Azure Service Bus handler in Azure Function

Question

I am straggling with that issue couple days and need help.

I send message to azure subscription in business layer using that code:

var sender = _serviceBusService.GetSender("event-send");

                    var message = new ServiceBusEvent()
                    {
                        SessionId = sessionId,
                        CourseId = courseId,
                        UserInfo = (BaseRequestUserInfo)userInfo,
                        PlaybackId = playBackId,
                        SsoProvider = userInfo?.SsoProvider,
                        Type = MessageType.SessionEvent
                    };
                    var body = JsonSerializer.Serialize(message);
                    var sbMessage = new ServiceBusMessage(body);
                    sbMessage.ApplicationProperties.Add("SsoProvider", userInfo.SsoProvider);
                    sbMessage.ApplicationProperties.Add("Type", MessageType.SessionEvent.ToString());
                    await sender.SendMessageAsync(sbMessage);

And I created Azure Function which will handle that message. I handle that message and in some cases I need to set that message to subscription one more time with EnqueueTime which depends on Delivery Count. When I debug my function, all properties in ServiceBusMessage object are null. Why does it happen? How could I fix that? Will I see Delicery Count in ApplicationProperties or there are only custom properties?

Azure Function

[FunctionName("VpSessionHandler")]
        public async Task Run([ServiceBusTrigger("event-send", "vp-session-event", Connection = "ServiceBusTopicConnectionString")] ServiceBusMessage mySbMsg,
            [ServiceBus("event-send", Microsoft.Azure.WebJobs.ServiceBus.ServiceBusEntityType.Topic, Connection = "ServiceBusTopicConnectionString")] ICollector<ServiceBusMessage> messageCollector)
        {
            try
            {
                var message = JsonSerializer.Deserialize<ServiceBusEvent>(mySbMsg.Body);
                var accessContext = _eventTrackerService.ChooseAccessTokenContext(message.SsoProvider);
                var accessToken = await accessContext.GetAccessTokenAsync(message.SsoProvider);
                var eventSender = _eventTrackerService.ChooseEventSessionSenderContext(message.SsoProvider);
                var sessionEventModel = new SessionEventModel()
                {
                    PlaybackId = message.PlaybackId,
                    UserInfo = message.UserInfo,
                    AccessToken = accessToken,
                    CourseId = message.CourseId,
                    SessionId = message.SessionId,
                };
                var rez = await eventSender.SendSessionEventApiAsync(sessionEventModel);

                if (!rez.IsSuccessStatusCode)
                {
                    if (mySbMsg.ApplicationProperties.DeliveryCount > 1)
                    {
                        var delayTime = TimeSpan.FromSeconds(Math.Pow(2, mySbMsg.ApplicationProperties.DeliveryCount));
                        mySbMsg.ScheduledEnqueueTime = DateTime.UtcNow.Add(delayTime);

                        messageCollector.Add(mySbMsg);
                    }
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
                throw;
            }
            _logger.LogInformation($"C# ServiceBus topic trigger function processed message: {mySbMsg}");
        }

P.S. As a first parameter I tried to use ServiceBusReceivedMessage, but I need ServiceBusMessage to add to subscription collection one more time. Additionally, new ServiceBusMessage will have new Delivery Count and it doesn't suit me.

Jesse Squire · Accepted Answer · 2023-04-14 16:59:06Z

1

There's a few things here that are important to consider:

The trigger cannot bind to ServiceBusMessage, you must use ServiceBusReceivedMessage. This is why the properties are null when your function is invoked.
The delivery count is a broker-owned field; your application should not be attempting to control this value. I'd suggest using an application property on the message to control your application logic.
You cannot send a ServiceBusReceivedMessage, you would have to use it to create a ServiceBusMessage regardless of how you were publishing it. This will intentionally remove the delivery count.
It is possible to set the delivery count for a ServiceBusMessage or ServiceBusReceivedMessage - if you do so directly on the underlying AmqpAnnotatedMessage.
Even if you set the delivery count via the AMQP message, the service may ignore or change it, as it sees fit - this is considered a broker-owned field. I don't know what the current behavior is, but you cannot depend on it not to change over time.

answered Apr 14, 2023 at 16:59

Jesse Squire

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5 Comments

Ilya Over a year ago

It is better to create a custom property instead of using delivery count, am I right? Depend on value of that custom property (for example 1,2,3 etc.) I would like to increase enqueue time.

Jesse Squire Over a year ago

Correct; using an application property would be a better approach.

Ilya Over a year ago

What could I do if changing for Delivery Count sometimes ignore by service bus? Should Service Bus stop handle message when it reach max delivery count which I set programmatically? Should I set ApplicationProperties in AmqpAnnotatedMessage too? I noticed that if I set ApplicationProperties just in ServiceBusMessage and than define AmqpAnnotatedMessage for that message, my custom property doesn't change, but if I set custom property in AmqpAnnotatedMessage it change correctly .

Jesse Squire Over a year ago

You cannot manipulate "DeliveryCount" via application properties - you'd be creating your own version of this field to drive your logic from. Service Bus behavior for a delivery count that you force via AMQP message is not guaranteed. You can do nothing to influence or control it. Again, "DeliveryCount" is a broker-owned field - your code should not be trying to control this.

Ilya Over a year ago

Right now I see that. Thanks very much for your help!

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