nadavwr / kamon-futures

Futures Instrumentation

Getting Started

The Futures instrumentation is currently available for Scala 2.10, 2.11 and 2.12.

Supported releases and dependencies are shown below.

kamon-futures	status	jdk	scala
1.0.0	stable	1.7+, 1.8+	2.10, 2.11, 2.12

To get started with SBT, simply add the following to your build.sbt file:

resolvers += Resolver.bintrayRepo("kamon-io", "snapshots")

libraryDependencies += "io.kamon" %% "kamon-scala-future" % "1.0.0"
libraryDependencies += "io.kamon" %% "kamon-scalaz-future" % "1.0.0"
libraryDependencies += "io.kamon" %% "kamon-twitter-future" % "1.0.0"

Automatic TraceContext Propagation with Futures

The kamon-futures module provides bytecode instrumentation for Scala, Scalaz and Twitter Futures that automatically propagates the Context across the asynchronous operations that might be scheduled for a given Future.

All modules in the kamon-futures project module require you to start your application using the AspectJ Weaver Agent.

Instrumenting Future's Body and Callbacks

In the following piece of code, the body of the future will be executed asynchronously on some other thread provided by the ExecutionContext available in implicit scope, but Kamon will capture the TraceContext available when the future was created and make it available while executing the future's body.

  val context = contextWithLocal("in-future-transformations")
        val baggageAfterTransformations = Kamon.withContext(context) {
            Future("Hello Kamon!")
              // The active span is expected to be available during all intermediate processing.
              .map(_.length)
              .flatMap(len => Future(len.toString))
              .map(_ => Kamon.currentContext().get(StringKey))
          }

Also, when you transform a future by using map/flatMap/filter and friends or you directly register a onComplete/onSuccess/onFailure callback on a future, Kamon will capture the Context available when transforming the future and make it available when executing the given callback. The code snippet above would print the same Context that was available when creating the future, during it's body execution and during the execution of all the asynchronous operations scheduled on it.