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From Erica Zhang <>
Subject Re: Questions on modules to provide cache functions for Apache
Date Tue, 06 Mar 2007 19:30:59 GMT
Well, my question is not on the usage of mod_cache. In fact, I have used 
local applications to add caching headers and configure mod_cache to 
catch those HTTP responses. However I could not catch those HTTP 
responses. So I wonder if mod_cache could catch dynamic responses which 
are responding for those XMLHttpRequest in Ajax technology. If no, I 
want to provide a general module to solve the problem.

I have send this kind of questions to user alias but none reply this.

For blind cache, I do not want to use.



Joe Lewis wrote:

> Erica Zhang wrote:
>> David,
>> Thanks a lot for your reply. While, I just want to cache HTTP 
>> responses produced by PHP scripts. Of course, those responses perhaps 
>> include PHP scripts. On the other hand,  I know I could do it by use 
>> of PHP itself. I just want to provide a general one. This means no 
>> matter what kind of script or languages used for server development, 
>> for example, ASP, PHP, Java and etc, I could use only one module to 
>> cache those HTTP responses. I thought Apache could handle or filter 
>> HTTP responses or requests. So I want to add modules to handle 
>> caching dynamic HTTP responses problems.
>> However, based on your suggestion, it seems that I have to developed 
>> separate ones for Java, ASP, PHP. Right ?
> If your server is acting as a proxy to another server and it's content 
> generation, no - which ever platform you want to develop your caching 
> on will cache.  If the local server is generating the response, then 
> the local application is responsible for either caching or using 
> appropriate caching headers.  If the caching mechanism is understood, 
> just use the existing "mod_cache" and it's associated extensions (e.g. 
> mod_mem_cache and mod_disk_cache).  Questions regarding those modules 
> would be better answered on the users' lists rather than here.
>> But is there some general way to cache responses ?
> Consider modifying whatever is generating the response to include the 
> caching headers - a system has been in place for cache control for 
> years.  If the headers exist, the browsers should only check the 
> modification times and request the new page if the modification time 
> has changed.
> If your server is acting as a proxy to another content, you only have 
> two options -
>  a) modify the content generation server to include the caching headers
>  b) Force your server to do caching regardless of the headers.  This 
> will have the wonderful effect in which the web browsers won't have 
> control over getting updated docs - and thereby causing network guru's 
> to run around like squirrels on caffeine until they realize that a 
> server in between is responding with data that should be dynamic but 
> isn't because it's been cached.  This is because there will be no 
> mechanism to determine when the file coming from the generator has 
> been updated.  It's a blind cache, and I would never suggest a blind 
> cache for the sanity of people using the system.
> Joe

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