INT-2311

modified implementation of MessageGroupQueue to use interruptible locks

Basically modeled it after LinkedBlockingQueue

changed to use ReadWriteLock

refactored MessageGroupQueue and added tests

changed MessageGroupQueue to use Condition

added messageGroupSize(groupId) method to MessageGroupStore and all the implementations

polishing based on Gary's comments

removed setStoreLock method in favor of additional constructors

polishing tests, decreased timeouts

made peek() thread safe

added logging

spring-integration-core/src/main/java/org/springframework/integration/store/AbstractKeyValueMessageStore.java

@@ -203,6 +203,16 @@ public abstract class AbstractKeyValueMessageStore extends AbstractMessageGroupS
 		return new MessageGroupIterator(idIterator);
 	}
 	
+	public int messageGroupSize(Object groupId) {
+		Object mgm = this.doRetrieve(MESSAGE_GROUP_KEY_PREFIX + groupId);
+		if (mgm != null) {
+			Assert.isInstanceOf(MessageGroupMetadata.class, mgm);
+			MessageGroupMetadata messageGroupMetadata = (MessageGroupMetadata) mgm;
+			return messageGroupMetadata.size();
+		}
+		return 0;
+	}
+	
 	protected abstract Object doRetrieve(Object id);
 	
 	protected abstract void doStore(Object id, Object objectToStore);
@@ -308,5 +318,4 @@ public abstract class AbstractKeyValueMessageStore extends AbstractMessageGroupS
 			throw new UnsupportedOperationException();
 		}
 	}
-
 }

spring-integration-core/src/main/java/org/springframework/integration/store/MessageGroupMetadata.java

@@ -76,6 +76,10 @@ public class MessageGroupMetadata implements Serializable{
 		return this.messageIds.iterator();
 	}
 	
+	public int size(){
+		return this.messageIds.size();
+	}
+	
 	public UUID firstId(){
 		if (this.messageIds.size() > 0){
 			return this.messageIds.iterator().next();

spring-integration-core/src/main/java/org/springframework/integration/store/MessageGroupQueue.java

@@ -21,8 +21,15 @@ import java.util.Collection;
 import java.util.Iterator;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 
 import org.springframework.integration.Message;
+import org.springframework.util.Assert;
 
 /**
  * A {@link BlockingQueue} that is backed by a {@link MessageGroupStore}. Can be used to ensure guaranteed delivery in
@@ -31,159 +38,223 @@ import org.springframework.integration.Message;
  * must be provided, so it needs to be unique but identifiable with a single logical instance of the queue.
  * 
  * @author Dave Syer
+ * @author Oleg Zhurakousky
  * @since 2.0
  * 
  */
 public class MessageGroupQueue extends AbstractQueue<Message<?>> implements BlockingQueue<Message<?>> {
+	
+	private final Log logger = LogFactory.getLog(getClass());
 
-	private static final int DEFAULT_CAPACITY = -1;
+	private static final int DEFAULT_CAPACITY = Integer.MAX_VALUE;
 
 	private final MessageGroupStore messageGroupStore;
 
 	private final Object groupId;
 
 	private final int capacity;
-
-	// This one could be a global semaphore
-	private volatile Object storeLock = new Object();
-
-	// This one only needs to be local
-	private final Object writeLock = new Object();
-
-	// This one only needs to be local
-	private final Object readLock = new Object();
-
+	
+	//This one could be a global semaphore
+	private final Lock storeLock;
+	
+	private final Condition messageStoreNotFull; 
+	
+	private final Condition messageStoreNotEmpty;  
+	
 	public MessageGroupQueue(MessageGroupStore messageGroupStore, Object groupId) {
-		this(messageGroupStore, groupId, DEFAULT_CAPACITY);
+		this(messageGroupStore, groupId, DEFAULT_CAPACITY, new ReentrantLock(true));
 	}
 
