[Twisted-Python] Timeout for Deferred objects
exarkun at divmod.com
Sat Dec 8 11:25:40 EST 2007
On Sat, 8 Dec 2007 11:52:00 +0200, Mustafa Sakalsiz <sakalsiz at gmail.com> wrote:
>I want set a timeout for Deferred objects. There is a method in
>Deferred class, setTimeout. It works well for me, but it gives a
>deprecation warning. If setTimeout is deprecated, what else I should
>use for timeouts.
It's deprecated because having a timeout for a Deferred doesn't make sense.
A Deferred is just a convenient API for associating a result with the code
which is interested in the result. It doesn't ever produce the result itself,
so it isn't the right object to give a timeout to.
Instead, the code which is responsible for calling back the Deferred is the
code which needs to be given a timeout. There's no general way to do this,
since the code for calling back Deferreds is different for each Deferred.
Some APIs support timeouts already - for example, reactor.resolve - but
not all of them do.
You can add a timeout to an API which doesn't support timeouts in one of
- Add it and implement whatever changes are necessary so that after the
timeout the underlying operation is cancelled. You may want to submit
- Wrap the original API with one which supports a timeout. This will
return a Deferred it creates and call it back when the underlying
Deferred is called back - unless the timeout has expired, then it will
just drop the result.
In either case, you'll probably use reactor.callLater to implement the
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