/*
* 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.
*/
using System;
using System.Text;
using System.Threading;
using Apache.NMS.Util;
using ZSendRecvOpt = ZMQ.SendRecvOpt;
using ZSocket = ZMQ.Socket;
using ZSocketType = ZMQ.SocketType;
namespace Apache.NMS.ZMQ
{
///
/// An object capable of receiving messages from some destination
///
public class MessageConsumer : IMessageConsumer
{
protected TimeSpan zeroTimeout = new TimeSpan(0);
private readonly Session session;
private readonly AcknowledgementMode acknowledgementMode;
///
/// Socket object
///
private ZSocket messageSubscriber = null;
///
/// Context binding string
///
private string contextBinding;
private Queue destination;
private event MessageListener listener;
private int listenerCount = 0;
private Thread asyncDeliveryThread = null;
private AutoResetEvent pause = new AutoResetEvent(false);
private Atomic asyncDelivery = new Atomic(false);
private ConsumerTransformerDelegate consumerTransformer;
public ConsumerTransformerDelegate ConsumerTransformer
{
get { return this.consumerTransformer; }
set { this.consumerTransformer = value; }
}
public MessageConsumer(Session session, AcknowledgementMode acknowledgementMode, IDestination destination, string selector)
{
if(null == Connection.Context)
{
throw new NMSConnectionException();
}
this.session = session;
this.acknowledgementMode = acknowledgementMode;
this.messageSubscriber = Connection.Context.Socket(ZSocketType.SUB);
if(null == this.messageSubscriber)
{
throw new ResourceAllocationException();
}
string clientId = session.Connection.ClientId;
this.contextBinding = session.Connection.BrokerUri.LocalPath;
this.destination = new Queue(this.contextBinding);
if(!string.IsNullOrEmpty(clientId))
{
this.messageSubscriber.StringToIdentity(clientId, Encoding.Unicode);
}
this.messageSubscriber.Connect(contextBinding);
this.messageSubscriber.Subscribe(selector ?? string.Empty, Encoding.ASCII);
}
public event MessageListener Listener
{
add
{
listener += value;
listenerCount++;
StartAsyncDelivery();
}
remove
{
if(listenerCount > 0)
{
listener -= value;
listenerCount--;
}
if(0 == listenerCount)
{
StopAsyncDelivery();
}
}
}
///
/// Receive message from subscriber
///
///
/// message interface
///
public IMessage Receive()
{
// TODO: Support decoding of all message types + all meta data (e.g., headers and properties)
return ToNmsMessage(messageSubscriber.Recv(Encoding.ASCII, ZSendRecvOpt.NONE));
}
///
/// Receive message from subscriber
///
///
/// message interface
///
public IMessage Receive(TimeSpan timeout)
{
// TODO: Support decoding of all message types + all meta data (e.g., headers and properties)
return ToNmsMessage(messageSubscriber.Recv(Encoding.ASCII, timeout.Milliseconds));
}
///
/// Receive message from subscriber
///
///
/// message interface
///
public IMessage ReceiveNoWait()
{
return Receive(zeroTimeout);
}
///
/// Clean up
///
public void Dispose()
{
Close();
}
///
/// Clean up
///
public void Close()
{
StopAsyncDelivery();
if(null != messageSubscriber)
{
messageSubscriber.Dispose();
messageSubscriber = null;
}
}
protected virtual void StopAsyncDelivery()
{
if(asyncDelivery.CompareAndSet(true, false))
{
if(null != asyncDeliveryThread)
{
Tracer.Info("Stopping async delivery thread.");
pause.Set();
if(!asyncDeliveryThread.Join(10000))
{
Tracer.Info("Aborting async delivery thread.");
asyncDeliveryThread.Abort();
}
asyncDeliveryThread = null;
Tracer.Info("Async delivery thread stopped.");
}
}
}
protected virtual void StartAsyncDelivery()
{
if(asyncDelivery.CompareAndSet(false, true))
{
asyncDeliveryThread = new Thread(new ThreadStart(DispatchLoop));
asyncDeliveryThread.Name = "Message Consumer Dispatch: " + contextBinding;
asyncDeliveryThread.IsBackground = true;
asyncDeliveryThread.Start();
}
}
protected virtual void DispatchLoop()
{
Tracer.Info("Starting dispatcher thread consumer: " + this);
while(asyncDelivery.Value)
{
try
{
IMessage message = Receive();
if(asyncDelivery.Value && message != null)
{
try
{
listener(message);
}
catch(Exception e)
{
HandleAsyncException(e);
}
}
}
catch(ThreadAbortException ex)
{
Tracer.InfoFormat("Thread abort received in thread: {0} : {1}", this, ex.Message);
break;
}
catch(Exception ex)
{
Tracer.ErrorFormat("Exception while receiving message in thread: {0} : {1}", this, ex.Message);
}
}
Tracer.Info("Stopping dispatcher thread consumer: " + this);
}
protected virtual void HandleAsyncException(Exception e)
{
session.Connection.HandleException(e);
}
///
/// Create nms message object
///
///
/// zmq message object
///
///
/// nms message object
///
protected virtual IMessage ToNmsMessage(string messageText)
{
IMessage nmsMessage = new TextMessage(messageText);
try
{
nmsMessage.NMSMessageId = "";
nmsMessage.NMSDestination = this.destination;
nmsMessage.NMSDeliveryMode = MsgDeliveryMode.NonPersistent;
nmsMessage.NMSPriority = MsgPriority.Normal;
nmsMessage.NMSTimestamp = DateTime.Now;
nmsMessage.NMSTimeToLive = new TimeSpan(0);
nmsMessage.NMSType = "";
}
catch(InvalidOperationException)
{
// Log error
}
if(null != this.ConsumerTransformer)
{
IMessage transformedMessage = ConsumerTransformer(this.session, this, nmsMessage);
if(null != transformedMessage)
{
nmsMessage = transformedMessage;
}
}
return nmsMessage;
}
}
}