 	public MessageGroupQueue(MessageGroupStore messageGroupStore, Object groupId, int capacity) {
+		this(messageGroupStore, groupId, capacity, new ReentrantLock(true));
+	}
+	
+	public MessageGroupQueue(MessageGroupStore messageGroupStore, Object groupId, Lock storeLock) {
+		this(messageGroupStore, groupId, DEFAULT_CAPACITY, storeLock);
+	}
+	
+	public MessageGroupQueue(MessageGroupStore messageGroupStore, Object groupId, int capacity, Lock storeLock) {
+		Assert.isTrue(capacity > 0, "'capacity' must be greater than 0");
+		Assert.notNull(storeLock, "'storeLock' must not be null");
+		Assert.notNull(messageGroupStore, "'messageGroupStore' must not be null");
+		Assert.notNull(groupId, "'groupId' must not be null");
+		this.storeLock = storeLock;
+		this.messageStoreNotFull = this.storeLock.newCondition();
+		this.messageStoreNotEmpty = this.storeLock.newCondition();
 		this.messageGroupStore = messageGroupStore;
 		this.groupId = groupId;
 		this.capacity = capacity;
 	}
-	
-	/**
-	 * @param storeLock the storeLock to set
-	 */
-	public void setStoreLock(Object storeLock) {
-		this.storeLock = storeLock;
-	}
 
 	public Iterator<Message<?>> iterator() {
 		return getMessages().iterator();
 	}
 
 	public int size() {
-		return this.messageGroupStore.getMessageGroup(groupId).size();
-	}
-
-	public boolean offer(Message<?> e) {
-		synchronized (storeLock) {
-			if (capacity>0 && messageGroupStore.getMessageGroup(groupId).size() >= capacity) {
-				return false;
-			}
-			messageGroupStore.addMessageToGroup(groupId, e);
-		}
-		synchronized (readLock) {
-			readLock.notifyAll();
-		}
-		return true;
+		return messageGroupStore.messageGroupSize(groupId);
 	}
 
 	public Message<?> peek() {
-		Collection<Message<?>> messages = getMessages();
-		if (messages.isEmpty()) {
-			return null;
-		}
-		return messages.iterator().next();
-	}
-
-	public Message<?> poll() {
-		Message<?> result = null;
-		synchronized (storeLock) {
-			result = this.messageGroupStore.pollMessageFromGroup(groupId);
-		}
-		synchronized (writeLock) {
-			writeLock.notifyAll();
-		}
-		return result;
-	}
-
-	public int drainTo(Collection<? super Message<?>> c) {
-		synchronized (storeLock) {
-			for (Message<?> message = this.messageGroupStore.pollMessageFromGroup(groupId); message != null;) {
-				c.add(message);	
+		Message<?> message = null;
+		final Lock storeLock = this.storeLock;
+		try {
+			storeLock.lockInterruptibly();
+			try {
+				Collection<Message<?>> messages = getMessages();
+				if (!messages.isEmpty()) {
+					message = messages.iterator().next();
+				}
+			} 
+			finally {
+				storeLock.unlock();
 			}
+		} 
+		catch (InterruptedException e) {
+			Thread.currentThread().interrupt();
 		}
-		synchronized (writeLock) {
-			writeLock.notifyAll();
-		}
-		return this.messageGroupStore.getMessageGroup(groupId).size();
+		return message;
 	}
-
-	public int drainTo(Collection<? super Message<?>> c, int maxElements) {
-		ArrayList<Message<?>> list = new ArrayList<Message<?>>();
-		synchronized (storeLock) {
-			Message<?> message = this.messageGroupStore.pollMessageFromGroup(groupId);
-			for (int i = 0; i < maxElements && message != null; i++) {
-				list.add(message);	
-				message = this.messageGroupStore.pollMessageFromGroup(groupId);
-			}
-		}
-		synchronized (writeLock) {
-			writeLock.notifyAll();
-		}
-		c.addAll(list);
-		return list.size();
-	}
-
-	public boolean offer(Message<?> e, long timeout, TimeUnit unit) throws InterruptedException {
-		long threshold = System.currentTimeMillis() + TimeUnit.MILLISECONDS.convert(timeout, unit);
-		boolean result = offer(e);
-		while (!result && System.currentTimeMillis() < threshold) {
-			synchronized (writeLock) {
-				writeLock.wait(threshold - System.currentTimeMillis());
-			}
-			result = offer(e);
-		}
-		return result;
-	}
-
+	
 	public Message<?> poll(long timeout, TimeUnit unit) throws InterruptedException {
-		Message<?> message = poll();
-		if (message != null) {
-			return message;
-		}
-		long threshold = System.currentTimeMillis() + TimeUnit.MILLISECONDS.convert(timeout, unit);
-		while (message == null && System.currentTimeMillis() < threshold) {
-			synchronized (readLock) {
-				readLock.wait(threshold - System.currentTimeMillis());
+		Message<?> message = null;
+		long timeoutInNanos = unit.toNanos(timeout);
+		final Lock storeLock = this.storeLock;
+		storeLock.lockInterruptibly();
+		
+		try {		
+			while (this.size() == 0 && timeoutInNanos > 0){
+				timeoutInNanos = this.messageStoreNotEmpty.awaitNanos(timeoutInNanos);	
 			}
-			message = poll();
+			message = this.doPoll();
+			
+		} 
+		finally {
+			storeLock.unlock();
 		}
 		return message;
 	}
 
