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Windows Azure Queues vs Service Bus Queues

If you have been wondering why you would use Windows Azure Queues that are part of the Storage Service or the queues that are part of the service bus then the following MSDN article will give you full details.

http://msdn.microsoft.com/en-us/library/hh767287(VS.103).aspx

Recent changes in pricing make the choice even harder. There are two specific areas I like that makes the service bus queue a better offering than the storage queues:

  1. Long connection timeout
  2. Topics

The long connection timeout means that I don't have to keep polling the service bus queue for messages. I can make a connection for say 20 minutes and then when a message is added to the queue my application immediately returns the data, which you then process and then reconnect to the queue to get the next message. After 20 minutes without a message the connection closes in the same way it does when a message is received except that the message is null. You then just reconnect again for another 20 minute. The makes your application a more event driven application rather than a polling application and it should be more responsive. You can make multiple connections to the queue this way and load balance in the same way as you would when polling queues.

The following code shows how you can connect with a long poll.

 1: NamespaceManager namespaceManager;
 2: MessagingFactory messagingFactory;
 3: Uri namespaceAddress = ServiceBusEnvironment.CreateServiceUri("sb", "yournamespace", string.Empty);
 4:  
 5: namespaceManager = new NamespaceManager(namespaceAddress, TokenProvider.CreateSharedSecretTokenProvider("yourIssuerName", "yourIssuerKey"));
 6: messagingFactory = MessagingFactory.Create(namespaceAddress, TokenProvider.CreateSharedSecretTokenProvider("yourIssuerName", "yourIssuerKey"));
 7:  
 8: WaitTimeInMinutes = 20;
 9:  
 10: // check to see if the queue exists. If not then create it
 11: if (!namespaceManager.QueueExists(queueName))
 12: {
 13:     namespaceManager.CreateQueue(queueName);
 14: }
 15:  
 16: QueueClient queueClient = messagingFactory.CreateQueueClient(queueName, ReceiveMode.PeekLock);
 17:  
 18: queueClient.BeginReceive(new TimeSpan(0, WaitTimeInMinutes, 0), this.ReceiveCompleted, messageCount);

When a message is received or the 20 minute timeout expires then the ReceiveCompleted delegate is called and a check is made to see if the message is not null before processing it.Once processed another long poll connecting is made and the process repeats. The beauty of this method is that you don’t have to manage timers or separate threads manage the queue.

Topics are private queues that are subscribed to by consumers and each private queue will receive a copy of the messages put into the original queue and are all manages individually. Topics can also apply filters to the message so that they only receive messages that they are interested in.

Further details of Service bus topics and queues

http://www.windowsazure.com/en-us/develop/net/how-to-guides/service-bus-topics/

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