private bool TryGetRequest(ConcurrentQueueingConsumer consumer, out HttpRequestPacket request, out MessageDispatch dispatch)
{
request = null;
dispatch = null;
BasicDeliverEventArgs item;
if (!consumer.TryInstantDequeue(out item, throwIfClosed: false))
{
return false;
}
//TODO: Pool MessageDispatch
//Get message
dispatch = new MessageDispatch { Consumer = consumer, Delivery = item };
//Deserialize message
bool wasDeserialized = true;
try
{
request = HttpRequestPacket.Deserialize(item.Body);
}
catch
{
wasDeserialized = false;
}
if (wasDeserialized)
{
//Add/Update Subscriber-Id header
request.Headers[Common.Shared.SUBSCRIBER_ID_HEADER] = this.subscriberIdHeader;
//Add redelivered header if item was redelivered.
if (item.Redelivered)
{
request.Headers[Common.Shared.REDELIVERED_HEADER] = TRUE_STRING_ARRAY;
}
}
//Reject message if deserialization failed.
else if (!wasDeserialized && Settings.AckBehavior != SubscriberAckBehavior.Automatic )
{
consumer.Model.BasicReject(item.DeliveryTag, false);
return false;
}
return true;
}
//Will block until a request is received from either queue
public MessageContext Dequeue()
{
if (disposed) throw new ObjectDisposedException(GetType().FullName);
if(workConsumer == null || subscriberConsumer == null) throw new InvalidOperationException("Start the subscriber prior to calling Dequeue");
//TODO: Test what happens if either of these consumers are cancelled by the server, should consumer.Cancelled be handled?
//In that scenario, requestQueued.Wait below should throw an exception and try to reconnect.
HttpRequestPacket request;
MessageDispatch dispatch;
ConcurrentQueueingConsumer queue1 = null, queue2 = null;
while (true)
{
if (disposed) throw new ObjectDisposedException(GetType().FullName);
if (lastProcessedConsumerQueue == subscriberConsumer)
{
queue1 = workConsumer;
queue2 = subscriberConsumer;
}
else
{
queue1 = subscriberConsumer;
queue2 = workConsumer;
}
try
{
if (TryGetRequest(queue1, out request, out dispatch))
{
lastProcessedConsumerQueue = queue1;
break;
}
if (TryGetRequest(queue2, out request, out dispatch))
{
lastProcessedConsumerQueue = queue2;
break;
}
}
catch (Exception e)
{
//TODO: Log this -- no exception is expected from the calls in the try block.
throw;
}
try
{
requestQueued.Wait(stopWaitingOnQueue.Token);
}
catch (OperationCanceledException)
{
if (!disposed && connectionBroken.IsCancellationRequested)
{
//Connection broken or consumer has been cancelled but client is not disposed
//So reconnect
Reconnect();
}
else
{
throw;
}
}
requestQueued.Reset();
}
return new MessageContext
{
Request = request,
ReplyToQueue = dispatch.Delivery.BasicProperties == null ? null : dispatch.Delivery.BasicProperties.ReplyTo,
CorrelationId = dispatch.Delivery.BasicProperties.CorrelationId,
Dispatch = dispatch
};
}
//TODO: REMOVE LATER: This method is never called because the DirectReplyToStrategy is used when the client decides to use
//the direct reply to feature.
/// <summary>
/// Discovers the Direct reply-to queue name ( https://www.rabbitmq.com/direct-reply-to.html ) by messaging itself.