-	public void put(Message<?> e) throws InterruptedException {
-		while (!offer(e)) {
-			synchronized (writeLock) {
-				writeLock.wait();
+	public Message<?> poll() {
+		Message<?> message = null;
+		final Lock storeLock = this.storeLock;
+		try {
+			storeLock.lockInterruptibly();
+			try {
+				message = this.doPoll();
+			} 
+			finally {
+				storeLock.unlock();
 			}
+		} 
+		catch (InterruptedException e) {
+			Thread.currentThread().interrupt();
+		}
+		return message;
+	}
+	
+	public int drainTo(Collection<? super Message<?>> c) {
+		return this.drainTo(c, Integer.MAX_VALUE);
+	}
+
+	public int drainTo(Collection<? super Message<?>> collection, int maxElements) {
+		Assert.notNull(collection, "'collection' must not be null");
+		int originalSize = collection.size();
+		ArrayList<Message<?>> list = new ArrayList<Message<?>>();
+		final Lock storeLock = this.storeLock;
+		try {
+			storeLock.lockInterruptibly();
+			try {		
+				Message<?> message = this.messageGroupStore.pollMessageFromGroup(groupId);
+				for (int i = 0; i < maxElements && message != null; i++) {
+					list.add(message);	
+					message = this.messageGroupStore.pollMessageFromGroup(groupId);
+				}
+				this.messageStoreNotFull.signal();
+			} 
+			finally {
+				storeLock.unlock();
+			}		
+		} 
+		catch (InterruptedException e) {
+			logger.warn("Queue may not have drained completely since this operation was interrupted", e);
+			Thread.currentThread().interrupt();
+		}
+		collection.addAll(list);
+		return collection.size() - originalSize;
+	}
+	
+	public boolean offer(Message<?> message) {
+		boolean offered = true;
+		final Lock storeLock = this.storeLock;	
+		try {
+			storeLock.lockInterruptibly();
+			try {		
+				offered = this.doOffer(message);
+			} 
+			finally {
+				storeLock.unlock();
+			}	
+		} 
+		catch (InterruptedException e) {
+			Thread.currentThread().interrupt();
+		}
+		return offered;
+	}
+
+	public boolean offer(Message<?> message, long timeout, TimeUnit unit) throws InterruptedException {
+		long timeoutInNanos = unit.toNanos(timeout);
+		boolean offered = false;
+		
+		final Lock storeLock = this.storeLock;
+		storeLock.lockInterruptibly();
+		try {
+			while (this.size() == capacity && timeoutInNanos > 0){
+				timeoutInNanos = this.messageStoreNotFull.awaitNanos(timeoutInNanos);	
+			}
+			
+			if (timeoutInNanos > 0){
+				offered = this.doOffer(message);
+			}
+		} 
+		finally {
+			storeLock.unlock();
+		}
+		return offered;	
+	}
+
+	public void put(Message<?> message) throws InterruptedException {
+		final Lock storeLock = this.storeLock;
+		storeLock.lockInterruptibly();
+		try {
+			while (this.size() == capacity){
+				this.messageStoreNotFull.await();			
+			}
+			
+			this.doOffer(message);
+		} 
+		finally {
+			storeLock.unlock();
 		}
 	}
 
