C# Azure Service Bus Queue OnMessage Callback

Question

I'm writing some functionality that responds to an Azure Service Bus Queue. This currently polls on a specified queue and OnMessage triggers a callback to a method in the original class that calls it:

    partial class Class1
    {
         private void BeginProcessing()
         {
             serviceBusHelper.Listen(QueueType.Inbound, HandleTransaction);
         }
         private bool HandleTransaction(BrokeredMessage message)
         {
             ...    
         }
    }

And then the service bus helper class:

public class ServiceBusHelper : IServiceBusHelper
{
    ManualResetEvent CompletedResetEvent = new ManualResetEvent(false);

    public void Listen(QueueType queue, Action<BrokeredMessage> callback)
    {

        switch (queue)
        {
            case QueueType.Inbound:
                inboundClient.OnMessage(message =>
                {
                    try
                    {
                        callback(message);
                    }
                    catch (Exception ex)
                    {
                        ...
                    }
                    CompletedResetEvent.WaitOne();
                });
                break;
            ...
        }
}

It is connecting correctly to the azure service bus queue and retrieving the message, however the callback never seems to actually trigger. What I'm trying to achieve is a service that will continuously respond to an OnMessage event, trigger a new worker (from within class1) despite the OnMessage actually being triggered from the ServiceBusHelper class.

score 0 · Answer 1 · answered Jul 13 '17 at 08:10

the callback never seems to actually trigger.

In order to reproduce the issue, I do a test in a console application with the following code on my side, which works fine.

public static void processmessage()
{
    string connectionString = "{connectionstring here}";

    var queueName = "{queue name}";

    var client = QueueClient.CreateFromConnectionString(connectionString, queueName);
    var options = new OnMessageOptions();
    options.AutoComplete = false;

    try
    {
        client.OnMessage(message =>
        {
            HandleTransaction(message);
        }, options);
    }
    catch (Exception)
    {

    }
}

private static void HandleTransaction(BrokeredMessage message)
{
    Console.WriteLine(String.Format("Message body: {0}", message.GetBody<String>()));
}

If possible, you can try to modify private bool HandleTransaction(BrokeredMessage message) to make it return void private void HandleTransaction(BrokeredMessage message), and check whether it works fine.

If possible, you could share us more code or sample to reproduce the issue. — Fei Han, Jul 13 '17 at 08:10

user8284748 · Accepted Answer · 2017-07-13T11:45:24.040

So I've managed to get this working by modifying to the asynchronous OnMessage counterpart. I believe the root cause was related to not specifing OnMessageOptions to the OnMessage, or the CompletedResetEvent not interacting how I expected.

    public void Listen(QueueType queue, Action<BrokeredMessage> callback)
    {
            OnMessageOptions options = new OnMessageOptions
            {   
                MaxConcurrentCalls = maxConcurrent,
                AutoComplete = false
            };

            switch (queue)
            {
                case QueueType.Inbound:
                    inboundClient.OnMessageAsync(async message =>
                    {
                        bool shouldAbandon = false;
                        try
                        {
                            callback(message);

                            // complete if successful processing
                            await message.CompleteAsync();
                        }
                        catch (Exception ex)
                        {
                            shouldAbandon = true;
                            Debug.WriteLine(ex);
                        }

                        if (shouldAbandon)
                        {
                            await m.AbandonAsync();
                        }
                    }, options);
                    break;

                ...
            }
    }

C# Azure Service Bus Queue OnMessage Callback

2 Answers2