ASP .NET Core With Apache On Ubuntu

Not too long ago, it would have been next to impossible to have softwares written on Windows or using Microsoft framework to be used on Linux. A lot have changed in the past five years. Microsoft started contributed a lot to the open source community. They released Visual Studio Code. They forked a version of SQL Server to run on Linux. They started to switch the frame work .NET to a newer framework .NET Core with the promise that .NET Core would work on all platform rather than just on Windows.
In this article, we will take the ASP .NET Core framework on a “Hello World” test drive. More specific, we will write the most simple web site in ASP .NET Core, then, set up an Apache web server that would serve this website. The Apache web server is hosted on a Ubuntu 18.04 machine.

Before getting into the detail of how to set up such a website, let’s take a step back to go over the detail overview of the configuration. When a web application is created using the ASP .NET Core framework, it would inherently be served using Kestrel, the web server provided along with the framework. But if the hosting machine has already had a web server of its own or if it had been decided previously to use another web server -like our example- then we would need to turn that server into a proxy server. You can see here for a few other reasons why you would need a proxy server. And what does it mean to have a web server function as a proxy server? In short, it means that the web server will forward all the request to the Kestrel server and then, pass all the return to the requester.

Back to the example, from an overview, these will be the steps to set up the web app.

1. Install the web server. Set it up to be a proxy for your web site.
2. Install the .NET Core on your machine. It would have been enough to install the runtime version on the server. But on the machine where development is done, the SDK must be installed.
3. Create a “service” configuration file where the Kestrel server would run. This “service” will receive the “message” forwarded from the proxy server.
4. Write the web application. Make sure the web application is appropriately equipped to send and receive data from the proxy web server.
5. Build the web application, copy the file to the appropriate folder specified in the configuration file in step 2. Restart the Apache web server, start the Kestrel service.

• Step 0: In doing development, for the sake of convenience and demonstration, it would be best to do all the above steps on a container. In that case, there would have to be a step 0 of setting up the container. Below is how this can be done.

  Create a container.

  sudo lxc-create -n <ContainerName> -t ubuntu

  Start the container

  sudo lxc-start -n <ContainerName>

  We would need to get the IP address exposed by the container for later use. To do that, use this command

  sudo lxc-ls --fancy

  The IP address of the newly created container. (picture?)

  Next create the .ssh directory for the ubuntu user in the newly created container
  ( remember the new container have user ubuntu, password ubuntu by default)

  After that, run the below command (assuming you have created the ssh key in .ssh in your current host machine).

  scp .ssh/id_res.pub ubuntu@<IPaddressOfContainer>:/home/ubuntu/.ssh/authorized_keys

  Now, we can ssh into the container without having to type the password.
  It would be best to update and install wget on the container.

  sudo apt update
  sudo apt upgrade
  sudo apt install wget
  

• Step 1: Installing Apache2

  Installing Apache2 on Ubuntu is straightforward.

  sudo apt install apache2

  Enabling the server to be a proxy server.

  sudo a2enmod proxy proxy_http proxy_html
  sudo sysctl restart apache2

  Create a file aspdotnetcoredemo.conf in /etc/apache2/conf-available/ and create a softlink of the same name in /etc/apache2/conf-enabled/ pointing to the above file. In general, it seems that the package Apache2 on Ubuntu would always have pairs of folder. One contains the available configuration. The other contains the symlink to the configurations that need to be enable.
  The content of the file aspdotnetcoredemo.conf is below

  <VirtualHost *:80>
      ProxyPreserveHost On
      ProxyPass / http://127.0.0.1:5000/
      ProxyPassReverse / http://127.0.0.1:5000/
      ErrorLog /var/log/apache2/aspnetcoredemo-error.log
      CustomLog /var/log/apache2/aspnetcoredemo-access.log common
  </VirtualHost>    
  

  Creating the symbolic link by the command below

  sudo ln -sf /etc/apache2/conf-available/aspdotnetcoredemo.conf /etc/apache2/conf-enabled/aspdotnetcoredemo.conf

• Step 2: Installing .NET Core SDK
  The best place for the instruction to do this is here.

  wget -q https://packages.microsoft.com/config/ubuntu/18.04/packages-microsoft-prod.deb
  sudo dpkg -i packages-microsoft-prod.deb
      
  sudo apt-get install apt-transport-https
  sudo apt-get update
  sudo apt-get install dotnet-sdk-2.1
  

• Step 3: Kestrel service

  Create a service file in /etc/systemd/system/ and call the file kestrel-aspdotnetcoredemo.service (or whatever name you choose). Just make sure to have the name correct for later steps. Note the line:

  ExecStart=/usr/bin/dotnet /var/aspdotnetcoredemo/WebDemo.dll

  This is because we will create an app and call it WebDemo. The WebDemo.dll is what we would get after build and release. In case the .dll file name is different, make sure we have the right name there.
  The user www-data is automatically created by the installation of Apache2 package released by Ubuntu. This is the user that has the privilege to access the files for the web server.
  Make sure to put the file in the right folder (or alter this file so that it would point to the right folder).

