(newbie) How to avoid proxy caching of my applet

I am using the OBJECT tag to deliver a java applet to the client
browser. My problem is that I have a customer that uses a Squid proxy
server, and I have found that when I update my applet on the Apache
web server, the old applet remains cached in the Squid proxy for some
time (days). I am generally familiar with the HTTP headers such as
Expires that, if sent with my response, would probably prevent the
proxy from caching the applet, however I don't know how I can control
the generation of those headers in Apache for an applet delivered via
the OBJECT tag. I don't see an attribute of the OBJECT tag I can set,
is there some other Apache configuration setting that could be used to
have apache generate an Expires header for this applet, or for all
OBJECT tag content ?

Headers come before any single tag is sent. They can not ever be
controlled through HTML tags - either scripting before them (PHP and Perl
can both help out here), or try to see if Apache can be told to send a
certain set of headers in advance for every document it serves (not sure on
this one, but it's very probably possible - check out Apache docs)

Dave wrote:

> I am using the OBJECT tag to deliver a java applet to the client
> browser. My problem is that I have a customer that uses a Squid proxy
> server, and I have found that when I update my applet on the Apache
> web server, the old applet remains cached in the Squid proxy for some
> time (days). I am generally familiar with the HTTP headers such as
> Expires that, if sent with my response, would probably prevent the
> proxy from caching the applet, however I don't know how I can control
> the generation of those headers in Apache for an applet delivered via
> the OBJECT tag. I don't see an attribute of the OBJECT tag I can set,
> is there some other Apache configuration setting that could be used to
> have apache generate an Expires header for this applet, or for all
> OBJECT tag content ?

On Tue, 28 Oct 2003, Dave wrote:

> I am generally familiar with the HTTP headers such as
> Expires that, if sent with my response, would probably prevent the
> proxy from caching the applet, however I don't know how I can control
> the generation of those headers in Apache for an applet delivered via
> the OBJECT tag.

I'd have to ask you to adjust your mental picture. Cacheability
of a resource depends on what the _server_ says about the resource
when it serves it out, and the server doesn't care in the least
whether the client agent retrieved the resource as the result of an
<a href...>, <img src...,>, <object...>, or whatever.

I definitely recommend the tutorial that you can find at
http://www.mnot.net/cache_docs/ (and the same author's cacheability
engine to test your own URLs).

> I don't see an attribute of the OBJECT tag I can set,

Because it's not involved in deciding cacheability.

> is there some other Apache configuration setting that could be used to
> have apache generate an Expires header for this applet,

Yes, several. That tutorial should give you reasonable pointers.

> or for all OBJECT tag content ?

No, the server settings apply to the content itself (in this case the
actual applet file), not to the means by which the client retrieves
it (the "object tag").

From the server side, once the object is cached (in client or
intermediate proxy) it it cached. There's nothing further that you
can do, directly, from the server side, to convince an intermediate
proxy to refresh itself. When it is good and ready, it will take a
look, and then it will see the new resource at the server and fetch
it. Until then, the only possible source of influence is from the
client side (a command-reload to punch through the proxy).

So it may be useful to try educating your users in the use of their
browsers, in addition to taking some measures to invite the proxy
to check more often than it would normally do.

hope this helps