/**
    *
    * 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.hbase.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 + ")";
    }
  
  
  }