lerna-http: Substream Source(EntitySource) cannot be materialized more than once が発生しアクセスログのリクエストボディが確認できないことがある

[negokaz]

ログ出力内容：

WARN Failed to get the request body  java.lang.IllegalStateException: Substream Source(EntitySource) cannot be materialized more than once
    at akka.stream.impl.fusing.SubSource$$anon$11.createMaterializedTwiceException(StreamOfStreams.scala:846)
    at akka.stream.impl.fusing.SubSource$$anon$11.<init>(StreamOfStreams.scala:816)
    at akka.stream.impl.fusing.SubSource.createLogic(StreamOfStreams.scala:812)
    at akka.stream.stage.GraphStage.createLogicAndMaterializedValue(GraphStage.scala:106)
    at akka.stream.stage.GraphStageWithMaterializedValue.createLogicAndMaterializedValue(GraphStage.scala:50)
    at akka.stream.impl.GraphStageIsland.materializeAtomic(PhasedFusingActorMaterializer.scala:705)
    at akka.stream.impl.PhasedFusingActorMaterializer.materialize(PhasedFusingActorMaterializer.scala:503)
    at akka.stream.impl.PhasedFusingActorMaterializer.materialize(PhasedFusingActorMaterializer.scala:452)
    at akka.stream.impl.PhasedFusingActorMaterializer.materialize(PhasedFusingActorMaterializer.scala:444)
    at akka.stream.scaladsl.RunnableGraph.run(Flow.scala:746)
    at akka.stream.scaladsl.Source.runWith(Source.scala:118)
    at akka.stream.scaladsl.Source.runFold(Source.scala:132)
    at akka.http.scaladsl.unmarshalling.PredefinedFromEntityUnmarshallers.$anonfun$byteStringUnmarshaller$3(PredefinedFromEntityUnmarshallers.scala:16)
    at akka.http.scaladsl.unmarshalling.Unmarshaller$$anon$1.apply(Unmarshaller.scala:58)
    at akka.http.scaladsl.unmarshalling.Unmarshaller$EnhancedUnmarshaller$.$anonfun$mapWithInput$3(Unmarshaller.scala:93)
    at akka.http.scaladsl.unmarshalling.Unmarshaller$$anon$1.apply(Unmarshaller.scala:58)
    at akka.http.scaladsl.unmarshalling.LowerPriorityGenericUnmarshallers.$anonfun$messageUnmarshallerFromEntityUnmarshaller$3(GenericUnmarshallers.scala:25)
    at akka.http.scaladsl.unmarshalling.Unmarshaller$$anon$1.apply(Unmarshaller.scala:58)
    at akka.http.scaladsl.unmarshalling.Unmarshal.to(Unmarshal.scala:25)
    at lerna.http.directives.RequestLogDirective.$anonfun$logRequestResultDirective$4(RequestLogDirective.scala:33)
    at akka.http.scaladsl.util.FastFuture$.$anonfun$map$1(FastFuture.scala:22)
    at akka.http.scaladsl.util.FastFuture$.strictTransform$1(FastFuture.scala:40)
    at akka.http.scaladsl.util.FastFuture$.$anonfun$transformWith$3(FastFuture.scala:50)
    at scala.concurrent.impl.Promise$Transformation.run(Promise.scala:448)
    at akka.dispatch.BatchingExecutor$AbstractBatch.processBatch(BatchingExecutor.scala:63)
    at akka.dispatch.BatchingExecutor$BlockableBatch.$anonfun$run$1(BatchingExecutor.scala:100)
    at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
    at scala.concurrent.BlockContext$.withBlockContext(BlockContext.scala:94)
    at akka.dispatch.BatchingExecutor$BlockableBatch.run(BatchingExecutor.scala:100)
    at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:49)
    at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(ForkJoinExecutorConfigurator.scala:48)
    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)

アクセスログ出力内容（一部抜粋）：

200 OK, ResponseHeaders: [], RequestBody: HttpEntity.Default(application/json,394 bytes total), ResponseBody: {}

関連情報：

• scala - Akka http -ERROR :Substream Source cannot be materialized more than once If Payload size increased - Stack Overflow
• Unmarshalling in Akka-HTTP: caveats of streaming | by Herve Eichwald | disney-streaming | Medium

リクエストボディがチャンクに分割され、当該エラーが発生することがあるとのこと。
toStrictEntity で一度リクエストボディをメモリ上にバッファリングすることで問題を回避できる。