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European ASP.NET Core Hosting :: RESTful WebAPI With Onion Architecture

clock April 9, 2019 11:29 by author Peter

Hello friends, here I will show you how to create a WebApi with the following characteristics:

  • ASP.Core 2.1
  • EntityFramework
  • FluentValidation
  • Nlogger
  • Swagger
  • Jwt

Let's start. First create an empty project, then add the following folders:

  • Application
  • Domain
  • Service
  • Infrastructure

Then in the Domain folder, we create a library project Net.Core 2.1 with the name WebApi.Domain add the following dependencies

FluentValidation.AspNetCore

In this project, we add the following folders:

  • Dtos
  • Entities
  • Interfaces

In the Entities folder, we create the BaseEntity class:

    namespace WebApi.Domain.Entities 
    { 
        public abstract class BaseEntity 
        { 
            public virtual int Id { get; set; } 
        } 
    } 

Our project classes will inherit the field Id from this abstract class (if you want you can add other fields like CreatedAt or CreatedBy).

Then we create the Country class with the properties that defines a Country.

    namespace WebApi.Domain.Entities 
    { 
        public class Country : BaseEntity 
        { 
            public string Name { get; set; } 
            public int Population { get; set; } 
            public decimal Area { get; set; } 
            public string ISO3166 { get; set; } 
            public string DrivingSide { get; set; } 
            public string Capital { get; set; } 
     
        } 
    } 

Now to make the exercise more interesting, we are going to assume that we do not want to expose all the Country class. In the Dtos folder, we create the following CountryDensityDTO class.

    using System; 
    using WebApi.Domain.Entities; 
     
    namespace WebApi.Domain.Dtos 
    { 
        public class CountryDensityDTO : BaseEntity 
        { 
            public string Name { get; set; } 
            public string Capital { get; set; } 
            public decimal Area { get; set; } 
            public int Population { get; set; } 
     
     
            public int Populationdensity 
            { 
                get 
                { 
                    return Decimal.ToInt32(Population / Area); 
                } 
            } 
        } 
    }

This class exposes Name, Capital Area, Population and a calculated field Populationdensity.
Now we will continue with the Infrastructure layer and then we will finish the missing parts.We go to the Infrastructure folder and create a library Net.Core 2.1. We name it WebApi.Infrastructure.Data.

We add the following Packages:

  • Microsoft.EntityFrameworkCore.SqlServer 2.1.4
  • Microsoft.EntityFrameworkCore.Tools 2.1.4
  • Microsoft.Extensions.Identity.Stores 2.1.1
  • Microsoft.VisualStudio.Web.CodeGeneration.Design 2.1.5
  • Add Project reference WebApi.Domain 

We create the following folders:

  • Context
  • EntityDbMapping
  • Repository

In the Context Folder, we add the SqlServerContext class. We refer to our Country entity with DbSet to work with the database. As we work with CodeFirst approach, we will create a mapping for our entity Country in the database.
"modelBuilder.Entity<Country>(new CountryMap().Configure);"

Optionally, in this part we can also add seed data when creating a table.

using Microsoft.AspNetCore.Identity.EntityFrameworkCore; 
using Microsoft.EntityFrameworkCore; 
using WebApi.Domain.Entities; 
using WebApi.Infrastructure.Data.EntityDbMapping; 

namespace WebApi.Infrastructure.Data.Context 

public class SqlServerContext :   IdentityDbContext<ApplicationUser> 

    public DbSet<Country> Country { get; set; } 

    public SqlServerContext(DbContextOptions<SqlServerContext> options) : base(options) 
    { 
      
    }     
    protected override void OnModelCreating(ModelBuilder modelBuilder) 
    { 
        base.OnModelCreating(modelBuilder); 
        modelBuilder.Entity<Country>(new CountryMap().Configure); 
        // ModelBuilderExtensions.Seed(modelBuilder); 

    } 

//Data for first time on table 
public static class ModelBuilderExtensions 

    public static void Seed(this ModelBuilder modelBuilder) 
    { 
        modelBuilder.Entity<Country>().HasData( 
            new Country 
            { 
                Id = 1, 
                Name = "Venezuela", 
                Population = 300000000, 
                Area = 230103 
              
            }, 
            new Country 
            { 
                Id = 2, 
                Name = "Peru", 
                Population = 260000000, 
                Area =33249               
            } 
        ); 
    } 


In the folder, EntityDbMapping, we create the CountryMap class. In this class, we define the physical representation of the properties of the Country class as fields in the table of the database.

