Hystrix with Scala

[Markus Lachinger]

Is anyone using Hystrix with Scala. If so, how?

I am thinking of creating something similar to hystrix-clj. What would the best approach to this be?

What features should the scala version have?

The main feature I am thinking of would be to use Scala Futures instead of Observables and Java Futures.

Then, what makes more sense: Wrapper vs. overloading/rewriting the current HystrixCommand class with Scala specific methods?

Thanks,

Markus

[Ben Christensen]

Sounds great Markus, two suggestions as you go down this path.

1) The observe() method can still be consumed as Observable from Scala with the RxJava-Scala project: https://github.com/Netflix/RxJava/tree/master/language-adaptors/rxjava-scala

2) The queue() method returning Future should be completely replaced by a Scala Future equivalent than uses observe() under the covers to get a callback to the Scala Future since Scala Futures support composition and callbacks. The Observable -> Scala Future bridge would retain the non-blocking behavior.

3) You may want to consider the RxJava-Scala approach of wrapping with a value class: https://github.com/Netflix/RxJava/blob/master/language-adaptors/rxjava-scala/src/main/scala/rx/lang/scala/Observable.scala#L73

Good luck!

-- 
Ben Christensen
+1.310.782.5511 @benjchristensen

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[Ben Christensen]

So it ended up being three :-)

... two suggestions as you go down this path ...

[Pablo Fernandez]

Just heard about hystrix on this year's AWS re:Invent. My question is: Isn't the Futures + Promises on scala.concurrent.* powerful enough? Why add a framework on top of that?

[Ben Christensen]

Hystrix is not about Futures and Promises, it is about bulk-heading and isolating dependencies by limiting concurrent execution, circuit breakers, real time monitoring and metrics. Futures are just a mechanism by which async execution is exposed. Futures by themselves do not provide the same degree of fault-tolerance functionality (though parts of it can be achieved with careful use of timeouts and thread-pool sizing). You could think of Hystrix as a hardened extension of a Future.

You can read more at https://github.com/Netflix/Hystrix/wiki or view a presentation at https://speakerdeck.com/benjchristensen/application-resilience-engineering-and-operations-at-netflix-with-hystrix-javaone-2013.

-- 
Ben Christensen
+1.310.782.5511  @benjchristensen

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