 	public int remainingCapacity() {
-		return (capacity>0 ? capacity : Integer.MAX_VALUE) - messageGroupStore.getMessageGroup(groupId).size();
+		return capacity - this.size();
 	}
 
 	public Message<?> take() throws InterruptedException {
-		Message<?> message = poll();
-		while (message == null) {
-			synchronized (readLock) {
-				readLock.wait();
+		Message<?> message = null;
+		final Lock storeLock = this.storeLock;
+		storeLock.lockInterruptibly();
+		
+		try {		
+			while (this.size() == 0){
+				this.messageStoreNotEmpty.await();	
 			}
-			message = poll();
+			message = this.doPoll();
+			
+		} 
+		finally {
+			storeLock.unlock();
 		}
 		return message;
 	}
@@ -192,4 +263,27 @@ public class MessageGroupQueue extends AbstractQueue<Message<?>> implements Bloc
 		return messageGroupStore.getMessageGroup(groupId).getMessages();
 	}
 
+	/**
+	 * It is assumed that the 'storeLock' is being held by the caller, otherwise
+	 * IllegalMonitorStateException may be thrown
+	 */
+	private Message<?> doPoll() {
+		Message<?> message = this.messageGroupStore.pollMessageFromGroup(groupId);
+		this.messageStoreNotFull.signal();
+		return message;
+	}
+	
+	/**
+	 * It is assumed that the 'storeLock' is being held by the caller, otherwise
+	 * IllegalMonitorStateException may be thrown
+	 */
+	private boolean doOffer(Message<?> message){
+		boolean offered = false;
+		if (this.size() < capacity){
+			messageGroupStore.addMessageToGroup(groupId, message);
+			offered = true;
+			this.messageStoreNotEmpty.signal();
+		}
+		return offered;
+	}
 }

spring-integration-core/src/main/java/org/springframework/integration/store/MessageGroupStore.java

@@ -46,6 +46,13 @@ public interface MessageGroupStore {
 	 */
 	@ManagedAttribute
 	int getMessageGroupCount();
+	
+	/**
+	 * Returns the size of this MessageGroup
+	 * @param groupId
+	 */
+	@ManagedAttribute
+	int messageGroupSize(Object groupId);
 
 	/**
 	 * Return all Messages currently in the MessageStore that were stored using

spring-integration-core/src/main/java/org/springframework/integration/store/SimpleMessageStore.java

@@ -202,4 +202,8 @@ public class SimpleMessageStore extends AbstractMessageGroupStore implements Mes
 		}
 		return lock;
 	}
+
+	public int messageGroupSize(Object groupId) {
+		return this.getMessageGroup(groupId).size();
+	}
 }

spring-integration-core/src/test/java/org/springframework/integration/store/MessageStoreTests.java

@@ -16,8 +16,6 @@
 
 package org.springframework.integration.store;
 
-import static org.junit.Assert.assertEquals;
-
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -25,10 +23,13 @@ import java.util.Iterator;
 import java.util.List;
 
 import org.junit.Test;
+
 import org.springframework.integration.Message;
 import org.springframework.integration.message.GenericMessage;
 import org.springframework.test.util.ReflectionTestUtils;
 
+import static org.junit.Assert.assertEquals;
+
 /**
  * @author Dave Syer
  */
@@ -94,18 +95,10 @@ public class MessageStoreTests {
 			return removed ? new SimpleMessageGroup(correlationKey) : testMessages;
 		}
 
-		public MessageGroup markMessageGroup(MessageGroup group) {
-			throw new UnsupportedOperationException();
-		}
-
 		public MessageGroup removeMessageFromGroup(Object key, Message<?> messageToRemove) {
 			throw new UnsupportedOperationException();
 		}
 
-		public MessageGroup markMessageFromGroup(Object key, Message<?> messageToMark) {
-			throw new UnsupportedOperationException();
-		}
-
 		public void removeMessageGroup(Object correlationKey) {
 			if (correlationKey.equals(testMessages.getGroupId())) {
 				removed = true;
@@ -122,10 +115,13 @@ public class MessageStoreTests {
 		}
 
 		public Message<?> pollMessageFromGroup(Object groupId) {
-			// TODO Auto-generated method stub
 			return null;
 		}
 
