Azure Service Bus broadcast to all worker role instances

Question

I am trying to use to Azure Service Bus to broadcast a message from a Web Role to all the instances of a single worker role. This is the code I use to receive messages:

// Create the topic if it does not exist already
            string connectionString = CloudConfigurationManager.GetSetting("Microsoft.ServiceBus.ConnectionString");
        var namespaceManager = NamespaceManager.CreateFromConnectionString(connectionString);

        // Configure Topic Settings
        TopicDescription td = new TopicDescription("CommandTopic");
        td.MaxSizeInMegabytes = 5120;
        td.DefaultMessageTimeToLive = new TimeSpan(0, 0, 1);

        if (!namespaceManager.TopicExists("CommandTopic"))
        {
            namespaceManager.CreateTopic(td);
        }

        Random rand = new Random();
        double randNum = rand.Next();

        if (!namespaceManager.SubscriptionExists("CommandTopic", "CommandSubscription"+randNum))
        {
            namespaceManager.CreateSubscription("CommandTopic", "CommandSubscription" + randNum);
        }

        Client = SubscriptionClient.CreateFromConnectionString(connectionString, "CommandTopic", "CommandSubscription" + randNum, ReceiveMode.ReceiveAndDelete);
        Trace.WriteLine("SUBSCRIPTION: COMMANDSUBSCRIPTION"+randNum);

In order to create a separate subscription for each worker role instance (so that all instances receive the message in the topic) I had to use a random number. Is there a way of using some Id of the instance instead of the random number. There is Instance.Id however it is too long to be used as a parameter for the subscription name. Is there a shorter version without using substring? Also, is creating a separate subscription for each instance the proper approach? Previously all instances subscribed to the same subscription and so only 1 instance was getting the message and deleting it from the subscription.

maartenba maartenba · Accepted Answer · 2013-03-13T07:03:12

Try adding a bogus InternalEndpoint for the worker role to your configuration. This ensures the list of instances of a role gets populated.

Azure Service Bus broadcast to all worker role instances

2 Answers