    using Microsoft.EntityFrameworkCore;   
    using Microsoft.EntityFrameworkCore.Metadata.Builders;   
    using WebApi.Domain.Entities;   
       
    namespace WebApi.Infrastructure.Data.EntityDbMapping   
    {   
        public class CountryMap : IEntityTypeConfiguration<Country>   
        {   
            public void Configure(EntityTypeBuilder<Country> builder)   
            {   
                builder.ToTable("Country");   
       
                builder.HasKey(c => c.Id);   
       
                builder.Property(c => c.Name)   
                    .IsRequired()   
                    .HasColumnName("Name")   
                    .HasColumnType("varchar(150)");   
       
                builder.Property(c => c.Population)   
                    .IsRequired()   
                    .HasColumnType("int")   
                    .HasColumnName("Population");   
       
                builder.Property(c => c.Area)   
                    .IsRequired()   
                    .HasColumnType("decimal(14,2)")   
                    .HasColumnName("Area");   
       
                builder.Property(c => c.ISO3166)   
                .IsRequired()   
                .HasColumnType("varchar(3)")   
                .HasColumnName("ISO3166");   
       
                builder.Property(c => c.DrivingSide)   
                .IsRequired()   
                .HasColumnType("varchar(50)")   
                .HasColumnName("DrivingSide");   
       
                builder.Property(c => c.Capital)   
                .IsRequired()   
                .HasColumnType("varchar(50)")   
                .HasColumnName("Capital");   
            }   
       
        }   
    }   


This is it for now.
In the next chapter, we will implement validations with FluentValidation. We will also configure Mapper to use it with our DTOs and will implement Identity using Jwt.



European ASP.NET Core Hosting :: Consuming RabbitMQ Messages In ASP.NET Core

clock March 26, 2019 11:42 by author Peter

Background tasks play a very important role when we are building a distributed system. The most common scenario is consuming the service bus's message. In this article, I'd like to present how to consume the RabbitMQ message via BackgroundService in ASP.NET Core.
Run RabbitMQ Host

We should set up an instance of RabbitMQ. The fastest way is to use Docker.
docker run -p 5672:5672 -p 15672:15672 rabbitmq:management  

After running the Docker container, we are able to view the management page via http://localhost:15672.

Consuming RabbitMQ Messages In ASP.NET Core
Setup the BackgroundService
Here, we create a new class named ConsumeRabbitMQHostedService that is inherited from BackgroundService.
BackgroundService is a base class for implementing a long-running IHostedService. It provides the main work needed to set up the background task.
Here is an example to demonstrate how to consume RabbitMQ messages.
public class ConsumeRabbitMQHostedService : BackgroundService 

    private readonly ILogger _logger; 
    private IConnection _connection; 
    private IModel _channel; 
 
    public ConsumeRabbitMQHostedService(ILoggerFactory loggerFactory) 
    { 
        this._logger = loggerFactory.CreateLogger<ConsumeRabbitMQHostedService>(); 
        InitRabbitMQ(); 
    } 
 
    private void InitRabbitMQ() 
    { 
        var factory = new ConnectionFactory { HostName = "localhost" }; 
 
        // create connection 
        _connection = factory.CreateConnection(); 
 
        // create channel 
        _channel = _connection.CreateModel(); 
 
        _channel.ExchangeDeclare("demo.exchange", ExchangeType.Topic); 
        _channel.QueueDeclare("demo.queue.log", false, false, false, null); 
        _channel.QueueBind("demo.queue.log", "demo.exchange", "demo.queue.*", null); 
        _channel.BasicQos(0, 1, false); 
 
        _connection.ConnectionShutdown += RabbitMQ_ConnectionShutdown; 
    } 
 
    protected override Task ExecuteAsync(CancellationToken stoppingToken) 
    { 
        stoppingToken.ThrowIfCancellationRequested(); 
 
        var consumer = new EventingBasicConsumer(_channel); 
        consumer.Received += (ch, ea) => 
        { 
            // received message 
            var content = System.Text.Encoding.UTF8.GetString(ea.Body); 
 
            // handle the received message 
            HandleMessage(content); 
            _channel.BasicAck(ea.DeliveryTag, false); 
        }; 
 
        consumer.Shutdown += OnConsumerShutdown; 
        consumer.Registered += OnConsumerRegistered; 
        consumer.Unregistered += OnConsumerUnregistered; 
        consumer.ConsumerCancelled += OnConsumerConsumerCancelled; 
 
