Question

我正在编写一些响应Azure Service Bus Queue的功能。这当前在指定队列上轮询，OnMessage触发对原始类中调用它的方法的回调：

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

然后是服务总线助手类：

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;
            ...
        }
}

它正确连接到azure服务总线队列并检索消息，但回调似乎永远不会实际触发。我想要实现的是一个服务，它将持续响应OnMessage事件，触发一个新的worker（从class1中），尽管OnMessage实际上是从ServiceBusHelper类触发的。

Answer 1

回调似乎永远不会触发。

为了重现这个问题，我在一个控制台应用程序中进行测试，我的代码中包含以下代码，这样可以正常工作。

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>()));
}

如果可能，您可以尝试将private bool HandleTransaction(BrokeredMessage message)修改为make it return void private void HandleTransaction(BrokeredMessage message)，并检查其是否正常。

Answer 2

所以我设法通过修改异步OnMessage对应来实现这一点。我认为根本原因与未指定OnMessage的OnMessageOptions或者CompletedResetEvent没有相互影响我的预期有关。

    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服务总线队列OnMessage回调

2 个答案: