[PEAK] Events Question: How bad of an idea is this?

Chad Rosenberg chad at idrankwhat.net
Wed Nov 10 19:24:09 EST 2004

The code I have been working on uses quite a bit of generators wrapped by
taskFactory and I am finding it increasing necessary to be able to call a
variety of other nested methods from those generators that make calls
involving Twisted Deferreds and EventLoop.runUntil in twisted_support.py.

Take, for instance, this sample code:

from peak.api import binding, commands, events

class Test(commands.EventDriven):
    eventLoop = binding.Obtain(events.IEventLoop)
    reactor   = binding.Obtain(commands.ITwistedReactor,

    def daemon(self):
        while True:
            yield self.eventLoop.sleep(4); events.resume()
            print 'daemon'

            print self.something

    daemon = binding.Make(events.taskFactory(daemon))

    def something(self):
        self.eventLoop.runUntil(self.eventLoop.sleep(3), True)
        return 'something'
    something = binding.Make(something)

    def _run(self):
        self.eventLoop.runUntil(self.eventLoop.sleep(3), True)
        print 'boo'
        self.eventLoop.runUntil(self.eventLoop.sleep(30), True)
        return 0

When I run the above example with Peak 0.5a3 under Gentoo Linux and
Python 2.3.3 I get a "StopIteration:  Unexpected reactor exit" in
"peak/events/twisted_support.py", line 191, in runUntil.

Trying to get it to work, I made the following change to
EventLoop.runUntil in twisted_support.py:

        if not exit:

  -- to --

        while not exit:

With this change the above sample code runs to completion without any
errors, as does the code I am working with.  I'm not sure of what, if any,
long term repercussion this may produce (stack overflows, infinite loops,
etc).  Hence my question, how bad of an idea is this?


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