/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.yarn.server.nodemanager.containermanager.monitor;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import org.apache.hadoop.yarn.server.nodemanager.metrics.NodeManagerMetrics;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.classification.InterfaceAudience.Private;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.service.AbstractService;
import org.apache.hadoop.util.StringUtils.TraditionalBinaryPrefix;
import org.apache.hadoop.yarn.api.records.ContainerExitStatus;
import org.apache.hadoop.yarn.api.records.ContainerId;
import org.apache.hadoop.yarn.api.records.Resource;
import org.apache.hadoop.yarn.api.records.ResourceUtilization;
import org.apache.hadoop.yarn.conf.YarnConfiguration;
import org.apache.hadoop.yarn.event.AsyncDispatcher;
import org.apache.hadoop.yarn.event.Dispatcher;
import org.apache.hadoop.yarn.server.nodemanager.ContainerExecutor;
import org.apache.hadoop.yarn.server.nodemanager.Context;
import org.apache.hadoop.yarn.server.nodemanager.containermanager.container.Container;
import org.apache.hadoop.yarn.server.nodemanager.containermanager.container.ContainerImpl;
import org.apache.hadoop.yarn.server.nodemanager.containermanager.container.ContainerKillEvent;
import org.apache.hadoop.yarn.server.nodemanager.containermanager.runtime.ContainerExecutionException;
import org.apache.hadoop.yarn.server.nodemanager.timelineservice.NMTimelinePublisher;
import org.apache.hadoop.yarn.server.nodemanager.util.NodeManagerHardwareUtils;
import org.apache.hadoop.yarn.util.ResourceCalculatorPlugin;
import org.apache.hadoop.yarn.util.ResourceCalculatorProcessTree;

import java.util.Arrays;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Monitors containers collecting resource usage and preempting the container
 * if it exceeds its limits.
 */
public class ContainersMonitorImpl extends AbstractService implements
    ContainersMonitor {

  private final static Logger LOG =
       LoggerFactory.getLogger(ContainersMonitorImpl.class);
  private final static Logger AUDITLOG =
       LoggerFactory.getLogger(ContainersMonitorImpl.class.getName()+".audit");

  private long monitoringInterval;
  private MonitoringThread monitoringThread;
  private boolean containerMetricsEnabled;
  private long containerMetricsPeriodMs;
  private long containerMetricsUnregisterDelayMs;

  @VisibleForTesting
  final Map<ContainerId, ProcessTreeInfo> trackingContainers =
      new ConcurrentHashMap<>();

  private final ContainerExecutor containerExecutor;
  private final Dispatcher eventDispatcher;
  private final Context context;
  private ResourceCalculatorPlugin resourceCalculatorPlugin;
  private Configuration conf;
  private static float vmemRatio;
  private Class<? extends ResourceCalculatorProcessTree> processTreeClass;

  private long maxVmemAllottedForContainers = UNKNOWN_MEMORY_LIMIT;
  private long maxPmemAllottedForContainers = UNKNOWN_MEMORY_LIMIT;

  private boolean pmemCheckEnabled;
  private boolean vmemCheckEnabled;
  private boolean containersMonitorEnabled;

  private long maxVCoresAllottedForContainers;

  private static final long UNKNOWN_MEMORY_LIMIT = -1L;
  private int nodeCpuPercentageForYARN;

  /**
   * Type of container metric.
   */
  @Private
  public enum ContainerMetric {
    CPU, MEMORY
  }

  private ResourceUtilization containersUtilization;

  private volatile boolean stopped = false;

  public ContainersMonitorImpl(ContainerExecutor exec,
      AsyncDispatcher dispatcher, Context context) {
    super("containers-monitor");

    this.containerExecutor = exec;
    this.eventDispatcher = dispatcher;
    this.context = context;

    this.monitoringThread = new MonitoringThread();

    this.containersUtilization = ResourceUtilization.newInstance(0, 0, 0.0f);
  }

  @Override
  protected void serviceInit(Configuration myConf) throws Exception {
    this.conf = myConf;
    this.monitoringInterval =
        this.conf.getLong(YarnConfiguration.NM_CONTAINER_MON_INTERVAL_MS,
            this.conf.getLong(YarnConfiguration.NM_RESOURCE_MON_INTERVAL_MS,
                YarnConfiguration.DEFAULT_NM_RESOURCE_MON_INTERVAL_MS));

