NullPointerException when running with recordMetrics

[gunjdesai]

I am trying to use the akka-http-metrics-prometheus registry

Scala Version: 2.12.11
Akka Http Version: 10.1.12
Akka Http Metrics Prometheus Version: 1.1.0

My Code looks like this

object Registry {

  def apply() = {

    val settings = PrometheusSettings
      .default
      .withDurationConfig(Buckets(1, 2, 3, 5, 8, 13, 21, 34))
      .withReceivedBytesConfig(Quantiles(0.5, 0.75, 0.9, 0.95, 0.99))
      .withSentBytesConfig(PrometheusSettings.DefaultQuantiles)

    val prometheus = new CollectorRegistry()

    PrometheusRegistry(settings = settings)

  }

}

Http().bindAndHandle(routes.recordMetrics(Registry()), appConfig.server.interface,  appConfig.server.port)

When i try to run any route, I am facing a NullPointerException.

Could not materialize handling flow for IncomingConnection(/127.0.0.1:8080,/127.0.0.1:64662,Flow(FlowShape(IncomingTCP.in(1710177258),GraphStages$Detacher.out(817845304))))
java.lang.NullPointerException
	at scala.concurrent.impl.Promise$DefaultPromise.onComplete(Promise.scala:307)
	at fr.davit.akka.http.metrics.core.HttpMetricsRegistry.onConnection(HttpMetricsRegistry.scala:126)
	at fr.davit.akka.http.metrics.core.scaladsl.server.HttpMetricsRoute.$anonfun$recordMetrics$1(HttpMetricsRoute.scala:65)
	at akka.stream.impl.Compose.apply(TraversalBuilder.scala:169)
	at akka.stream.impl.PhasedFusingActorMaterializer.materialize(PhasedFusingActorMaterializer.scala:529)
	at akka.stream.impl.PhasedFusingActorMaterializer.materialize(PhasedFusingActorMaterializer.scala:449)
	at akka.stream.impl.PhasedFusingActorMaterializer.materialize(PhasedFusingActorMaterializer.scala:441)
	at akka.stream.scaladsl.RunnableGraph.run(Flow.scala:703)
	at akka.http.scaladsl.HttpExt.$anonfun$bindAndHandle$1(Http.scala:252)
	at akka.stream.impl.fusing.MapAsyncUnordered$$anon$31.onPush(Ops.scala:1401)
	at akka.stream.impl.fusing.GraphInterpreter.processPush(GraphInterpreter.scala:541)
	at akka.stream.impl.fusing.GraphInterpreter.processEvent(GraphInterpreter.scala:495)
	at akka.stream.impl.fusing.GraphInterpreter.execute(GraphInterpreter.scala:390)
	at akka.stream.impl.fusing.GraphInterpreterShell.runBatch(ActorGraphInterpreter.scala:624)
	at akka.stream.impl.fusing.GraphInterpreterShell$AsyncInput.execute(ActorGraphInterpreter.scala:501)
	at akka.stream.impl.fusing.GraphInterpreterShell.processEvent(ActorGraphInterpreter.scala:599)
	at akka.stream.impl.fusing.ActorGraphInterpreter.akka$stream$impl$fusing$ActorGraphInterpreter$$processEvent(ActorGraphInterpreter.scala:768)
	at akka.stream.impl.fusing.ActorGraphInterpreter$$anonfun$receive$1.applyOrElse(ActorGraphInterpreter.scala:783)
	at akka.actor.Actor.aroundReceive(Actor.scala:534)
	at akka.actor.Actor.aroundReceive$(Actor.scala:532)
	at akka.stream.impl.fusing.ActorGraphInterpreter.aroundReceive(ActorGraphInterpreter.scala:690)
	at akka.actor.ActorCell.receiveMessage(ActorCell.scala:573)
	at akka.actor.ActorCell.invoke(ActorCell.scala:543)
	at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:269)
	at akka.dispatch.Mailbox.run(Mailbox.scala:230)
	at akka.dispatch.Mailbox.exec(Mailbox.scala:242)
	at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
	at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
	at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)

I am pretty sure that i have made some sort of mistake during initialisation and hence the issue.
Would really appreciate if you can point me in the right direction.