/// </summary>
private static string DiscoverDirectReplyToQueueName(IModel channel, string indirectReplyToQueueName)
{
DeclareIndirectReplyToQueue(channel, indirectReplyToQueueName);
var receiver = new ConcurrentQueueingConsumer(channel);
var receiverTag = channel.BasicConsume(indirectReplyToQueueName, true, receiver);
channel.BasicPublish(String.Empty, indirectReplyToQueueName, true, new BasicProperties { ReplyTo = RPCStrategyHelpers.DIRECT_REPLY_TO_QUEUENAME_ARG }, new byte[0]);
BasicDeliverEventArgs delivery;
using (ManualResetEventSlim messageReturned = new ManualResetEventSlim())
{
EventHandler<BasicReturnEventArgs> returnHandler = null;
Interlocked.Exchange(ref returnHandler, (a, e) => { messageReturned.Set(); try { receiver.Model.BasicReturn -= returnHandler; } catch { } });
receiver.Model.BasicReturn += returnHandler;
System.Diagnostics.Stopwatch watch = new System.Diagnostics.Stopwatch();
watch.Start();
while (!receiver.TryInstantDequeue(out delivery, throwIfClosed: false))
{
Thread.Sleep(1);
if (watch.Elapsed > TimeSpan.FromSeconds(10) || messageReturned.IsSet)
{
break;
}
}
watch.Stop();
if (!messageReturned.IsSet)
{
try
{
receiver.Model.BasicReturn -= returnHandler;
}
catch { }
}
try
{
channel.BasicCancel(receiverTag);
}
catch { }
}
if (delivery == null)
{
throw new InvalidOperationException("Unable to determine direct reply-to queue name.");
}
var result = delivery.BasicProperties.ReplyTo;
if (result == null || result == RPCStrategyHelpers.DIRECT_REPLY_TO_QUEUENAME_ARG || !result.StartsWith(RPCStrategyHelpers.DIRECT_REPLY_TO_QUEUENAME_ARG))
{
throw new InvalidOperationException("Discovered direct reply-to queue name (" + (result ?? "null") + ") was not in expected format.");
}
return result;
}
public void Restart()
{
hasStarted.Set(true);
//CLose connections and channels
if (subscriberChannel != null)
{
if (subscriberConsumer != null)
{
try
{
subscriberChannel.Channel.BasicCancel(subscriberConsumer.ConsumerTag);
}
catch { }
}
try
{
subscriberChannel.Close();
}
catch
{
}
}
if (workChannel != null)
{
if (workConsumer != null)
{
try
{
workChannel.Channel.BasicCancel(workConsumer.ConsumerTag);
}
catch { }
}
try
{
workChannel.Close();
}
catch
{
}
}
if (_subscriberPool != null)
{
_subscriberPool.Dispose();
}
//NOTE: CreateConnection() can throw BrokerUnreachableException
//That's okay because the exception needs to propagate to Reconnect() or Start()
var conn = connectionFactory.CreateConnection();
if (connectionBroken != null) connectionBroken.Dispose();
connectionBroken = new CancellationTokenSource();
if (stopWaitingOnQueue != null) stopWaitingOnQueue.Dispose();
stopWaitingOnQueue = CancellationTokenSource.CreateLinkedTokenSource(disposedCancellationSource.Token, connectionBroken.Token);
var pool = new AmqpChannelPooler(conn);
_subscriberPool = pool;
//Use pool reference henceforth.
//Create work channel and declare exchanges and queues
workChannel = pool.GetModel(ChannelFlags.Consumer);
//Redeclare exchanges and queues
AmqpUtils.DeclareExchangeAndQueues(workChannel.Channel, messageMapper, messagingConfig, serviceName, exchangeDeclareSync, Id);
//Listen on work queue
workConsumer = new ConcurrentQueueingConsumer(workChannel.Channel, requestQueued);
string workQueueName = AmqpUtils.GetWorkQueueName(messagingConfig, serviceName);
workChannel.Channel.BasicQos(0, (ushort)Settings.PrefetchCount, false);
workChannel.Channel.BasicConsume(workQueueName, Settings.AckBehavior == SubscriberAckBehavior.Automatic, workConsumer);
//Listen on subscriber queue
subscriberChannel = pool.GetModel(ChannelFlags.Consumer);
subscriberConsumer = new ConcurrentQueueingConsumer(subscriberChannel.Channel, requestQueued);
string subscriberWorkQueueName = AmqpUtils.GetSubscriberQueueName(serviceName, Id);
subscriberChannel.Channel.BasicQos(0, (ushort)Settings.PrefetchCount, false);
subscriberChannel.Channel.BasicConsume(subscriberWorkQueueName, Settings.AckBehavior == SubscriberAckBehavior.Automatic, subscriberConsumer);
//Cancel connectionBroken on connection/consumer problems
pool.Connection.ConnectionShutdown += (s, e) => { connectionBroken.Cancel(); };
workConsumer.ConsumerCancelled += (s, e) => { connectionBroken.Cancel(); };
subscriberConsumer.ConsumerCancelled += (s, e) => { connectionBroken.Cancel(); };
}
private void StartCallbackQueueConsumer(AmqpChannelPooler pool)
{
//TODO: Double-checked locking -- make this better
if (callbackConsumer == null || !isInConsumerLoop || !pool.Connection.IsOpen)
{
lock (restartConsumerSync)
{
if (!(callbackConsumer == null || !isInConsumerLoop || !pool.Connection.IsOpen)) return;
//This method waits on this signal to make sure the callbackprocessor thread either started successfully or failed.