    this.resourceCalculatorPlugin =
        ResourceCalculatorPlugin.getContainersMonitorPlugin(this.conf);
    LOG.info(" Using ResourceCalculatorPlugin : "
        + this.resourceCalculatorPlugin);
    processTreeClass = this.conf.getClass(
            YarnConfiguration.NM_CONTAINER_MON_PROCESS_TREE, null,
            ResourceCalculatorProcessTree.class);
    LOG.info(" Using ResourceCalculatorProcessTree : "
        + this.processTreeClass);

    this.containerMetricsEnabled =
        this.conf.getBoolean(YarnConfiguration.NM_CONTAINER_METRICS_ENABLE,
            YarnConfiguration.DEFAULT_NM_CONTAINER_METRICS_ENABLE);
    this.containerMetricsPeriodMs =
        this.conf.getLong(YarnConfiguration.NM_CONTAINER_METRICS_PERIOD_MS,
            YarnConfiguration.DEFAULT_NM_CONTAINER_METRICS_PERIOD_MS);
    this.containerMetricsUnregisterDelayMs = this.conf.getLong(
        YarnConfiguration.NM_CONTAINER_METRICS_UNREGISTER_DELAY_MS,
        YarnConfiguration.DEFAULT_NM_CONTAINER_METRICS_UNREGISTER_DELAY_MS);

    long configuredPMemForContainers =
        NodeManagerHardwareUtils.getContainerMemoryMB(
            this.resourceCalculatorPlugin, this.conf) * 1024 * 1024L;

    long configuredVCoresForContainers =
        NodeManagerHardwareUtils.getVCores(this.resourceCalculatorPlugin,
            this.conf);

    // Setting these irrespective of whether checks are enabled. Required in
    // the UI.
    // ///////// Physical memory configuration //////
    this.maxPmemAllottedForContainers = configuredPMemForContainers;
    this.maxVCoresAllottedForContainers = configuredVCoresForContainers;

    // ///////// Virtual memory configuration //////
    vmemRatio = this.conf.getFloat(YarnConfiguration.NM_VMEM_PMEM_RATIO,
        YarnConfiguration.DEFAULT_NM_VMEM_PMEM_RATIO);
    Preconditions.checkArgument(vmemRatio > 0.99f,
        YarnConfiguration.NM_VMEM_PMEM_RATIO + " should be at least 1.0");
    this.maxVmemAllottedForContainers =
        (long) (vmemRatio * configuredPMemForContainers);

    pmemCheckEnabled = this.conf.getBoolean(
        YarnConfiguration.NM_PMEM_CHECK_ENABLED,
        YarnConfiguration.DEFAULT_NM_PMEM_CHECK_ENABLED);
    vmemCheckEnabled = this.conf.getBoolean(
        YarnConfiguration.NM_VMEM_CHECK_ENABLED,
        YarnConfiguration.DEFAULT_NM_VMEM_CHECK_ENABLED);
    LOG.info("Physical memory check enabled: " + pmemCheckEnabled);
    LOG.info("Virtual memory check enabled: " + vmemCheckEnabled);

    containersMonitorEnabled =
        isContainerMonitorEnabled() && monitoringInterval > 0;
    LOG.info("ContainersMonitor enabled: " + containersMonitorEnabled);

    nodeCpuPercentageForYARN =
        NodeManagerHardwareUtils.getNodeCpuPercentage(this.conf);

    if (pmemCheckEnabled) {
      // Logging if actual pmem cannot be determined.
      long totalPhysicalMemoryOnNM = UNKNOWN_MEMORY_LIMIT;
      if (this.resourceCalculatorPlugin != null) {
        totalPhysicalMemoryOnNM = this.resourceCalculatorPlugin
            .getPhysicalMemorySize();
        if (totalPhysicalMemoryOnNM <= 0) {
          LOG.warn("NodeManager's totalPmem could not be calculated. "
              + "Setting it to " + UNKNOWN_MEMORY_LIMIT);
          totalPhysicalMemoryOnNM = UNKNOWN_MEMORY_LIMIT;
        }
      }

      if (totalPhysicalMemoryOnNM != UNKNOWN_MEMORY_LIMIT &&
          this.maxPmemAllottedForContainers > totalPhysicalMemoryOnNM * 0.80f) {
        LOG.warn("NodeManager configured with "
            + TraditionalBinaryPrefix.long2String(maxPmemAllottedForContainers,
                "", 1)
            + " physical memory allocated to containers, which is more than "
            + "80% of the total physical memory available ("
            + TraditionalBinaryPrefix.long2String(totalPhysicalMemoryOnNM, "",
                1) + "). Thrashing might happen.");
      }
    }
    super.serviceInit(this.conf);
  }

  private boolean isContainerMonitorEnabled() {
    return conf.getBoolean(YarnConfiguration.NM_CONTAINER_MONITOR_ENABLED,
        YarnConfiguration.DEFAULT_NM_CONTAINER_MONITOR_ENABLED);
  }

