Basically it does the lookup/dispatch once per filter in the filterchain per request. It checks that filter's providers until it finds a match. So for anything you could do with an [Add|Set]OutputFilter[ByType] that's one lookup per request.
Okay, so if I have three rules and ten filters, we'll be doing thirty checks, right? And, this will happen even if mod_filter isn't configured - as mod_filter still needs to check ten times that it doesn't have anything to do, right? Hmm. How expensive is this again?
mod_filter takes the content-type as it is at that point in the chain.
Isn't the real nightmare where a filter calls ap_set_content_type and some AddOutputFilterByTypes are in effect? I guess what *really* bothers me is the idea of adding filters *as a side-effect*.
How wouldn't it be a side-effect? It's intentional from the admin perspective, but a side-effect from the developer's perspective.
And, then mod_deflate needs to be conditionally added (sub-case #1: it needs to be added for 'text/plain'; sub-case #2: it needs to be added for 'text/html'). How and where is it added? Are you inserting dummy filters?
I'm not sure I follow. It will dispatch to deflate based on the content-type (or other dispatch criterion) as it is at that point in the chain.
The question is at which point in the chain does deflate get added?
So if the handler sets application/xml but that goes through an XSLT filter which sets it to text/html, then mod_filter sees application/xml if it's before the XSLT filter in the chain, or text/html after it.
How can AddOutputFilterByType expect to cope with that?
I thought you suggested that mod_filter could easily handle this case. I'm still not seeing how.
But FWIW I have that working locally with
FilterDeclare filter1 Content-Type CONTENT_SET FilterDeclare filter2 Content-Length CONTENT_SET
FilterProvider filter1 filter2 $text FilterProvider filter2 DEFLATE >4000
FilterChain filter1
to deflate all "text/*" documents of 4k or greater.
Can I comment that I think a clearer configuration syntax is going to be needed if we are going to axe all of the current filter directives?
AddOutputFilterByType, for all of its internal oddness, is a simple directive for an administrator to understand. So, perhaps keep 'AddOutputFilterByType' and having it internally converted to a mod_filter directive. But, I'm just not overly excited about moving all filter configuration directives to something akin to mod_rewrite. Ouch. -- justin
