Azure Service Bus

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Description

It is a message broker with message queues and publish-subscribe topics.

Name Description
Queue Allows for Sending and Receiving of messages. Often used for point-to-point communication.
Topic As opposed to Queues, Topics are better suited to publish/subscribe scenarios.
A topic can be sent to, but requires a subscription, of which there can be multiple in parallel, to consume from.
Subscription The mechanism to consume from a Topic.
Each subscription is independent, and receives a copy of each message sent to the topic.
Rules and Filters can be used to tailor which messages are received by a specific subscription.

AzureServiceBusQueue.png

AzureServiceBusTopic.png

Configure the service bus on Azure

  • Azure portal → Service Bus → Add
  • Create namespace: the namespace will be the url use by the service bus [namespace].servicebus.windows.net
  • Pricing tiers: Basic, Standard (Topics), Premium (private network, dedicated capacity)
  • Once deployed, go to the newly create service bus namespace
    • add queue
    • add topic then add subscription

Sender

Add Nuget package Azure.Messaging.ServiceBus

Program.cs
private const string ConnectionString = "get it from Azure Portal → Service Bus Namespace → Shared access policy → Primary Connection String";
private const string QueueName = "queue1";
private const string TopicName = "topic1";

static async Task Main(string[] args)
{
    var client = new ServiceBusClient(ConnectionString);
    try  // use await using in C# 8 / .Net Core
    {
        var sender = client.CreateSender(QueueName);
        var sender = client.CreateSender(TopicName);

        var message = new ServiceBusMessage("Hello!");
        await sender.SendMessageAsync(message);
        Console.WriteLine($"Sent {message.Body}");
    }
    finally
    {
        await client.DisposeAsync();
    }
}

Receiver

Add Nuget package Azure.Messaging.ServiceBus

1 receiver for 1 subscription.
Program.cs
private const string ConnectionString = "get it from Azure Portal → Service Bus Namespace → Shared access policy → Primary Connection String";
private const string QueueName = "queue1";
private const string SubscriptionName = "subscription1";

static async Task Main(string[] args)
{
    var client = new ServiceBusClient(ConnectionString);
    var processor = client.CreateProcessor(QueueName);
    var processor = client.CreateProcessor(TopicName, SubscriptionName);

    try
    {
        processor.ProcessMessageAsync += MessageHandler;
        processor.ProcessErrorAsync += ErrorHandler;

        await processor.StartProcessingAsync();

        Console.ReadKey();
    }
    finally
    {
        await processor.DisposeAsync();
        await client.DisposeAsync();
    }
}

static async Task MessageHandler(ProcessMessageEventArgs args)
{
    string body = args.Message.Body.ToString();
    Console.WriteLine(body);

    // we can evaluate application logic and use that to determine how to settle the message.
    await args.CompleteMessageAsync(args.Message);
}

static Task ErrorHandler(ProcessErrorEventArgs args)
{
    // the error source tells me at what point in the processing an error occurred
    Console.WriteLine(args.ErrorSource);

    // the fully qualified namespace is available
    Console.WriteLine(args.FullyQualifiedNamespace);

    // as well as the entity path
    Console.WriteLine(args.EntityPath);
    Console.WriteLine(args.Exception.ToString());
    return Task.CompletedTask;
}

ServiceBusProcessorOptions

Cs.svg
var options = new ServiceBusProcessorOptions
{
    ReceiveMode = ServiceBusReceiveMode.PeekLock,
    AutoCompleteMessages = true,
    MaxAutoLockRenewalDuration = TimeSpan.FromMinutes(5),  //  renew the lock automatically till duration
    MaxConcurrentCalls = 1,  // number of messages processed concurrently
    PrefetchCount = 0,  // quietly acquire messages, up to the PrefetchCount limit
    SubQueue = SubQueue.None
};
var processor = client.CreateProcessor(TopicName, SubscriptionName, options);
Receive mode Description
PeekLock The client sends a request to receive a message from Service Bus.
Then it sends a request to complete / abandon / defer / dead-letter the message.
ReceiveAndDelete The send of a request to receive a message and the send of the request to complete the message are combined in a single request.
This reduces the overall number of operations, and can improve the overall message throughput.
This performance gain comes at the risk of losing messages.
Auto-complete messages Description
true Automatically complete messages after the message handler has completed processing without any exception raised.
No need to call await args.CompleteMessageAsync(message);
false Don't complete the message processing automatically.
A request is required to manually complete / abandon / defer / dead-letter the message.
SubQueue Description
None No subqueue
DeadLetter Add a secondary subqueue to hold messages that can't be delivered to any receiver.
TransferDeadLetter Add a secondary subqueue to hold messages that can't be delivered to any receiver when the following conditions apply:
  • a message passes through more than four queues or topics that are chained together
  • the destination queue or topic is disabled or deleted
  • the destination queue or topic exceeds the maximum entity size