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From Martin Algesten <mar...@taglab.com>
Subject Re: production quality?
Date Thu, 31 Oct 2002 15:35:15 GMT
I don't see how chaning the Content-Type can be right in this scenario 
(yes, generally content-type changes might be ok), can you explain. If I 
understood this correctly we are asking Tomcat if a specific object has 
changed (If-Modified-Since), and any response should surely be true 
about the resource we're asking about. E.g. if we're asking if a certain 
gif file has changed since yesterday, then tomcat tells us that it is 
unchanged content wise, but meta-wise it is no longer a gif, but an html 
document?!

Martin



jean-frederic clere wrote:

> Martin Algesten wrote:
>
>> 1. Tomcat should either not send any headers on a 304, or if it does 
>> then make sure that they do reflect the correct values for the 
>> requested object (e.g. not call a gif a text).
>
>
> Changing a Content-Type is legitimate, but changing the
> Content-Length is probably not.
>
> But I do not think that Tomcat has to change the Content-Type.
>
>>
>> 2. Not entirely sure here. Reading the HTTP/1.1 
>> http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.5
>> It states:
>> "If a cache uses a received 304 response to update a cache entry, the 
>> cache MUST update the entry to reflect any new field values given in 
>> the response."
>>
>> I suspect that is what we're seeing in mod_proxy. But I just realised 
>> that I have some reading to do, the stuff about weak and strong 
>> validator didn't make much sense to me...
>
>
> It changes the Content-Type and I think that is OK.
>
>>
>> Martin
>>
>> jean-frederic clere wrote:
>>
>>> Pier Fumagalli wrote:
>>>
>>>> On 30/10/02 20:02, "Martin Algesten" <martin@taglab.com> wrote:
>>>>
>>>>
>>>>> In a nutshell mod_proxy updates its cached entries with whatever new
>>>>> headers are given to it. E.g. first request comes into mod_proxy 
>>>>> and it
>>>>> can't find the requested resource in its cache. It forwards on to my
>>>>> tomcat who responds with something like:
>>>>> HTTP/1.1 200
>>>>> Content-Type: image/gif
>>>>> Content-Length: 12345
>>>>>
>>>>> Second call comes into mod_proxy this time with an "If-Modified-Since"
>>>>> for the same resource. mod_proxy needs to revalidate its cached entry
>>>>> against tomcat and does an "If-Modifed-Since" against tomcat and 
>>>>> tomcat
>>>>> answers:
>>>>> HTTP/1.1 304
>>>>> Content-Type: text/html
>>>>> Content-Length: 0
>>>>>
>>>>> At this point mod_proxy updates it's cached entry and ends up with 
>>>>> a gif
>>>>> that has got a Content-Type set to text/html.
>>>>>
>>>>> Further requests to mod_proxy without "If-Modified-Since" results in
>>>>> GIFs with strange content types. Thank god for IE not trusting the
>>>>> content type :)
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Nope, that's not it, but it's a good catch. We don't keep proxied 
>>>> content
>>>> cached... Thanks a lot for the clarification...
>>>
>>>
>>>
>>>
>>> If I got it right there are 2 errors:
>>> 1 - Tomcat should not send a Content-Type nor Content-Length.
>>> 2 - mod_proxy should complain because we are sending "garbages" or 
>>> ignore the "invalid" headers.
>>>
>>>>
>>>>     Pier (gone diggin' mirrors)
>>>>
>>>>
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>>>>
>>>
>>>
>>>
>>>
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>>
>>
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>
>
>
>
>
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