Add shortcut for HEAD requests on slower views

We sometimes see some web bots and crawlers make HEAD requests to verify
existence of certain pages in the application. However, they are less
than kind as 20-50 requests might arrive at the same time, and package
search and details pages are some of the slowest rendering pages we have
due to the Django template engine.

Rather than waste time generating the content only to throw it away,
response as soon as we can with either a 404 or 200 response as
appropriate, omitting the 'Content-Length' header completely, which
seems to be acceptable by the HTTP spec.

Signed-off-by: Dan McGee <dan@archlinux.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/main/utils.py b/main/utils.py
index cdd4ff7..8394e5c 100644
--- a/main/utils.py
+++ b/main/utils.py
@@ -8,6 +8,7 @@ import hashlib
 
 from django.core.cache import cache
 from django.db import connections, router
+from django.http import HttpResponse
 from django.utils.timezone import now
 from django.template.defaultfilters import slugify
 
@@ -55,6 +56,14 @@ def clear_cache_function(func, args, kwargs):
     cache.delete(key)
 
 
+def empty_response():
+    empty = HttpResponse('')
+    # designating response as 'streaming' forces ConditionalGetMiddleware to
+    # not add a 'Content-Length: 0' header
+    empty.streaming = True
+    return empty
+
+
 def format_http_headers(request):
     headers = sorted((k, v) for k, v in request.META.items()
             if k.startswith('HTTP_'))