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Posted to users@tomcat.apache.org by Christopher Schultz <ch...@christopherschultz.net> on 2013/03/26 15:58:23 UTC
Adding Content-Length response header
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Hash: SHA256
All,
Like most folks on the list, I have quite a few dynamic resources
being served through Tomcat. For nearly all of them, the
Content-Length response header is /not/ included in the response
because either content length isn't known when the response is
committed, and therefore the Content-Length header simply cannot be
sent or the response is not being buffered in the application, and so
the application isn't counting bytes and doesn't know the content
length even if it could be reported.
I'm wondering if Tomcat can do anything about that.
Here's the situation I have: I've got a response that I'm fairly sure
fits into the response's buffer size, and I'd like to send a
Content-Length header in that case. I could probably put a wrapper
around the response's ServletOutputStream that counts bytes and then
looks for "done" conditions (OutputStream.close, etc.), then adds a
Content-Length header if the response hasn't yet been committed.
I wonder if Tomcat could do something like that more easily -- since
the buffer is being managed by Tomcat already, and Tomcat knows when
the response will be committed/completed.
So,
A: Is this something that Tomcat can do already? I don't see any
configuration options that sound like they would do this kind of thing.
B: Is this something appropriate for a container to do in general?
C: If I were to write a Filter to accomplish this manually, are there
any potential dangers if a traditional non-synchronous
request/response is being processed?
Thanks,
- -chris
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Re: Adding Content-Length response header
Posted by Nick Williams <ni...@nicholaswilliams.net>.
On Mar 26, 2013, at 3:15 PM, Christopher Schultz wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> Konstantin,
>
> On 3/26/13 11:08 AM, Konstantin Kolinko wrote:
>> 2013/3/26 Christopher Schultz <ch...@christopherschultz.net>:
>>>
>>> Like most folks on the list, I have quite a few dynamic
>>> resources being served through Tomcat. For nearly all of them,
>>> the Content-Length response header is /not/ included in the
>>> response because either content length isn't known when the
>>> response is committed, and therefore the Content-Length header
>>> simply cannot be sent or the response is not being buffered in
>>> the application, and so the application isn't counting bytes and
>>> doesn't know the content length even if it could be reported.
>>>
>>> I'm wondering if Tomcat can do anything about that.
>>>
>>> Here's the situation I have: I've got a response that I'm fairly
>>> sure fits into the response's buffer size, and I'd like to send
>>> a Content-Length header in that case. I could probably put a
>>> wrapper around the response's ServletOutputStream that counts
>>> bytes and then looks for "done" conditions (OutputStream.close,
>>> etc.), then adds a Content-Length header if the response hasn't
>>> yet been committed.
>>>
>>> I wonder if Tomcat could do something like that more easily --
>>> since the buffer is being managed by Tomcat already, and Tomcat
>>> knows when the response will be committed/completed.
>>>
>>> So,
>>>
>>> A: Is this something that Tomcat can do already? I don't see any
>>> configuration options that sound like they would do this kind of
>>> thing.
>>>
>>> B: Is this something appropriate for a container to do in
>>> general?
>>>
>>> C: If I were to write a Filter to accomplish this manually, are
>>> there any potential dangers if a traditional non-synchronous
>>> request/response is being processed?
>>
>> 1. Your Tomcat version = ?
>
> Duh. I'm running both Tomcat 6.0.36 and Tomcat 7.0.35.
>
>> 2. Are you interested in GET/POST requests, or HEAD requests?
>>
>> HEAD requests were fixed by this commit, from 5 days ago
>> http://svn.apache.org/r1459087
>
> Mostly POST requests. I'll take a look at the commit to see what was
> changed and see if it might be relevant.
FYI, that commit 5 days ago was just when it was merged to 7.x. The issue was actually fixed nearly a year ago in trunk. I just pointed out last week that it should be merged to 7.
https://issues.apache.org/bugzilla/show_bug.cgi?id=53454
>
>> 3. Tomcat is already able to provide Content-Length header when
>> all response fits into a buffer.
>>
>> But, if an explicit flush() is called, Tomcat has to start sending
>> data (usually using chunked encoding) and thus content length is
>> not known at the time when response headers are being sent.
>
> Hmm... I might be flushing the buffer explicitly. That's probably a
> stupid idea because Tomcat should ultimately flush everything for me.
> I'll check on that.
>
>> What generates your response? A servlet, a filter, or a JSP?
>
> All servlets in these cases. I'll follow-up with better answers to the
> above.
>
> Thanks,
> - -chris
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Re: Adding Content-Length response header
Posted by Christopher Schultz <ch...@christopherschultz.net>.
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Hash: SHA256
Konstantin,
On 3/26/13 11:08 AM, Konstantin Kolinko wrote:
> 2013/3/26 Christopher Schultz <ch...@christopherschultz.net>:
>>
>> Like most folks on the list, I have quite a few dynamic
>> resources being served through Tomcat. For nearly all of them,
>> the Content-Length response header is /not/ included in the
>> response because either content length isn't known when the
>> response is committed, and therefore the Content-Length header
>> simply cannot be sent or the response is not being buffered in
>> the application, and so the application isn't counting bytes and
>> doesn't know the content length even if it could be reported.
>>
>> I'm wondering if Tomcat can do anything about that.
>>
>> Here's the situation I have: I've got a response that I'm fairly
>> sure fits into the response's buffer size, and I'd like to send
>> a Content-Length header in that case. I could probably put a
>> wrapper around the response's ServletOutputStream that counts
>> bytes and then looks for "done" conditions (OutputStream.close,
>> etc.), then adds a Content-Length header if the response hasn't
>> yet been committed.
