How to use Shared Access Signature with queues from Windows Azure

In the last post we talk about how we can use Shared Access Signature with blobs. In this post we will see how we can use this feature with queues. First of all we should know that this is a new feature that appeared with the February release of the new version Windows Azure.
The new version of Windows Azure added to the Sharing Access Signature new functionalities for queues. The following features are supported for queues:

• Add, remove, update delete queue message
• Message Count of a queue
• Access queue metadata
• For a give queue we can set the following restrictions:
• Time range – define the time interval when the user has access to the queue
• Access permissions – what type of actions a user can make on the queue (read, peak, update/add/process message)
• Server stored access policy – to generate offline Shared Access Signatures that can be very easily revoke or re-issues without having to change the account key

In the next example we will see how we can create a Shred Access Signature for a given queue. The first step is to get a reference to our queue.

CloudQueueClient queueClient = myAccount
                    .CreateCloudQueueClient();
CloudQueue myQueue = queueClient
                    .GetQueueReference("myQueue");
myQueue.CreateIfNotExist();

Next, we need to create the access policy for our queue. In our case we will permit the consumer to process the messages from our queue for an hour. In this example the consumer have an hour from the moment when we generated this access policy, but we could set also a start time from when this policy is available.

SharedAccessQueuePolicy sharedAccessPolicy = new SharedAccessQueuePolicy()
{
    Permissions = SharedAccessQueuePermissions
                    .ProcessMessages,
    SharedAccessExpiryTime =
                    DateTime.UtcNow +  TimeSpan.FromHours(1)
};

The shared access policy that we created need to be added to the queue. Each policy is identifying by a unique id. Based on this id we can remove a policy. After we set the permissions the consumer will be able to access our queue.

string policyIdentifier = "QueuePolicy1";
QueuePermissions queuePermissions=
    new QueuePermissions();
queuePermissions.SharedAccessPolicies.Add(
    policyIdentifier,
    sharedAccessPolicy);
myQueue.SetPermissions(queuePermissions);

Now, we have set the permissions on the queue. What we need now is the shared access signature. This signature is a token that need to be shared with the consumer. Using this token any consumer will be able to access our queue and process our messages.

string accessSignature =
          myQueue.GetSharedAccessSignature(
               new SharedAccessQueuePolicy(),
               policyIdentifier);

The only think that the consumer needs to do is to use the Shared Access Signature that we provided to generate a storate credentials. Based on this credential we can get a reference to the queue.

StorageCredentials storageCredentials =
     new StorageCredentialsSharedAccessSignature(    
          accessSignature);
queue = new CloudQueueClient(
               "http://myExampleQueue.queue.core.windows.net",
                storageCredentials)
                    .GetQueueReference("myQueue");
CloudQueueMessage messageFromQueue =
          queue.GetMessage(TimeSpan.FromMinutes(2));

In this post we saw how we can create a Shared Access Signature for a queue. It is very similar with the methods that were used for blobs. The big advantage to use Shared Access Signature to a queue is that we provide a limited time and a specific access type for a consumer of messages (or for a producer). In this way it is very easy to manage the persons that have access to the queue. Also using Shared Access Signature we can provide access only to a queue and not to all the storage account.
Tutorials about Shared Access Signature:

1. Overview
2. How to use Shared Access Signature with tables from Windows Azure
3. How to use Shared Access Signature with blobs from Windows Azure
4. How to use Shared Access Signature with queues from Windows Azure
5. How to remove or edit a Shared Access Signature from Windows Azure 
6. Some scenarios when we can use Shared Access Signature from Windows Azure