ManualResetEventSlim consumerSignal = new ManualResetEventSlim(false);
Exception consumerSignalException = null;
Thread callBackProcessor = new Thread(p =>
{
ConcurrentQueueingConsumer consumer = null;
try
{
//Start consumer
AmqpModelContainer channelContainer = null;
try
{
channelContainer = pool.GetModel(ChannelFlags.Consumer);
IModel channel = channelContainer.Channel;
if (clientSettings.DisableDirectReplies || !channelContainer.IsDirectReplyToCapable)
{
DeclareIndirectReplyToQueue(channel, indirectReplyToQueueName);
}
consumer = new ConcurrentQueueingConsumer(channel, responseQueued);
//Set consumerCancelled to true on consumer cancellation
consumerCancelled = false;
consumer.ConsumerCancelled += (s, e) => { consumerCancelled = true; };
channel.BasicQos(0, (ushort)clientSettings.PrefetchCount, false);
//Start consumer:
string replyToQueueName;
if (clientSettings.DisableDirectReplies || !channelContainer.IsDirectReplyToCapable)
{
channel.BasicConsume(indirectReplyToQueueName, clientSettings.AckBehavior == ClientAckBehavior.Automatic, consumer);
replyToQueueName = indirectReplyToQueueName;
}
else
{
//TODO: REMOVE LATER: This clause is never called because in this case the DirectReplyToRPCStrategy would be in use
//instead of this strategy.
//throw an InvalidOperationException instead
channel.BasicConsume(RPCStrategyHelpers.DIRECT_REPLY_TO_QUEUENAME_ARG, true, consumer);
//Discover direct reply to queue name
replyToQueueName = DiscoverDirectReplyToQueueName(channel, indirectReplyToQueueName);
}
//Set callbackConsumer to consumer
callbackQueueName = replyToQueueName;
callbackConsumer = consumer;
//Notify outer thread that channel has started consumption
consumerSignal.Set();
BasicDeliverEventArgs evt;
ExpectedResponse expected;
isInConsumerLoop = true;
while (true)
{
try
{
evt = DequeueCallbackQueue();
}
catch
{
//TODO: Log this exception except it's ObjectDisposedException or OperationCancelledException
throw;
}
expected = null;
if (!String.IsNullOrEmpty(evt.BasicProperties.CorrelationId) && expectedResponses.TryRemove(evt.BasicProperties.CorrelationId, out expected))
{
RPCStrategyHelpers.ReadAndSignalDelivery(expected, evt);
}
//Acknowledge receipt:
//In ClientBehavior.Automatic mode
//Client acks all received messages, even if it wasn't the expected one or even if it wasn't expecting anything.
//This prevents a situation where crap messages are sent to the client but the good expected message is stuck behind the
//crap ones and isn't delivered because the crap ones in front of the queue aren't acked and crap messages exceed prefetchCount.
//In ClientAckBehavior.ValidResponses mode (and Direct Reply to is not in effect):
//Client only acks expected messages if they could be deserialized
//If not, they are rejected.
if ((clientSettings.DisableDirectReplies || !channelContainer.IsDirectReplyToCapable) && clientSettings.AckBehavior == ClientAckBehavior.ValidResponses)
{
if (expected != null && expected.DeserializationException != null)
{
channel.BasicAck(evt.DeliveryTag, false);
}
else
{
channel.BasicReject(evt.DeliveryTag, false);
}
}
//Exit loop if consumer is cancelled.
if (consumerCancelled)
{
break;
}
}
}
finally
{
isInConsumerLoop = false;
pool.SetRecycle();
if (channelContainer != null)
{
if (consumer != null && !consumerCancelled)
{
try
{
channelContainer.Channel.BasicCancel(consumer.ConsumerTag);
}
catch { }
}
channelContainer.Close();
}
}
}
catch (Exception ex)
{
//TODO: Log error (Except it's object disposed exception)
//Set Exception object which will be throw by signal waiter
consumerSignalException = ex;
//Notify outer thread to move on, in case it's still waiting
try
{
consumerSignal.Set();
}
catch { }
}
finally
{
if (pool != null)
{
pool.Dispose();
}
}
});
//Start Thread
callBackProcessor.Name = "RestBus RabbitMQ Client Callback Queue Consumer";
callBackProcessor.IsBackground = true;
callBackProcessor.Start();
//Wait for Thread to start consuming messages
consumerSignal.Wait();
consumerSignal.Dispose();
//Examine exception if it were set and rethrow it
Thread.MemoryBarrier(); //Ensure we have the non-cached version of consumerSignalException
if (consumerSignalException != null)
{
throw consumerSignalException;
}
//No more code from this point in this method
}
}
}