        _channel.BasicConsume("demo.queue.log", false, consumer); 
        return Task.CompletedTask; 
    } 
 
    private void HandleMessage(string content) 
    { 
        // we just print this message  
        _logger.LogInformation($"consumer received {content}"); 
    } 
     
    private void OnConsumerConsumerCancelled(object sender, ConsumerEventArgs e)  {  } 
    private void OnConsumerUnregistered(object sender, ConsumerEventArgs e) {  } 
    private void OnConsumerRegistered(object sender, ConsumerEventArgs e) {  } 
    private void OnConsumerShutdown(object sender, ShutdownEventArgs e) {  } 
    private void RabbitMQ_ConnectionShutdown(object sender, ShutdownEventArgs e)  {  } 
 
    public override void Dispose() 
    { 
        _channel.Close(); 
        _connection.Close(); 
        base.Dispose(); 
    } 


Configure Services
We should configure this hosted service with the background task logic in ConfigureServices method.
public void ConfigureServices(IServiceCollection services) 

    // others ... 
     
    services.AddHostedService<ConsumeRabbitMQHostedService>(); 
}  

Result

After running this app, we may get the following output in the terminal.Turning to the Management UI of RabbitMQ, we find that it creates a new exchange and a new queue.

The next time we try to publish a message to show the background task is running well, we get the following result.




European ASP.NET Core Hosting :: Using Docker to Store ASP.NET Core Kestrel Certificates

clock March 22, 2019 08:48 by author Scott

When working with ASP.Net Core in Docker containers, it can be cumbersome to deal with certificates. While there is a documentation about setting certificate for dev environment, there’s no real guidance on how to make it work when deploying containers in a Swarm for example.
In this article we are going to see how to take advantage of Docker secrets to store ASP.Net Core Kestrel certificates in the context of Docker Swarm.

Hosting the service

First of all, we are going to create à Swarm service on our machine that use the sample Asp.Net Core app. The purpose of this article is to make SSL work in the container withoutchanging anything to an existing image.

docker service create --name mywebsite --publish published=8080,target=80,mode=host microsoft/dotnet-samples:aspnetapp

We are creating service mywebsite, publishing only one port 8080 bound to the port 80 in the container using the host mode and using the image microsoft/dotnet-samples:aspnetapp. Please note that you can use others configuration (for example expose port in routing mesh mode).

Preparing the certificate

We need a certificate. It can be created via an external certificate authority but here for the sake of the article, we are going to create a self signed certificate (of course, don’t use this in production). We are using Powershell for this task (you can skip this if you already have a pfx certificate signed by a real CA).

$cert = New-SelfSignedCertificate -DnsName "mywebsite" -CertStoreLocation "cert:\LocalMachine\My"
$password = ConvertTo-SecureString -String "mylittlesecret" -Force -AsPlainText
$cert | Export-PfxCertificate -FilePath c:\temp\mywebsite.pfx -Password $password

Once you have your pfx, we are goind to unprotect it from the password. It might be seem unsecure but when it will be added to the Docker secret store, it will be stored securedly. For this task I will use OpenSSL (not possible with Powerhsell as far as I know). OpenSSL is provided with Git for example.

& 'C:\Program Files\Git\mingw64\bin\openssl.exe' pkcs12 -in c:\temp\mywebsite.pfx -nodes -out c:\temp\mywebsite.pem -passin pass:mylittlesecret
& 'C:\Program Files\Git\mingw64\bin\openssl.exe' pkcs12 -export -in c:\temp\mywebsite.pem -out c:\temp\mywebsite.unprotected.pfx -passout pass:

Now that the pfx is un protected, we can add it to the docker store certificate and display it.

docker secret create kestrelcertificate c:\temp\mywebsite.unprotected.pfx

docker secret ls

ID                          NAME                 DRIVER              CREATED             UPDATED

iapy6rolt7po1mwm9aw6z0qc5   kestrelcertificate                       13 minutes ago      13 minutes ago

Our secret being in the store, you can delete (or store securely somewhere else your pfx).

Making it work

We can now update our service to take in account this secret. When adding a secret to a service, Docker will create a file in a specific directory containing the value of the secret. On Windows it’s c:\programdata\docker\secrets.

Let’s update our service and see what happened inside the container.

docker service update --secret-add kestrelcertificate mywebsite

docker exec 4b51e736ce65 cmd.exe /c dir c:\programdata\docker\secrets

 Volume in drive C has no label.
 Volume Serial Number is 3CBB-E577

 Directory of c:\programdata\docker\secrets

11/15/2018  10:38 PM    <DIR>          .
11/15/2018  10:38 PM    <DIR>          ..
11/15/2018  10:38 PM    <SYMLINK>      kestrelcertificate [C:\ProgramData\Docker\internal\secrets\iapy6rolt7po1mwm9aw6z0qc5]
               1 File(s)              0 bytes
               2 Dir(s)  21,245,009,920 bytes free

We can see that our secret exists and is named kestrelcertificate, as we named it in the command line.

