[Twisted-Python] HTTP PUT a GET's streaming response with treq

[Phil Mayers]

On 05/05/17 12:10, Cory Benfield wrote:

> As a second note, you may lock yourself out of HTTP/2. HTTP/2 is not
> guaranteed to give you access to a raw transport object (though it

FWIW this kind of thing was, more or less, what I was thinking. It seems 
unlikely that stealing the TCP connection from Response for a few bytes 
was wise...

> As a third note, your code does not handle the possibility that
> original._transport may not implement IPushProducer. While *in

IIUC IResponse.deliverBody *does* guarantee (currently) to provide a 
transport implementing IPushProducer to the supplied IProtocol, at least 
as far as the docstring says?

Obviously that doesn't make accessing the private _transport safe - an 
implementation could wrap the transport to implement the IPushProducer 
semantics.

> practice* it tends to, it needn’t. On top of that, it is not
> forbidden for an IPushProducer implementation to call write() even
> when paused, and code that wants to be correct in the face of all
> situations will need to be able to buffer anyway.

Thanks for confirming this. I suspected as much, but was not certain (I 
make relatively little use of producer/consumer APIs in my own code).

> use case. Right now it’s a bit of an annoyance that t.w._newclient
> doesn’t allow the body receiving protocol to exert backpressure on
> the data.

How does that square with deliverBody providing an IPushProducer? Is it 
the case that the transport may just disobey the pauseProducing requests 
as you've noted above?