+		public int messageGroupSize(Object groupId) {
+			return 0;
+		}
+
 	}
 
 }

spring-integration-jdbc/src/main/java/org/springframework/integration/jdbc/JdbcMessageStore.java

@@ -95,7 +95,7 @@ public class JdbcMessageStore extends AbstractMessageGroupStore implements Messa
 
 	private static final String COUNT_ALL_GROUPS = "SELECT COUNT(GROUP_KEY) from %PREFIX%MESSAGE_GROUP where REGION=?";
 
-	private static final String COUNT_ALL_MARKED_MESSAGES_IN_GROUPS = "SELECT COUNT(MESSAGE_ID) from %PREFIX%MESSAGE_GROUP where MARKED=1 AND REGION=?";
+	private static final String COUNT_ALL_MESSAGES_IN_GROUP = "SELECT COUNT(MESSAGE_ID) from %PREFIX%MESSAGE_GROUP where GROUP_KEY=? AND REGION=?";
 
 	private static final String COUNT_ALL_MESSAGES_IN_GROUPS = "SELECT COUNT(MESSAGE_ID) from %PREFIX%MESSAGE_GROUP where REGION=?";
 
@@ -348,8 +348,9 @@ public class JdbcMessageStore extends AbstractMessageGroupStore implements Messa
 	}
 
 	@ManagedAttribute
-	public int getMarkedMessageCountForAllMessageGroups() {
-		return jdbcTemplate.queryForInt(getQuery(COUNT_ALL_MARKED_MESSAGES_IN_GROUPS), region);
+	public int messageGroupSize(Object groupId) {
+		String key = getKey(groupId);
+		return jdbcTemplate.queryForInt(getQuery(COUNT_ALL_MESSAGES_IN_GROUP), key, region);  
 	}
 
 	public MessageGroup getMessageGroup(Object groupId) {
@@ -467,7 +468,6 @@ public class JdbcMessageStore extends AbstractMessageGroupStore implements Messa
 	public Message<?> pollMessageFromGroup(final Object groupId) {
 		String key = getKey(groupId);
 		
-		
 		Message<?> message = jdbcTemplate.query(getQuery(LIST_MESSAGEIDS_BY_GROUP_KEY), new Object[] { key, region },
 				new ResultSetExtractor<Message<?>>() {
 			public Message<?> extractData(ResultSet rs)

spring-integration-jdbc/src/test/java/org/springframework/integration/jdbc/JdbcMessageStoreChannelIntegrationTests-context.xml

@@ -28,7 +28,7 @@
 	<bean id="storeQueue" class="org.springframework.integration.store.MessageGroupQueue">
 		<constructor-arg ref="messageStore" />
 		<constructor-arg value="JdbcMessageStoreChannelIntegrationTests" />
-		<property name="storeLock" ref="lock" />
+		<constructor-arg ref="lock" />
 	</bean>
 
 	<int:channel id="output" />

spring-integration-jdbc/src/test/java/org/springframework/integration/jdbc/LockInterceptor.java

@@ -13,6 +13,8 @@
 
 package org.springframework.integration.jdbc;
 
+import java.util.concurrent.locks.ReentrantLock;
+
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
 
@@ -20,7 +22,9 @@ import org.aopalliance.intercept.MethodInvocation;
  * @author Dave Syer
  *
  */
-public class LockInterceptor implements MethodInterceptor {
+public class LockInterceptor extends ReentrantLock implements MethodInterceptor {
+
+	private static final long serialVersionUID = 1L;
 
 	public synchronized Object invoke(MethodInvocation invocation) throws Throwable {
 		return invocation.proceed();

spring-integration-jdbc/src/test/java/org/springframework/integration/jdbc/MessageGroupQueueTests.java

