Materialization Metrics Collector Stage


MaterializationMetricsCollector is an Akka Streams GraphStage to collect materialization metrics for a stream:

  • active materialization counts
  • new materialization creation rates
  • materialization termination rates (aggregation of successful termination and failures)

A prominent use case for the MaterializationMetricsCollector is with server-side Akka HTTP, where each new connection results in a stream materialization and therefore each connection termination results in the termination of the associated stream materialization. For this reason, the MaterializationMetricsCollector is out-of-the-box integrated with squbs HTTP(S) service implementations publishing active connection, connection creation, and connection termination metrics.


Add the following dependency to your build.sbt or scala build file:

"org.squbs" %% "squbs-ext" % squbsVersion


The usage is very similar to standard Akka Stream stages. In below examples, you should see JMX beans with names that contain:

  • my-stream-active-count with Count value 2 at the beginning, but will go down to 0 once the materializations terminate.
  • my-stream-creation-count with Count value 2.
  • my-stream-termination-count will shows up only after a stream terminates and will have Count value 2 ultimately.
val stream = Source(1 to 10)
  .to(Sink.ignore) // Materializing the stream a second time, thus increasing the Count value to 2
RunnableGraph<NotUsed> stream =
        Source.range(1, 10)
                .via(MaterializationMetricsCollector.create("my-stream", system))
                .to(Sink.ignore());;; // Materializing the stream a second time, thus increasing the Count value to 2