Windows Azure Queue Storage

In my previous post I explained about Windows Azure Storage and how to create it via Azure portal. In this post I'll explain about Azure Queue storage.

Windows Azure Queue storage is a service for storing large numbers of messages that can be accessed from anywhere in the world via authenticated calls using HTTP or HTTPS.

If you are going to use development storage you may have to consider about azure storage client library version and emulator version. When I was using development storage version 2.2 with Azure storage client library version 3, I got some errors related to invalid HTTP headers and 400 Bad request issues. Please go through this link if you are going to use development storage.

Add new cloud project and add web role and a worker role.

Expand server explorer, you can see the azure storage explorer.

Add QueueStorage connection string to the web role cloud service config file.

Add following code to Home controller.

You must consider following naming conventions for Azure Queues.

• A queue name must start with a letter or number, and can only contain letters, numbers, and the dash (-) character. 
• The first and last letters in the queue name must be alphanumeric. The dash (-) character cannot be the first or last character. Consecutive dash characters are not permitted in the queue name.
• All letters in a queue name must be lowercase.
• A queue name must be from 3 through 63 characters long.

After run this code it will create a new queue container in Azure and add a message. But you won't be able to see the Queue container in Azure portal. Because that feature is not facilitated yet by Azure team. Refresh the storage explorer in Visual Studio. Open the queue. You can see the queue message in queue container. In Azure queue message will expire after 7 days.

Now we'll look at how to consume queue messages from worker role.
Add following code to worker role.

After you call queue.GetMesage(), that message becomes invisible. That means no one allows to read that message. At the end you can delete the message. But if that process crashed after a few time message again visible in queue. That means there is an invisibility time for a queue message. You can further read about Poison Message handling in Queues.

Windows Azure Storage

Windows Azure storage consists of blobs, tables, and queues. It is accessible with HTTP/HTTPS requests. It is distinct from SQL Azure.
If you try to create a storage account from Azure Portal, you have to enter following details.

Location/Affinity group - A geographic location of you cloud service deployments which will affects for the performance by putting near to your target audience.

Geo redundant replication - This enables replicating your data in to a secondary location within the same region. This enable the fail over handling.

Locally redundant storage - Locally redundant data is replicated three times in same data center. All storage in Windows Azure is locally redundant.

After you create the storage account in the dash board you can see the end point URLs. This represents the namespace of blob, queue and table in your storage.

Container - This provides set of storage types. A storage account can contain an unlimited number of containers.