r4880 - trunk/varnish-cache/doc/sphinx/tutorial

[perbu at varnish-cache.org]

Author: perbu
Date: 2010-06-02 21:01:05 +0200 (Wed, 02 Jun 2010)
New Revision: 4880

Modified:
   trunk/varnish-cache/doc/sphinx/tutorial/increasing_your_hitrate.rst
Log:
on vary and user agents

Modified: trunk/varnish-cache/doc/sphinx/tutorial/increasing_your_hitrate.rst
===================================================================
--- trunk/varnish-cache/doc/sphinx/tutorial/increasing_your_hitrate.rst	2010-06-02 18:51:21 UTC (rev 4879)
+++ trunk/varnish-cache/doc/sphinx/tutorial/increasing_your_hitrate.rst	2010-06-02 19:01:05 UTC (rev 4880)
@@ -221,6 +221,17 @@
 The code sets the Accept-Encoding header from the client to either
 gzip, deflate with a preference for gzip.
 
+Pitfall - Vary: User-Agent
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Some applications or application servers send *Vary: User-Agent* along
+with their content. This instructs Varnish to cache a separate copy
+for every variation of User-Agent there is. There are plenty. Even a
+single patchlevel of the same browser will generate at least 10
+different User-Agent headers based just on what operating system they
+are running. So if you need to Vary based on User-Agent be sure to
+normalize the header or your hit rate will suffer badly.
+
 .. _tutorial-increasing_your_hitrate-pragma:
 
 Pragma