Merge pull request #613 from CTPUG/schedule-caching

Support client-side caching of schedules

wafer/schedule/models.py

@@ -1,5 +1,6 @@
 from uuid import UUID
 
+from django.core.cache import cache
 from django.core.exceptions import ValidationError
 from django.db import models
 from django.db.models.signals import post_save, post_delete
@@ -360,6 +361,14 @@ def guid(self):
         return UUID(bytes=hmac.digest()[:16])
 
 
+def get_schedule_version():
+    """Return the current schedule version as a string"""
+    version = cache.get('wafer_schedule_version')
+    if not version:
+        version = update_schedule_version()
+    return version
+
+
 def invalidate_check_schedule(*args, **kw):
     sender = kw.pop('sender', None)
     if sender is Talk or sender is Page:
@@ -381,7 +390,7 @@ def update_schedule_items(*args, **kw):
         return
     for item in slot.scheduleitem_set.all():
         item.save(update_fields=['last_updated'])
-    # We also need to update the next slot, in case we changed it's
+    # We also need to update the next slot, in case we changed its
     # times as well
     next_slot = slot.slot_set.all()
     if next_slot.count():
@@ -391,15 +400,24 @@ def update_schedule_items(*args, **kw):
             item.save(update_fields=['last_updated'])
 
 
-post_save.connect(invalidate_check_schedule, sender=ScheduleBlock)
-post_save.connect(invalidate_check_schedule, sender=Venue)
-post_save.connect(invalidate_check_schedule, sender=Slot)
-post_save.connect(invalidate_check_schedule, sender=ScheduleItem)
+def update_schedule_version(*args, **kwargs):
+    """Store the schedule version in the Django cache.
+
+    The version is used to allow clients to perform conditional HTTP requests
+    on the schedule.
+
+    We don't just rely on max(ScheduleItem.updated_at) as that misses
+    deletions.
+    """
+    version = localtime().isoformat()
+    cache.set('wafer_schedule_version', version, timeout=None)
+    return version
+
 
-post_delete.connect(invalidate_check_schedule, sender=ScheduleBlock)
-post_delete.connect(invalidate_check_schedule, sender=Venue)
-post_delete.connect(invalidate_check_schedule, sender=Slot)
-post_delete.connect(invalidate_check_schedule, sender=ScheduleItem)
+for sender in (ScheduleBlock, Venue, Slot, ScheduleItem):
+    for receiver in (invalidate_check_schedule, update_schedule_version):
+        post_save.connect(receiver, sender=sender)
+        post_delete.connect(receiver, sender=sender)
 
 # We also hook up calls from Page and Talk, so
 # changes to those reflect in the schedule immediately

wafer/schedule/templates/wafer.schedule/penta_schedule.xml

@@ -2,7 +2,7 @@
 {% load i18n %}
 <schedule>
   <generator name="wafer" version="{{ wafer_version }}" />
-  <version>{# FIXME: We have no schedule versions #}</version>
+  <version>{{ schedule_version }}</version>
   <conference>
     <title>{{ WAFER_CONFERENCE_NAME }}</title>
       {% if schedule_pages %}

wafer/schedule/tests/test_views.py

@@ -1,11 +1,11 @@
-import json
 import datetime as D
+import json
 import os.path
 from io import BytesIO
 from xml.etree import ElementTree
 
 from django.test import Client, TestCase
-from django.utils import timezone
+from django.utils import http, timezone
 
 import icalendar
 import lxml.etree
@@ -125,6 +125,8 @@ def test_simple_table(self):
             response = c.get('/schedule/')
             self.assertTrue(len(tracker.queries) < 60)
 
+        self.assertIn('Last-Modified', response)
+
         [day1] = response.context['schedule_pages']
 
         assert len(day1.rows) == 3
@@ -1495,6 +1497,7 @@ def test_pentabarf_view(self):
         # have the basic details we expect present
         c = Client()
         response = c.get('/schedule/pentabarf.xml')
+        self.assertIn('Last-Modified', response)
         parsed = ElementTree.XML(response.content)
         self.assertEqual(parsed.tag, 'schedule')
         self.assertEqual(parsed[0].tag, 'generator')
@@ -1537,6 +1540,7 @@ def test_ics_view(self):
         # and some of the required details
         c = Client()
         response = c.get('/schedule/schedule.ics')
+        self.assertIn('Last-Modified', response)
         calendar = icalendar.Calendar.from_ical(response.content)
         # No major errors
         self.assertFalse(calendar.is_broken)
@@ -1549,6 +1553,31 @@ def test_ics_view(self):
         # Check that we have the page slug in the ical event
         self.assertTrue('/test0/' in event['url'])
 
