Azure Service Bus Send throughput .Net SDK

Question

I am currently implementing a library to send the messages faster to the Service bus queue. What is observed is that, if I used the same ServiceBusClient and use the same sender to send the messages in Parallel.For, the throughput is not so high and my network upload speed is not fully utilized. The moment I make individual clients and use them to send, the throughput increases drastically and even utilizes my upload bandwidth very well.

Is my understanding correct or a single client-sender must do? Also, I am averse to create multiple clients as it will use a lot of resources to establish the client connection. Any articles that throw some light on this?

There is a throughput test tool and its code also creates multiple client.

protected override Task OnStartAsync()
        {
            for (int i = 0; i < this.Settings.SenderCount; i++)
            {
                this.senders.Add(Task.Run(SendTask));
            }
            return Task.WhenAll(senders);
        }

        async Task SendTask()
        {
            var client = new ServiceBusClient(this.Settings.ConnectionString);
            ServiceBusSender sender = client.CreateSender(this.Settings.SendPath);
            var payload = new byte[this.Settings.MessageSizeInBytes];
            var semaphore = new DynamicSemaphoreSlim(this.Settings.MaxInflightSends.Value);
            var done = new SemaphoreSlim(1);
            done.Wait();
            long totalSends = 0;

https://github.com/Azure-Samples/service-bus-dotnet-messaging-performance

Is there a library to manage the connections in a pool?

Answer 1

From the patterns in your code, I'm assuming that you're using the Azure.Messaging.ServiceBus package. If that isn't the case, please ignore the remainder of this post.

ServiceBusClient represents a single AMQP connection to the service. Any senders, receivers, and processors spawned from this client will share that connection. This gives your application the ability to control the number of connections used and pool them in the manner that works best in your context.

It is recommended to reuse clients, senders, receivers, and processors for the lifetime of your application; though the connection is shared, each time a new child type is spawned, it must establish a new AMQP link and perform the authorization handshake - which is non-trivial overhead.

These types are self-managing with respect to resources. For idle periods, connections and links will be closed to avoid waste, and they'll automatically be recreated for the first operation that requires them.

With respect to using multiple clients, senders, receivers, and processors - it is a valid approach and can yield better performance in some scenarios. The one caveat that I'll mention is that using more clients than the number of CPU cores in your host environment comes with an increased risk of causing contention in the thread pool. The Service Bus library is highly asynchronous, and its performance relies on continuations for async calls being scheduled in a timely manner.

Unfortunately, performance tuning is very difficult to generalize due to how much it varies for different application and hosting contexts. To find the right number of senders to maximize throughput for your application, we recommend that you spend time testing different values and observing the performance characteristics in your specific system.