  /**
   * Get the best process tree calculator.
   * @param pId container process id
   * @return process tree calculator
   */
  private ResourceCalculatorProcessTree
      getResourceCalculatorProcessTree(String pId) {
    return ResourceCalculatorProcessTree.
        getResourceCalculatorProcessTree(
            pId, processTreeClass, conf);
  }

  private boolean isResourceCalculatorAvailable() {
    if (resourceCalculatorPlugin == null) {
      LOG.info("ResourceCalculatorPlugin is unavailable on this system. " + this
          .getClass().getName() + " is disabled.");
      return false;
    }
    if (getResourceCalculatorProcessTree("0") == null) {
      LOG.info("ResourceCalculatorProcessTree is unavailable on this system. "
          + this.getClass().getName() + " is disabled.");
      return false;
    }
    return true;
  }

  @Override
  protected void serviceStart() throws Exception {
    if (containersMonitorEnabled) {
      this.monitoringThread.start();
    }
    super.serviceStart();
  }

  @Override
  protected void serviceStop() throws Exception {
    if (containersMonitorEnabled) {
      stopped = true;
      this.monitoringThread.interrupt();
      try {
        this.monitoringThread.join();
      } catch (InterruptedException e) {
        LOG.info("ContainersMonitorImpl monitoring thread interrupted");
      }
    }
    super.serviceStop();
  }

  /**
   * Encapsulates resource requirements of a process and its tree.
   */
  public static class ProcessTreeInfo {
    private ContainerId containerId;
    private String pid;
    private ResourceCalculatorProcessTree pTree;
    private long vmemLimit;
    private long pmemLimit;
    private int cpuVcores;

    public ProcessTreeInfo(ContainerId containerId, String pid,
        ResourceCalculatorProcessTree pTree, long vmemLimit, long pmemLimit,
        int cpuVcores) {
      this.containerId = containerId;
      this.pid = pid;
      this.pTree = pTree;
      this.vmemLimit = vmemLimit;
      this.pmemLimit = pmemLimit;
      this.cpuVcores = cpuVcores;
    }

    public ContainerId getContainerId() {
      return this.containerId;
    }

    public String getPID() {
      return this.pid;
    }

    public void setPid(String pid) {
      this.pid = pid;
    }

    ResourceCalculatorProcessTree getProcessTree() {
      return this.pTree;
    }

    void setProcessTree(ResourceCalculatorProcessTree mypTree) {
      this.pTree = mypTree;
    }

    /**
     * @return Virtual memory limit for the process tree in bytes
     */
    public synchronized long getVmemLimit() {
      return this.vmemLimit;
    }

    /**
     * @return Physical memory limit for the process tree in bytes
     */
    public synchronized long getPmemLimit() {
      return this.pmemLimit;
    }

    /**
     * @return Number of cpu vcores assigned
     */
    public synchronized int getCpuVcores() {
      return this.cpuVcores;
    }

    /**
     * Set resource limit for enforcement.
     * @param myPmemLimit
     *          Physical memory limit for the process tree in bytes
     * @param myVmemLimit
     *          Virtual memory limit for the process tree in bytes
     * @param myCpuVcores
     *          Number of cpu vcores assigned
     */
    synchronized void setResourceLimit(
        long myPmemLimit, long myVmemLimit, int myCpuVcores) {
      this.pmemLimit = myPmemLimit;
      this.vmemLimit = myVmemLimit;
      this.cpuVcores = myCpuVcores;
    }
  }

  /**
   * Check whether a container's process tree's current memory usage is over
   * limit.
   *
   * When a java process exec's a program, it could momentarily account for
   * double the size of it's memory, because the JVM does a fork()+exec()
   * which at fork time creates a copy of the parent's memory. If the
   * monitoring thread detects the memory used by the container tree at the
   * same instance, it could assume it is over limit and kill the tree, for no
   * fault of the process itself.
   *
   * We counter this problem by employing a heuristic check: - if a process
   * tree exceeds the memory limit by more than twice, it is killed
   * immediately - if a process tree has processes older than the monitoring
   * interval exceeding the memory limit by even 1 time, it is killed. Else it
   * is given the benefit of doubt to lie around for one more iteration.
   *
   * @param containerId
   *          Container Id for the container tree
   * @param currentMemUsage
   *          Memory usage of a container tree
   * @param curMemUsageOfAgedProcesses
   *          Memory usage of processes older than an iteration in a container
   *          tree
   * @param vmemLimit
   *          The limit specified for the container
   * @return true if the memory usage is more than twice the specified limit,
   *         or if processes in the tree, older than this thread's monitoring
   *         interval, exceed the memory limit. False, otherwise.
   */
  private boolean isProcessTreeOverLimit(String containerId,
                                  long currentMemUsage,
                                  long curMemUsageOfAgedProcesses,
                                  long vmemLimit) {
    boolean isOverLimit = false;

