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From ppod...@apache.org
Subject svn commit: r1235298 - in /openjpa/trunk/openjpa-lib/src: main/java/org/apache/openjpa/lib/util/ThreadGate.java test/java/org/apache/openjpa/lib/util/TestGate.java
Date Tue, 24 Jan 2012 15:31:36 GMT
Author: ppoddar
Date: Tue Jan 24 15:31:35 2012
New Revision: 1235298

URL: http://svn.apache.org/viewvc?rev=1235298&view=rev
Log:
OPENJPA-2099: Create thread gateto protect Select

Added:
    openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/ThreadGate.java  
(with props)
    openjpa/trunk/openjpa-lib/src/test/java/org/apache/openjpa/lib/util/TestGate.java   (with
props)

Added: openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/ThreadGate.java
URL: http://svn.apache.org/viewvc/openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/ThreadGate.java?rev=1235298&view=auto
==============================================================================
--- openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/ThreadGate.java (added)
+++ openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/ThreadGate.java Tue
Jan 24 15:31:35 2012
@@ -0,0 +1,60 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.    
+ */
+package org.apache.openjpa.lib.util;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * A thread gate that guards on first invocation and remains open after the first invocation.
+ * Used when a structure (such as Select) is constructed and populated first-time in a
+ * thread-safe manner and can be used later with minimal thread synchronization overhead.
+ * 
+ * @author Pinaki Poddar
+ *
+ */
+@SuppressWarnings("serial")
+public class ThreadGate extends ReentrantLock {
+	private AtomicBoolean _once = new AtomicBoolean(false);
+	
+	/**
+	 * Lock the gate only if it has never been locked.
+	 */
+	@Override
+	public void lock() {
+		synchronized (_once) {
+			if (!_once.get()) {
+				super.lock();
+			}
+		}
+	}
+	
+	/**
+	 * Unlock the gate and keep it open for ever.
+	 */
+	@Override
+	public void unlock() {
+		if (_once.compareAndSet(false, true)) {
+			super.unlock();
+			synchronized (_once) {
+				_once.notifyAll();
+			}
+		}
+	}
+}

Propchange: openjpa/trunk/openjpa-lib/src/main/java/org/apache/openjpa/lib/util/ThreadGate.java
------------------------------------------------------------------------------
    svn:eol-style = native

Added: openjpa/trunk/openjpa-lib/src/test/java/org/apache/openjpa/lib/util/TestGate.java
URL: http://svn.apache.org/viewvc/openjpa/trunk/openjpa-lib/src/test/java/org/apache/openjpa/lib/util/TestGate.java?rev=1235298&view=auto
==============================================================================
--- openjpa/trunk/openjpa-lib/src/test/java/org/apache/openjpa/lib/util/TestGate.java (added)
+++ openjpa/trunk/openjpa-lib/src/test/java/org/apache/openjpa/lib/util/TestGate.java Tue
Jan 24 15:31:35 2012
@@ -0,0 +1,152 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.    
+ */
+package org.apache.openjpa.lib.util;
+
+import java.io.PrintStream;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import junit.framework.TestCase;
+
+import org.apache.openjpa.lib.util.ThreadGate;
+
+/**
+ * Tests a thread gate.
+ * 
+ * @author Pinaki Poddar
+ *
+ */
+public class TestGate extends TestCase {
+	public static enum Op {ENTER, EXIT};
+	public static int MAX_THREAD  = 10;
+	public static int THREAD_TIME = 10;
+	private static ExecutorService threadPool = Executors.newCachedThreadPool();
+	
+	public void testAllThreadsBlockUntilFirstAccessIsComplete() throws Exception {
+		final Info info = new Info();
+		final ThreadGate gate = new ThreadGate();
+		final AtomicBoolean first = new AtomicBoolean(true);
+		List<Future<?>> futures = new ArrayList<Future<?>>();
+		for (int i = 0; i < MAX_THREAD; i++) {
+			Runnable r = new Runnable() {
+				@Override
+				public void run() {
+					gate.lock();
+					try {
+						info.enter();
+                        Thread.sleep(first.compareAndSet(true, false) 
+                        		? THREAD_TIME*10 : THREAD_TIME);
+						info.exit();
+					} catch (InterruptedException e) {
+						fail();
+					} finally {
+						gate.unlock();
+					}
+				}
+			};
+			futures.add(threadPool.submit(r));
+		}
+		
+		for (Future<?> f : futures) {
+			try {
+				f.get();
+			} catch (Exception e) {
+				fail();
+			}
+		}
+		assertEquals(2*MAX_THREAD, info.msg.size());
+		Token enter = info.msg.get(0);
+		Token exit  = info.msg.get(1);
+		assertEquals(Op.ENTER, enter.op);
+		assertEquals(Op.EXIT, exit.op);
+		assertSame(enter.thread, exit.thread);
+		
+		for (int i = 2; i < info.msg.size(); i++) {
+			Token token = info.msg.get(i);
+			if (token.op == Op.ENTER) {
+				Token pair = info.find(i+1, token);
+				assertNotNull("No pair for " + token.thread, pair);
+			}
+		}
+	}
+	
+	/**
+	 * Records starting and stopping of threads.
+	 *
+	 */
+	public class Info {
+		List<Token> msg = new ArrayList<Token>();
+		
+		/**
+		 * Record entry of the current thread.
+		 */
+		public void enter() {
+			msg.add(new Token(Thread.currentThread(), Op.ENTER));
+		}
+		
+		/**
+		 * Record exit of the current thread.
+		 */
+		public void exit() {
+			msg.add(new Token(Thread.currentThread(), Op.EXIT));
+		}
+
+		/**
+		 * Find the exit record corresponding to a given entry record.
+		 */
+		
+		public Token find(int start, Token t) {
+			for (int i = start; i < msg.size(); i++) {
+				if (msg.get(i).thread.getName().equals(t.thread.getName()))
+						return msg.get(i);
+			}
+			return null;
+		}
+		
+		public void print(PrintStream out) {
+			for (Token t : msg) {
+				out.println(t);
+			}
+		}
+	}
+	
+	/**
+	 * Info about a thread activity.
+	 */
+	public class Token {
+		final Thread thread;
+		final Op     op;
+		final long   time;
+		
+		public Token(Thread t, Op op) {
+			super();
+			this.thread = t;
+			this.op = op;
+			this.time = System.currentTimeMillis();
+		}
+		
+		public String toString() {
+			return time + " " + op + " " + thread.getName();
+		}
+	}
+}

Propchange: openjpa/trunk/openjpa-lib/src/test/java/org/apache/openjpa/lib/util/TestGate.java
------------------------------------------------------------------------------
    svn:eol-style = native



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