  File content:

  [Unit]
  Description=Example ASP .NET Web Application running on Ubuntu 18.04
  
  [Service]
  WorkingDirectory=/var/aspdotnetcoredemo
  ExecStart=/usr/bin/dotnet /var/aspdotnetcoredemo/WebDemo.dll
  Restart=always
  RestartSec=10
  SyslogIdentifier=dotnet-demo
  User=www-data
  Environment=ASPNETCORE_ENVIRONMENT=Production
  
  [Install]
  WantedBy=multi-user.target
  

• Step 4: Create the app

  Make a folder for the code.

  mkdir WebDemo
  cd WebDemo
  dotnet new web
  

  The dotnet new web will create the most primitive web project on .NET Core. For more information, use the command dotnet new –help.
  For inventory purpose, at this point, there are two .cs files (Startup.cs and Program.cs) and the file WebDemo.csproj in the WebDemo folder.
  The content of WebDemo.csproj is below.

  <Project Sdk="Microsoft.NET.Sdk.Web">
      <PropertyGroup>
          <TargetFramework>netcoreapp2.1</TargetFramework>
      </PropertyGroup>
        
      <ItemGroup>
          <Folder Include="wwwroot\" />
      </ItemGroup>
        
      <ItemGroup>
          <PackageReference Include="Microsoft.AspNetCore.App" />
          <PackageReference Include="Microsoft.AspNetCore.Razor.Design" Version="2.1.2" PrivateAssets="All" />
      </ItemGroup>  
  </Project>
  

  Run this command to add the package HttpOverrides to the project. The Kestrel service will need this package to communicate with the proxy web server.

  dotnet add package Microsoft.AspNetCore.HttpOverrides --version 2.1.1

  Try viewing the WebDemo.csproj after the command. You will see something like below (Note of a new PackageReference created):

  <Project Sdk="Microsoft.NET.Sdk.Web">
      <PropertyGroup>
          <TargetFramework>netcoreapp2.1</TargetFramework>
      </PropertyGroup>
        
      <ItemGroup>
          <Folder Include="wwwroot\" />
      </ItemGroup>
        
      <ItemGroup>
          <PackageReference Include="Microsoft.AspNetCore.App" />
          <PackageReference Include="Microsoft.AspNetCore.HttpOverrides" Version="2.1.1" />
          <PackageReference Include="Microsoft.AspNetCore.Razor.Design" Version="2.1.2" PrivateAssets="All" />
      </ItemGroup>  
  </Project>
  

  Modify the Startup.cs in two places.
  Add the line below to the header:

  using Microsoft.AspNetCore.HttpOverrides;

  Change the Configure method to this (the middle section was added).

  public void Configure(IApplicationBuilder app, IHostingEnvironment env)
  {
      if (env.IsDevelopment())
      {
          app.UseDeveloperExceptionPage();
      }
      app.UseForwardedHeaders(new ForwardedHeadersOptions
      {
          ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
      });
      app.Run(async (context) =>
      {
          await context.Response.WriteAsync("Hello World from my little app!");
      });
  }
  

  After all this, try running the project to see if there is any error (from the WebDemo directory)

  dotnet run

  Next, publish the application.

  dotnet publish -c Release

  Copy all the files in the folder bin/Release/netcoreapp2.1/publish/ to the folder /var/aspdotnetcoredemo/

  Start the application by running the commans.

  sudo systemctl enable kestrel-aspdotnetcoredemo.service
  sudo systemctl start kestrel-aspdotnetcoredemo.service
  

  Note: if you every change the content of /var/aspdotnetcoredemo or the .service file and you need to reload, run these command

  sudo systemctl daemon-reload
  sudo systemctl restart kestrel-aspdotnetcoredemo.service
  sudo systemctl restart apache2
  

  Now, from the web browser from your computer, type in the IP address of your container, you should see the website. The content should be the phrase Hello World from my little app.

• Bonus: Create the app in Fsharp
  If we want to create an app using F#, the step in step 4 are nearly the same, with some modification.
  Add a parameter to tell dotnet new that you will use F#.

  dotnet new web -lang F#

  The Startup.fs file will need to be like below.

  namespace FsharpWebDemo
  open System
  open Microsoft.AspNetCore.Builder
  open Microsoft.AspNetCore.Hosting
  open Microsoft.AspNetCore.Http
  open Microsoft.Extensions.DependencyInjection
  open Microsoft.AspNetCore.HttpOverrides
  
  type Startup() 
  
      // This method gets called by the runtime. Use this method to add services to the container.
      // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
      member this.ConfigureServices(services: IServiceCollection) =
          ()
  
      // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
      member this.Configure(app: IApplicationBuilder, env: IHostingEnvironment) =
          if env.IsDevelopment() then
              app.UseDeveloperExceptionPage() |> ignore
  
          let options = new ForwardedHeadersOptions(ForwardedHeaders = (ForwardedHeaders.XForwardedFor ||| ForwardedHeaders.XForwardedProto))
          app.UseForwardedHeaders( options ) |> ignore
  
          app.Run(fun context -> context.Response.WriteAsync("Hello World with F#!")) |> ignore
      
  

  Compare the files to see the difference.

So above is an elementary example of taking ASP .NET Core on a test drive. There are a few other things that can be done, for example, how to have the Kestrel listen from a different port than 5000 (in case there are more than one such services). But this one showed the capability of it to play nice with Apache.