VMStatTimerTask.java

package com.orbitz.monitoring.lib.timertask;

import static java.lang.management.ManagementFactory.getGarbageCollectorMXBeans;

import com.orbitz.monitoring.api.Monitor;
import com.orbitz.monitoring.api.MonitoringLevel;
import com.orbitz.monitoring.api.monitor.EventMonitor;

import java.lang.management.GarbageCollectorMXBean;
import java.lang.management.ManagementFactory;
import java.lang.management.MemoryMXBean;
import java.lang.management.MemoryPoolMXBean;
import java.lang.management.MemoryType;
import java.lang.management.MemoryUsage;
import java.lang.management.ThreadMXBean;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicLong;

/**
 * VMStatTimerTask uses jdk5 MXBeans access garbage collection and thread stats.  EventMonitors 
 * named GarbageCollectorStats and ThreadStats are fired containing the stats as attributes.
 *
 * @since 3.5
 *
 * @author Matt O'Keefe
 */
public class VMStatTimerTask extends MonitorEmittingTimerTask {

  // 2 ^ 20 = 1024 * 1024 = 1048576
  private static final int BASE_2_EXP_MEGABYTE = 20; 

  private final Map<String,AtomicLong> gc;

  public VMStatTimerTask() {
    super();
    gc = new HashMap<String,AtomicLong>(8);
    for (GarbageCollectorMXBean garbageCollectorMXBean : getGarbageCollectorMXBeans()) {
      final String name = garbageCollectorMXBean.getName();
      gc.put(name + ".count", new AtomicLong());
      gc.put(name + ".time", new AtomicLong());
    }
  }

  /**
   * The action to be performed by this timer task.
   */
  public Collection<Monitor> emitMonitors() {
    Set<Monitor> monitors = new HashSet<Monitor>();
    for (GarbageCollectorMXBean garbageCollectorMXBean : getGarbageCollectorMXBeans()) {
      String name = garbageCollectorMXBean.getName();
      long count = setGCAndGetDelta(name + ".count", garbageCollectorMXBean.getCollectionCount());
      long time = setGCAndGetDelta(name + ".time", garbageCollectorMXBean.getCollectionTime());
      monitors.add(fireJvmStat("GarbageCollector." + name, count, time));
    }

    ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();
    monitors.add(fireJvmStat("Thread", (long) threadBean.getThreadCount()));

    MemoryMXBean memoryMXBean = ManagementFactory.getMemoryMXBean();
    long objectPendingFinalizationCount = memoryMXBean.getObjectPendingFinalizationCount();
    monitors.add(fireJvmStat("Memory.objectPendingFinalization", objectPendingFinalizationCount));
    monitors.add(fireJvmStat("Memory.Heap.memoryUsage", memoryMXBean.getHeapMemoryUsage()));
    monitors.add(fireJvmStat("Memory.NonHeap.memoryUsage", memoryMXBean.getNonHeapMemoryUsage()));
    
    for (MemoryPoolMXBean memoryPoolMXBean: ManagementFactory.getMemoryPoolMXBeans()) {
      String type = (MemoryType.HEAP == memoryPoolMXBean.getType()) ? "Heap" : "NonHeap";
      String name = "Memory." + type + ".Pool." + memoryPoolMXBean.getName();
      monitors.add(fireJvmStat(name + ".memoryUsage", memoryPoolMXBean.getUsage()));

      MemoryUsage usage = memoryPoolMXBean.getCollectionUsage();
      if (usage != null) {
        monitors.add(fireJvmStat(name + ".memoryCollectionUsage", toMegaBytes(usage.getUsed())));
      }
    }
    return monitors;
  }

  // calculates a gc delta value
  private long setGCAndGetDelta(final String key, final long newValue) {
    final long oldValue = gc.get(key).getAndSet(newValue);
    return newValue - oldValue;
  }

  // convert a number from bytes to megabytes
  private long toMegaBytes(final long number) {
    return number >> BASE_2_EXP_MEGABYTE;
  }

  // get the percentage used
  private double getUsedPercentage(MemoryUsage usage) {
    return (100.0 * usage.getUsed()) / usage.getMax();
  }

  // fire JvmStats monitor; sets the name, type, count, time and percent
  private EventMonitor fireJvmStat(String type, MemoryUsage usage) {
    long usedMegaBytes = toMegaBytes(usage.getUsed());
    double usedPercentage = getUsedPercentage(usage);
    return fireJvmStat(type, usedMegaBytes, null, usedPercentage);
  }
  
  private EventMonitor fireJvmStat(String type, Long count) {
    return fireJvmStat(type, count, null, null);
  }
  
  private EventMonitor fireJvmStat(String type, Long count, Long time) {
    return fireJvmStat(type, count, time, null);
  }

  private EventMonitor fireJvmStat(String type, Long count, Long time, Double percent) {
    final EventMonitor monitor = new EventMonitor("JvmStats", MonitoringLevel.ESSENTIAL);
    monitor.set("type", type);
    if (count != null) {
      monitor.set("count", count);
    }
    if (time != null) {
      monitor.set("time", time);
    }
    if (percent != null) {
      monitor.set("percent", percent);
    }
    monitor.fire();
    return monitor;
  }
}