Thanks

[RustedBones]

Hi @gunjdesai

Thanks a lot for the detailed report. It's actually not your fault but mine.
I've actually introduced a regression in the the 1.1.0 release in recordMetrics:

recordMetrics has a default value for the implicit ExecutionContextExecutor set to null (as akka-http does on the route conversion). I forgot to override the null with a default value for the connection metrics. I Will create a bugfix release.

For now you can add this to your code:

  implicit val system: ActorSystem = ActorSystem()
  implicit val ec: ExecutionContextExecutor =  implicitly[Materializer].executionContext

This import the default materializer explicitly and should make your project run.

Sorry for the inconvenience.

[gunjdesai]

Thanks @RustedBones for looking into this so fast, adding the execution context executor does work for other routes, but still facing an issue while trying /metrics route.

Error during processing of request: 'java.lang.NullPointerException (No error message supplied)'. Completing with 500 Internal Server Error response. To change default exception handling behavior, provide a custom ExceptionHandler.
java.lang.NullPointerException
	at fr.davit.akka.http.metrics.prometheus.marshalling.PrometheusMarshallers.$anonfun$marshaller$1(PrometheusMarshallers.scala:36)
	at akka.http.scaladsl.marshalling.Marshaller$.$anonfun$opaque$2(Marshaller.scala:162)
	at akka.http.scaladsl.marshalling.Marshalling$Opaque.$anonfun$map$7(Marshaller.scala:215)
	at akka.http.scaladsl.marshalling.Marshal.$anonfun$toResponseFor$1(Marshal.scala:71)
	at akka.http.scaladsl.util.FastFuture$.$anonfun$map$1(FastFuture.scala:23)
	at akka.http.scaladsl.util.FastFuture$.strictTransform$1(FastFuture.scala:41)
	at akka.http.scaladsl.util.FastFuture$.transformWith$extension1(FastFuture.scala:45)
	at akka.http.scaladsl.util.FastFuture$.map$extension(FastFuture.scala:23)
	at akka.http.scaladsl.marshalling.Marshal.toResponseFor(Marshal.scala:55)
	at akka.http.scaladsl.marshalling.ToResponseMarshallable.apply(ToResponseMarshallable.scala:17)
	at akka.http.scaladsl.marshalling.ToResponseMarshallable.apply$(ToResponseMarshallable.scala:16)
	at akka.http.scaladsl.marshalling.ToResponseMarshallable$$anon$1.apply(ToResponseMarshallable.scala:22)
	at akka.http.scaladsl.server.RequestContextImpl.complete(RequestContextImpl.scala:42)
	at akka.http.scaladsl.server.directives.RouteDirectives.$anonfun$complete$1(RouteDirectives.scala:47)
	at akka.http.scaladsl.server.StandardRoute$$anon$1.apply(StandardRoute.scala:19)
	at akka.http.scaladsl.server.StandardRoute$$anon$1.apply(StandardRoute.scala:19)
	at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$mapRouteResult$2(BasicDirectives.scala:68)
	at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$textract$2(BasicDirectives.scala:161)
	at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$mapRequestContext$2(BasicDirectives.scala:45)
	at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$textract$2(BasicDirectives.scala:161)
	at akka.http.scaladsl.server.RouteConcatenation$RouteWithConcatenation.$anonfun$$tilde$2(RouteConcatenation.scala:47)
	at akka.http.scaladsl.util.FastFuture$.strictTransform$1(FastFuture.scala:41)
	at akka.http.scaladsl.util.FastFuture$.transformWith$extension1(FastFuture.scala:45)
	at akka.http.scaladsl.util.FastFuture$.flatMap$extension(FastFuture.scala:26)
