Using twisted words in a WSGI container

Question

I am running django on twisted in a wsgi container. Obviously I am avoiding all the async stuff with deferreds inside my django code because according to the documentation, twisted async abilities are not allowed inside WSGI apps.

However, I would like to use twisted.words inside my WSGI app to send requests to a jabber server. Does this count as async stuff or can I use it inside my app? What could happen if I sent twisted.words jabber requests to an xmpp server inside a WSGI anyway?

Moreover, I have a more general question. Is there any reason twisted's WSGI container is multithreaded (is it multithreaded?) since it is well known python's GIL only reduces the overall performance of a script with threads.

Thanks for any replies.

Answer 1

To call a function in the main event loop (I/O thread) in Twisted from another thread (non-I/O thread i.e., a WSGI application thread) you could use reactor.callFromThread(). If you'd like to wait for results then use threads.blockingCallFromThread(). Thus you could call functions that use twisted.words See Using Threads in Twisted.

To find out whether a wsgi container is multi-threaded inspect wsgi.multithread it should return true for twisted container.

WSGI containers are multi-threaded to support more than one request at a time (it is not strictly necessary but it makes life easier using existing software). Otherwise (if you don't use other means to solve it) your whole server blocks while your request handler waits for an answer from a database. Some people find it simpler to write request handlers less worrying about blocking other requests if there are not many concurrent requests.

Functions in Python that perform CPU-intensive jobs when performance matters can use libraries that release GIL during calculations or offload them to other processes. Network, disk I/O that are frequent in webapps are usually much slower than CPU.