We can therefore update our service to remove the old binding on port 80, replace it with a binding on port 443, tell Kestrel to use this port and finally give Kestrel the path of our secret.
This can be done with only one command:

docker service update --publish-rm published=8080,target=80,mode=host --publish-add published=8080,target=443,mode=host --env-add ASPNETCORE_URLS=https://+:443 --env-add Kestrel__Certificates__Default__Path=c:\programdata\docker\secrets\kestrelcertificate mywebsite

Wait a while that your service update, try to browse and it should work ! Well, actually it should only works on Linux.

Making it work on Windows

If you try to have a look a the logs generated by your service, you should end with something like this.

docker service logs mywebsite

mywebsite.1.uy3vm8txwxec@nmarchand-lt    | crit: Microsoft.AspNetCore.Server.Kestrel[0]
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |       Unable to start Kestrel.
mywebsite.1.uy3vm8txwxec@nmarchand-lt    | Internal.Cryptography.CryptoThrowHelper+WindowsCryptographicException: Unspecified error
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Internal.Cryptography.Pal.CertificatePal.FromBlobOrFile(Byte[] rawData, String fileName, SafePasswordHandle password, X509KeyStorageFlags keyStorageFlags)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at System.Security.Cryptography.X509Certificates.X509Certificate..ctor(String fileName, String password, X509KeyStorageFlags keyStorageFlags)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at System.Security.Cryptography.X509Certificates.X509Certificate2..ctor(String fileName, String password)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.LoadCertificate(CertificateConfig certInfo, String endpointName)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.LoadDefaultCert(ConfigurationReader configReader)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.Load()
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServer.ValidateOptions()
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServer.StartAsync[TContext](IHttpApplication`1 application, CancellationToken cancellationToken)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |
mywebsite.1.uy3vm8txwxec@nmarchand-lt    | Unhandled Exception: Internal.Cryptography.CryptoThrowHelper+WindowsCryptographicException: Unspecified error
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Internal.Cryptography.Pal.CertificatePal.FromBlobOrFile(Byte[] rawData, String fileName, SafePasswordHandle password, X509KeyStorageFlags keyStorageFlags)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at System.Security.Cryptography.X509Certificates.X509Certificate..ctor(String fileName, String password, X509KeyStorageFlags keyStorageFlags)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at System.Security.Cryptography.X509Certificates.X509Certificate2..ctor(String fileName, String password)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.LoadCertificate(CertificateConfig certInfo, String endpointName)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.LoadDefaultCert(ConfigurationReader configReader)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.Load()
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServer.ValidateOptions()
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServer.StartAsync[TContext](IHttpApplication`1 application, CancellationToken cancellationToken)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Hosting.Internal.WebHost.StartAsync(CancellationToken cancellationToken)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Hosting.WebHostExtensions.RunAsync(IWebHost host, CancellationToken token, String shutdownMessage)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Hosting.WebHostExtensions.RunAsync(IWebHost host, CancellationToken token)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Hosting.WebHostExtensions.Run(IWebHost host)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at aspnetapp.Program.Main(String[] args) in C:\app\aspnetapp\Program.cs:line 18

We can see a nasty bug of Windows here (Github issue).
What did happen ? If you look closely at the dir command we made in the container, you’ll see that the secret is not really a file but instead a symbolic link to an other file. Unfortunately, Windows is unable to use a certificate that is a symlink. One solution could be to manually read the certificate with File.ReadAllBytes() and pass it to the constructor of X509Certificate. However, it would be against the purpose of this article which is to not modify the Docker image.

We can find a workaround by browsing the Docker documentation which states that the real file containing the secret (which in fact is the target of the symlink) can be found in the path c:\programdata\docker\internal\secrets\<secretid> where secretid is the id of the secret (as shown by docker secret ls).

We can update our service to change the path by updating the environment variable. It now works also on windows!

docker service update --env-rm
Kestrel__Certificates__Default__Path=c:\programdata\docker\secrets\kestrelcertificate --env-add Kestrel__Certificates__Default__Path=c:\programdata\docker\internal\secrets\iapy6rolt7po1mwm9aw6z0qc5 mywebsite

docker logs 7b54cdc42a86

Hosting environment: Production
Content root path: C:\app
Now listening on: https://[::]:443
Application started. Press Ctrl+C to shut down.

Final word

We have seen in this article how to use Docker secrets to store ASP.Net Core Kestrel certificates in our Docker Swarm. However, please keep in mind that the Windows workaround should be used with care as written in the Docker documentation.

Another word also about SSL Offloading : I know that usually the reverse proxy (Nginx, Traefik, etc.) is used to be the SSL termination but sometimes you still want SSL end to end. 



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