Users of mod_proxy_html should upgrade to libxml2 version 2.5.10. This fixes bugs in earlier versions that can in some cases have a severe impact on performance.
mod_proxy_html is based on one specific capability of mod_accessibility, namely that of rewriting HTML links so that they don't break in a reverse proxy. The need for it was identified in a Usenet thread.
The problem arises when links such as <a
href="http://private-address.example.com/"> are used in
a proxied page, when the server private-address.example.com
needs to be proxied (for example, because its address is not valid
beyond a private network). mod_proxy_html rewrites
such URLs into the proxy's own namespace.
The key directive required for this is ProxyHTMLURLMap. This is functionally identical to AccessibilityURLMap, which is documented in the mod_accessibility pages.
mod_proxy_html.c source code is available under the GNU General Public License (GPL). As with other opensource modules, we can consider alternative licenses by request.