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

[Jim Fulton]

Ian Bicking wrote:
> Jim Fulton wrote:
...
>> Why do I want this?  It appears that this would be needed to enable
>> middleware components that manage application threads.  I can imagine
>> though that there aren't any existing servers that handle what I've
>> suggested correctly.
>>
>> I do think it would be straightforward for servers to handle this
>> correctly, especially for asynchronous servers like Twisted
>> and ayncore-based servers.  Perhaps this could be an optional feature
>> of the servers.  Servers supporting this feature would be prepared to
>> delay response output until start_response is called.  Servers unable
>> to do this would generate errors if start_response hasn't been called
>> by the time the result iterator has been constructed.
> 
> 
> I suppose this wouldn't be particularly bad for threaded or multiprocess 
> servers either -- they use a thread/process until the request is 
> completed regardless of what happens. 

Exacept that it makes the implementation a bit more complex.

 > I can see how it could be used to
> greater effect in an asynchronous server.  However, I'd rather it not be 
> optional, as most WSGI apps won't do this, and so servers won't get good 
> testing on this or may just not implement it, and then some apps and 
> some servers won't be compatible.

I mostly agree, except that I think this feature may only be useful for
asynchronous servers.

Jim

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