I'm not sure about adding a TemporaryTaskFailure
(TransientTaskFailure?) exception, but regardless of whether we do or
not, it seems that the Deferrable.doTask method should be declared to
throw Exception. Otherwise, implementations will be restricted to
throwing only RuntimeException (or subclasses thereof). Think of cases
where you're using third-party libraries and you simply want
exceptions to propagate up.
My current implementation is based on the Python implementation, which
says this about task failures:
"'Failure' in the case of a deferred task is defined as your task
throwing any uncaught exception. Normally, automatic retries are what
you want - for example, if the task does datastore operations, and the
datastore threw a Timeout exception. If you want to deliberately cause
your task to fail so it will be retried, you can simply throw an
exception."
That seems reasonable: any uncaught exception causes a task retry;
normal termination or PermanentTaskFailure exception do not retry.
Vince
On Tue, Nov 10, 2009 at 1:35 AM, Roy <roy.smith....@googlemail.com> wrote:
>
> I've started looking at using Vince's Defer helper class.
>
> As a suggestion, could we add a TemporaryTaskFailure exception so it
> is explicit what behaviour is expected. I realise that a task retry is
> the default behaviour by propagating an exception, I just think it's
> better documentation if it's explicit.
>
>
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