@@ -0,0 +1,318 @@
+/*
+ * Copyright 2002-2011 the original author or authors.
+ *
+ * Licensed 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.springframework.integration.jdbc;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
+
+import org.junit.Test;
+import org.mockito.Mockito;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
+
+import org.springframework.integration.Message;
+import org.springframework.integration.message.GenericMessage;
+import org.springframework.integration.store.MessageGroup;
+import org.springframework.integration.store.MessageGroupQueue;
+import org.springframework.integration.store.MessageGroupStore;
+import org.springframework.integration.store.SimpleMessageStore;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+/**
+ * @author Oleg Zhurakousky
+ */
+public class MessageGroupQueueTests {
+
+	
+	@Test
+	public void validateMgqInterruption() throws Exception{
+		
+		final MessageGroupQueue queue = new MessageGroupQueue(new SimpleMessageStore(), 1, 1);
+		
+		final AtomicReference<InterruptedException> exceptionHolder = new AtomicReference<InterruptedException>();
+		
+		Thread t = new Thread(new Runnable() {
+			
+			public void run() {
+				queue.offer(new GenericMessage<String>("hello"));
+				try {
+					queue.offer(new GenericMessage<String>("hello"), 100, TimeUnit.SECONDS);
+				} catch (InterruptedException e) {
+					exceptionHolder.set(e);
+				}
+			}
+		});
+		t.start();
+		Thread.sleep(1000);
+		t.interrupt();
+		Thread.sleep(1000);
+		assertTrue(exceptionHolder.get() instanceof InterruptedException);
+	}
+	
+	@Test
+	public void testConcurrentReadWrite() throws Exception{
+		final MessageGroupQueue queue = new MessageGroupQueue(new SimpleMessageStore(), 1, 1);
+		final AtomicReference<Message<?>> messageHolder = new AtomicReference<Message<?>>();
+		
+		Thread t1 = new Thread(new Runnable() {		
+			public void run() {
+				try {
+					messageHolder.set(queue.poll(1000, TimeUnit.SECONDS));
+				} catch (Exception e) {
+					e.printStackTrace();
+				}
+			}
+		});
+		Thread t2 = new Thread(new Runnable() {		
+			public void run() {
+				try {
+					queue.offer(new GenericMessage<String>("hello"), 1000, TimeUnit.SECONDS);
+				} catch (Exception e) {
+					e.printStackTrace();
+				}
+			}
+		});
+		t1.start();
+		t2.start();
+		Thread.sleep(1000);
+		assertTrue(messageHolder.get() instanceof Message);
+	}
+	
+	@Test
+	public void testConcurrentWriteRead() throws Exception{
+		final MessageGroupQueue queue = new MessageGroupQueue(new SimpleMessageStore(), 1, 1);
+		final AtomicReference<Message<?>> messageHolder = new AtomicReference<Message<?>>();
+		
+		queue.offer(new GenericMessage<String>("hello"), 1000, TimeUnit.SECONDS);
+		
+		Thread t1 = new Thread(new Runnable() {		
+			public void run() {
+				try {
+					queue.offer(new GenericMessage<String>("Hi"), 1000, TimeUnit.SECONDS);
+				} catch (Exception e) {
+					e.printStackTrace();
+				}
+			}
+		});
+		Thread t2 = new Thread(new Runnable() {		
+			public void run() {
+				try {
+					queue.poll(1000, TimeUnit.SECONDS);
+					messageHolder.set(queue.poll(1000, TimeUnit.SECONDS));
+				} catch (Exception e) {
+					e.printStackTrace();
+				}
+			}
+		});
+		
+		t1.start();
+		Thread.sleep(1000);
+		t2.start();
+		Thread.sleep(1000);
+		assertTrue(messageHolder.get().getPayload().equals("Hi"));
+	}
+	
+	@Test
+	public void testConcurrentReadersWithTimeout() throws Exception{
+		final MessageGroupQueue queue = new MessageGroupQueue(new SimpleMessageStore(), 1, 1);
+		final AtomicReference<Message<?>> messageHolder1 = new AtomicReference<Message<?>>();
+		final AtomicReference<Message<?>> messageHolder2 = new AtomicReference<Message<?>>();
+		final AtomicReference<Message<?>> messageHolder3 = new AtomicReference<Message<?>>();
+		
+		Thread t1 = new Thread(new Runnable() {		
+			public void run() {
+				try {
+					messageHolder1.set(queue.poll(10, TimeUnit.SECONDS));
+				} catch (Exception e) {
+					e.printStackTrace();
+				}
+			}
+		});
+		Thread t2 = new Thread(new Runnable() {		
+			public void run() {
+				try {
+					messageHolder2.set(queue.poll(10, TimeUnit.SECONDS));
+				} catch (Exception e) {
+					e.printStackTrace();
+				}
+			}
+		});
+		Thread t3 = new Thread(new Runnable() {		
+			public void run() {
+				try {
+					messageHolder3.set(queue.poll(10, TimeUnit.SECONDS));
+				} catch (Exception e) {
+					e.printStackTrace();
+				}
+			}
+		});
+		Thread t4 = new Thread(new Runnable() {		
+			public void run() {
+				try {
+					queue.offer(new GenericMessage<String>("Hi"), 10, TimeUnit.SECONDS);
+				} catch (Exception e) {
+					e.printStackTrace();
+				}
+			}
+		});
+		t1.start();
+		Thread.sleep(1000);
+		t2.start();
+		Thread.sleep(1000);
+		t3.start();
+		Thread.sleep(1000);
+		t4.start();
+		Thread.sleep(1000);
+		assertTrue(messageHolder1.get().getPayload().equals("Hi"));
+		Thread.sleep(4000);
+		assertTrue(messageHolder2.get() == null);
+	}
+	
+	@Test
+	public void testConcurrentWritersWithTimeout() throws Exception{
+		final MessageGroupQueue queue = new MessageGroupQueue(new SimpleMessageStore(), 1, 1);
+		final AtomicReference<Boolean> booleanHolder1 = new AtomicReference<Boolean>(true);
