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From jean-frederic clere <jfrederic.cl...@fujitsu-siemens.com>
Subject Re: production quality?
Date Thu, 31 Oct 2002 16:06:37 GMT
Martin Algesten wrote:
> 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?!

Yes, in the scenario that is a bug. So report it as a bug.

But think of an ISO image incorrectly transferted as text/html due to _bad_ mime 
type configuration, would not it be nice to just change the mime type and not 
resend the whole file?

> 
> 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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> 
> 
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> 




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