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.