/**
* Redistribution and use of this software and associated documentation
* ("Software"), with or without modification, are permitted provided
* that the following conditions are met:
*
* 1. Redistributions of source code must retain copyright
* statements and notices. Redistributions must also contain a
* copy of this document.
*
* 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 name "Exolab" must not be used to endorse or promote
* products derived from this Software without prior written
* permission of Exoffice Technologies. For written permission,
* please contact info@exolab.org.
*
* 4. Products derived from this Software may not be called "Exolab"
* nor may "Exolab" appear in their names without prior written
* permission of Exoffice Technologies. Exolab is a registered
* trademark of Exoffice Technologies.
*
* 5. Due credit should be given to the Exolab Project
* (http://www.exolab.org/).
*
* THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
* ``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
* EXOFFICE TECHNOLOGIES OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, 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.
*
* Copyright 2005 (C) Exoffice Technologies Inc. All Rights Reserved.
*
* $Id: SessionConsumer.java,v 1.4 2007/01/24 12:00:28 tanderson Exp $
*/
package org.exolab.jms.server;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.exolab.jms.client.JmsMessageListener;
import org.exolab.jms.message.MessageImpl;
import org.exolab.jms.messagemgr.Condition;
import org.exolab.jms.messagemgr.ConsumerEndpoint;
import org.exolab.jms.messagemgr.ConsumerEndpointListener;
import org.exolab.jms.messagemgr.Flag;
import org.exolab.jms.messagemgr.MessageHandle;
import org.exolab.jms.messagemgr.QueueBrowserEndpoint;
import org.exolab.jms.messagemgr.TimedCondition;
import org.exolab.jms.persistence.DatabaseService;
import org.exolab.jms.persistence.PersistenceException;
import org.exolab.jms.scheduler.Scheduler;
import org.exolab.jms.scheduler.SerialTask;
import javax.jms.JMSException;
import java.rmi.RemoteException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
/**
* Manages all consumers for a session.
*
* @author <a href="mailto:tma@netspace.net.au">Tim Anderson</a>
* @version $Revision: 1.4 $ $Date: 2007/01/24 12:00:28 $
*/
class SessionConsumer implements ConsumerEndpointListener {
/**
* The message listener is the reference to a remote client that will
* receive the messages.
*/
private JmsMessageListener _listener;
/**
* Maintain a set of ConsumerEndpoint instances, keyed on id.
*/
private final HashMap _consumers = new HashMap();
/**
* Caches all sent messages.
*/
private final SentMessageCache _sent;
/**
* The database service.
*/
private final DatabaseService _database;
/**
* The set of consumer endpoints with messages pending.
*/
private final LinkedList _pending = new LinkedList();
/**
* Determines if the sender is stopping/stopped.
*/
private Flag _stop = new Flag(true);
/**
* Stop/start lock.
*/
private final Object _restartLock = new Object();
/**
* The active consumer lock.
*/
private final Object _removeLock = new Object();
/**
* The consumer currently being dispatched to.
*/
private long _consumerId = -1;
/**
* The maximum number of messages that a dispatch can deliver at any one
* time
*/
private final int MAX_MESSAGES = 200;
/**
* The logger.
*/
private static final Log _log = LogFactory.getLog(SessionConsumer.class);
private final SerialTask _runner;
/**
* Construct a new <code>SessionConsumer</code>.
*
* @param ackMode the message acknowledgement mode, or
* <code>Session.TRANSACTED_SESSION</code>
* if the session is transactional
* @param database the database service
* @param scheduler the scheduler
*/
public SessionConsumer(int ackMode, DatabaseService database,
Scheduler scheduler) {
_database = database;
_sent = new SentMessageCache(ackMode);
Runnable task = new Runnable() {
public void run() {
dispatch();
}
};
_runner = new SerialTask(task, scheduler);
}
/**
* Set the listener for this session.
* <p/>
* The listener is notified whenever a message for the session is present.
*
* @param listener the message listener
*/
public synchronized void setMessageListener(JmsMessageListener listener) {
_listener = listener;
}
/**
* Register a consumer.
*
* @param consumer the consumer to add
*/
public synchronized void addConsumer(ConsumerEndpoint consumer) {
final long id = consumer.getId();
_consumers.put(new Long(id), consumer);
consumer.setListener(this);
}
/**
* Deregister a consumer.
