Service Bus SDK 3.0.x Part 1

Last week we released our new Service Bus SDK for .NET and we want to publish a series of blogs about it addressing the major changes. This may end up being a fairly long series… but we'll see.

First and foremost was the move away from the Asynchronous Programming Model (APM) pattern. This pattern, which dates from the earliest days of .NET, required Begin and End operations for all asynchronous methods. APM was a very useful model and was fairly easy to work with considering what it enabled. All scalable systems are asynchronous in nature and Service Bus has always supported asynchronous programing. It's the only way to get really good performance.

The move to the Task-based Asynchronous Pattern (TAP) uses a single method to represent both the initiation and completion of asynchronous operations. TAP, which was introduced in .NET Framework 4 is the recommended approach to asynchronous programming in the .NET Framework. The async and await keywords were added to support TAP within the C# language.

This provides several key advantages; performance and ease of use being the most compelling.

As a simple example look at the implementation below for Read method implemented first as a synchronous method, then with APM, and finally with TAP.

 public class MyClass
{
 public int Read(byte [] buffer, int offset, int count);
}

public class MyClass
{
 public IAsyncResult BeginRead(byte [] buffer, int offset, int count, AsyncCallback callback, object state);
 public int EndRead(IAsyncResult asyncResult);
}

public class MyClass
{
 public Task<int> ReadAsync(byte [] buffer, int offset, int count);
}
 

The TAP approach works much more like a synchronous approach. It is easier to understand and doesn't required tracking of IAsyncResult objects or callbacks. Also the framework can do a lot more optimization with this model.

The easiest way to see these changes is to examine the ClientEntity classes in the SDK - like QueueClient.

Below we can see screenshots of the 2.7.x SDK on the top and 3.0.1 SDK on the bottom. Notice how much smaller the scroll is. All those Begin/End pairs a gone. A simple API is a useable API. Step 1.

If you're a long time user of Service Bus who has implemented as asynchronous implementation good for you! Like I said, this is how all software scales. Now it's time to update your approach to TAP.

The TAP approach also enables more sophisticated mechanisms like cancellation tokens, which will be added to future versions of the SDK. We'll talk about these when we introduce them.

For more about Asynchronous Programming Patterns.