[Web-SIG] When must applications call the WSGI start_response callable.

[Jim Fulton]

James Y Knight wrote:
> On Dec 15, 2005, at 3:01 PM, Jim Fulton wrote:
> 
>> Normally an application will call the start_response callable when the
>> application is called or when the result iterator is constructed, as
>> shown in the first 2 examples. An application, or more commonly, a
>> middleware component that provides it's own thread management might
>> delay starting the response.  A server should not begin iterating
>> over the result until the start_response callable has been called."
> 
> 
> But it's my understanding that this is valid:
> 
>     def test_calledStartResponseLate(self):
>         def application(environ, start_response):
>             start_response("200 OK", {})
>             yield "Foo"
> 
> start_response is called _inside_ the first iteration of the result.  So 
> the server has to iterate at least once, even if start_response  was not 
> called...
> 
> I was led to believe this was a valid thing to do from the following  
> wording:
> 
>> (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.)

Aargh, I didn't see that, despite looking for it.  I said I may have missed
it.

Hm.

Jim

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