    async_capable = True
+
     def __init__(self, get_response):
         self.get_response = get_response
+        # If get_response is a coroutine function, turns us into async mode so
+        # a thread is not consumed during a whole request.
+        self.async_mode = iscoroutinefunction(self.get_response)
+
+        if self.async_mode:
+            # Mark the class as async-capable, but do the actual switch inside
+            # __call__ to avoid swapping out dunder methods.
+            markcoroutinefunction(self)
 
     def __call__(self, request):
         # Decide whether the toolbar is active for this request.
+        if self.async_mode:
+            return self.__acall__(request)
+        # Decide whether the toolbar is active for this request.
         show_toolbar = get_show_toolbar()
         if not show_toolbar(request) or DebugToolbar.is_toolbar_request(request):
             return self.get_response(request)
+        toolbar = DebugToolbar(request, self.get_response)
+        # Activate instrumentation ie. monkey-patch.
+        for panel in toolbar.enabled_panels:
+            panel.enable_instrumentation()
+        try:
+            # Run panels like Django middleware.
+            response = toolbar.process_request(request)
+        finally:
+            clear_stack_trace_caches()
+            # Deactivate instrumentation ie. monkey-unpatch. This must run
+            # regardless of the response. Keep 'return' clauses below.
+            for panel in reversed(toolbar.enabled_panels):
+                panel.disable_instrumentation()
+
+        return self._postprocess(request, response, toolbar)
+
+    async def __acall__(self, request):
+        # Decide whether the toolbar is active for this request.
+        show_toolbar = get_show_toolbar()
+        if not show_toolbar(request) or DebugToolbar.is_toolbar_request(request):
+            response = await self.get_response(request)
+            return response
 
         toolbar = DebugToolbar(request, self.get_response)
 
@@ -78,14 +115,20 @@ def __call__(self, request):
             panel.enable_instrumentation()
         try:
             # Run panels like Django middleware.
-            response = toolbar.process_request(request)
+            response = await toolbar.process_request(request)
         finally:
             clear_stack_trace_caches()
             # Deactivate instrumentation ie. monkey-unpatch. This must run
             # regardless of the response. Keep 'return' clauses below.
             for panel in reversed(toolbar.enabled_panels):
                 panel.disable_instrumentation()
 
+        return self._postprocess(request, response, toolbar)
+
+    def _postprocess(self, request, response, toolbar):
+        """
+        Post-process the response.
+        """
         # Generate the stats for all requests when the toolbar is being shown,
         # but not necessarily inserted.
         for panel in reversed(toolbar.enabled_panels):

debug_toolbar/panels/__init__.py

@@ -1,3 +1,4 @@
+from django.core.handlers.asgi import ASGIRequest
 from django.template.loader import render_to_string
 
 from debug_toolbar import settings as dt_settings
@@ -9,6 +10,8 @@ class Panel:
     Base class for panels.
     """
 
+    is_async = True
+
     def __init__(self, toolbar, get_response):
         self.toolbar = toolbar
         self.get_response = get_response
@@ -21,6 +24,10 @@ def panel_id(self):
 
     @property
     def enabled(self) -> bool:
+        # check if the panel is async compatible
+        if not self.is_async and isinstance(self.toolbar.request, ASGIRequest):
+            return False
+
         # The user's cookies should override the default value
         cookie_value = self.toolbar.request.COOKIES.get("djdt" + self.panel_id)
         if cookie_value is not None:

debug_toolbar/panels/profiling.py

@@ -136,6 +136,7 @@ class ProfilingPanel(Panel):
     Panel that displays profiling information.
     """
 
+    is_async = False
     title = _("Profiling")
 
     template = "debug_toolbar/panels/profiling.html"

debug_toolbar/panels/redirects.py

@@ -9,6 +9,7 @@ class RedirectsPanel(Panel):
     Panel that intercepts redirects and displays a page with debug info.
     """
 
+    is_async = False
     has_content = False
 
     nav_title = _("Intercept redirects")

debug_toolbar/panels/request.py

@@ -15,6 +15,8 @@ class RequestPanel(Panel):
 
     title = _("Request")
 
+    is_async = False
+
     @property
     def nav_subtitle(self):
         """

debug_toolbar/panels/sql/panel.py

@@ -109,6 +109,8 @@ class SQLPanel(Panel):
     the request.
     """
 
+    is_async = False
+
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self._sql_time = 0

debug_toolbar/panels/staticfiles.py

@@ -73,6 +73,7 @@ class StaticFilesPanel(panels.Panel):
     A panel to display the found staticfiles.
     """
 
