Squid, Reload and cache hierarchies

I have some problems understanding the behaviour of Squid in a cache
hierarchy when an user chooses "Reload" on his browser.

Symptom: Lynx ("This page looks great with Lynx, download it now!") and
Netscape have two different results.

Configuration: a Squid 1.0.0 cache running on FreeBSD, child of a Squid
1.0.0 cache running on Alpha/OSF1. Users are clients of the first one,
they use Netscape or Lynx on Unix boxes.

Explanation: Lynx does a "hard" reload, sending "Pragma: no-cache" but no
"If-Modified-Since" while Netscape uses both headers.

Therefore, when a Lynx reload hits Squid, Squid sends an ICP request to
its parent which does *not* include the "Pragma: no-cache" :-( (Weakness
in ICP?) If the parent has the page in its cache, it sends it back and no
real reload was done.

On the other hand, when Netscape reloads, Squid bypasses the hierarchy
because of the "If-Modified-Since" :-( (See Release-Notes-1.0.txt.) So,
the desire of Netscape to save bandwidth leads to more resource
comsuption.

Debug tools: source of icp.c and "debug_options ALL,1 12,5" (great tool,
you can see all the HTTP headers and the whole request handling
algorithm).
Received on Wed Jul 17 1996 - 09:21:39 MDT