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From Nick Kew <>
Subject Re: [users@httpd] What happend to the URLs in mod_proxy_html
Date Mon, 18 Oct 2004 12:23:24 GMT
On Mon, 18 Oct 2004, Robert Andersson wrote:

> I would, if possible, try to get the software fixed. It is not functional.
> It looks horrible; it is just a coincident that it works in any browser at
> all!

A browser is a heavyweight application that expects to have a substantial
share of the total resources of a workstation.  It can attempt a great deal
of error correction.  No great problem if it consumes (tens of) megabytes
of memory, and a couple of seconds of CPU time.

mod_proxy_html is different.  It may be processing hundreds (or given
beefy hardware even thousands) of documents in parallel.  It has to be
much more aware of resources consumed, and use them efficiently.

In practical terms, that means using a SAX parser, which is of course
by far the quickest and most efficient way to process markup.  And it
means using Apache's pipelined filter architecture.  Bearing that in
mind, it has to forego expensive error correction methods such as
backtracking, that a browser with the entire document in memory might use.

There is an unpublished version that deals much better with seriously
broken backends, at the expense of performance (still much less overhead
than a browser of course).  I have contemplated releasing it, but it would
want a bit of work first - e.g. the admin has to have full control of the
error-correction, and should normally disable it for performance.

> Another note, mod_proxy_html doesn't seem to add a valid doctype? A doctype
> declaration should include the DTD URI, eg:
>     "">

The System ID (URI for DTD) is not required for HTML (unlike XHTML).
What mod_proxy_html does is controlled by the ProxyHTMLDoctype directive.

Nick Kew

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