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
