001: /* ====================================================================
002: * The Apache Software License, Version 1.1
003: *
004: * Copyright (c) 1997-2003 The Apache Software Foundation. All rights
005: * reserved.
006: *
007: * Redistribution and use in source and binary forms, with or without
008: * modification, are permitted provided that the following conditions
009: * are met:
010: *
011: * 1. Redistributions of source code must retain the above copyright
012: * notice, this list of conditions and the following disclaimer.
013: *
014: * 2. Redistributions in binary form must reproduce the above copyright
015: * notice, this list of conditions and the following disclaimer in
016: * the documentation and/or other materials provided with the
017: * distribution.
018: *
019: * 3. The end-user documentation included with the redistribution,
020: * if any, must include the following acknowledgment:
021: * "This product includes software developed by the
022: * Apache Software Foundation (http://www.apache.org/)."
023: * Alternately, this acknowledgment may appear in the software
024: * itself, if and wherever such third-party acknowledgments
025: * normally appear.
026: *
027: * 4. The names "Jakarta", "Avalon", and "Apache Software Foundation"
028: * must not be used to endorse or promote products derived from this
029: * software without prior written permission. For written
030: * permission, please contact apache@apache.org.
031: *
032: * 5. Products derived from this software may not be called "Apache",
033: * nor may "Apache" appear in their name, without prior written
034: * permission of the Apache Software Foundation.
035: *
036: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
037: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
038: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
039: * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
040: * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
041: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
042: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
043: * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
044: * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
045: * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
046: * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
047: * SUCH DAMAGE.
048: * ====================================================================
049: *
050: * This software consists of voluntary contributions made by many
051: * individuals on behalf of the Apache Software Foundation. For more
052: * information on the Apache Software Foundation, please see
053: * <http://www.apache.org/>.
054: */
055: package org.apache.log.output;
056:
057: import java.util.LinkedList;
058: import org.apache.log.ErrorAware;
059: import org.apache.log.ErrorHandler;
060: import org.apache.log.LogEvent;
061: import org.apache.log.LogTarget;
062:
063: /**
064: * An asynchronous LogTarget that sends entries on in another thread.
065: * It is the responsibility of the user of this class to start
066: * the thread etc.
067: *
068: * <pre>
069: * LogTarget mySlowTarget = ...;
070: * AsyncLogTarget asyncTarget = new AsyncLogTarget( mySlowTarget );
071: * Thread thread = new Thread( asyncTarget );
072: * thread.setPriority( Thread.MIN_PRIORITY );
073: * thread.start();
074: *
075: * logger.setLogTargets( new LogTarget[] { asyncTarget } );
076: * </pre>
077: *
078: * @author <a href="mailto:dev@avalon.apache.org">Avalon Development Team</a>
079: * @author <a href="mailto:peter@apache.org">Peter Donald</a>
080: */
081: public class AsyncLogTarget extends AbstractTarget implements Runnable {
082: private final LinkedList m_list;
083: private final int m_queueSize;
084: private final LogTarget m_logTarget;
085:
086: /**
087: * Creation of a new async log target.
088: * @param logTarget the underlying target
089: */
090: public AsyncLogTarget(final LogTarget logTarget) {
091: this (logTarget, 15);
092: }
093:
094: /**
095: * Creation of a new async log target.
096: * @param logTarget the underlying target
097: * @param queueSize the queue size
098: */
099: public AsyncLogTarget(final LogTarget logTarget, final int queueSize) {
100: m_logTarget = logTarget;
101: m_list = new LinkedList();
102: m_queueSize = queueSize;
103: open();
104: }
105:
106: /**
107: * Provide component with ErrorHandler.
108: *
109: * @param errorHandler the errorHandler
110: */
111: public synchronized void setErrorHandler(
112: final ErrorHandler errorHandler) {
113: super .setErrorHandler(errorHandler);
114:
115: if (m_logTarget instanceof ErrorAware) {
116: ((ErrorAware) m_logTarget).setErrorHandler(errorHandler);
117: }
118: }
119:
120: /**
121: * Process a log event by adding it to queue.
122: *
123: * @param event the log event
124: */
125: public void doProcessEvent(final LogEvent event) {
126: synchronized (m_list) {
127: final int size = m_list.size();
128: while (m_queueSize <= size) {
129: try {
130: m_list.wait();
131: } catch (final InterruptedException ie) {
132: //This really should not occur ...
133: //Maybe we should log it though for
134: //now lets ignore it
135: }
136: }
137:
138: m_list.addFirst(event);
139:
140: if (size == 0) {
141: //tell the "server" thread to wake up
142: //if it is waiting for a queue to contain some items
143: m_list.notify();
144: }
145: }
146: }
147:
148: /**
149: * Thread startup.
150: */
151: public void run() {
152: //set this variable when thread is interupted
153: //so we know we can shutdown thread soon.
154: boolean interupted = false;
155:
156: while (true) {
157: LogEvent event = null;
158:
159: synchronized (m_list) {
160: while (null == event) {
161: final int size = m_list.size();
162:
163: if (size > 0) {
164: event = (LogEvent) m_list.removeLast();
165:
166: if (size == m_queueSize) {
167: //tell the "client" thread to wake up
168: //if it is waiting for a queue position to open up
169: m_list.notify();
170: }
171:
172: } else if (interupted || Thread.interrupted()) {
173: //ie there is nothing in queue and thread is interrupted
174: //thus we stop thread
175: return;
176: } else {
177: try {
178: m_list.wait();
179: } catch (final InterruptedException ie) {
180: //Ignore this and let it be dealt in next loop
181: //Need to set variable as the exception throw cleared status
182: interupted = true;
183: }
184: }
185: }
186: }
187:
188: try {
189: //actually process an event
190: m_logTarget.processEvent(event);
191: } catch (final Throwable throwable) {
192: getErrorHandler().error("Unknown error writing event.",
193: throwable, event);
194: }
195: }
196: }
197: }
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