>>
>> I wonder if Tomcat could do something like that more easily --
>> since the buffer is being managed by Tomcat already, and Tomcat
>> knows when the response will be committed/completed.
>>
>> So,
>>
>> A: Is this something that Tomcat can do already? I don't see any
>> configuration options that sound like they would do this kind of
>> thing.
>>
>> B: Is this something appropriate for a container to do in
>> general?
>>
>> C: If I were to write a Filter to accomplish this manually, are
>> there any potential dangers if a traditional non-synchronous
>> request/response is being processed?
>
> 1. Your Tomcat version = ?
Duh. I'm running both Tomcat 6.0.36 and Tomcat 7.0.35.
> 2. Are you interested in GET/POST requests, or HEAD requests?
>
> HEAD requests were fixed by this commit, from 5 days ago
> http://svn.apache.org/r1459087
Mostly POST requests. I'll take a look at the commit to see what was
changed and see if it might be relevant.
> 3. Tomcat is already able to provide Content-Length header when
> all response fits into a buffer.
>
> But, if an explicit flush() is called, Tomcat has to start sending
> data (usually using chunked encoding) and thus content length is
> not known at the time when response headers are being sent.
Hmm... I might be flushing the buffer explicitly. That's probably a
stupid idea because Tomcat should ultimately flush everything for me.
I'll check on that.
> What generates your response? A servlet, a filter, or a JSP?
All servlets in these cases. I'll follow-up with better answers to the
above.
Thanks,
- -chris
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Re: Adding Content-Length response header
Posted by Christopher Schultz <ch...@christopherschultz.net>.
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Hash: SHA256
Konstantin,
On 3/26/13 11:08 AM, Konstantin Kolinko wrote:
> 2. Are you interested in GET/POST requests, or HEAD requests?
>
> HEAD requests were fixed by this commit, from 5 days ago
> http://svn.apache.org/r1459087
I am dealing almost entirely with POST requests.
> 3. Tomcat is already able to provide Content-Length header when
> all response fits into a buffer.
>
> But, if an explicit flush() is called, Tomcat has to start sending
> data (usually using chunked encoding) and thus content length is
> not known at the time when response headers are being sent.
It seems I am flushing the buffer twice: once after emitting the XML
header (processing instruction and document element) and then once
again just before the end of the doPost method.
I'll try removing those to see if I can get a Content-Length in the
response. If that works, I'll do a bunch of testing to see if the lack
of flush presents a problem: I want my servlet to handle all
interaction with the client -- that is, the container shouldn't
respond with text/plain or text/html or anything like that. I should
be handling all exceptions except for IOExceptions writing to the
OutputStream, so that probably isn't a problem.
Thanks,
- -chris
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Re: Adding Content-Length response header
Posted by Konstantin Kolinko <kn...@gmail.com>.
2013/3/26 Christopher Schultz <ch...@christopherschultz.net>:
>
> Like most folks on the list, I have quite a few dynamic resources
> being served through Tomcat. For nearly all of them, the
> Content-Length response header is /not/ included in the response
> because either content length isn't known when the response is
> committed, and therefore the Content-Length header simply cannot be
> sent or the response is not being buffered in the application, and so
> the application isn't counting bytes and doesn't know the content
> length even if it could be reported.
>
> I'm wondering if Tomcat can do anything about that.
>
> Here's the situation I have: I've got a response that I'm fairly sure
> fits into the response's buffer size, and I'd like to send a
> Content-Length header in that case. I could probably put a wrapper
> around the response's ServletOutputStream that counts bytes and then
> looks for "done" conditions (OutputStream.close, etc.), then adds a
> Content-Length header if the response hasn't yet been committed.
>
> I wonder if Tomcat could do something like that more easily -- since
> the buffer is being managed by Tomcat already, and Tomcat knows when
> the response will be committed/completed.
>
> So,
>
> A: Is this something that Tomcat can do already? I don't see any
> configuration options that sound like they would do this kind of thing.
>
> B: Is this something appropriate for a container to do in general?
>
> C: If I were to write a Filter to accomplish this manually, are there
> any potential dangers if a traditional non-synchronous
> request/response is being processed?
1. Your Tomcat version = ?
2. Are you interested in GET/POST requests, or HEAD requests?
HEAD requests were fixed by this commit, from 5 days ago
http://svn.apache.org/r1459087
3. Tomcat is already able to provide Content-Length header when all
response fits into a buffer.
But, if an explicit flush() is called, Tomcat has to start sending
data (usually using chunked encoding) and thus content length is not
known at the time when response headers are being sent.
What generates your response? A servlet, a filter, or a JSP?
Best regards,
Konstantin Kolinko
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RE: Adding Content-Length response header
Posted by Leo Donahue - RDSA IT <Le...@mail.maricopa.gov>.
>-----Original Message-----
>From: Christopher Schultz [mailto:chris@christopherschultz.net]
>Subject: Adding Content-Length response header
>
>-----BEGIN PGP SIGNED MESSAGE-----
>Hash: SHA256
>
>All,
>
>Here's the situation I have: I've got a response that I'm fairly sure fits into the
>response's buffer size, and I'd like to send a Content-Length header in that
>case. I could probably put a wrapper around the response's
>ServletOutputStream that counts bytes and then looks for "done" conditions
>(OutputStream.close, etc.), then adds a Content-Length header if the
>response hasn't yet been committed.
What about using a ByteArrayOutputStream?
It has a size method and you could use that in the response.setContentLength() and write out the ByteArrayOutputStream to your ServletOutputStream?
Maybe?
>
>Thanks,
>- -chris