[Twisted-Python] Service dependencies

Moof moof at metamoof.net
Thu Jan 19 18:16:19 EST 2006

On 1/19/06, Matt Goodall <matt at pollenation.net> wrote:
> Hi,
> I have a couple of services. The second is dependent on the first being
> fully initialised before the second gets set up.


In other words, what is the recommended way of starting services in the
> correct order, including waiting for them to get initialised fully,
> these days?

I actually wrote something like this today, a subclass of MultiService,
because my main service was dependant on there being no other services
running on the same machine, and I had to implement a PB client/server to
ask the other instance to shut down. This is mostly because Windows sucks,
and doesn't allow me to just do a "kill <pid>" on the old one, but gave me
an excuse to start the PB integration of my app. I just subclassed
MultiService and reimplemented startService and stopService appropriately,
not chaining my sub-service starts until I was certain I had managed to
start my own service, and not stopping my service until my sub-services had

It's a fairly simple idiom, so it's probably pretty easy to implement
yourself, but I'm surprised a generic one hasn't been written yet. Similarly
I've had to write a new LoopingService that runs a "setup" callable before
looping the main service, and also has a "minimum wait between calls" timer
going on it. None of these have been particulalrly difficult.
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