Push new status immediately if possible instead of invalidating and forcing a reload.

fear_tracker/routing.py

@@ -0,0 +1,17 @@
+from channels.http import AsgiHandler
+from channels.routing import ProtocolTypeRouter, URLRouter
+
+from django.conf.urls import url
+
+from . import views
+
+# No async routing currently; just default sync http.
+application = ProtocolTypeRouter({
+    "http": URLRouter([
+        url(r'^(?P<access_code>[a-zA-Z]{6})/', URLRouter([
+            url(r"status/(?P<hashcode>[a-z0-9]{64})/",
+                views.StatusLongPollConsumer, name='status'),
+        ])),
+        url(r"", AsgiHandler),
+    ]),
+})

fear_tracker/templates/game.html

@@ -360,13 +360,23 @@
         el.addEventListener("change", formElementChanged);
       }
 
-      setInterval(function() {
+      function checkStatus() {
         if(activeRequests.size != 0) return;
+        // From https://stackoverflow.com/a/50101022
+
+        const abort = new AbortController();
+        const signal = abort.signal;
+
+        // 50 second timeout:
+        const timeoutId = setTimeout(() => abort.abort(), 50000);
+
         fetch(new Request("{% url 'status' access_code=access_code %}"
                            + (statusObj.hash != ""
                               ? statusObj.hash + "/"
-                              : "")))
+                              : "")),
+              {signal})
           .then(response => {
+            clearTimeout(timeoutId);
             if(response.status === 304) {
               // TODO Just skip the next step?
               return statusObj;
@@ -381,8 +391,14 @@
             } else {
               statusObj = data;
             }
+          })
+          .then(checkStatus)
+          .catch(() => {
+            // If something went wrong, wait a few seconds before retrying.
+            setTimeout(checkStatus, 5000);
           });
-      }, 5000);
+      }
+      checkStatus();
     });
   </script>
 {% endif %}

fear_tracker/urls.py

@@ -27,7 +27,5 @@ urlpatterns = [
         path('update/', views.update_game, name='update_game'),
         path('qr/', views.qr_code, name='qr_code'),
         path('status/', views.status, name='status'),
-        url('^status/(?P<hashcode>[a-z0-9]{64})/',
-            views.status, name='status'),
     ])),
 ]

fear_tracker/views.py

@@ -5,12 +5,18 @@ import hashlib
 import json
 import qrcode
 
+from asgiref.sync import async_to_sync
+
+from channels.generic.http import AsyncHttpConsumer
+from channels.layers import get_channel_layer
+
+from django.conf import settings
 from django.db import transaction
 from django.http import HttpResponse
 from django.shortcuts import get_object_or_404, redirect, render
 from django.views.decorators.http import require_safe, require_http_methods,\
                                          require_POST
-from django.urls import reverse
+from django.urls import reverse, set_script_prefix
 
 from .forms import NewGameForm, JoinGameForm, PlayerFormSet
 from .models import Game, Player, Fear
@@ -288,12 +294,22 @@ def handle_game_request(request, game, update):
                 res['value'] = current_value
         else:
             res = {'success': True}
+            async_to_sync(get_channel_layer().group_send)(
+                    "%s_status" % game.access_code,
+                    {"type": "fear_tracker.invalidate_status"})
         return HttpResponse(json.dumps(res))
 
     players = get_players_with_fear(game, current_phase, players)
     status_obj = game_status_object(game, current_phase, players)
     status_string = json.dumps(status_obj)
 
+    async_to_sync(get_channel_layer().group_send)(
+            "%s_status" % game.access_code, {
+                "type": "fear_tracker.hashcode_seen",
+                "hashcode": status_obj['hash'],
+                "status_string": status_string,
+            })
+
     for player in players.values():
         info = player.fear
         if not info:
@@ -324,4 +340,63 @@ def status(request, game, hashcode=None):
         return HttpResponse(status=HTTPStatus.NOT_MODIFIED)
     else:
         status_string = json.dumps(status_obj)
+        async_to_sync(get_channel_layer().group_send)(
+                "%s_status" % game.access_code, {
+                    "type": "fear_tracker.hashcode_seen",
+                    "hashcode": status_obj['hash'],
+                    "status_string": status_string,
+                })
         return HttpResponse(status_string)
+
+
+class StatusLongPollConsumer(AsyncHttpConsumer):
+    async def handle(self, body):
+        self.access_code = self.scope["url_route"]["kwargs"]["access_code"]
+        self.hashcode = self.scope["url_route"]["kwargs"]["hashcode"]
+
+        await self.channel_layer.group_add("%s_status" % self.access_code,
+                                           self.channel_name)
+        await self.channel_layer.group_send(
+                "%s_status" % self.access_code, {
+                    "type": "fear_tracker.hashcode_seen",
+                    "hashcode": self.hashcode,
+                })
+
+    async def http_request(self, message):
+        """
+        Async entrypoint - concatenates body fragments and hands off control
+        to ``self.handle`` when the body has been completely received.
+        """
+        if "body" in message:
+            self.body.append(message["body"])
+        if not message.get("more_body"):
+            await self.handle(b"".join(self.body))
+
+    async def disconnect(self):
+        await self.channel_layer.group_discard("%s_status" % self.access_code,
+                                               self.channel_name)
+
+    async def fear_tracker_hashcode_seen(self, event):
+        if self.hashcode != event["hashcode"]:
+            if event["status_string"]:
+                body = event["status_string"].encode('utf-8')
+                await self.send_response(200, body)
+                await self.disconnect()
+            await self.channel_layer.group_send(
+                    "%s_status" % self.access_code, {
+                        "type": "fear_tracker.invalidate_status",
+                    })
+
+    async def fear_tracker_invalidate_status(self, event):
+        # get script_prefix for reverse()
+        script_prefix = self.scope.get("root_path", "") or ""
+        if settings.FORCE_SCRIPT_NAME:
+            script_prefix = settings.FORCE_SCRIPT_NAME
+        set_script_prefix(script_prefix)
+
+        no_hash_status = reverse('status',
+                                 kwargs={'access_code': self.access_code})
+        await self.send_response(302, b'', headers=[
+            (b"Location", no_hash_status.encode('utf-8'))
+        ])
+        await self.http_disconnect(None)

fear_tracker_site/routing.py

@@ -1,4 +1,3 @@
-from channels.routing import ProtocolTypeRouter
+import fear_tracker.routing
 
-# No async routing currently; just default sync http.
+application = fear_tracker.routing.application
-application = ProtocolTypeRouter({})

fear_tracker_site/settings.py

@@ -31,6 +31,7 @@ ALLOWED_HOSTS = []
 # Application definition
 
 INSTALLED_APPS = [
+    'channels',
     'fear_tracker',
     'django.contrib.admin',
     'django.contrib.auth',
@@ -82,6 +83,12 @@ DATABASES = {
     }
 }
 
+CHANNEL_LAYERS = {
+    "default": {
+        "BACKEND": "channels.layers.InMemoryChannelLayer"
+    }
+}
+
 
 # Password validation
 # https://docs.djangoproject.com/en/2.2/ref/settings/#auth-password-validators