+    def test_xml_conditional_requests(self):
+        # All the public schedule views implement these, but we'll just check
+        # one of them
+        c = Client()
+        response = c.get('/schedule/pentabarf.xml')
+        self.assertEqual(response.status_code, 200)
+        last_modified = response['Last-Modified']
+
+        with QueryTracker() as tracker:
+            not_modified_response = c.get(
+                '/schedule/pentabarf.xml', HTTP_IF_MODIFIED_SINCE=last_modified)
+        self.assertEqual(not_modified_response.status_code, 304)
+        self.assertLess(len(tracker.queries), 2)
+
+        last_modified_seconds = http.parse_http_date(last_modified)
+        last_modified_seconds -= 1
+        before_last_modified = http.http_date(last_modified_seconds)
+
+        with QueryTracker() as tracker:
+            modified_response = c.get(
+                '/schedule/pentabarf.xml',
+                HTTP_IF_MODIFIED_SINCE=before_last_modified)
+        self.assertEqual(modified_response.status_code, 200)
+        self.assertGreater(len(tracker.queries), 10)
+
 
 class JsonViewTests(TestCase):
 

wafer/schedule/views.py

@@ -5,20 +5,24 @@
 
 from icalendar import Calendar, Event
 
-from django.db.models import Q
-from django.views.generic import TemplateView, View
+from django.conf import settings
 from django.contrib.sites.shortcuts import get_current_site
 from django.core.exceptions import ObjectDoesNotExist, PermissionDenied
+from django.db.models import Q
 from django.http import HttpResponse, JsonResponse
 from django.utils import timezone
-from django.conf import settings
+from django.utils.dateparse import parse_datetime
+from django.utils.decorators import method_decorator
+from django.views.decorators.http import condition
+from django.views.generic import TemplateView, View
 
 from bakery.views import BuildableDetailView, BuildableTemplateView, BuildableMixin
 from rest_framework import viewsets
 from rest_framework.permissions import IsAdminUser
 from wafer import __version__
 from wafer.pages.models import Page
-from wafer.schedule.models import Venue, Slot, ScheduleBlock, ScheduleItem
+from wafer.schedule.models import (
+    Venue, Slot, ScheduleBlock, ScheduleItem, get_schedule_version)
 from wafer.schedule.admin import check_schedule, validate_schedule
 from wafer.schedule.serializers import ScheduleItemSerializer
 from wafer.talks.models import ACCEPTED, CANCELLED
@@ -144,6 +148,15 @@ def lookup_highlighted_venue(request):
     return None
 
 
+def schedule_version_last_modified(request, **kwargs):
+    """Return the current schedule version as a datetime"""
+    version = get_schedule_version()
+    return parse_datetime(version)
+
+
+@method_decorator(
+    condition(last_modified_func=schedule_version_last_modified),
+    name='dispatch')
 class ScheduleView(BuildableTemplateView):
     template_name = 'wafer.schedule/full_schedule.html'
     build_path = 'schedule/index.html'
@@ -181,6 +194,7 @@ def get_context_data(self, **kwargs):
             if pos < len(blocks) - 1:
                 context['next_block'] = blocks[pos + 1]
         context['schedule_pages'] = generate_schedule(this_block)
+        context['schedule_version'] = get_schedule_version()
         return context
 
 
@@ -381,6 +395,9 @@ def get_context_data(self, block_id=None, **kwargs):
         return context
 
 
+@method_decorator(
+    condition(last_modified_func=schedule_version_last_modified),
+    name='dispatch')
 class ICalView(View, BuildableMixin):
     build_path = 'schedule/schedule.ics'
 
@@ -429,6 +446,9 @@ def build(self):
         self.build_file(path, self.get_content())
 
 
+@method_decorator(
+    condition(last_modified_func=schedule_version_last_modified),
+    name='dispatch')
 class JsonDataView(View, BuildableMixin):
     build_path = "schedule/schedule.json"