On Wed, Nov 27, 2013, at 19:20, exar...@twistedmatrix.com wrote:
...
> What about something like this instead?
>
> @implementer(IService)
> class Runner(object):
> ...
> @classmethod
> def loadFromWhatever(cls, name):
> return deferLater(reactor, Runner, name)
>
> def __init__(self, name):
> self.name = name
>
> def startService(self):
> self.running = True
> print 'realStartService', self.name, reactor.running
>
> def parent(service):
> application.setServiceParent(service)
A small detail: should this be service.setServiceParent(application)?
Peter.
> loading = Runner.initializeFromWhatever("foo")
> loading.addCallback(parent)
> loading.addCallback(lambda ignored:
> Runner.initializeFromWhatever("bar"))
> loading.addCallback(parent)
> loading.addErrback(stopTheReactorOrWhatever)
>
> The advantage I see of this approach is that a `Runner` never exists in
> the service hierarchy until it is fully initialized, started, and
> running.
>
> If a `Runner` is only partially ready and the process shuts down then
> its `stopService` method isn't called because it's not part of the
> service hierarchy.
>
> I could definitely imagine a library to help with this kind of thing.
> For example, perhaps you want the above encapsulated as:
>
> asynchronouslySetUpServices(application, [
> lambda: Runner.initializeFromWhatever("foo"),
> lambda: Runner.initialifrFromWhatever("bar")])
>
> And maybe then you want to add in some logic so that if the application
> gets shut down while some things are still being initialized then you
> cancel their Deferred. Then you have good cleanup support for the
> uninitialized case - without complicating `stopService` (the cleanup
> logic is isolated in the implementation of Deferred cancellation where
> it belongs - eg, with this `deferLater`-based asynchronousness it's
> alreay present since deferLater implements cancellation already).
>
> Jean-Paul
>
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