At 01:27 PM 12/20/2007 +0100, Manlio Perillo wrote: >Hi. > >It seems that there is a little error in the WSGI spec. > >In the "Specification Details" chapter there is this note: > >"""(Note: the application must invoke the start_response() callable >before the iterable yields its first body string, so that the server can >send the headers before any body content. However, this invocation may >be performed by the iterable's first iteration, so servers must not >assume that start_response() has been called before they begin iterating >over the iterable.)""" > > >What's wrong is that the invocation of start_response may be performed >at any iteration of the iterable, as long as the application yields >empty strings.
You're right - the intent here was before the iterable yields its first non-empty body string. >There is also a little problem in the "The start_response() Callable" >chapter, in this phrase: > >"""The start_response callable must not actually transmit the response >headers. Instead, it must store them for the server or gateway to >transmit only after the first iteration of the application return value >that yields a non-empty string, or upon the application's first >invocation of the write() callable""" > > > From this it seems that the response headers should be transmitted >after the first invocation of the write() callable, even if it returns >an empty string, but this is in contradiction with the following phrase: > >"""In other words, response headers must not be sent until there is >actual body data available, or until the application's returned iterable >is exhausted""" There is no sane reason to call write() with an empty string, so I don't really see a conflict here. Please note that both write() and iteration in the normal case should be sending the entire response body in a single call or yield. Multiple yields or write() calls should ONLY be used when streaming output is *required*: i.e. server push or sending large files. (In addition, write() is intended strictly for legacy apps and frameworks only; new code should use iteration only, especially as WSGI 2 will drop the start_response() and write() functions altogether.) _______________________________________________ Web-SIG mailing list Web-SIG@python.org Web SIG: http://www.python.org/sigs/web-sig Unsubscribe: http://mail.python.org/mailman/options/web-sig/archive%40mail-archive.com
