package sample.java.cluster.factorial;

import akka.actor.AbstractActor;
import akka.cluster.Cluster;
import akka.cluster.ClusterEvent.CurrentClusterState;
import akka.cluster.metrics.ClusterMetricsChanged;
import akka.cluster.metrics.NodeMetrics;
import akka.cluster.metrics.StandardMetrics;
import akka.cluster.metrics.StandardMetrics.HeapMemory;
import akka.cluster.metrics.StandardMetrics.Cpu;
import akka.cluster.metrics.ClusterMetricsExtension;
import akka.event.Logging;
import akka.event.LoggingAdapter;

public class MetricsListener extends AbstractActor {
  LoggingAdapter log = Logging.getLogger(getContext().system(), this);

  Cluster cluster = Cluster.get(getContext().system());
  
  ClusterMetricsExtension extension = ClusterMetricsExtension.get(getContext().system());

  
  // Subscribe unto ClusterMetricsEvent events.
  @Override
  public void preStart() {
	  extension.subscribe(self());
  }

  // Unsubscribe from ClusterMetricsEvent events.
  @Override
  public void postStop() {
	  extension.unsubscribe(self());
  }

  @Override
  public Receive createReceive() {
    return receiveBuilder()
      .match(ClusterMetricsChanged.class, clusterMetrics -> {
        for (NodeMetrics nodeMetrics : clusterMetrics.getNodeMetrics()) {
          if (nodeMetrics.address().equals(cluster.selfAddress())) {
            logHeap(nodeMetrics);
            logCpu(nodeMetrics);
          }
        }
      })
      .match(CurrentClusterState.class, message -> {
        // Ignore.
      })
      .build();
  }

  void logHeap(NodeMetrics nodeMetrics) {
    HeapMemory heap = StandardMetrics.extractHeapMemory(nodeMetrics);
    if (heap != null) {
      log.info("Used heap: {} MB", ((double) heap.used()) / 1024 / 1024);
    }
  }

  void logCpu(NodeMetrics nodeMetrics) {
    Cpu cpu = StandardMetrics.extractCpu(nodeMetrics);
    if (cpu != null && cpu.systemLoadAverage().isDefined()) {
      log.info("Load: {} ({} processors)", cpu.systemLoadAverage().get(), 
        cpu.processors());
    }
  }

}