    if (currentMemUsage > (2 * vmemLimit)) {
      LOG.warn("Process tree for container: " + containerId
          + " running over twice " + "the configured limit. Limit=" + vmemLimit
          + ", current usage = " + currentMemUsage);
      isOverLimit = true;
    } else if (curMemUsageOfAgedProcesses > vmemLimit) {
      LOG.warn("Process tree for container: " + containerId
          + " has processes older than 1 "
          + "iteration running over the configured limit. Limit=" + vmemLimit
          + ", current usage = " + curMemUsageOfAgedProcesses);
      isOverLimit = true;
    }

    return isOverLimit;
  }

  // method provided just for easy testing purposes
  boolean isProcessTreeOverLimit(ResourceCalculatorProcessTree pTree,
      String containerId, long limit) {
    long currentMemUsage = pTree.getVirtualMemorySize();
    // as processes begin with an age 1, we want to see if there are processes
    // more than 1 iteration old.
    long curMemUsageOfAgedProcesses = pTree.getVirtualMemorySize(1);
    return isProcessTreeOverLimit(containerId, currentMemUsage,
                                  curMemUsageOfAgedProcesses, limit);
  }

  private class MonitoringThread extends Thread {
    MonitoringThread() {
      super("Container Monitor");
    }

    @Override
    public void run() {

      while (!stopped && !Thread.currentThread().isInterrupted()) {
        // Print the processTrees for debugging.
        if (LOG.isDebugEnabled()) {
          StringBuilder tmp = new StringBuilder("[ ");
          for (ProcessTreeInfo p : trackingContainers.values()) {
            tmp.append(p.getPID());
            tmp.append(" ");
          }
          LOG.debug("Current ProcessTree list : "
              + tmp.substring(0, tmp.length()) + "]");
        }

        // Temporary structure to calculate the total resource utilization of
        // the containers
        ResourceUtilization trackedContainersUtilization  =
            ResourceUtilization.newInstance(0, 0, 0.0f);

        // Now do the monitoring for the trackingContainers
        // Check memory usage and kill any overflowing containers
        long vmemUsageByAllContainers = 0;
        long pmemByAllContainers = 0;
        long cpuUsagePercentPerCoreByAllContainers = 0;
        for (Entry<ContainerId, ProcessTreeInfo> entry : trackingContainers
            .entrySet()) {
          ContainerId containerId = entry.getKey();
          ProcessTreeInfo ptInfo = entry.getValue();
          try {
            // Initialize uninitialized process trees
            initializeProcessTrees(entry);

            String pId = ptInfo.getPID();
            if (pId == null || !isResourceCalculatorAvailable()) {
              continue; // processTree cannot be tracked
            }
            if (LOG.isDebugEnabled()) {
              LOG.debug("Constructing ProcessTree for : PID = " + pId
                  + " ContainerId = " + containerId);
            }
            ResourceCalculatorProcessTree pTree = ptInfo.getProcessTree();
            pTree.updateProcessTree();    // update process-tree
            long currentVmemUsage = pTree.getVirtualMemorySize();
            long currentPmemUsage = pTree.getRssMemorySize();

            // if machine has 6 cores and 3 are used,
            // cpuUsagePercentPerCore should be 300%
            float cpuUsagePercentPerCore = pTree.getCpuUsagePercent();
            if (cpuUsagePercentPerCore < 0) {
              // CPU usage is not available likely because the container just
              // started. Let us skip this turn and consider this container
              // in the next iteration.
              LOG.info("Skipping monitoring container " + containerId
                  + " since CPU usage is not yet available.");
              continue;
            }

            recordUsage(containerId, pId, pTree, ptInfo, currentVmemUsage,
                    currentPmemUsage, trackedContainersUtilization);

            checkLimit(containerId, pId, pTree, ptInfo,
                    currentVmemUsage, currentPmemUsage);

