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     */
017    package org.apache.activemq.util;
018    
019    import java.util.HashMap;
020    import java.util.Map.Entry;
021    
022    import org.slf4j.Logger;
023    import 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     */
036    public 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")
076    class 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")
093    class 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    }