1 /* 2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 24 package jdk.test.lib.log; 25 26 import java.util.Collection; 27 import java.util.Comparator; 28 import java.util.Map; 29 import java.util.concurrent.ConcurrentHashMap; 30 import java.util.concurrent.ConcurrentLinkedQueue; 31 import java.util.concurrent.atomic.AtomicInteger; 32 import java.util.stream.Collectors; 33 34 /** 35 * A log manager designed specifically to allow collecting ordered log messages 36 * in a multi-threaded environment without involving any kind of locking. 37 * <p> 38 * It is particularly useful in situations when one needs to assert various 39 * details about the tested thread state or the locks it hold while also wanting 40 * to produce diagnostic log messages. 41 * <p> 42 * The log manager does not provide any guarantees about the completness of the 43 * logs written from different threads - it is up to the caller to make sure 44 * {@code toString()} method is called only when all the activity has ceased 45 * and the per-thread logs contain all the necessary data. 46 * 47 * @author Jaroslav Bachorik 48 **/ 49 public class LockFreeLogManager { 50 private final AtomicInteger logCntr = new AtomicInteger(0); 51 private final Collection<Map<Integer, String>> allRecords = new ConcurrentLinkedQueue<>(); 52 private final ThreadLocal<Map<Integer, String>> records = ThreadLocal.withInitial(ConcurrentHashMap::new); 53 54 public LockFreeLogManager() { 55 allRecords.add(records.get()); 56 } 57 58 /** 59 * Log a message 60 * @param format Message format 61 * @param params Message parameters 62 */ 63 public void log(String format, Object ... params) { 64 int id = logCntr.getAndIncrement(); 65 records.get().put(id, String.format(format, params)); 66 } 67 68 /** 69 * Will generate an aggregated log of chronologically ordered messages. 70 * <p> 71 * Make sure that you call this method only when all the related threads 72 * have finished; otherwise you might get incomplete data. 73 * 74 * @return An aggregated log of chronologically ordered messages 75 */ 76 @Override 77 public String toString() { 78 return allRecords.stream() 79 .flatMap(m -> m.entrySet().stream()) 80 .sorted(Comparator.comparing(Map.Entry::getKey)) 81 .map(Map.Entry::getValue) 82 .collect(Collectors.joining()); 83 } 84 }