*
* @param consumerId the consumer identifier
* @return the consumer
* @throws JMSException if the consumer can't be removed
*/
public ConsumerEndpoint removeConsumer(long consumerId)
throws JMSException {
ConsumerEndpoint consumer;
synchronized (_removeLock) {
while (consumerId == _consumerId) {
try {
_removeLock.wait();
} catch (InterruptedException ignore) {
// do nothing
}
}
synchronized (this) {
consumer = (ConsumerEndpoint) _consumers.remove(
new Long(consumerId));
if (consumer == null) {
throw new JMSException("No consumer with id=" + consumerId);
}
consumer.setListener(null);
}
synchronized (_pending) {
_pending.remove(consumer);
}
}
return consumer;
}
/**
* Returns the consumers.
*
* @return the consumers
*/
public synchronized ConsumerEndpoint[] getConsumers() {
return (ConsumerEndpoint[]) _consumers.values()
.toArray(new ConsumerEndpoint[0]);
}
/**
* Enable or disable asynchronous message delivery for a consumer.
*
* @param consumerId the consumer identifier
* @param enable <code>true</code> to enable; <code>false</code> to
* disable
* @throws JMSException for any JMS error
*/
public void setAsynchronous(long consumerId, boolean enable)
throws JMSException {
ConsumerEndpoint consumer = getConsumer(consumerId);
consumer.setAsynchronous(enable);
if (enable && consumer.getMessageCount() != 0) {
messageAvailable(consumer);
}
}
/**
* Stop message delivery.
*/
public void stop() {
synchronized (_restartLock) {
_stop.set(true);
_runner.stop();
_log.debug("stopped delivery");
}
}
/**
* Start message delivery.
*/
public void start() throws JMSException {
synchronized (_restartLock) {
_log.debug("start");
_stop.set(false);
for (Iterator i = _consumers.values().iterator(); i.hasNext();) {
ConsumerEndpoint consumer = (ConsumerEndpoint) i.next();
if (needsScheduling(consumer)) {
queue(consumer);
}
}
try {
_runner.schedule();
} catch (InterruptedException exception) {
_log.error("Failed to start worker", exception);
throw new JMSException("Failed to start worker: " + exception);
}
}
}
/**
* Recover the session.
* <p/>
* This will cause all unacknowledged messages to be redelivered.
*
* @throws JMSException if the session can't be recovered
*/
public synchronized void recover() throws JMSException {
stop(); // stop message delivery
try {
_database.begin();
_sent.clear(); // clear the messages in the sent message cache
_database.commit();
} catch (Exception exception) {
rethrow(exception.getMessage(), exception);
}
start(); // restart message delivery
}
/**
* Commit the sesion.
* <p/>
* This will acknowledge all sent messages for all consumers.
*
* @throws JMSException if the session fails to commit
*/
public synchronized void commit() throws JMSException {
try {
_database.begin();
_sent.acknowledgeAll();
_database.commit();
} catch (OutOfMemoryError exception) {
rethrow("Failed to commit session due to out-of-memory error",
exception);
} catch (Exception exception) {
rethrow(exception.getMessage(), exception);
}
}
/**
* Rollback the session.
* <p/>
* This will cause all unacknowledged messages to be redelivered.
*
* @throws JMSException for any error
*/
public synchronized void rollback() throws JMSException {
stop(); // stop message delivery
try {
_database.begin();
_sent.clear(); // clear the messages in the sent message cache
_database.commit();
} catch (Exception exception) {
rethrow(exception.getMessage(), exception);
}
start(); // restart message delivery
}
/**
* Return the next available mesage to the specified consumer.
* <p/>
* This method is non-blocking. If no messages are available, it will return
* immediately.
*
* @param consumerId the consumer identifier
* @return the next message or <code>null</code> if none is available
* @throws JMSException for any JMS error
*/
public MessageImpl receiveNoWait(long consumerId) throws JMSException {
MessageImpl result = null;
if (!_stop.get()) {
result = doReceive(consumerId, null);
}
return result;
}
/**
* Return the next available message to the specified consumer.
* <p/>
* This method is non-blocking. However, clients can specify a
* <code>wait</code> interval to indicate how long they are prepared to wait
* for a message. If no message is available, and the client indicates that
* it will wait, it will be notified via the registered {@link
* JmsMessageListener} if one subsequently becomes available.
*
* @param consumerId the consumer identifier
* @param wait number of milliseconds to wait. A value of <code>0
* </code> indicates to wait indefinitely
* @return the next message or <code>null</code> if none is available
* @throws JMSException for any JMS error
*/
public MessageImpl receive(long consumerId, long wait) throws JMSException {
MessageImpl result = null;
Condition condition;
if (wait > 0) {
condition = TimedCondition.before(wait);
} else {
condition = new Flag(true);
}
if (!_stop.get()) {
result = doReceive(consumerId, condition);
} else {
ConsumerEndpoint consumer = getConsumer(consumerId);
consumer.setWaitingForMessage(condition);
}
return result;
}
/**
* Browse up to count messages.