+		final AtomicReference<Boolean> booleanHolder2 = new AtomicReference<Boolean>(true);
+		final AtomicReference<Boolean> booleanHolder3 = new AtomicReference<Boolean>(true);
+		
+		Thread t1 = new Thread(new Runnable() {		
+			public void run() {
+				try {
+					booleanHolder1.set(queue.offer(new GenericMessage<String>("Hi-1"), 2, TimeUnit.SECONDS));
+				} catch (Exception e) {
+					e.printStackTrace();
+				}
+			}
+		});
+		Thread t2 = new Thread(new Runnable() {		
+			public void run() {
+				try {
+					boolean offered = queue.offer(new GenericMessage<String>("Hi-2"), 2, TimeUnit.SECONDS);
+					System.out.println(offered);
+					booleanHolder2.set(offered);
+				} catch (Exception e) {
+					e.printStackTrace();
+				}
+			}
+		});
+		Thread t3 = new Thread(new Runnable() {		
+			public void run() {
+				try {
+					boolean offered = queue.offer(new GenericMessage<String>("Hi-3"), 2, TimeUnit.SECONDS);
+					System.out.println(offered);
+					booleanHolder3.set(offered);
+				} catch (Exception e) {
+					e.printStackTrace();
+				}
+			}
+		});
+		t1.start();
+		Thread.sleep(1000);
+		t2.start();
+		Thread.sleep(100);
+		t3.start();
+		Thread.sleep(4000);
+		assertTrue(booleanHolder1.get());
+		assertFalse(booleanHolder2.get());
+		assertFalse(booleanHolder3.get());
+	}
+	@Test
+    public void testConcurrentWriteReadMulti() throws Exception{
+            final MessageGroupQueue queue = new MessageGroupQueue(new SimpleMessageStore(), 1, 4);
+            final AtomicReference<Message<?>> messageHolder = new AtomicReference<Message<?>>();
+            
+            queue.offer(new GenericMessage<String>("hello"), 1000, TimeUnit.SECONDS);
+            
+            Thread t1 = new Thread(new Runnable() {                
+                    public void run() {
+                            try {
+                                    queue.offer(new GenericMessage<String>("Hi"), 1000, TimeUnit.SECONDS);
+                                    queue.offer(new GenericMessage<String>("Hi"), 1000, TimeUnit.SECONDS);
+                                    queue.offer(new GenericMessage<String>("Hi"), 1000, TimeUnit.SECONDS);
+                            } catch (Exception e) {
+                                    e.printStackTrace();
+                            }
+                    }
+            });
+            Thread t2 = new Thread(new Runnable() {                
+                    public void run() {
+                            try {
+                                    queue.poll(1000, TimeUnit.SECONDS);
+                                    messageHolder.set(queue.poll(1000, TimeUnit.SECONDS));
+                                    queue.poll(1000, TimeUnit.SECONDS);
+                                    queue.poll(1000, TimeUnit.SECONDS);
+                            } catch (Exception e) {
+                                    e.printStackTrace();
+                            }
+                    }
+            });
+            
+            t1.start();
+            Thread.sleep(1000);
+            t2.start();
+            Thread.sleep(1000);
+            assertTrue(messageHolder.get().getPayload().equals("Hi"));
+            assertNull(queue.poll(5, TimeUnit.SECONDS));
+    }
+	
+	@Test
+    public void validateMgqInterruptionStoreLock() throws Exception{
+            
+            MessageGroupStore mgs = Mockito.mock(MessageGroupStore.class);
+            Mockito.doAnswer(new Answer<MessageGroup>() {
+                    public MessageGroup answer(InvocationOnMock invocation)
+                                    throws Throwable {
+                            Thread.sleep(5000);
+                            return null;
+                    }
+            }).when(mgs).addMessageToGroup(Mockito.any(Integer.class), Mockito.any(Message.class));
+            
+            MessageGroup mg = Mockito.mock(MessageGroup.class);
+            Mockito.when(mgs.getMessageGroup(Mockito.any())).thenReturn(mg);
+            Mockito.when(mg.size()).thenReturn(0);
+            
+            final MessageGroupQueue queue = new MessageGroupQueue(mgs, 1, 1);
+            
+            final AtomicReference<InterruptedException> exceptionHolder = new AtomicReference<InterruptedException>();
+            
+            Thread t1 = new Thread(new Runnable() {
+                    
+                    public void run() {
+                            queue.offer(new GenericMessage<String>("hello"));
+                    }
+            });
+            t1.start();
+            Thread.sleep(500);
+            Thread t2 = new Thread(new Runnable() {
+                    
+                    public void run() {
+                            queue.offer(new GenericMessage<String>("hello"));
+                            try {
+                                    queue.offer(new GenericMessage<String>("hello"), 100, TimeUnit.SECONDS);
+                            } catch (InterruptedException e) {
+                                    exceptionHolder.set(e);
+                            }
+                    }
+            });
+            t2.start();
+            Thread.sleep(1000);
+            t2.interrupt();
+            Thread.sleep(1000);
+            assertTrue(exceptionHolder.get() instanceof InterruptedException);
+    }
+}

spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/store/MongoDbMessageStore.java

@@ -245,6 +245,12 @@ public class MongoDbMessageStore extends AbstractMessageGroupStore implements Me
 		this.updateGroup(groupId);
 		return message;
 	}
+	
+	public int messageGroupSize(Object groupId) {
+		long lCount = this.template.count(new Query(where(GROUP_ID_KEY).is(groupId)), this.collectionName);
+		Assert.isTrue(lCount <= Integer.MAX_VALUE, "Message count is out of Integer's range");
+		return (int) lCount;
+	}
 
 	/*
 	 * Common Queries

spring-integration-mongodb/src/test/java/org/springframework/integration/mongodb/store/MongoDbMessageGroupStoreTests.java

@@ -75,6 +75,19 @@ public class MongoDbMessageGroupStoreTests extends MongoDbAvailableTests {
 		assertNull(retrievedMessage.getHeaders().get("message_group"));
 	}
 	
+	@Test
+	@MongoDbAvailable
+	public void testCountMessagesInGroup() throws Exception{	
+		MongoDbFactory mongoDbFactory = this.prepareMongoFactory();
+		MongoDbMessageStore store = new MongoDbMessageStore(mongoDbFactory);
+		
+		Message<?> messageA = new GenericMessage<String>("A");
+		Message<?> messageB = new GenericMessage<String>("B");
+		store.addMessageToGroup(1, messageA);
+		store.addMessageToGroup(1, messageB);
+		assertEquals(2, store.messageGroupSize(1));
+	}
+	
 	@Test
 	@MongoDbAvailable
 	public void testMessageGroupUpdatedDateChangesWithEachAddedMessage() throws Exception{