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From Manik Taneja <mtan...@movik.net>
Subject Re: [users@httpd] way for me to turn off if-modified-since & always return 304 reply ?
Date Fri, 12 Sep 2008 09:46:40 GMT
dave selby wrote:
> 2008/9/12 André Warnier <aw@ice-sa.com>:
>   
>> Manik Taneja wrote:
>>     
>>> Nope, there is no way you can prevent the client from sending you an IMS
>>> request.
>>>       
>> The above is correct, but if I understand the OP question correctly, the
>> basic issue is to make sure that the client does not re-use a cached page,
>> but always retrieves the latest page from the server.
>>     
>
> Sorry, its me not explaining myself very clearly. Its the opposite.
>
> If you look at kmotion v1 you will see why ....
> http://code.google.com/p/kmotion/wiki/ScreenShots its more like an
> application than a conventional web page. I have a directory that is
> constantly updated with new images, because the directory is
> constantly having its 'last modified' date changed apache keeps
> resending images that do not need to be sent. And these are not small
> files.
>   
You could try by setting the Age and Expires header in the response to a 
largish value. However, that will still not guarantee clients not 
sending a freshness check to the server.

> None of the images are ever changed, they each have a unique name and
> are deleted by background daemons so once loaded I really don't want
> to have to reload it again if for arguments sake I need to flip back
> to the last frame.
>
> kmotion v1 is alive and well but I am writting v2 & am trying to
> improve responsiveness etc.
>
> Sorry for the long explanation - but I hope this explains my problem.
>
>   
>> There is a whole array of things one can do on the server side, to at least
>> try to achieve this. I don't recall all the specifics, but look for instance
>> at HTTP headers such as "Cache-control".
>> See here
>> http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
>> section 14.9
>>
>> The general idea is : the server, by a combination of HTTP headers sent
>> along with the documents, and tags in the documents themselves, should be
>> able to tell the client whether this page can, or cannot, be cached and
>> re-used.
>> And according to the HTTP specifications, the client (and any intermediate
>> proxies) should obey these instructions.
>>
>> Now whether they always actually do, is anothet issue.
>> (But in the practice I have noticed that they generally do).
>>
>> To modify the HTTP headers that Apache sends along with documents, you could
>> use something like this :
>> http://httpd.apache.org/docs/2.2/mod/mod_headers.html
>> or mod_perl handlers.
>>
>>
>> André
>>
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>>
>>     
>
>
>
>   


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