Merge lp:~tribaal/squid-deb-proxy/refresh-ims into lp:squid-deb-proxy

[Chris Glass]

This branch adds "refresh-ims" options to the refresh patterns for index files.

The reason for this is that archives usually set a cache-control header on them, and so in some cases the proxy will have mismatching indexes/packages (I see "Hash sum mismatch" errors when this happens).

The proposed change tells squid to forward the request upstream if it has a If-Modified-Since header (that apt sets), and so we let the upstream archive decide if the cache is fresh or not.

Since it answers only a simple 304, bandwidth overhead is minimal, and that prevents users from seeing errors in this rare but possible case (we see his more often on automated system deployments, obviously).

=== modified file 'squid-deb-proxy.conf'
--- squid-deb-proxy.conf	2013-09-20 10:08:11 +0000
+++ squid-deb-proxy.conf	2014-07-17 16:09:37 +0000
@@ -56,9 +56,9 @@
 refresh_pattern tar.gz$  129600 100% 129600
 
 # always refresh Packages and Release files
-refresh_pattern \/(Packages|Sources)(|\.bz2|\.gz|\.xz)$ 0 0% 0
-refresh_pattern \/Release(|\.gpg)$ 0 0% 0
-refresh_pattern \/InRelease$ 0 0% 0
+refresh_pattern \/(Packages|Sources)(|\.bz2|\.gz|\.xz)$ 0 0% 0 refresh-ims
+refresh_pattern \/Release(|\.gpg)$ 0 0% 0 refresh-ims
+refresh_pattern \/InRelease$ 0 0% 0 refresh-ims
 
 # handle meta-release and changelogs.ubuntu.com special
 # (fine to have this on debian too)