/**
 *
 * 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.hbase.monitoring;

import java.lang.management.ManagementFactory;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;

import org.apache.hadoop.classification.InterfaceAudience;

@InterfaceAudience.Private
public abstract class ThreadMonitoring {

  private static final ThreadMXBean threadBean = 
    ManagementFactory.getThreadMXBean();
  private static final int STACK_DEPTH = 20;

  public static ThreadInfo getThreadInfo(Thread t) {
    long tid = t.getId();
    return threadBean.getThreadInfo(tid, STACK_DEPTH);
  }
    

  /**
   * Format the given ThreadInfo object as a String.
   * @param indent a prefix for each line, used for nested indentation
   */
  public static String formatThreadInfo(ThreadInfo threadInfo, String indent) {
    StringBuilder sb = new StringBuilder();
    appendThreadInfo(sb, threadInfo, indent);
    return sb.toString();
  }

  /**
   * Print all of the thread's information and stack traces.
   * 
   * @param sb
   * @param info
   * @param indent
   */
  public static void appendThreadInfo(StringBuilder sb,
                                      ThreadInfo info,
                                      String indent) {
    boolean contention = threadBean.isThreadContentionMonitoringEnabled();

    if (info == null) {
      sb.append(indent).append("Inactive (perhaps exited while monitoring was done)\n");
      return;
    }
    String taskName = getTaskName(info.getThreadId(), info.getThreadName());
    sb.append(indent).append("Thread ").append(taskName).append(":\n");
    
    Thread.State state = info.getThreadState();
    sb.append(indent).append("  State: ").append(state).append("\n");
    sb.append(indent).append("  Blocked count: ").append(info.getBlockedCount()).append("\n");
    sb.append(indent).append("  Waited count: ").append(info.getWaitedCount()).append("\n");
    if (contention) {
      sb.append(indent).append("  Blocked time: " + info.getBlockedTime()).append("\n");
      sb.append(indent).append("  Waited time: " + info.getWaitedTime()).append("\n");
    }
    if (state == Thread.State.WAITING) {
      sb.append(indent).append("  Waiting on ").append(info.getLockName()).append("\n");
    } else  if (state == Thread.State.BLOCKED) {
      sb.append(indent).append("  Blocked on ").append(info.getLockName()).append("\n");
      sb.append(indent).append("  Blocked by ").append(
        getTaskName(info.getLockOwnerId(), info.getLockOwnerName())).append("\n");
    }
    sb.append(indent).append("  Stack:").append("\n");
    for (StackTraceElement frame: info.getStackTrace()) {
      sb.append(indent).append("    ").append(frame.toString()).append("\n");
    }
  }
  
  private static String getTaskName(long id, String name) {
    if (name == null) {
      return Long.toString(id);
    }
    return id + " (" + name + ")";
  }


}