001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.activemq.util;
018
019import java.util.HashMap;
020import java.util.Map.Entry;
021
022import org.slf4j.Logger;
023import org.slf4j.LoggerFactory;
024
025/**
026 * Debugging tool to track entry points through code, useful to see runtime call paths
027 * To use, add to a method as follows:<code>
028 *  public void someMethod() {
029 *      ThreadTracker.track("someMethod");
030 *      ...
031 *  }</code>
032 *  and at some stage call <code>result</code> to get a LOG
033 *  output of the callers with an associated call count
034 *      
035 */
036public class ThreadTracker {
037
038    static final Logger LOG = LoggerFactory.getLogger(ThreadTracker.class);  
039    static HashMap<String, Tracker> trackers = new HashMap<String, Tracker>();
040    
041    /**
042     * track the stack trace of callers
043     * @param name the method being tracked
044     */
045    public static void track(final String name) {
046        Tracker t;
047        final String key = name.intern();
048        synchronized(trackers) {
049            t = trackers.get(key);
050            if (t == null) {
051                t = new Tracker();
052                trackers.put(key, t);
053            }
054        }
055        t.track();
056    }
057    
058    /**
059     * output the result of stack trace capture to the log
060     */
061    public static void result() {
062        synchronized(trackers) {
063            for (Entry<String, Tracker> t: trackers.entrySet()) {
064                LOG.info("Tracker: " + t.getKey() + ", " + t.getValue().size() + " entry points...");
065                for (Trace trace : t.getValue().values()) {
066                    LOG.info("count: " + trace.count, trace);
067                }
068                LOG.info("Tracker: " + t.getKey() + ", done.");
069            }
070        }
071    }
072
073}
074
075@SuppressWarnings("serial")
076class Trace extends Throwable {
077    public int count = 1;
078    public final long id;
079    Trace() {
080        super();
081        id = calculateIdentifier();
082    }
083    private long calculateIdentifier() {
084        int len = 0;
085        for (int i=0; i<this.getStackTrace().length; i++) {
086            len += this.getStackTrace()[i].toString().intern().hashCode();
087        }
088        return len;
089    }
090}
091
092@SuppressWarnings("serial")
093class Tracker extends HashMap<Long, Trace> {
094    public void track() {
095        Trace current = new Trace();
096        synchronized(this) {
097            Trace exist = get(current.id);
098            if (exist != null) {
099                exist.count++;
100            } else {
101                put(current.id, current);
102            }
103        }
104    }
105}