            // Accounting the total memory in usage for all containers
            vmemUsageByAllContainers += currentVmemUsage;
            pmemByAllContainers += currentPmemUsage;
            // Accounting the total cpu usage for all containers
            cpuUsagePercentPerCoreByAllContainers += cpuUsagePercentPerCore;

            reportResourceUsage(containerId, currentPmemUsage,
                    cpuUsagePercentPerCore);
          } catch (Exception e) {
            // Log the exception and proceed to the next container.
            LOG.warn("Uncaught exception in ContainersMonitorImpl "
                + "while monitoring resource of {}", containerId, e);
          }
        }
        if (LOG.isDebugEnabled()) {
          LOG.debug("Total Resource Usage stats in NM by all containers : "
              + "Virtual Memory= " + vmemUsageByAllContainers
              + ", Physical Memory= " + pmemByAllContainers
              + ", Total CPU usage(% per core)= "
              + cpuUsagePercentPerCoreByAllContainers);
        }

        // Save the aggregated utilization of the containers
        setContainersUtilization(trackedContainersUtilization);

        // Publish the container utilization metrics to node manager
        // metrics system.
        NodeManagerMetrics nmMetrics = context.getNodeManagerMetrics();
        if (nmMetrics != null) {
          nmMetrics.setContainerUsedMemGB(
              trackedContainersUtilization.getPhysicalMemory());
          nmMetrics.setContainerUsedVMemGB(
              trackedContainersUtilization.getVirtualMemory());
          nmMetrics.setContainerCpuUtilization(
              trackedContainersUtilization.getCPU());
        }

        try {
          Thread.sleep(monitoringInterval);
        } catch (InterruptedException e) {
          LOG.warn(ContainersMonitorImpl.class.getName()
              + " is interrupted. Exiting.");
          break;
        }
      }
    }

    /**
     * Initialize any uninitialized processTrees.
     * @param entry process tree entry to fill in
     */
    private void initializeProcessTrees(
            Entry<ContainerId, ProcessTreeInfo> entry)
        throws ContainerExecutionException {
      ContainerId containerId = entry.getKey();
      ProcessTreeInfo ptInfo = entry.getValue();
      String pId = ptInfo.getPID();

      // Initialize any uninitialized processTrees
      if (pId == null) {
        // get pid from ContainerId
        pId = containerExecutor.getProcessId(ptInfo.getContainerId());
        if (pId != null) {
          // pId will be null, either if the container is not spawned yet
          // or if the container's pid is removed from ContainerExecutor
          if (LOG.isDebugEnabled()) {
            LOG.debug("Tracking ProcessTree " + pId + " for the first time");
          }
          ResourceCalculatorProcessTree pt =
              getResourceCalculatorProcessTree(pId);
          ptInfo.setPid(pId);
          ptInfo.setProcessTree(pt);

          if (containerMetricsEnabled) {
            ContainerMetrics usageMetrics = ContainerMetrics
                    .forContainer(containerId, containerMetricsPeriodMs,
                      containerMetricsUnregisterDelayMs);
            usageMetrics.recordProcessId(pId);
          }

          Container container = context.getContainers().get(containerId);

          if (container != null) {
            String[] ipAndHost = containerExecutor.getIpAndHost(container);

            if ((ipAndHost != null) && (ipAndHost[0] != null) &&
                (ipAndHost[1] != null)) {
              container.setIpAndHost(ipAndHost);
              LOG.info(containerId + "'s ip = " + ipAndHost[0]
                  + ", and hostname = " + ipAndHost[1]);
            } else {
              LOG.info("Can not get both ip and hostname: "
                  + Arrays.toString(ipAndHost));
            }
          } else {
            LOG.info(containerId + " is missing. Not setting ip and hostname");
          }
        }
      }
      // End of initializing any uninitialized processTrees
    }

    /**
     * Record usage metrics.
     * @param containerId container id
     * @param pId process id
     * @param pTree valid process tree entry with CPU measurement
     * @param ptInfo process tree info with limit information
     * @param currentVmemUsage virtual memory measurement
     * @param currentPmemUsage physical memory measurement
     * @param trackedContainersUtilization utilization tracker to update
     */
    private void recordUsage(ContainerId containerId, String pId,
                             ResourceCalculatorProcessTree pTree,
                             ProcessTreeInfo ptInfo,
                             long currentVmemUsage, long currentPmemUsage,
                             ResourceUtilization trackedContainersUtilization) {
      // if machine has 6 cores and 3 are used,
      // cpuUsagePercentPerCore should be 300% and
      // cpuUsageTotalCoresPercentage should be 50%
      float cpuUsagePercentPerCore = pTree.getCpuUsagePercent();
      float cpuUsageTotalCoresPercentage = cpuUsagePercentPerCore /
              resourceCalculatorPlugin.getNumProcessors();

