The code I have written is similar to Doug Lea's ReaderWriterLock. Actually, my code was inspired from Allen Holub's Reader/writer locks article (See JavaWorld April 1999) which was itself inspired by Doug Lea's code.
Anyway, the ReaderWriterLock as it exists in log4j cvs is considerably simpler but it also offers much less functionality. (No free luch here.) You can test it by calling 'ant ReaderWriterLock' from the LOG4J_HOME/tests/ directory. (You have to have jakarta-oro and junit in your classpath and check out the latest from CVS.)
The test takes about half an hour using a fast machine. I've tested it with JDK 1.3.1 and JDK 1.4.1 under Windows XP. Tests with other OSs and JDKs are highly encouraged and would be much appreciated.
As for reentrance, as far as I can tell, we do not need it.
At 08:38 AM 5/27/2003 -0500, Ebersole, Steven wrote:
I wrote a reader/writer impl, but the target was caching, not a file. However, the basic implementation was based on Doug Lea's excellent concurrency package using his ReentrantWriterPreferenceReadWriteLock class. The purpose of this class is what you describe, waiting writers are given preference over waiting readers. The nice thing about his package is that all the Object wait/notify stuff is hidden behind the scenes and simply presented as a Lock which clients acquire() and release().
Not sure how you would feel about use of his package, but if you are interested I can whip up some code to convert this cache stuff I have now.
|-----Original Message----- |From: Ceki Gülcü [mailto:[EMAIL PROTECTED] |Sent: Saturday, May 24, 2003 4:11 PM |To: Log4J Developers List |Subject: ReaderWriterLock, faster implementation? | | | |I have just committed a remarkably simple implementation of a |ReaderWriterLock. A ReaderWriterLock allows simultaneous read |operations but only one write operation. Waiting writers |have priority |over waiting readers. | |The code seems to be working but will be massively tested |just to make |sure. | |If you know of a faster implementation do not hesitate to show the |way. In particular, I'd like to be able to avoid the notifyAll call |and replace it with notify(). | |At 09:04 PM 5/24/2003 +0000, you wrote: |>ceki 2003/05/24 14:04:00 |> |> Modified: tests build.xml |> Added: src/java/org/apache/log4j/helpers |ReaderWriterLock.java |> tests/src/java/org/apache/log4j/helpers |> ReaderWriterLockTestCase.java |> Log: |> |> A remarkably simple implementation of a |ReaderWriterLock with priority |> to writers. |> |> Revision Changes Path |> 1.1 |> |jakarta-log4j/src/java/org/apache/log4j/helpers/ReaderWrite |rLock.java |> |> Index: ReaderWriterLock.java |> |=================================================================== |> /* |> * |> |=========================================================== |================= |> * The Apache Software License, Version 1.1 |> * |> |=========================================================== |================= |> * |> * Copyright (C) 1999 The Apache Software |Foundation. All rights |> reserved. |> * |> * Redistribution and use in source and binary forms, |with or without |> modifica- |> * tion, are permitted provided that the following |conditions are met: |> * |> * 1. Redistributions of source code must retain the above |> copyright notice, |> * this list of conditions and the following disclaimer. |> * |> * 2. Redistributions in binary form must reproduce |the above copyright |> notice, |> * this list of conditions and the following |disclaimer in the |> documentation |> * and/or other materials provided with the distribution. |> * |> * 3. The end-user documentation included with the |redistribution, if |> any, must |> * include the following acknowledgment: "This product |> includes software |> * developed by the Apache Software |> Foundation (http://www.apache.org/)." |> * Alternately, this acknowledgment may appear in |the software |> itself, if |> * and wherever such third-party acknowledgments |normally appear. |> * |> * 4. The names "log4j" and "Apache Software |Foundation" must not be |> used to |> * endorse or promote products derived from this | software |> without prior |> * written permission. For written permission, |please contact |> * [EMAIL PROTECTED] |> * |> * 5. Products derived from this software may not be |called "Apache", |> nor may |> * "Apache" appear in their name, without prior written |> permission of the |> * Apache Software Foundation. |> * |> * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY |EXPRESSED OR IMPLIED |> WARRANTIES, |> * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |> MERCHANTABILITY AND |> * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | IN NO EVENT |> SHALL THE |> * APACHE SOFTWARE FOUNDATION OR ITS CONTRIBUTORS |BE LIABLE FOR ANY |> DIRECT, |> * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |CONSEQUENTIAL DAMAGES |> (INCLU- |> * DING, BUT NOT LIMITED TO, PROCUREMENT OF |SUBSTITUTE GOODS OR |> SERVICES; LOSS |> * OF USE, DATA, OR PROFITS; OR BUSINESS |INTERRUPTION) HOWEVER |> CAUSED AND ON |> * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |> LIABILITY, OR TORT |> * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |ANY WAY OUT OF |> THE USE OF |> * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY |OF SUCH DAMAGE. |> * |> * This software consists of voluntary contributions |made by many |> individuals |> * on behalf of the Apache Software Foundation. For |> more information on the |> * Apache Software Foundation, please see |<http://www.apache.org/>. |> * |> */ |> package org.apache.log4j.helpers; |> |> /** |> * |> * A RederWriterLock allows multiple readers to obtain |the lock at the |> same time |> * but allows only one writer at a time. |> * |> * Priority is given to waiting writers |> * |> * @author Ceki Gülcü |> * |> */ |> public class ReaderWriterLock { |> |> int readers = 0; |> int writers = 0; |> int waitingWriters = 0; |> |> public synchronized void getReadLock() { |> while(writers > 0 || waitingWriters > 0) { |> try {wait();} catch (InterruptedException ie) {} |> } |> readers++; |> } |> |> public synchronized void releaseReadLock() { |> readers --; |> if(waitingWriters >0) |> notifyAll(); |> } |> |> public synchronized void getWriteLock() { |> waitingWriters++; |> while(readers > 0 || writers > 0) { |> try {wait();} catch (InterruptedException ie) {} |> } |> waitingWriters--; |> writers++; |> } |> |> public synchronized void releaseWriteLock() { |> writers--; |> notifyAll(); |> } |> |> } |> |> |> |> 1.32 +9 -1 jakarta-log4j/tests/build.xml |> |> Index: build.xml |> |=================================================================== |> RCS file: /home/cvs/jakarta-log4j/tests/build.xml,v |> retrieving revision 1.31 |> retrieving revision 1.32 |> diff -u -r1.31 -r1.32 |> --- build.xml 23 May 2003 14:15:05 -0000 1.31 |> +++ build.xml 24 May 2003 21:04:00 -0000 1.32 |> @@ -409,7 +409,15 @@ |> <!-- ========================= Very long Tests |> ======================= --> |> <!-- |> |=========================================================== |====== --> |> |> - <!-- none yet, but StressCategory is a good candidate... --> |> + |> + <target name="ReaderWriterLock" depends="build, |cleanOutputDir"> |> + <junit printsummary="yes" fork="no" haltonfailure="yes"> |> + <classpath refid="tests.classpath"/> |> + <formatter type="plain" usefile="false"/> |> + <test |name="org.apache.log4j.helpers.ReaderWriterLockTestCase" /> |> + </junit> |> + </target> |> + |> |> </project> |> |> |> |> |> 1.1 |> |jakarta-log4j/tests/src/java/org/apache/log4j/helpers/Reade |rWriterLockTestCase.java |> |> Index: ReaderWriterLockTestCase.java |> |=================================================================== |> /* |> * |> |=========================================================== |================= |> * The Apache Software License, Version 1.1 |> * |> |=========================================================== |================= |> * |> * Copyright (C) 1999 The Apache Software |Foundation. All rights |> reserved. |> * |> * Redistribution and use in source and binary forms, |with or without |> modifica- |> * tion, are permitted provided that the following |conditions are met: |> * |> * 1. Redistributions of source code must retain the above |> copyright notice, |> * this list of conditions and the following disclaimer. |> * |> * 2. Redistributions in binary form must reproduce |the above copyright |> notice, |> * this list of conditions and the following |disclaimer in the |> documentation |> * and/or other materials provided with the distribution. |> * |> * 3. The end-user documentation included with the |redistribution, if |> any, must |> * include the following acknowledgment: "This product |> includes software |> * developed by the Apache Software |> Foundation (http://www.apache.org/)." |> * Alternately, this acknowledgment may appear in |the software |> itself, if |> * and wherever such third-party acknowledgments |normally appear. |> * |> * 4. The names "log4j" and "Apache Software |Foundation" must not be |> used to |> * endorse or promote products derived from this | software |> without prior |> * written permission. For written permission, |please contact |> * [EMAIL PROTECTED] |> * |> * 5. Products derived from this software may not be |called "Apache", |> nor may |> * "Apache" appear in their name, without prior written |> permission of the |> * Apache Software Foundation. |> * |> * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY |EXPRESSED OR