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From Joe Lewis <...@joe-lewis.com>
Subject Re: apache module or CGI
Date Mon, 26 Mar 2007 16:47:17 GMT
Ralf Mattes wrote:
> On Mon, 2007-03-26 at 10:14 -0600, Joe Lewis wrote:
>   
>>> Sam Carleton wrote:
>>>   
>>>       
>>>> On 3/26/07, Issac Goldstand <margol@beamartyr.net> wrote:
>>>>     
>>>>         
>>>>> If the images are already on the server, and needed for the response
>>>>> immediately, you'd need to do it inline, but you could still make life
>>>>> easier on yourself (somewhat) by caching the reduced images to avoid
>>>>> reprocessing.
>>>>>
>>>>> I could give more specific advice if you could share a bit more about
>>>>> what you're trying to accomplish in general.
>>>>>           
>> Another alternative is to cause the image links to point to a directory, 
>> and use
>>
>> ErrorDocument 404 /cgi-bin/script-to-generate-thumbnails.pl
>>
>>     
>
> No -- please don't do that. You are terribly abusing the protocol.
> An "Error Document" is just this - an indication of what went wrong.
> The client will still receive a 404 status, and, expecting an _image_,
> just display the dreaded broken image icon ...
>   
If the script responds with the generated image and the proper content 
type, it would work.  I never said it would be "pleasant".  But my 
question is : how does the use of an ErrorDocument generator to generate 
content that doesn't exist into a static form become abuse of the 
protocol?  The ErrorDocument in Apache 2.2 really creates a sub request 
to grab that, so I don't think it's really a bad idea.  Isn't that why 
the ErrorDocument directive was even implemented, so that the 
administrators could customize the responses on certain error codes?  
Yes, it may not be as "cool" as building a separate process to do what 
needs to be done, but it is similar to generating the content and 
caching it.

(Oh, and feel free to use any extension that maps to a packaged 
thumbnail generator - as long as the script to generate it works).  Yes, 
it may not be as "cool" as building a separate process to do what needs 
to be done, but it is similar to generating the content and caching it.  
(Sam - is this supposed to be "O.S. independent"?  Are you shipping the 
source code?)

Joe

> BTW, with HTTP/1.1 and chunked encoding there shouldn't be any problem
> generating the image on the fly and then storing it in the cache.
> And there _are_ response status that indicate a lengthy content
> generation ...
>
>  HTH Ralf Mattes
>   
>   
>> Which CGI generates the image and dumps it to the browser as well as 
>> storing it.  Then, each subsequent image request comes from the static 
>> file.  If you need them to be cleaned up once in a while and 
>> regenerated, just create a cron job with "find" to locate the "old" 
>> thumbnails and delete them, which causes the 404 and regenerates the images.
>>
>> Joe
>>     
>
>   


-- 
Joseph Lewis <http://sharktooth.org/>
"Divide the fire, and you will sooner put it out." - Publius Syrus

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