Merge pull request #359 from CTPUG/feature/cached_pages

Hacky approach to caching the page rendering for dynamic page content

wafer/pages/admin.py

@@ -8,7 +8,8 @@
 class PageAdmin(CompareVersionAdmin, admin.ModelAdmin):
     prepopulated_fields = {"slug": ("name",)}
     list_display = ('name', 'slug', 'get_absolute_url',
-                    'get_people_display_names', 'get_in_schedule')
+                    'cache_time', 'get_people_display_names',
+                    'get_in_schedule')
 
     list_filter = (DateModifiedFilter,)
 

wafer/pages/migrations/0005_page_cache_time.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10 on 2017-07-28 12:53
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pages', '0004_allow_blank_files_description'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='page',
+            name='cache_time',
+            field=models.IntegerField(default=-1, help_text='Length of time (in seconds) to cache the page for dynamic page content. A negative value means this page is not dynamic and it will be not be regenerated until it is next edited.'),
+        ),
+    ]

wafer/pages/models.py

@@ -6,11 +6,12 @@
 from django.core.exceptions import ValidationError, NON_FIELD_ERRORS
 from django.conf import settings
 from django.db import models
+from django.core.cache import caches
 from django.db.models.signals import post_save
 from django.utils.encoding import python_2_unicode_compatible
 
 
-from markitup.fields import MarkupField
+from markitup.fields import MarkupField, render_func
 from wafer.menu import MenuError, refresh_menu_cache
 
 
@@ -51,9 +52,18 @@ class Page(models.Model):
         help_text=_("People associated with this page for display in the"
                     " schedule (Session chairs, panelists, etc.)"))
 
+    cache_time = models.IntegerField(
+        default=-1,
+        help_text=_("Length of time (in seconds) to cache the page for "
+                    "dynamic page content. A negative value means this page "
+                    "is not dynamic and it will be not be regenerated "
+                    "until it is next edited."))
+
     def __str__(self):
         return u'%s' % (self.name,)
 
+    cache_name = settings.WAFER_CACHE
+
     def get_path(self):
         path, parent = [self.slug], self.parent
         while parent is not None:
@@ -68,6 +78,26 @@ def get_absolute_url(self):
         url = "/".join(self.get_path())
         return reverse('wafer_page', args=(url,))
 
+    def _cache_key(self):
+        return "wafer.pages:rendered:%s" % self.get_absolute_url()
+
+    def cached_render(self):
+        if self.cache_time < 0:
+            return self.content.rendered
+        cache = caches[self.cache_name]
+        cache_key = self._cache_key()
+        rendered = cache.get(cache_key)
+        if rendered is None:
+            rendered = render_func(self.content.raw)
+            # Should reset the database copy, but this is enough for
+            # now
+            cache.set(cache_key, rendered, self.cache_time)
+        return rendered
+
+    def invalidate_cache(self):
+        cache = caches[self.cache_name]
+        cache.delete(self._cache_key())
+
     get_absolute_url.short_description = 'page url'
 
     def get_in_schedule(self):
@@ -121,6 +151,11 @@ def validate_unique(self, exclude=None):
                 })
         return super(Page, self).validate_unique(exclude)
 
+    def save(self, *args, **kwargs):
+        """Ensure we invalidate the cache after saving"""
+        super(Page, self).save(*args, **kwargs)
+        self.invalidate_cache()
+
 
 def page_menus(root_menu):
     """Add page menus."""

wafer/pages/templates/wafer.pages/page.html

@@ -3,7 +3,7 @@
 {% block title %}{{ page.name }} - {{ WAFER_CONFERENCE_NAME }}{% endblock %}
 {% block content %}
 <div>
-  {{ page.content.rendered|safe }}
+  {{ page.cached_render|safe }}
   {% if perms.pages.change_page %}
     <div class="clearfix">
       <a href="{{ page.get_absolute_url }}?compare"

wafer/pages/tests/test_pages.py

@@ -1,9 +1,10 @@
 # Simple test of the edit logic around pages
 
-from django.test import Client, TestCase
+from django.test import Client, TestCase, override_settings
 from django.contrib.auth import get_user_model
 from django.contrib.auth.models import Permission
 from django.contrib.contenttypes.models import ContentType
+from django.core.cache import caches
 
 from wafer.pages.models import Page
 
@@ -88,3 +89,26 @@ def test_root_page(self):
         templates = [x.name for x in response.templates]
         self.assertTrue('wafer.pages/page_form.html' in templates)
         self.assertEqual(response.status_code, 200)
+
+    def test_cache_time(self):
+        """Test the behaviour of cache_time"""
+        uncached_page = Page.objects.create(name="not cached", slug="no_cache",
+                                            content="*aa*")
+        cached_page = Page.objects.create(name="Cached Page", slug="cached",
+                                          content="*bb*",
+                                          cache_time=100)
+        # We use a memory cache here to actually check caching behaviour
+        with override_settings(CACHES={"default": {'BACKEND': 'django.core.cache.backends.locmem.LocMemCache'},
+                                       "wafer_cache": {'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
+                                                       'LOCATION': 'test_cache'}}):
+            cache = caches['wafer_cache']
+            result = uncached_page.cached_render()
+            self.assertEqual(result, uncached_page.content.rendered)
+            self.assertEqual(cache.get(uncached_page._cache_key()), None)
+            result = cached_page.cached_render()
+            self.assertEqual(result, cached_page.content.rendered)
+            self.assertEqual(cache.get(cached_page._cache_key()), result)
+            # Check that updating the page content invalidates the cache
+            cached_page.content = '*cc*'
+            cached_page.save()
+            self.assertEqual(cache.get(cached_page._cache_key()), None)