      // Multiply by 1000 to avoid losing data when converting to int
      int milliVcoresUsed = (int) (cpuUsageTotalCoresPercentage * 1000
              * maxVCoresAllottedForContainers /nodeCpuPercentageForYARN);
      long vmemLimit = ptInfo.getVmemLimit();
      long pmemLimit = ptInfo.getPmemLimit();
      if (AUDITLOG.isDebugEnabled()) {
        AUDITLOG.debug(String.format(
            "Resource usage of ProcessTree %s for container-id %s:" +
                " %s CPU:%f CPU/core:%f",
            pId, containerId.toString(),
            formatUsageString(
                currentVmemUsage, vmemLimit,
                currentPmemUsage, pmemLimit),
            cpuUsagePercentPerCore,
            cpuUsageTotalCoresPercentage));
      }

      // Add resource utilization for this container
      trackedContainersUtilization.addTo(
              (int) (currentPmemUsage >> 20),
              (int) (currentVmemUsage >> 20),
              milliVcoresUsed / 1000.0f);

      // Add usage to container metrics
      if (containerMetricsEnabled) {
        ContainerMetrics.forContainer(
                containerId, containerMetricsPeriodMs,
                containerMetricsUnregisterDelayMs).recordMemoryUsage(
                (int) (currentPmemUsage >> 20));
        ContainerMetrics.forContainer(
                containerId, containerMetricsPeriodMs,
                containerMetricsUnregisterDelayMs).recordCpuUsage((int)
                cpuUsagePercentPerCore, milliVcoresUsed);
      }
    }

    /**
     * Check resource limits and take actions if the limit is exceeded.
     * @param containerId container id
     * @param pId process id
     * @param pTree valid process tree entry with CPU measurement
     * @param ptInfo process tree info with limit information
     * @param currentVmemUsage virtual memory measurement
     * @param currentPmemUsage physical memory measurement
     */
    @SuppressWarnings("unchecked")
    private void checkLimit(ContainerId containerId, String pId,
                            ResourceCalculatorProcessTree pTree,
                            ProcessTreeInfo ptInfo,
                            long currentVmemUsage,
                            long currentPmemUsage) {
      boolean isMemoryOverLimit = false;
      long vmemLimit = ptInfo.getVmemLimit();
      long pmemLimit = ptInfo.getPmemLimit();
      // as processes begin with an age 1, we want to see if there
      // are processes more than 1 iteration old.
      long curMemUsageOfAgedProcesses = pTree.getVirtualMemorySize(1);
      long curRssMemUsageOfAgedProcesses = pTree.getRssMemorySize(1);
      String msg = "";
      int containerExitStatus = ContainerExitStatus.INVALID;
      if (isVmemCheckEnabled()
              && isProcessTreeOverLimit(containerId.toString(),
              currentVmemUsage, curMemUsageOfAgedProcesses, vmemLimit)) {
        // The current usage (age=0) is always higher than the aged usage. We
        // do not show the aged size in the message, base the delta on the
        // current usage
        long delta = currentVmemUsage - vmemLimit;
        // Container (the root process) is still alive and overflowing
        // memory.
        // Dump the process-tree and then clean it up.
        msg = formatErrorMessage("virtual",
                formatUsageString(currentVmemUsage, vmemLimit,
                  currentPmemUsage, pmemLimit),
                pId, containerId, pTree, delta);
        isMemoryOverLimit = true;
        containerExitStatus = ContainerExitStatus.KILLED_EXCEEDED_VMEM;
      } else if (isPmemCheckEnabled()
              && isProcessTreeOverLimit(containerId.toString(),
              currentPmemUsage, curRssMemUsageOfAgedProcesses,
              pmemLimit)) {
        // The current usage (age=0) is always higher than the aged usage. We
        // do not show the aged size in the message, base the delta on the
        // current usage
        long delta = currentPmemUsage - pmemLimit;
        // Container (the root process) is still alive and overflowing
        // memory.
        // Dump the process-tree and then clean it up.
        msg = formatErrorMessage("physical",
                formatUsageString(currentVmemUsage, vmemLimit,
                  currentPmemUsage, pmemLimit),
                pId, containerId, pTree, delta);
        isMemoryOverLimit = true;
        containerExitStatus = ContainerExitStatus.KILLED_EXCEEDED_PMEM;
      }

      if (isMemoryOverLimit) {
        // Virtual or physical memory over limit. Fail the container and
        // remove
        // the corresponding process tree
        LOG.warn(msg);
        // warn if not a leader
        if (!pTree.checkPidPgrpidForMatch()) {
          LOG.error("Killed container process with PID " + pId
                  + " but it is not a process group leader.");
        }
        // kill the container
        eventDispatcher.getEventHandler().handle(
                new ContainerKillEvent(containerId,
                      containerExitStatus, msg));
        trackingContainers.remove(containerId);
        LOG.info("Removed ProcessTree with root " + pId);
      }
    }