	at akka.http.scaladsl.server.RouteConcatenation$RouteWithConcatenation.$anonfun$$tilde$1(RouteConcatenation.scala:44)
	at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$mapRouteResultWith$2(BasicDirectives.scala:74)
	at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$textract$2(BasicDirectives.scala:161)
	at akka.http.scaladsl.server.directives.ExecutionDirectives.$anonfun$handleExceptions$2(ExecutionDirectives.scala:32)
	at akka.http.scaladsl.server.directives.BasicDirectives.$anonfun$textract$2(BasicDirectives.scala:161)
	at akka.http.scaladsl.server.Route$.$anonfun$asyncHandler$1(Route.scala:86)
	at fr.davit.akka.http.metrics.core.scaladsl.server.HttpMetricsRoute.$anonfun$recordMetricsAsync$3(HttpMetricsRoute.scala:90)
	at akka.stream.impl.fusing.MapAsyncUnordered$$anon$31.onPush(Ops.scala:1401)
	at akka.stream.impl.fusing.GraphInterpreter.processPush(GraphInterpreter.scala:541)
	at akka.stream.impl.fusing.GraphInterpreter.execute(GraphInterpreter.scala:423)
	at akka.stream.impl.fusing.GraphInterpreterShell.runBatch(ActorGraphInterpreter.scala:624)
	at akka.stream.impl.fusing.GraphInterpreterShell$AsyncInput.execute(ActorGraphInterpreter.scala:501)
	at akka.stream.impl.fusing.GraphInterpreterShell.processEvent(ActorGraphInterpreter.scala:599)
	at akka.stream.impl.fusing.ActorGraphInterpreter.akka$stream$impl$fusing$ActorGraphInterpreter$$processEvent(ActorGraphInterpreter.scala:768)
	at akka.stream.impl.fusing.ActorGraphInterpreter$$anonfun$receive$1.applyOrElse(ActorGraphInterpreter.scala:783)
	at akka.actor.Actor.aroundReceive(Actor.scala:534)
	at akka.actor.Actor.aroundReceive$(Actor.scala:532)
	at akka.stream.impl.fusing.ActorGraphInterpreter.aroundReceive(ActorGraphInterpreter.scala:690)
	at akka.actor.ActorCell.receiveMessage(ActorCell.scala:573)
	at akka.actor.ActorCell.invoke(ActorCell.scala:543)
	at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:269)
	at akka.dispatch.Mailbox.run(Mailbox.scala:230)
	at akka.dispatch.Mailbox.exec(Mailbox.scala:242)
	at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
	at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
	at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)

Any idea what i am missing here ?

[RustedBones]

I tested the marshaling too yesterday, and it serialized the metrics properly.
Release 1.1.1 should be available now. Can you update and give it another try ?

[gunjdesai]

Tried 1.1.1, dont need the variable for ExecutionContextExecutor anymore, thank you so much for that update but still facing issue with the metrics api. I am assuming its because of the way, i have initialised it and not because of the library. Will try to debug
Below is the code FYR

import fr.davit.akka.http.metrics.core.scaladsl.server.HttpMetricsDirectives._
import fr.davit.akka.http.metrics.prometheus.marshalling.PrometheusMarshallers._
import com.api.server.Start.registry

object Metrics {

  val metricRoute = path("metrics") {

    get {

        metrics(registry)

    }

  }

  val routes = this.metricRoute

}

[RustedBones]

looking at the stack trace, it seems the registry, or the underlying registry is null.
How is your the com.api.server.Start.registry initialized ?

[gunjdesai]

@RustedBones, extremely sorry, very basic miss, registry was imported from a variable initialised in try - catch block, hence was null.
Thank you so much for helping me out really appreciate it. Kudos !!

[RustedBones]

Glad I could help :)