HADOOP-13466. Add an AutoCloseableLock class. (Chen Liang)
Project: http://git-wip-us.apache.org/repos/asf/hadoop/repo Commit: http://git-wip-us.apache.org/repos/asf/hadoop/commit/331ef251 Tree: http://git-wip-us.apache.org/repos/asf/hadoop/tree/331ef251 Diff: http://git-wip-us.apache.org/repos/asf/hadoop/diff/331ef251 Branch: refs/heads/YARN-2915 Commit: 331ef251527f2cb7f1bfa8e1b745b889e538e8a0 Parents: b8ca84a Author: Arpit Agarwal <a...@apache.org> Authored: Thu Aug 4 12:25:39 2016 -0700 Committer: Arpit Agarwal <a...@apache.org> Committed: Thu Aug 4 12:25:39 2016 -0700 ---------------------------------------------------------------------- .../apache/hadoop/util/AutoCloseableLock.java | 122 +++++++++++++++++++ .../hadoop/util/TestAutoCloseableLock.java | 95 +++++++++++++++ 2 files changed, 217 insertions(+) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/hadoop/blob/331ef251/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/AutoCloseableLock.java ---------------------------------------------------------------------- diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/AutoCloseableLock.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/AutoCloseableLock.java new file mode 100644 index 0000000..2aa8578 --- /dev/null +++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/AutoCloseableLock.java @@ -0,0 +1,122 @@ +/** + * 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.hadoop.util; + +import java.util.concurrent.locks.ReentrantLock; + +/** + * This is a wrap class of a ReentrantLock. Extending AutoCloseable + * interface such that the users can use a try-with-resource syntax. + */ +public class AutoCloseableLock implements AutoCloseable { + + private final ReentrantLock lock; + + /** + * Creates an instance of {@code AutoCloseableLock}, initializes + * the underlying {@code ReentrantLock} object. + */ + public AutoCloseableLock() { + this.lock = new ReentrantLock(); + } + + /** + * A wrapper method that makes a call to {@code lock()} of the underlying + * {@code ReentrantLock} object. + * + * Acquire teh lock it is not held by another thread, then sets + * lock held count to one, then returns immediately. + * + * If the current thread already holds the lock, increase the lock + * help count by one and returns immediately. + * + * If the lock is held by another thread, the current thread is + * suspended until the lock has been acquired by current thread. + * + * @return The {@code ReentrantLock} object itself. This is to + * support try-with-resource syntax. + */ + public AutoCloseableLock acquire() { + lock.lock(); + return this; + } + + /** + * A wrapper method that makes a call to {@code unlock()} of the + * underlying {@code ReentrantLock} object. + * + * Attempts to release the lock. + * + * If the current thread holds the lock, decrements the hold + * count. If the hold count reaches zero, the lock is released. + * + * If the current thread does not hold the lock, then + * {@link IllegalMonitorStateException} is thrown. + */ + public void release() { + lock.unlock(); + } + + /** + * Attempts to release the lock by making a call to {@code release()}. + * + * This is to implement {@code close()} method from {@code AutoCloseable} + * interface. This allows users to user a try-with-resource syntax, where + * the lock can be automatically released. + */ + @Override + public void close() { + release(); + } + + /** + * A wrapper method that makes a call to {@code tryLock()} of + * the underlying {@code ReentrantLock} object. + * + * If the lock is not held by another thread, acquires the lock, set the + * hold count to one and returns {@code true}. + * + * If the current thread already holds the lock, the increment the hold + * count by one and returns {@code true}. + * + * If the lock is held by another thread then the method returns + * immediately with {@code false}. + * + * @return {@code true} if the lock was free and was acquired by the + * current thread, or the lock was already held by the current + * thread; and {@code false} otherwise. + */ + public boolean tryLock() { + return lock.tryLock(); + } + + /** + * A wrapper method that makes a call to {@code isLocked()} of + * the underlying {@code ReentrantLock} object. + * + * Queries if this lock is held by any thread. This method is + * designed for use in monitoring of the system state, + * not for synchronization control. + * + * @return {@code true} if any thread holds this lock and + * {@code false} otherwise + */ + public boolean isLocked() { + return lock.isLocked(); + } +} http://git-wip-us.apache.org/repos/asf/hadoop/blob/331ef251/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestAutoCloseableLock.java ---------------------------------------------------------------------- diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestAutoCloseableLock.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestAutoCloseableLock.java new file mode 100644 index 0000000..cd5447d --- /dev/null +++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestAutoCloseableLock.java @@ -0,0 +1,95 @@ +/** + * 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.hadoop.util; + +import static org.junit.Assert.assertFalse; +import static org.junit.Assert.assertTrue; +import static org.junit.Assert.assertEquals; + +import org.junit.Test; +/** + * A test class for AutoCloseableLock. + */ +public class TestAutoCloseableLock { + + /** + * Test the basic lock and unlock operation. + */ + @Test + public void testLockAcquireRelease() { + AutoCloseableLock lock = new AutoCloseableLock(); + AutoCloseableLock newlock = lock.acquire(); + // Ensure acquire the same lock object. + assertEquals(newlock, lock); + // Ensure it locked now. + assertTrue(lock.isLocked()); + lock.release(); + // Ensure it is unlocked now. + assertFalse(lock.isLocked()); + } + + /** + * Test when lock is acquired, no other thread can + * lock it. + * + * @throws Exception + */ + @Test + public void testMultipleThread() throws Exception { + AutoCloseableLock lock = new AutoCloseableLock(); + lock.acquire(); + assertTrue(lock.isLocked()); + Thread competingThread = new Thread() { + @Override + public void run() { + assertTrue(lock.isLocked()); + assertFalse(lock.tryLock()); + } + }; + competingThread.start(); + competingThread.join(); + assertTrue(lock.isLocked()); + lock.release(); + assertFalse(lock.isLocked()); + } + + /** + * Test the correctness under try-with-resource syntax. + * + * @throws Exception + */ + @Test + public void testTryWithResourceSyntax() throws Exception { + AutoCloseableLock lock = new AutoCloseableLock(); + try(AutoCloseableLock localLock = lock.acquire()) { + assertEquals(localLock, lock); + assertTrue(lock.isLocked()); + Thread competingThread = new Thread() { + @Override + public void run() { + assertTrue(lock.isLocked()); + assertFalse(lock.tryLock()); + } + }; + competingThread.start(); + competingThread.join(); + assertTrue(localLock.isLocked()); + } + assertFalse(lock.isLocked()); + } +} --------------------------------------------------------------------- To unsubscribe, e-mail: common-commits-unsubscr...@hadoop.apache.org For additional commands, e-mail: common-commits-h...@hadoop.apache.org