    /**
     * Report usage metrics to the timeline service.
     * @param containerId container id
     * @param currentPmemUsage physical memory measurement
     * @param cpuUsagePercentPerCore CPU usage
     */
    private void reportResourceUsage(ContainerId containerId,
        long currentPmemUsage, float cpuUsagePercentPerCore) {
      ContainerImpl container =
              (ContainerImpl) context.getContainers().get(containerId);
      if (container != null) {
        NMTimelinePublisher nmMetricsPublisher =
                container.getNMTimelinePublisher();
        if (nmMetricsPublisher != null) {
          nmMetricsPublisher.reportContainerResourceUsage(container,
                  currentPmemUsage, cpuUsagePercentPerCore);
        }
      } else {
        LOG.info(containerId + " does not exist to report");
      }
    }

    /**
     * Format string when memory limit has been exceeded.
     * @param memTypeExceeded type of memory
     * @param usageString general memory usage information string
     * @param pId process id
     * @param containerId container id
     * @param pTree process tree to dump full resource utilization graph
     * @return formatted resource usage information
     */
    private String formatErrorMessage(String memTypeExceeded,
        String usageString, String pId, ContainerId containerId,
        ResourceCalculatorProcessTree pTree, long delta) {
      return
        String.format("Container [pid=%s,containerID=%s] is " +
            "running %dB beyond the '%S' memory limit. ",
            pId, containerId, delta, memTypeExceeded) +
        "Current usage: " + usageString +
        ". Killing container.\n" +
        "Dump of the process-tree for " + containerId + " :\n" +
        pTree.getProcessTreeDump();
    }

    /**
     * Format memory usage string for reporting.
     * @param currentVmemUsage virtual memory usage
     * @param vmemLimit virtual memory limit
     * @param currentPmemUsage physical memory usage
     * @param pmemLimit physical memory limit
     * @return formatted memory information
     */
    private String formatUsageString(long currentVmemUsage, long vmemLimit,
        long currentPmemUsage, long pmemLimit) {
      return String.format("%sB of %sB physical memory used; " +
          "%sB of %sB virtual memory used",
          TraditionalBinaryPrefix.long2String(currentPmemUsage, "", 1),
          TraditionalBinaryPrefix.long2String(pmemLimit, "", 1),
          TraditionalBinaryPrefix.long2String(currentVmemUsage, "", 1),
          TraditionalBinaryPrefix.long2String(vmemLimit, "", 1));
    }
  }

  private void updateContainerMetrics(ContainersMonitorEvent monitoringEvent) {
    if (!containerMetricsEnabled || monitoringEvent == null) {
      return;
    }

    ContainerId containerId = monitoringEvent.getContainerId();
    ContainerMetrics usageMetrics;

    int vmemLimitMBs;
    int pmemLimitMBs;
    int cpuVcores;
    switch (monitoringEvent.getType()) {
    case START_MONITORING_CONTAINER:
      usageMetrics = ContainerMetrics
          .forContainer(containerId, containerMetricsPeriodMs,
          containerMetricsUnregisterDelayMs);
      ContainerStartMonitoringEvent startEvent =
          (ContainerStartMonitoringEvent) monitoringEvent;
      usageMetrics.recordStateChangeDurations(
          startEvent.getLaunchDuration(),
          startEvent.getLocalizationDuration());
      cpuVcores = startEvent.getCpuVcores();
      vmemLimitMBs = (int) (startEvent.getVmemLimit() >> 20);
      pmemLimitMBs = (int) (startEvent.getPmemLimit() >> 20);
      usageMetrics.recordResourceLimit(
          vmemLimitMBs, pmemLimitMBs, cpuVcores);
      break;
    case STOP_MONITORING_CONTAINER:
      ContainerStopMonitoringEvent stopEvent =
          (ContainerStopMonitoringEvent) monitoringEvent;
      usageMetrics = ContainerMetrics.getContainerMetrics(
          containerId);
      if (usageMetrics != null) {
        usageMetrics.finished(stopEvent.isForReInit());
      }
      break;
    case CHANGE_MONITORING_CONTAINER_RESOURCE:
      usageMetrics = ContainerMetrics
          .forContainer(containerId, containerMetricsPeriodMs,
          containerMetricsUnregisterDelayMs);
      ChangeMonitoringContainerResourceEvent changeEvent =
          (ChangeMonitoringContainerResourceEvent) monitoringEvent;
      Resource resource = changeEvent.getResource();
      pmemLimitMBs = (int) resource.getMemorySize();
      vmemLimitMBs = (int) (pmemLimitMBs * vmemRatio);
      cpuVcores = resource.getVirtualCores();
      usageMetrics.recordResourceLimit(
          vmemLimitMBs, pmemLimitMBs, cpuVcores);
      break;
    default:
      break;
    }
  }