IMPLIED |> WARRANTIES, |> * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |> MERCHANTABILITY AND |> * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | IN NO EVENT |> SHALL THE |> * APACHE SOFTWARE FOUNDATION OR ITS CONTRIBUTORS |BE LIABLE FOR ANY |> DIRECT, |> * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |CONSEQUENTIAL DAMAGES |> (INCLU- |> * DING, BUT NOT LIMITED TO, PROCUREMENT OF |SUBSTITUTE GOODS OR |> SERVICES; LOSS |> * OF USE, DATA, OR PROFITS; OR BUSINESS |INTERRUPTION) HOWEVER |> CAUSED AND ON |> * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |> LIABILITY, OR TORT |> * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |ANY WAY OUT OF |> THE USE OF |> * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY |OF SUCH DAMAGE. |> * |> * This software consists of voluntary contributions |made by many |> individuals |> * on behalf of the Apache Software Foundation. For |> more information on the |> * Apache Software Foundation, please see |<http://www.apache.org/>. |> * |> */ |> |> package org.apache.log4j.helpers; |> |> import junit.framework.Test; |> import junit.framework.TestCase; |> import junit.framework.TestSuite; |> |> import org.apache.log4j.ConsoleAppender; |> import org.apache.log4j.LogManager; |> import org.apache.log4j.Logger; |> import org.apache.log4j.PatternLayout; |> |> |> /** |> * @author Ceki |> * |> * To change the template for this generated type comment go to |> * Window>Preferences>Java>Code Generation>Code and Comments |> */ |> public class ReaderWriterLockTestCase extends TestCase { |> double value1 = 0; |> double value2 = 0; |> ReaderWriterLock lock = new ReaderWriterLock(); |> |> /** |> * Constructor for ReaderWriterLockTestCasae. |> * @param arg0 |> */ |> public ReaderWriterLockTestCase(String arg0) { |> super(arg0); |> } |> |> protected void setUp() throws Exception { |> System.out.println("====================="); |> Logger root = Logger.getRootLogger(); |> root.addAppender(new ConsoleAppender(new |PatternLayout("%4r [%t] - |> %m%n"))); |> } |> |> protected void tearDown() throws Exception { |> System.out.println("------------------------"); |> LogManager.shutdown(); |> } |> |> public void test1() { |> int maxReaders = 3; |> int maxWriters = 2; |> Thread[] threads = new Thread[maxReaders + maxWriters]; |> |> for (int i = 0; i < maxReaders; i++) { |> threads[i] = new ReaderThread(i); |> } |> |> for (int i = 0; i < maxWriters; i++) { |> threads[maxReaders + i] = new WriterThread(i); |> } |> |> for (int i = 0; i < (maxWriters + maxReaders); i++) { |> threads[i].start(); |> } |> |> for (int i = 0; i < (maxWriters + maxReaders); i++) { |> try { |> threads[i].join(); |> } catch (InterruptedException e) { |> } |> } |> } |> |> public static Test suite() { |> TestSuite suite = new TestSuite(); |> suite.addTest(new ReaderWriterLockTestCase("test1")); |> |> return suite; |> } |> |> class ReaderThread extends Thread { |> ReaderThread(int i) { |> super("Reader-" + i); |> } |> |> public void run() { |> Logger root = Logger.getRootLogger(); |> root.debug("In run()"); |> |> for (int l = 0; l < 150; l++) { |> root.debug("Asking for read lock."); |> lock.getReadLock(); |> root.debug("Got read lock."); |> root.debug("Value1 is " + value1); |> root.debug("Value2 is " + value2); |> try {sleep(10);} catch (InterruptedException e) {} |> root.debug("About to release read lock."); |> lock.releaseReadLock(); |> } |> } |> } |> |> class WriterThread extends Thread { |> WriterThread(int i) { |> super("WRITER-" + i); |> } |> |> public void run() { |> Logger root = Logger.getRootLogger(); |> root.debug("In run()"); |> |> for (int l = 0; l < 50; l++) { |> try {sleep(30);} catch (InterruptedException e) {} |> root.debug("Asking for write lock."); |> lock.getWriteLock(); |> root.debug("Got write lock."); |> root.debug("About to increment values."); |> value1 += 1; |> value2 += 10; |> try {sleep(10);} catch (InterruptedException e) {} |> root.debug("About to release write lock."); |> lock.releaseWriteLock(); |> |> } |> } |> } |> } |> |> |> |> |>---------------------------------------------------------- |----------- |>To unsubscribe, e-mail: [EMAIL PROTECTED] |>For additional commands, e-mail: [EMAIL PROTECTED] | |-- |Ceki For log4j documentation consider "The complete log4j manual" | ISBN: 2970036908 http://www.qos.ch/shop/products/clm_t.jsp | | |----------------------------------------------------------- |---------- |To unsubscribe, e-mail: [EMAIL PROTECTED] |For additional commands, e-mail: [EMAIL PROTECTED] |
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Ceki For log4j documentation consider "The complete log4j manual"
ISBN: 2970036908 http://www.qos.ch/shop/products/clm_t.jsp
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