*
* @param consumerId the consumer identifier
* @param count the maximum number of messages to receive
* @return a list of {@link MessageImpl} instances
* @throws JMSException for any JMS error
*/
public List browse(long consumerId, int count) throws JMSException {
ConsumerEndpoint consumer = getConsumer(consumerId);
if (!(consumer instanceof QueueBrowserEndpoint)) {
throw new JMSException("Can't browse messages: invalid consumer");
}
List messages = new ArrayList(count);
try {
_database.begin();
for (int i = 0; i < count && !_stop.get();) {
MessageHandle handle = consumer.receive(_stop);
if (handle == null) {
break;
}
MessageImpl orig = handle.getMessage();
if (orig != null) {
messages.add(copy(orig, handle));
++i;
}
}
_database.commit();
} catch (Exception exception) {
rethrow("Failed to browse messages", exception);
}
return messages;
}
/**
* Acknowledge that a message has been processed.
*
* @param consumerId the identity of the consumer performing the ack
* @param messageId the message identifier
* @throws JMSException for any error
*/
public synchronized void acknowledge(long consumerId, String messageId)
throws JMSException {
try {
_database.begin();
_sent.acknowledge(messageId, consumerId);
_database.commit();
} catch (Exception exception) {
rethrow("Failed to acknowledge message", exception);
}
}
/**
* Close the consumer.
*
* @throws JMSException for any eror
*/
public synchronized void close() throws JMSException {
_log.debug("close");
stop();
_listener = null;
try {
_database.begin();
_sent.clear();
_database.commit();
} catch (Exception exception) {
rethrow(exception.getMessage(), exception);
}
}
/**
* Notifies that a message is available for a particular consumer.
*
* @param consumer the consumer
*/
public void messageAvailable(ConsumerEndpoint consumer) {
if (queue(consumer)) {
try {
_runner.schedule();
} catch (InterruptedException exception) {
_log.error("Failed to schedule worker", exception);
}
}
}
/**
* Send messages to the client.
*/
private void dispatch() {
final Condition timeout = TimedCondition.after(30 * 1000);
Condition done = new Condition() {
public boolean get() {
return _stop.get() || timeout.get();
}
};
_log.debug("dispatch");
int sent = 0;
while (sent < MAX_MESSAGES && !done.get()) {
ConsumerEndpoint consumer;
synchronized (_pending) {
if (!_pending.isEmpty()) {
consumer = (ConsumerEndpoint) _pending.removeFirst();
} else {
break;
}
}
if (wantsMessages(consumer)) {
if (consumer.isAsynchronous()) {
if (send(consumer, done)) {
++sent;
}
if (needsScheduling(consumer)) {
queue(consumer);
}
} else {
notifyMessageAvailable();
}
}
}
boolean empty;
synchronized (_pending) {
empty = _pending.isEmpty();
}
if (!empty && !_stop.get()) {
// reschedule this if needed
try {
_runner.schedule();
} catch (InterruptedException exception) {
_log.error("Failed to reschedule worker", exception);
}
}
_log.debug("dispatch[sent=" + sent + "]");
}
private void notifyMessageAvailable() {
try {
// notify the client sesssion.
_listener.onMessageAvailable();
} catch (RemoteException exception) {
_log.debug("Failed to notify client", exception);
}
}
private boolean queue(ConsumerEndpoint consumer) {
boolean queued = false;
if (!_stop.get()) {
synchronized (_pending) {
if (!_pending.contains(consumer)) {
_pending.add(consumer);
queued = true;
}
}
}
return queued;
}
private boolean send(ConsumerEndpoint consumer, Condition cancel) {
boolean sent = false;
MessageHandle handle = null;
try {
_database.begin();
try {
synchronized (_removeLock) {
_consumerId = consumer.getId();
}
handle = consumer.receive(cancel);
if (handle != null) {
MessageImpl message = handle.getMessage();
if (message != null) {
// send the client a copy.
message = copy(message, handle);
// clear any wait condition
// @todo - possible race condition? Could
// syncbronous client timeout and request again,
// and this trash subsequent wait?
consumer.setWaitingForMessage(null);
_sent.preSend(handle);
_database.commit();
// send the message
sent = send(message);
if (sent) {
_database.begin();
_sent.postSend(handle);
_database.commit();
}
}
} else {
_database.commit();
}
} finally {
synchronized (_removeLock) {
_consumerId = -1;
_removeLock.notify();
}
}
} catch (Exception exception) {
cleanup(exception.getMessage(), exception);
}
if (!sent && handle != null) {
try {
_database.begin();
handle.release();
_database.commit();
} catch (Exception exception) {
cleanup("Failed to release unsent message", exception);
}
}
return sent;
}
/**
* Send the specified message to the client.
