* Cory Benfield wrote: > > On 20 Jan 2016, at 06:04, Graham Dumpleton <graham.dumple...@gmail.com> > > wrote: > > > > For response content, if a WSGI application currently doesn’t set a > > Content-Length on response, A HTTP/1.1 web server is at liberty to chunk > > the response. > > > > So I am not sure what is missing. > > My specific concern is the distinction between “at liberty to” and > “required to”. Certain behaviours that make sense with chunked transfer > encoding do not make sense without it: for example, streaming API endpoints > that return events as they arrive. Sending this kind of response with a > HTTP/1.0-style content-length absent response (framed by connection > termination) is utterly confusing, especially as some APIs consider the > chunk framing to be semantic.
Those APIs are just broken then. The HTTP RFCs state very clearly [1], that any hop may modify the transfer encoding. In other words: the transfer encoding is transparent to the representation layer. > This can and does bite people, because while all major production WSGI > servers use chunked transfer encoding in this situation, not all WSGI > implementations do: in fact, wsgiref does not. This means that if an > application has a production design requirement to use chunked transfer > encoding in its responses it cannot rely on the server actually providing > it. > > I see two solutions to this problem: we could mandate that HTTP/1.1 > responses that have no content length must be chunked, rather than falling > back to HTTP/1.0 style connection-termination-framed responses, or we could > have servers stuff something in the environ dictionary that can be checked > by applications. Or, I suppose, we can conclude that this problem is not > large enough, and that it’s “caveat developer”. WSGI is a gateway working with the representation layer. I think, it should not concern itself with underlying transport issues that much. Regarding chunked requests - in my own WSGI implementation I went the most pragmatic way and simply provided a CONTENT_LENGTH of -1 for unknown request sizes (it maps very well to file.read(size)). Something like this would be my suggestion for a future WSGI spec. Cheers, nd [1] https://tools.ietf.org/html/rfc7230#section-3.3.1 -- If God intended people to be naked, they would be born that way. -- Oscar Wilde _______________________________________________ Web-SIG mailing list Web-SIG@python.org Web SIG: http://www.python.org/sigs/web-sig Unsubscribe: https://mail.python.org/mailman/options/web-sig/archive%40mail-archive.com
