Maximum size of POST data

Dave Cragg dcragg at lacscentre.co.uk
Tue Apr 20 12:41:43 EDT 2004


At 10:02 am -0500 20/4/04, Ken Ray wrote:
>Really? My understanding is that it has a limit of 24K, and that GET has a
>limit of 4K...

Was I too hasty?

There is no limit for POST from the Rev end. As 
far as I know, the http spec imposes no limits. 
But what limits are imposed on specific servers 
may vary.  I hear PHP has a 2MB default limit, 
but that it can be altered. I think Perl has a 
default limit of 32MB, but again it may be 
possible to change this. Also, I think it's 
possible to set a limit for Apache in the 
configuration file (LimitRequestBody) but this 
isn't set on my machine.

I guess the only way is to test with a specific server/cgi/script combination.

I don't know for sure about GET. The http spec 
(rfc 2616) doesn't specify a limit on URL length. 
But I read that Internet Explorer has a 2048 char 
limit. libUrl imposes no limit.

At 12:09 pm -0300 20/4/04, Andre Garzia wrote:
>Theres a way to transfer huge data using chunked data transfer from
>HTTP 1.1 spec. Best way to look for info is online doc "HTTP Made
>Easy" at http://www.jmarshall.com/easy/http/
>there you see that you can use this to transfer huge data.

I'm not sure that chunked encoding will allow 
posting larger quantities of data. It's main use 
is for http servers that send data when the total 
data size isn't known in advance and so a 
Content-Length header can't be set. For example, 
Apache uses this by default if you have a Rev cgi 
script that writes data without setting a 
Content-Length header. If you dig into the libUrl 
code you can see how it handles chunked encoding 
from the client side.

By the way, if you're posting files or other data 
to scripts that expect the data to be in 
"multipart/formdata" format, the latest beta 
version of libUrl has a  libUrlMultipartFormData 
funcion that lets you build suitably structured 
data.
<http://www.runrev.com/resources/liburl/releases.shtml>

However, this still loads the file into RAM before posting.

But as someone pointed out, if you're scripting 
your own CGIs in Rev, you can format the data 
anyway you like.

Cheers
Dave


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