Akka/Scala example source code file (MetricsListener.scala)

This example Akka source code file (MetricsListener.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actor, actorlogging, akka, cluster, cpu, factorial, heapmemory, load, metricslistener, nodemetrics, some, unit, used

The MetricsListener.scala Akka example source code

package sample.cluster.factorial

import akka.actor.ActorLogging
import akka.actor.Actor

//#metrics-listener
import akka.cluster.Cluster
import akka.cluster.ClusterEvent.ClusterMetricsChanged
import akka.cluster.ClusterEvent.CurrentClusterState
import akka.cluster.NodeMetrics
import akka.cluster.StandardMetrics.HeapMemory
import akka.cluster.StandardMetrics.Cpu

class MetricsListener extends Actor with ActorLogging {
  val selfAddress = Cluster(context.system).selfAddress

  // subscribe to ClusterMetricsChanged
  // re-subscribe when restart
  override def preStart(): Unit =
    Cluster(context.system).subscribe(self, classOf[ClusterMetricsChanged])
  override def postStop(): Unit =
    Cluster(context.system).unsubscribe(self)

  def receive = {
    case ClusterMetricsChanged(clusterMetrics) =>
      clusterMetrics.filter(_.address == selfAddress) foreach { nodeMetrics =>
        logHeap(nodeMetrics)
        logCpu(nodeMetrics)
      }
    case state: CurrentClusterState => // ignore
  }

  def logHeap(nodeMetrics: NodeMetrics): Unit = nodeMetrics match {
    case HeapMemory(address, timestamp, used, committed, max) =>
      log.info("Used heap: {} MB", used.doubleValue / 1024 / 1024)
    case _ => // no heap info
  }

  def logCpu(nodeMetrics: NodeMetrics): Unit = nodeMetrics match {
    case Cpu(address, timestamp, Some(systemLoadAverage), cpuCombined, processors) =>
      log.info("Load: {} ({} processors)", systemLoadAverage, processors)
    case _ => // no cpu info
  }
}

//#metrics-listener