Sorry - hit send too soon.
foo.recover {
case (NonFatal(e), failedValue) =>
log.error(e, "Problem processing stream value of {}", failedValue)
"UNKNOWN VALUE"
}
On Wednesday, May 20, 2015 at 11:23:02 AM UTC-5, dpratt wrote:
>
> What if I have an existing stage/Flow that I do not have control over, or
> where it would not make sense to conflate the flow logic with the exception
> handling?
>
> For example
>
> val foo: Flow[String, String, Unit] =
> SomeLibrary.somethingThatGeneratesAFlow()
>
> how would I wrap foo with error handling? I can't use map or mapAsync,
> since those are compositional - namely, the value to map has already been
> calculated. What I really want is a recover block on the flow itself -
> something like
>
> foo.recover {
>
> }
>
>
>
>
> On Wednesday, May 20, 2015 at 4:37:37 AM UTC-5, Patrik Nordwall wrote:
>>
>> I think we considered adding this to the stream supervision mechanism,
>> but since it is not possible to express the types of the elements there in
>> any sane way we decided to not do it. Instead we said that this specific
>> recover scenario should be handled with try-catch within the function/stage
>> of yours. For mapAsync you can use recover on the Future.
>>
>> By the way, you can define the supervision for individual stages by using
>> the withAttributes.
>>
>> Regards,
>> Patrik
>>
>> On Fri, May 15, 2015 at 7:50 PM, dpratt <[email protected]> wrote:
>>
>>> I've been using the Streams API to build a few things for the past
>>> couple months, and I have a humble suggestion for an API enhancement. I'm
>>> not sure if this is even possible to do given the contract of how a Flow
>>> operates, adding a method to FlowOps with the following signature would be
>>> quite useful -
>>>
>>> def recover(f: PartialFunction[(In, Throwable), Out]): Repr[Out, Mat]
>>>
>>> It's likely due to the fact that I have yet to fully internalize the
>>> Flow API, but I've found that the supervision functionality isn't exactly
>>> what I need. On the top-level, it makes complete sense, but there is no way
>>> to deal with an error in a stream and not have at least one message
>>> silently dropped. It would be nice to be able to set up more fine-grained
>>> error handling.
>>>
>>> As an example, imagine a stream that was processing incoming deltas to a
>>> set of records held either in memory or some persistent data store. A
>>> failure of a given delta should not necessarily shut down the whole
>>> pipeline, but the associated record should be marked as inconsistent and
>>> dealt with appropriately. Using the current supervision API, there's no way
>>> to determine the actual element that caused the failure, and thus there's
>>> no real way to handle it or signal an external system with the details of
>>> the error.
>>>
>>> Of course, you can work around this by making the stream operate on a
>>> Try[T] instead of T, but that just seems unwieldy.
>>>
>>> Am I looking at this the wrong way?
>>>
>>> --
>>> >>>>>>>>>> Read the docs: http://akka.io/docs/
>>> >>>>>>>>>> Check the FAQ:
>>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>> >>>>>>>>>> Search the archives:
>>> https://groups.google.com/group/akka-user
>>> ---
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>>>
>>
>>
>>
>> --
>>
>> Patrik Nordwall
>> Typesafe <http://typesafe.com/> - Reactive apps on the JVM
>> Twitter: @patriknw
>>
>>
--
>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>> Check the FAQ:
>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user
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