ASP.NET Core Middleware - · PDF fileEXPOWARE SOFT - 2016 Coordinating Multiple Middleware...

EXPOWARE SOFT - 2016

Dino Esposito

ASP.NET Core Middleware

@despos facebook.com/naa4e Press


IIS and ASP.NET forever together


Then it came OWIN…

OWIN is a specification on how web servers and web applications should be built in order to decouple one from another.

and allow ASP.NET applications to run in environments different from IIS

http://owin.org/


Web

Forms

MVC

Web API

system.web MVC model

Katana

ASP.NET Core

SignalR


New Pipeline


New and Old Pipeline

HTTP module

IISASP.NET

HTTP module

Process

RequestInternet


Kestrel

Minimalistic web server for ASP.NET Core

Based on libuv, multi-platform library for async I/O

Not a fully-fledged web server

Better if standing behind a reverse proxy

- i.e., NGINX


Reverse ProxyRetrieves resources on behalf of a client from one or more servers.

REVERSE PROXY

KestrelProtected from

direct accessPrimary reason is security


Reverse vs. Forward

BROWSER

ACTUALSERVER

BROWSER

ACTUALSERVER

REVERSE PROXY PROXY


public class Program{

public static void Main(){

var host = new WebHostBuilder().UseKestrel().UseUrls("http://localhost:5000").UseStartup<Startup>().Build();

host.Run();}

}UseIISIntegration()to configure IIS as reverse proxy


Startup

Middleware to be added to the pipeline and configured

Only configured middleware runs

Nothing like “free” middleware

All you have is only all you add (and configure)


Startup

Middleware to be added to the pipeline and configured

Only configured middleware runs

Nothing like “free” middleware Not even static files

All you have is only all you add (and configure)


public class Startup{

public void ConfigureServices(IServiceCollection services){

// Add services here}

public void Configure(IApplicationBuilder app){

app.Run(async (context) =>{

await context.Response.WriteAsync(DateTime.Now)});

}}


Static Files


app.UseStaticFiles();app.UseDefaultFiles();

}

Default root folder is wwwroot

Change it with UseWebRoot("Content") in program.cs

ContentRoot vs WebRoot


Static Files—more control


app.UseStaticFiles(); // wwwroot

app.UseStaticFiles(new StaticFileOptions(){

FileProvider = new PhysicalFileProvider(Path.Combine(Directory.GetCurrentDirectory(), @"Content"),

RequestPath = new PathString("/Assets")});

}


Static Files—even more control


app.UseStaticFiles(new StaticFileOptions(){

OnPrepareResponse = ctx =>{

ctx.Context.Response.Headers.Append("Cache-Control", "public,max-age=600");

}});

}

No authorization checks on static files. Go through your own controllers.


Mini Web Server


app.Run(async (context) =>{

var code = context.Request.Query["c"];var size = context.Request.Query["s"];var file = FindAndResizeFlag(code, file);

await context.Response.SendFileAsync(file);});

}


Extreme Granularity


services.AddMvc();}


var builder = services.AddMvcCore();builder.AddViews();builder.AddRazorViewEngine();builder.AddJsonFormatters();

}


// Any chunk like this adds custom behaviorapp.Use(async (context, nextMiddleware) =>{

// first pass here

await nextMiddleware(); // optional, but ...

// second pass here});


Terminating middleware

// Proceeds to the end of the list of registered middleware components;// Then back to the beginning in the reverse order.

app.Run(async context =>{

await context.Response.WriteAsync("...");});

Terminating middleware may work as a catch-all route for MVC routes


public delegate Task RequestDelegate(HttpContext context);

Signature of a piece of ASP.NET Core middleware

Register middleware with Use(func)

app.Use(async (context, next) => {

// ...});


Acting on routes

app.Map(url, middleware =>{

middleware.Run( ... );});

public static IAppBuilder Map(this IAppBuilder app, PathString pathMatch, Action<IAppBuilder> configuration)

app.MapWhen(ctx => IsConditionVerified(ctx), middleware =>{

middleware.Run( ... );});


Coordinating Multiple Middleware

Always be a good citizen- Keep in mind headers can’t be written anymore once the body has begun

- Think before you write to the body

- Document clearly when and how you might be writing to the body

Always be a good neighbor- Be on the safe side

- Register your headers to be added at the last possible minute before the

body is written


Writing Headers from the Middleware

app.Use(async (context, nextMiddleware) =>{

context.Response.OnStarting(() =>{

context.Response.Headers.Add("hello", "world");return Task.FromResult(0);

});

await nextMiddleware();});


Middleware Conventions

public class YourMiddleware{

private RequestDelegate _next; public YourMiddleware(RequestDelegate middleware) {

_nextMiddleware = middleware; }

public async Task Invoke(HttpContext context) {

// Possibly do something here before yielding_nextMiddleware(context);

} }


Middleware Conventions—extension methods

public static class YourMiddlewareExtensions{

public static IApplicationBuilder UseYours(this IApplicationBuilder builder)

{return builder.UseMiddleware<YourMiddleware>();

}}

public void Configure(IApplicationBuilder app) {

app.UseYours(); }


Scoping Services

public class YourMiddleware{

private RequestDelegate _next; public YourMiddleware(RequestDelegate middleware) {

_nextMiddleware = middleware; }

public async Task Invoke(HttpContext ctx, ISomeService svc) {

// Possibly do something here before yielding_nextMiddleware(ctx);

} }

Per-request

dependency

ASP.NET Core Middleware - · PDF fileEXPOWARE SOFT - 2016 Coordinating Multiple Middleware...

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