[Ironpython-users] requests hang on get or post http request

[Daniel Fernandez]

Hi Jeff,
Is this something we want to go forward with the change in the PythonBinaryReader:Read 
if(size == 0) {
   return string.Empty;
 }
Thanks.
Danny
From: fernandez_dan2 at hotmail.com
To: jdhardy at gmail.com
Date: Fri, 22 Aug 2014 06:45:23 -0600
CC: ironpython-users at python.org
Subject: Re: [Ironpython-users] requests hang on get or post http request




Hi Jeff,
I'm  working on .NET 4.0.30319.18444 (32-bit).  Yup I like the way you handle the scenario. I did the same thing I couldn't tell from the docs if NetworkStream with size == 0 if it should block or not. 
Danny
> Date: Fri, 22 Aug 2014 10:44:27 +0100
> Subject: Re: [Ironpython-users] requests hang on get or post http request
> From: jdhardy at gmail.com
> To: fernandez_dan2 at hotmail.com
> CC: ironpython-users at python.org
> 
> On Thu, Aug 21, 2014 at 5:37 PM, Daniel Fernandez
> <fernandez_dan2 at hotmail.com> wrote:
> > Hi All,
> >
> > I'm using the latest 2.7.5 b3 code and I wanted to see if requests works. I
> > pulled the latest from github. It would hang on simple requests.get or
> > requests.post. It would hang on the reading the http response.  I attached
> > the debugger and traced it to PythonBinaryReader:Read method. in the
> > PythonFile.cs  It hangs when size = 0. It hangs specifically in this loop
> >
> > int leftCount = size;
> >  while (true) {
> >                 int count = _stream.Read(data, offset, leftCount);
> >                 if (count <= 0) break;
> >                 leftCount -= count;
> >                 if (leftCount <= 0) break;
> >                 offset += count;
> >             }
> >
> > It hangs on the _stream.read where offset is  0 and leftCount is zero and
> > the stream is a NetworkStream.
> 
> That's very odd. What's the result of _stream.Read in this case (i.e.
> what is count set to)? The docs for NetworkStream.Read[1] don't really
> specify what should happen if size (leftCount in the code above) is 0.
> If just says that it returns the number of bytes read, or 0 if there
> is nothing left to read ... but what if we only ask for 0 bytes, and
> there's still data left to read?
> 
> My instinct would be that it should return 0 and then break on the
> next line, but that's clearly not happening. Also, why does it not
> break on the `if (leftCount <= 0) break;` line?
> 
> Unless a size of 0 means for NetworkStream.Read to block and read
> everything until the stream closes. But the NetworkStream docs don't
> say that. They don't specify at all what happens when size is 0. And
> the comments for PythonBinaryReader.Read don't say what should happen
> when size = 0 either.
> 
> Playing with the CPython interpreter, though, calling f.read(0) always
> returns an empty string (f.read(-1) is read-to-end), so that seems
> like the behaviour. I don't know what's going on with
> NetworkStream.Read (maybe a bug?) but IP should work around it.
> 
> [1] http://msdn.microsoft.com/en-us/library/system.net.sockets.networkstream.read(v=vs.110).aspx
> 
> > I ran a quick experiment and just added one line, didn't want to change too
> > much. I changed.
> > int leftCount = size;
> > while (true) {
> >                 if (leftCount <= 0) break;
> >                 int count = _stream.Read(data, offset, leftCount);
> >                 if (count <= 0) break;
> >                 leftCount -= count;
> >                 if (leftCount <= 0) break;
> >                 offset += count;
> >             }
> >
> >
> 
> It would be better to move the check out of the loop and check
> if(size==0) instead. That makes it clearer what case is being handled.
> You could skip the whole thing and just do
> 
>   if(size == 0) {
>     return string.Empty;
>   }
> 
> at the start of the function.
> 
> > After this I was able to get all HTTP GETs and POSTs working. I did this
> > with rest type calls and normal web transactions.
> >
> > I was just wanted to check if any ran into this issue before? I'm not sure
> > if this was just a me thing.
> 
> I'd be curious to know which version of the .NET framework you're running on.
> 
> - Jeff
 		 	   		  

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