  @Override
  public long getVmemAllocatedForContainers() {
    return this.maxVmemAllottedForContainers;
  }

  /**
   * Is the total physical memory check enabled?
   *
   * @return true if total physical memory check is enabled.
   */
  @Override
  public boolean isPmemCheckEnabled() {
    return this.pmemCheckEnabled;
  }

  @Override
  public long getPmemAllocatedForContainers() {
    return this.maxPmemAllottedForContainers;
  }

  @Override
  public long getVCoresAllocatedForContainers() {
    return this.maxVCoresAllottedForContainers;
  }

  /**
   * Is the total virtual memory check enabled?
   *
   * @return true if total virtual memory check is enabled.
   */
  @Override
  public boolean isVmemCheckEnabled() {
    return this.vmemCheckEnabled;
  }

  @Override
  public ResourceUtilization getContainersUtilization() {
    return this.containersUtilization;
  }

  private void setContainersUtilization(ResourceUtilization utilization) {
    this.containersUtilization = utilization;
  }

  @Override
  public void subtractNodeResourcesFromResourceUtilization(
      ResourceUtilization resourceUtil) {
    resourceUtil.subtractFrom((int) (getPmemAllocatedForContainers() >> 20),
        (int) (getVmemAllocatedForContainers() >> 20), 1.0f);
  }

  @Override
  public float getVmemRatio() {
    return vmemRatio;
  }

  @Override
  @SuppressWarnings("unchecked")
  public void handle(ContainersMonitorEvent monitoringEvent) {
    ContainerId containerId = monitoringEvent.getContainerId();

    switch (monitoringEvent.getType()) {
    case START_MONITORING_CONTAINER:
      onStartMonitoringContainer(monitoringEvent, containerId);
      break;
    case STOP_MONITORING_CONTAINER:
      onStopMonitoringContainer(monitoringEvent, containerId);
      break;
    case CHANGE_MONITORING_CONTAINER_RESOURCE:
      onChangeMonitoringContainerResource(monitoringEvent, containerId);
      break;
    default:
      // TODO: Wrong event.
    }
  }

  private void onChangeMonitoringContainerResource(
      ContainersMonitorEvent monitoringEvent, ContainerId containerId) {
    ChangeMonitoringContainerResourceEvent changeEvent =
        (ChangeMonitoringContainerResourceEvent) monitoringEvent;
    if (containersMonitorEnabled) {
      ProcessTreeInfo processTreeInfo = trackingContainers.get(containerId);
      if (processTreeInfo == null) {
        LOG.warn("Failed to track container "
            + containerId.toString()
            + ". It may have already completed.");
        return;
      }
      LOG.info("Changing resource-monitoring for " + containerId);
      updateContainerMetrics(monitoringEvent);
      long pmemLimit =
          changeEvent.getResource().getMemorySize() * 1024L * 1024L;
      long vmemLimit = (long) (pmemLimit * vmemRatio);
      int cpuVcores = changeEvent.getResource().getVirtualCores();
      processTreeInfo.setResourceLimit(pmemLimit, vmemLimit, cpuVcores);
    }
  }

  private void onStopMonitoringContainer(
      ContainersMonitorEvent monitoringEvent, ContainerId containerId) {
    LOG.info("Stopping resource-monitoring for " + containerId);
    updateContainerMetrics(monitoringEvent);
    trackingContainers.remove(containerId);
  }

  private void onStartMonitoringContainer(
      ContainersMonitorEvent monitoringEvent, ContainerId containerId) {
    ContainerStartMonitoringEvent startEvent =
        (ContainerStartMonitoringEvent) monitoringEvent;
    LOG.info("Starting resource-monitoring for " + containerId);
    updateContainerMetrics(monitoringEvent);
    trackingContainers.put(containerId,
        new ProcessTreeInfo(containerId, null, null,
            startEvent.getVmemLimit(), startEvent.getPmemLimit(),
            startEvent.getCpuVcores()));
  }
}