+    is_async = False
     name = "Static files"
     template = "debug_toolbar/panels/staticfiles.html"
 

debug_toolbar/panels/timer.py

@@ -17,6 +17,8 @@ class TimerPanel(Panel):
     Panel that displays the time a response took in milliseconds.
     """
 
+    is_async = False
+
     def nav_subtitle(self):
         stats = self.get_stats()
         if hasattr(self, "_start_rusage"):

docs/architecture.rst

@@ -79,6 +79,10 @@ Problematic Parts
   when the panel module is loaded
 - ``debug.panels.sql``: This package is particularly complex, but provides
   the main benefit of the toolbar
-- Support for async and multi-threading: This is currently unsupported, but
-  is being implemented as per the
-  `Async compatible toolbar project <https://github.com/orgs/jazzband/projects/9>`_.
+- Support for async and multi-threading: ``debug_toolbar.middleware.DebugToolbarMiddleware``
+  is now async compatible and can process async requests. However certain
+  panels such as ``SQLPanel``, ``TimerPanel``,  ``StaticFilesPanel``,
+  ``RequestPanel``, ``RedirectsPanel`` and ``ProfilingPanel`` aren't fully
+  compatible and currently being worked on. For now, these panels
+  are disabled by default when running in async environment.
+  follow the progress of this issue in `Async compatible toolbar project <https://github.com/orgs/jazzband/projects/9>`_.

tests/panels/test_async_panel_compatibility.py

@@ -0,0 +1,39 @@
+from django.http import HttpResponse
+from django.test import AsyncRequestFactory, RequestFactory, TestCase
+
+from debug_toolbar.panels import Panel
+from debug_toolbar.toolbar import DebugToolbar
+
+
+class MockAsyncPanel(Panel):
+    is_async = True
+
+
+class MockSyncPanel(Panel):
+    is_async = False
+
+
+class PanelAsyncCompatibilityTestCase(TestCase):
+    def setUp(self):
+        self.async_factory = AsyncRequestFactory()
+        self.wsgi_factory = RequestFactory()
+
+    def test_panels_with_asgi(self):
+        async_request = self.async_factory.get("/")
+        toolbar = DebugToolbar(async_request, lambda request: HttpResponse())
+
+        async_panel = MockAsyncPanel(toolbar, async_request)
+        sync_panel = MockSyncPanel(toolbar, async_request)
+
+        self.assertTrue(async_panel.enabled)
+        self.assertFalse(sync_panel.enabled)
+
+    def test_panels_with_wsgi(self):
+        wsgi_request = self.wsgi_factory.get("/")
+        toolbar = DebugToolbar(wsgi_request, lambda request: HttpResponse())
+
+        async_panel = MockAsyncPanel(toolbar, wsgi_request)
+        sync_panel = MockSyncPanel(toolbar, wsgi_request)
+
+        self.assertTrue(async_panel.enabled)
+        self.assertTrue(sync_panel.enabled)

tests/test_middleware_compatibility.py

@@ -0,0 +1,44 @@
+import asyncio
+
+from django.http import HttpResponse
+from django.test import AsyncRequestFactory, RequestFactory, TestCase
+
+from debug_toolbar.middleware import DebugToolbarMiddleware
+
+
+class MiddlewareSyncAsyncCompatibilityTestCase(TestCase):
+    def setUp(self):
+        self.factory = RequestFactory()
+        self.async_factory = AsyncRequestFactory()
+
+    def test_sync_mode(self):
+        """
+        test middlware switches to sync (__call__) based on get_response type
+        """
+
+        request = self.factory.get("/")
+        middleware = DebugToolbarMiddleware(
+            lambda x: HttpResponse("<html><body>Django debug toolbar</body></html>")
+        )
+
+        self.assertFalse(asyncio.iscoroutinefunction(middleware))
+
+        response = middleware(request)
+        self.assertEqual(response.status_code, 200)
+
+    async def test_async_mode(self):
+        """
+        test middlware switches to async (__acall__) based on get_response type
+        and returns a coroutine
+        """
+
+        async def get_response(request):
+            return HttpResponse("<html><body>Django debug toolbar</body></html>")
+
+        middleware = DebugToolbarMiddleware(get_response)
+        request = self.async_factory.get("/")
+
+        self.assertTrue(asyncio.iscoroutinefunction(middleware))
+
+        response = await middleware(request)
+        self.assertEqual(response.status_code, 200)