*
* @param message the message
* @return <code>true</code> if the message was successfully sent
*/
protected boolean send(MessageImpl message) {
boolean delivered = false;
try {
// send the message to the listener.
delivered = _listener.onMessage(message);
if (_log.isDebugEnabled()) {
_log.debug("send[JMSMessageID=" + message.getMessageId()
+ ", delivered=" + delivered + "]");
}
} catch (RemoteException exception) {
_log.info("Failed to notify client", exception);
}
return delivered;
}
private boolean wantsMessages(ConsumerEndpoint consumer) {
boolean result = false;
if (consumer.isAsynchronous() || consumer.isWaitingForMessage()) {
result = true;
}
return result;
}
private boolean needsScheduling(ConsumerEndpoint consumer) {
boolean result = false;
if (wantsMessages(consumer) && consumer.getMessageCount() != 0) {
result = true;
}
return result;
}
private MessageImpl doReceive(long consumerId, final Condition wait)
throws JMSException {
ConsumerEndpoint consumer = getConsumer(consumerId);
Condition cancel;
if (wait != null) {
cancel = new Condition() {
public boolean get() {
return _stop.get() || !wait.get();
}
};
} else {
cancel = _stop;
}
MessageImpl message = null;
try {
_database.begin();
MessageHandle handle = consumer.receive(cancel);
if (handle != null) {
// retrieve the message and copy it
message = handle.getMessage();
if (message != null) {
message = copy(message, handle);
}
}
if (message == null) {
// no message available. Mark the consumer as (possibly) waiting
// for a message.
consumer.setWaitingForMessage(wait);
} else {
// clear any wait condition
consumer.setWaitingForMessage(null);
// if we have a non-null message then add it to the sent message
// cache. Additionally, if we are part of a global transaction
// then we must also send it to the ResourceManager for recovery.
_sent.preSend(handle);
}
_database.commit();
} catch (Exception exception) {
rethrow(exception.getMessage(), exception);
}
if (_log.isDebugEnabled()) {
if (message != null) {
_log.debug("doReceive(consumerId=" + consumerId +
") -> JMSMesssageID=" + message.getMessageId());
}
}
return message;
}
/**
* Helper to copy a message.
*
* @param message the message to copy
* @param handle the handle the message came from
* @return a copy of the message
* @throws JMSException if the copy fails
*/
private MessageImpl copy(MessageImpl message, MessageHandle handle)
throws JMSException {
MessageImpl result;
try {
result = (MessageImpl) message.clone();
result.setJMSRedelivered(handle.getDelivered());
result.setConsumerId(handle.getConsumerId());
} catch (JMSException exception) {
throw exception;
} catch (CloneNotSupportedException exception) {
_log.error(exception, exception);
throw new JMSException(exception.getMessage());
}
return result;
}
/**
* Returns the consumer endpoint given its identifier.
*
* @param consumerId the consumer identifier
* @return the consumer endpoint corresponding to <code>consumerId</code>
* @throws JMSException if the consumer doesn't exist
*/
private ConsumerEndpoint getConsumer(long consumerId)
throws JMSException {
ConsumerEndpoint consumer
= (ConsumerEndpoint) _consumers.get(new Long(consumerId));
if (consumer == null) {
throw new JMSException("Consumer not registered: " + consumerId);
}
return consumer;
}
/**
* Helper to clean up after a failed call.
*
* @param message the message to log
* @param exception the exception to log
*/
private void cleanup(String message, Throwable exception) {
_log.error(message, exception);
try {
if (_database.isTransacted()) {
_database.rollback();
}
} catch (PersistenceException error) {
_log.warn("Failed to rollback after error", error);
}
}
/**
* Helper to clean up after a failed call, and rethrow.
*
* @param message the message to log
* @param exception the exception
* @throws JMSException the original exception adapted to a
* <code>JMSException</code> if necessary
*/
private void rethrow(String message, Throwable exception)
throws JMSException {
cleanup(message, exception);
if (exception instanceof JMSException) {
throw (JMSException) exception;
}
throw new JMSException(exception.getMessage());
}
}