[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [libmicrohttpd] Big incoming requests
|
From: |
Christian Grothoff |
|
Subject: |
Re: [libmicrohttpd] Big incoming requests |
|
Date: |
Thu, 29 Oct 2015 19:35:40 +0100 |
|
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.7.0 |
Look at connection.c:1032, which is the only place where this error is
generated:
if (connection->read_buffer_offset ==
connection->read_buffer_size)
{
if ((MHD_YES != try_grow_read_buffer (connection)) &&
(0 != (connection->daemon->options &
(MHD_USE_SELECT_INTERNALLY |
MHD_USE_THREAD_PER_CONNECTION))))
{
/* failed to grow the read buffer, and the
client which is supposed to handle the
received data in a *blocking* fashion
(in this mode) did not handle the data as
it was supposed to!
=> we would either have to do busy-waiting
(on the client, which would likely fail),
or if we do nothing, we would just timeout
on the connection (if a timeout is even
set!).
Solution: we kill the connection with an error */
transmit_error_response (connection,
MHD_HTTP_INTERNAL_SERVER_ERROR,
INTERNAL_ERROR);
The situation: you are called to handle upload data, but did not
(effectively, your callback failed to update *upload_data_size when
called). Additionally, the IO buffer is full. So your application
doesn't handle the data that is in the buffer, and we can't read more to
give your app a bigger chunk. That's deadly, as MHD shouldn't then go
into busy waiting, hence the 500 internal error.
You could specify a larger memory limit, but the better solution is to
properly handle the 'upload_data' *incrementally*. The
MHD_PostProcessor logic is an example for how to do this.
Happy hacking!
Christian
On 10/29/2015 03:20 PM, Ken Zangelin wrote:
> On 29/10/15 14:13, Christian Grothoff wrote:
>> It limits the length of the URL and the headers, not the size of
>> uploaded POST data. -Christian
>>
>> On 10/29/2015 12:08 PM, Ken Zangelin wrote:
>>> Hi, I have a basic question regarding the
>>> MHD_OPTION_CONNECTION_MEMORY_LIMIT option to MHD_start_daemon.
>>>
>>> Will the size given to MHD_OPTION_CONNECTION_MEMORY_LIMIT limit the
>>> maximum permitted size of any request?
>>>
>>> Thank you,
>>>
>>> /KZ
>>>
>
> OK, in that case I have a follow-up question.
>
> We recently started to play with this connection memory limit option
> (MHD_OPTION_CONNECTION_MEMORY_LIMIT)
> and we have seen that requests with larged payload stops working for low
> memory limits.
>
> To give some detail, changing MHD_OPTION_CONNECTION_MEMORY_LIMIT to 64k,
> the max accepted size of payload seems to be 33509 bytes.
>
> If a bigger payload is sent, then MHD responds with the following message:
>
> HTTP/1.1 500 Internal Server Error
> Content-Length: 132
> Date: Thu, 29 Oct 2015 13:53:15 GMT
>
>
> <?xml version="1.0"?>
> <html>
> <head>
> <title>Internal server error</title>
> </head>
> <body>Some programmer needs to study the manual more
> carefully.</body>
> </html>
>
>
> Our MHD_AccessHandlerCallback function is called twice with payload
> (apart from the first call), and then
> the MHD_OPTION_NOTIFY_COMPLETED callback is called and MHD responds by
> itself.
>
> With a bigger value for MHD_OPTION_CONNECTION_MEMORY_LIMIT this did not
> happen.
>
> The version of the MHD we use:
> #define MHD_VERSION 0x00093300
>
>
>
> So, we might be doing something the wrong way.
> Please tell us what to do to be able to receive large payloads with a
> "small" MHD_OPTION_CONNECTION_MEMORY_LIMIT.
>
> Thank you again,
>
> /KZ
>
>
> ________________________________
>
> Este mensaje y sus adjuntos se dirigen exclusivamente a su destinatario,
> puede contener información privilegiada o confidencial y es para uso
> exclusivo de la persona o entidad de destino. Si no es usted. el
> destinatario indicado, queda notificado de que la lectura, utilización,
> divulgación y/o copia sin autorización puede estar prohibida en virtud
> de la legislación vigente. Si ha recibido este mensaje por error, le
> rogamos que nos lo comunique inmediatamente por esta misma vía y proceda
> a su destrucción.
>
> The information contained in this transmission is privileged and
> confidential information intended only for the use of the individual or
> entity named above. If the reader of this message is not the intended
> recipient, you are hereby notified that any dissemination, distribution
> or copying of this communication is strictly prohibited. If you have
> received this transmission in error, do not read it. Please immediately
> reply to the sender that you have received this communication in error
> and then delete it.
>
> Esta mensagem e seus anexos se dirigem exclusivamente ao seu
> destinatário, pode conter informação privilegiada ou confidencial e é
> para uso exclusivo da pessoa ou entidade de destino. Se não é vossa
> senhoria o destinatário indicado, fica notificado de que a leitura,
> utilização, divulgação e/ou cópia sem autorização pode estar proibida em
> virtude da legislação vigente. Se recebeu esta mensagem por erro,
> rogamos-lhe que nos o comunique imediatamente por esta mesma via e
> proceda a sua destruição
>