Support for Future?

[marylin13]

Does this project have any plan to support trace for Future? Or is it a good idea to extend it to support Future?
I believe for projects that use akka ecosystem is really useful.

Thanks

[rossabaker]

Short answer

No.

Pedantic answer

The interfaces are in a "tagless final" style, and can work with anything of kind F[_], that is, any type that takes one parameter. Like Future!

The existing implementations use type class constraints. One, Tracer.noop[F], requires an instance of cats.Applicative[F]. That exists for Future, so you can do Tracer.noop[Future] and get a tracer that returns Futures. The problem is, as the name implies, noop doesn't do anything.

Another implementation comes via OtelJava.local[F], which requires an Async[F]. In Cats Effect, we take our side effects -- like recording traces -- and suspend them by wrapping them up. There is no Async[Future], because Future runs eagerly and can't suspend side effects. The forthcoming all-Scala implementation will have the same problem with Future.

So, it's already supported ... as long as you don't actually want the traces.

Side effects, schmide effects. I just want to trace my Akka!

You could implement the Otel4s interface for Future. And you could reuse every piece of Otel4s that uses nothing stronger than MonadError[F, Throwable] to build it. But Otel4s uses Cats Effect and provides implementations such that are "referentially transparent", or more easily composable, refactorable, reasonable, and optimizable. An Tracer[Future] would be the same shape as other Tracer[F], but with a mostly different implementation and substantially different axioms. It would work fine within those axioms, but it wouldn't really be Otel4s.

Bummer. Is there anything else I can do?

If you have IO on the outside and can treat Akka as a single span, you can call IO.fromFuture`.

Alternatively, you can use the Java SDK. There is some instrumentation for akka-http already. And there is an ongoing discussion to improve Java SDK interop in Otel4s. This is probably your best bet, but I can't speak to the depth of the existing Akka instruementation.

[IvannKurchenko]

@mary-element I assume what you are looking for is Kamon or Akka OTEL instrumentation.

[marylin13]

@IvannKurchenko not really.
We choose to not use Kamon for some reason.
Do mean the Otel java auto instrument for "Akka OTEL instrumentation"? I actually also need to do manual instrument for both methods return Future and IO.

[iRevive]

Do mean the Otel java auto instrument for "Akka OTEL instrumentation"? I actually also need to do manual instrument for both methods return Future and IO.

There is a way to enable Akka instrumentation, but you need to use the agent:
https://opentelemetry.io/docs/languages/java/automatic/agent-config/

As mentioned above, we don't have plans to support Future.