Code Generation

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Concepts

Code Generation

By default, the server will use the reflection APIs to analyze and execute webservice methods. For improved performance, there is an experimental code generation mode that compiles a delegate that fetches the input arguments from the request, executes the webservice method, and maps the result into an HTTP response.

This feature will be enabled by default with GenHTTP 11.

Code generation is not supported on ARM-based CPUs due to limitations of the .NET framework on this platform. As code generation is performed at runtime, this mode is not available for AoT apps. The service framework will automatically fall back to reflection in affected environments.

Compilation is currently performed during first execution of an endpoint, which can cause a delay for the first request. In GenHTTP 11, compilation will be done on startup.

Enabling Code Generation

Code generation can be enabled by passing ExecutionMode.Auto to the framework handlers (in contrast to ExecutionMode.Reflection, which is the default value).

using GenHTTP.Engine.Internal;

using GenHTTP.Modules.Layouting;
using GenHTTP.Modules.Practices;
using GenHTTP.Modules.Reflection;
using GenHTTP.Modules.Webservices;

// http://localhost:8080/my/

var api = Layout.Create()
                .AddService<MyService>("my", mode: ExecutionMode.Auto);

await Host.Create()
          .Handler(api)
          .Defaults()
          .Console()
          .RunAsync();

public class MyService
{

    [ResourceMethod]
    public string SayHello() => "Hello World!";

}

using GenHTTP.Engine.Internal;

using GenHTTP.Modules.Functional;
using GenHTTP.Modules.Practices;
using GenHTTP.Modules.Reflection;

// http://localhost:8080/

var api = Inline.Create()
                .Get(() => "Hello World!")
                .ExecutionMode(ExecutionMode.Auto);

await Host.Create()
          .Handler(api)
          .Defaults()
          .Console()
          .RunAsync();

using GenHTTP.Engine.Internal;

using GenHTTP.Modules.Controllers;
using GenHTTP.Modules.Layouting;
using GenHTTP.Modules.Practices;
using GenHTTP.Modules.Reflection;

// http://localhost:8080/my/say-hello/

var api = Layout.Create()
                .AddController<MyController>("my", mode: ExecutionMode.Auto);

await Host.Create()
          .Handler(api)
          .Defaults()
          .Console()
          .RunAsync();

public class MyController
{

    public string SayHello() => "Hello World!";

}

Benchmarks

The code generated for a service method is highly optimized to directly read values from the request, similar as you would do it in a handwritten IHandler instance. Nevertheless, the routing required to find and invoke the requested service method adds a small overhead. The following table shows the performance of the different modes. As there were a lot of improvements when the code generation feature has been added to the reflection module, there is also a comparison to version 10.3 without those optimizations.

Mode	Requests / s	Result
Native Handler	123,031	100%
Code Generation	121,465	98.7%
Reflection	118,230	96.1%
Reflection (10.3)	115,157	93.6%

Error Handling

If the server fails to compile a delegate for a given method signature, an error page will be rendered when the corresponding endpoint is called. If you encounter such an issue, please report a bug to our GitHub repository.

An error shown due to a compilation failure