Gustavo Narea ha scritto: > Hello, > > Maybe I'm missing something obvious, but if the gateway doesn't support > applications that return write() callables, then it's not WSGI. > > A callable that raises an exception does not even count. It's obvious > that they must not raise exceptions -- Then what's the point of > providing the callable? >
Nothing is obvious in an official specification ;-). The reason I choose to not completely remove the write callable is because it will raise a nice error message if someone even try to use my implementation to execute a WSGI application that requires the write callable. Moreover some middlewares or applications may assume the write callable exists and the value returned by start_response is not None, even if it is never used. > That said, I *think* it might be OK to disable support for the write() > callable *optionally* on a per application basis. For example, the > gateway could look at the "requires_write" attribute of the application > callable, if any: > """ > def wsgi_app(environ, start_response): > # ... process the request and return a response.... > > wsgi_app.requires_write = False > """ > > That way, applications which don't use the write() callable can let your > gateway know and thus it won't pass one on. > The problem is that applications that requires the write callable, are not aware of this extension. This is really a no problem, IMHO. If you try to execute an application, and you get a NotImplementedError extension, then you *know* that write callable is required. Then, you just configure the WSGI gateway to use the required adapter. See http://bitbucket.org/mperillo/txwsgi/src/tip/doc/examples/demo_write.py for a pratical example using txwsgi. With ngx_http_wsgi_module, you just have to add a wsgi_middleware txwsgi.greenlet write_adapter; directive in Nginx configuration file. > We could even standardize this (at wsgi.org) so that any WSGI middleware > which wraps an application can expose the "requires_write" attribute of > the wrapped application... As long as such a middleware doesn't use > write() either. > > On the other hand, I would avoid using "middleware" in this context for > something specific to your implementation as people will believe it's a > proper WSGI middleware. Yes. I now use the term "adapter". Regards Manlio _______________________________________________ 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
