The slides used during the talk "Owin and Katana" from the NCrafts Conference (http://ncrafts.io) on the 16 May in Paris.

1. Katana & OWIN
A new lightweight Web server for .NET
Simone Chiaretta
@simonech
http://codeclimber.net.nz
Ugo Lattanzi
@imperugo
http://tostring.it

2. Agenda
 What is OWIN
 OWIN Specs
 Introducing Katana
 Katana pipeline
 Using Katana
 Building OWIN middleware
 A look at the future

3. What is OWIN

4. What is OWIN
OWIN defines a standard interface between .NET web
servers and web applications. The goal of the OWIN interface
is to decouple server and application, encourage the
development of simple modules for .NET web development,
and, by being an open standard, stimulate the open source
ecosystem of .NET web development tools.
http://owin.org

5. What is OWIN
The design of OWIN is inspired by node.js, Rack (Ruby)
and WSGI (Phyton).
In spite of everything there are important differences between
Node and OWIN.
OWIN specification mentions a web server like something that is
running on the server, answer to the http requests and forward
them to our middleware. Differently Node.Js is the web server that
runs under your code, so you have totally the control of it.

6. IIS and OS
 It is released with the OS
 It means you have to wait the new release of Windows to
have new features (i.e.: WebSockets are available only on
the latest version of Windows)
 There aren’t update for webserver;
 Ask to your sysadmin “I need the latest version of Windows
because of Web Sockets“

7. System.Web
 I was 23 year old (now I’m 36) when System.Web was born!
 It’s not so cool (in fact it’s missing in all new FW)
 Testing problems
 2.5 MB for a single dll
 Performance

8. Support OWIN/Katana
Many application frameworks support OWIN/Katana
 Web API
 SignalR
 Nancy
 ServiceStack
 FubuMVC
 Simple.Web
 RavenDB

9. OWIN specs

10. OWIN Specs: AppFunc
using AppFunc = Func<
IDictionary<string, object>, // Environment
Task>; // Done
http://owin.org

11. OWIN Specs: Environment
Some compulsory keys in the dictionary (8 request, 5 response, 2
others)
 owin.RequestBody – Stream
 owin.RequestHeaders - IDictionary<string, string[]>
 owin.Request*
 owin.ResponseBody – Stream
 owin.ResponseHeaders - IDictionary<string, string[]>
 owin.ResponseStatusCode – int
 owin.Response*
 owin.CallCancelled - CancellationToken

12. OWIN Specs: Layers
• Startup, initialization and process management
Host
• Listens to socket
• Calls the first middleware
Server
• Pass-through components
Middleware
• That’s your code
Application

13. Introducing Katana aka Fruit Ninja

14. Why Katana
 ASP.NET made to please ASP Classic (HTTP req/res object
model) and WinForm devs (Event handlers): on fits all
approach, monolithic (2001)
 Web evolves faster then the FW: first OOB release of
ASP.NET MVC (2008)
 Trying to isolate from System.Web and IIS with Web API
(2011)
 OWIN and Katana fits perfectly with the evolution, removing
dependency on IIS

15. Katana pillars
 It’s Portable
 Components should be able to be easily substituted for new
components as they become available
 This includes all types of components, from the framework to the
server and host

16. Katana pillars
 It’s Modular/flexible
 Unlike many frameworks which include a myriad of features that
are turned on by default, Katana project components should be
small and focused, giving control over to the application
developer in determining which components to use in her
application.

17. Katana pillars
 It’s Lightweight/performant/scalable
 Fewer computing resources;
 As the requirements of the application demand more features
from the underlying infrastructure, those can be added to the
OWIN pipeline, but that should be an explicit decision on the part
of the application developer

18. Katana Pipeline

19. Katana Pipeline
Host
IIS
OwinHost.exe
Custom Host
Server
System.Web
HttpListener
Middleware
Logger
WebApi
And more
Application
That’s your
code

20. Using Katana

21. Hello Katana: Hosting on IIS

22. Hello Katana: Hosting on IIS

23. Hello Katana: Hosting on IIS
public void Configuration(IAppBuilder app)
{
app.Use<yourMiddleware>();
app.Run(context =>
{
context.Response.ContentType = "text/plain";
return context.Response.WriteAsync("Hello Paris!");
});
}

24. Changing Host: OwinHost

25. Changing Host: OwinHost

26. Changing Host: Self-Host

27. Changing Host: Self-Host
static void Main(string[] args)
{
using (WebApp.Start<Startup>("http://localhost:9000"))
{
Console.WriteLine("Press [enter] to quit...");
Console.ReadLine();
}
}

28. Real World Katana
 Just install the framework of choice and use it as before

29. Real World Katana: WebAPI

30. Real World Katana: WebAPI
public void Configuration(IAppBuilder app)
{
HttpConfiguration config = new HttpConfiguration();
config.Routes.MapHttpRoute("default", "api/{controller");
app.UseWebApi(config);
}

31. Katana Diagnostic
install-package Microsoft.Owin.Diagnostics

32. Securing Katana
 Can use traditional cookies (Form Authentication)
 CORS
 Twitter
 Facebook
 Google
 Active Directory

33. OWIN Middleware

34. OWIN Middleware: IAppBuilder
 Non normative conventions
 Formalizes application startup pipeline
namespace Owin
{
public interface IAppBuilder
{
IDictionary<string, object> Properties { get; }
IAppBuilder Use(object middleware, params object[] args);
object Build(Type returnType);
IAppBuilder New();
}
}

35. Building Middleware: Inline
app.Use(new Func<AppFunc, AppFunc>(next => (async env =>
{
var response = environment["owin.ResponseBody"] as Stream;
await response.WriteAsync(Encoding.UTF8.GetBytes("Before"),0,6);
await next.Invoke(env);
await response.WriteAsync(Encoding.UTF8.GetBytes(“After"),0,5);
})));

36. Building Middleware: raw OWIN
using AppFunc = Func<IDictionary<string, object>, Task>;
public class RawOwinMiddleware
{
private AppFunc next;
public RawOwinMiddleware(AppFunc next)
{
this.next = next;
}
public async Task Invoke(IDictionary<string, object> env)
{
var response = env["owin.ResponseBody"] as Stream;
await response.WriteAsync(Encoding.UTF8.GetBytes("Before"),0,6);
await next.Invoke(env);
await response.WriteAsync(Encoding.UTF8.GetBytes(“After"),0,5);
}
}

37. Building Middleware: Katana way
public class LoggerMiddleware : OwinMiddleware
{
public LoggerMiddleware(OwinMiddleware next) : base(next)
{}
public override async Task Invoke(IOwinContext context)
{
await context.Response.WriteAsync("before");
await Next.Invoke(context);
await context.Response.WriteAsync("after");
}
}

38. A look at the future

39. Project K and ASP.NET vNext
 Owin/Katana is the first stone of the new ASP.NET
 Project K where the K is Katana
 Microsoft is rewriting from scratch
 vNext will be fully OSS (https://github.com/aspnet);
 MVC, WEB API and SignalR will be merged (MVC6)
 It uses Roslyn for compilation (build on fly)
 It runs also on *nix, OSx
 Cloud and server-optimized
 POCO Controllers

40. OWIN Succinctly
Soon available online on
http://www.syncfusion.com/resources/techportal/ebooks

41. Demo code
https://github.com/imperugo/ncrafts.owin.katana

42. Merci
Merci pour nous avoir invités à cette magnifique
conférence.