[Python-Dev] Twisted Isn't Specific (was Re: Trial balloon: microthreads library in stdlib) (original) (raw)

Larry Hastings larry at hastings.org
Thu Feb 15 17:02:54 CET 2007

Bob Ippolito wrote:

There is no single PerfectReactor. There are several use cases where you need to wait on >1 different event systems, which guarantees at least two OS threads (and two event loops). In general it's nice to have a single Python event loop ("the reactor") to act on said threads (e.g. something just sitting on a mutex waiting for messages) but waiting for IO to occur should probably happen on one or more ancillary threads -- one per event system (e.g. select, GTK, WaitForMultipleEvents, etc.) Why couldn't PerfectReactor be a reactor for other reactors? A sort of concentrator for these multiple event systems and multiple threads.

You ask to listen to sockets, so it instantiates a singleton PerfectReactor which instantiates a select() reactor and listens to it directly in a single-threaded manner. If you then ask to listen to Win32 messages, the PerfectReactor instantiates a GetMessage() reactor.
Then, realizing it has two "event systems", it spawns a thread for each child reactor with a listener that serializes the incoming events into the PerfectReactor's queue. Bingo, your application doesn't need to be written thread-safe, PerfectReactor is platform-agnostic, and you don't have to know in advance all the event types you might ever listen to.

Sorry if this is a dumb question (or if I'm mangling the terminology),

/larry/

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