content: /**
   * 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.activemq.util;
  
  import java.util.HashMap;
  import java.util.Map.Entry;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Debugging tool to track entry points through code, useful to see runtime call paths
   * To use, add to a method as follows:<code>
   *  public void someMethod() {
   *      ThreadTracker.track("someMethod");
   *      ...
   *  }</code>
   *  and at some stage call <code>result</code> to get a LOG
   *  output of the callers with an associated call count
   *      
   */
  public class ThreadTracker {
  
      static final Logger LOG = LoggerFactory.getLogger(ThreadTracker.class);  
      static HashMap<String, Tracker> trackers = new HashMap<String, Tracker>();
      
      /**
       * track the stack trace of callers
       * @param name the method being tracked
       */
      public static void track(final String name) {
          Tracker t;
          final String key = name.intern();
          synchronized(trackers) {
              t = trackers.get(key);
              if (t == null) {
                  t = new Tracker();
                  trackers.put(key, t);
              }
          }
          t.track();
      }
      
      /**
       * output the result of stack trace capture to the log
       */
      public static void result() {
          synchronized(trackers) {
              for (Entry<String, Tracker> t: trackers.entrySet()) {
                  LOG.info("Tracker: " + t.getKey() + ", " + t.getValue().size() + " entry points...");
                  for (Trace trace : t.getValue().values()) {
                      LOG.info("count: " + trace.count, trace);
                  }
                  LOG.info("Tracker: " + t.getKey() + ", done.");
              }
          }
      }
  
  }
  
  @SuppressWarnings("serial")
  class Trace extends Throwable {
      public int count = 1;
      public final long id;
      Trace() {
          super();
          id = calculateIdentifier();
      }
      private long calculateIdentifier() {
          int len = 0;
          for (int i=0; i<this.getStackTrace().length; i++) {
              len += this.getStackTrace()[i].toString().intern().hashCode();
          }
          return len;
      }
  }
  
  @SuppressWarnings("serial")
  class Tracker extends HashMap<Long, Trace> {
      public void track() {
          Trace current = new Trace();
          synchronized(this) {
              Trace exist = get(current.id);
              if (exist != null) {
                  exist.count++;
              } else {
                  put(current.id, current);
              }
          }
      }
  }
  