[akka-user] streams: why pulls the concat combinator both sides eagerly and the merge combinator not

[EXTERNAL Wachter Stefan (Keybird IT Consulting und Vetriebs GmbH, INST-ICM/BSV-BS)]

Hi,

I stumbled accross the surprising behaviour that the concat combinator uses so 
called "detached" inputs that pull eagerly (without signalled demand; 
effectively being a buffer of size 1). The comment indicates that this is a 
means to avoid deadlocks in graphs with cycles. Yet, when implementing graphs 
with cycles I usually use the merge combinator that does not exhibit that 
behaviour.

Additional proposal: Maybe the "eager pulling" behaviour should be documented 
in the API because it may be a surprising behaviour. (E.g. expensive operations 
might happend without need)

Mit freundlichen Grüßen / Best regards

Dr. Stefan Wachter

Bosch Software Innovations GmbH
Communications (INST-ICM/BSV-BS)
Stuttgarterstr. 130
71332 Waiblingen
GERMANY
www.bosch-si.de
www.blog.bosch-si.com

Tel. +49 711 811 58 477
Fax +49 711 811 58 100
external.stefan.wach...@bosch-si.com

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[akka-user] invalid materialized value

[EXTERNAL Wachter Stefan (Keybird IT Consulting und Vetriebs GmbH, INST-ICM/BSV-BS)]

Hi all,

the following line of code


val ((pub, mat), sub) = 
TestSource.probe[Int].viaMat(Flow[Int])(Keep.both).toMat(TestSink.probe)(Keep.both).run()

throws a ClassCastException:


java.lang.ClassCastException: akka.stream.testkit.TestPublisher$Probe cannot be 
cast to scala.Tuple2

it seems that the viaMat(...)(Keep.both) does not what it promises.

Mit freundlichen Grüßen / Best regards

Dr. Stefan Wachter

Bosch Software Innovations GmbH
Communications (INST-ICM/BSV-BS)
Stuttgarterstr. 130
71332 Waiblingen
GERMANY
www.bosch-si.de
www.blog.bosch-si.com

Tel. +49 711 811 58 477
Fax +49 711 811 58 100
external.stefan.wach...@bosch-si.com

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[akka-user] Akka Http ResponseTimeout

[EXTERNAL Wachter Stefan (Keybird IT Consulting und Vetriebs GmbH, INST-ICM/BSV-BS)]

Hi all,

what is the recommended (correct?) way to ensure a certain response timeout 
when using superPool flow? I think flow.completionTimeout (and friends) are not 
apropriate because they affect the whole flow of requests to responses whereas 
only a single request-response pair might have been affected by the timeout.

Studying the configuration options there seem to be only two settings that 
might be useful: connecting-timeout and idle-timeout. The first setting however 
does not track responses and the second setting is only indirectly linked with 
the original problem of having timeouts for responses.

Can anyone advice?

(PS: One could use nested flows of single requests to single responses and 
flatten / recover them or use the "Future-Based" variant of the API instead. 
Yet, I wonder if there is an easier solution.)


Mit freundlichen Grüßen / Best regards

Dr. Stefan Wachter

Bosch Software Innovations GmbH
Communications (INST-ICM/BSV-BS)
Stuttgarterstr. 130
71332 Waiblingen
GERMANY
www.bosch-si.de
www.blog.bosch-si.com

Tel. +49 711 811 58 477
Fax +49 711 811 58 100
external.stefan.wach...@bosch-si.com

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[akka-user] Completion of a Graph with a Cycle

[EXTERNAL Wachter Stefan (Keybird IT Consulting und Vetriebs GmbH, INST-ICM/BSV-BS)]

Hi all,

is there a principled way to complete a graph that contains a cycle? The basic 
problem is that the initial Merge component can either complete eagerly or not. 
Both settings are suboptimal (if it completes not eager it will complete never, 
if it completes eager elements in the feedback cycle get lost).

I think that using some kind of poison pill could be used. However, is there 
some principled mechanism that might be used?

Mit freundlichen Grüßen / Best regards

Dr. Stefan Wachter

Bosch Software Innovations GmbH
Communications (INST-ICM/BSV-BS)
Stuttgarterstr. 130
71332 Waiblingen
GERMANY
www.bosch-si.de
www.blog.bosch-si.com

Tel. +49 711 811 58 477
Fax +49 711 811 58 100
external.stefan.wach...@bosch-si.com

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