Agfdhyk

I am currently working on deploying a .NET Core web api on a server. I wanted to do it using docker compose for easy management. In my Startup.cs I have this code:

public class Startup

{

    public Startup (IConfiguration configuration)

    {

        Configuration = configuration;

    }



    public IConfiguration Configuration { get; }



    public void ConfigureServices (IServiceCollection services)

    {

        var databaseHost = Configuration["DB_HOST"] ?? "localhost";

        // ........

    }

    // ........

}

My Dockerfile is pretty standard, as Microsoft's documentation states it should be:

FROM microsoft/dotnet:sdk AS build-env

WORKDIR /app



# Copy csproj and restore as distinct layers

COPY *.csproj ./

RUN dotnet restore



# Copy everything else and build

COPY . ./

RUN dotnet publish -c Release -o out



# Build runtime image

FROM microsoft/dotnet:aspnetcore-runtime

WORKDIR /app

COPY --from=build-env /app/out .

EXPOSE 80/tcp

ENTRYPOINT ["dotnet", "ApiProject.dll"]

I define my environment variables in my docker-compose.yml file:

version: '3'

services:

restapi:

    build:

    context: ./ApiProject

    dockerfile: Dockerfile

    depends_on:

    - db

    ports:

    - "5000:80"

    restart: always

    environment:

    - DB_HOST=db

db:

image: postgres

ports:

    - "5432:5432"

restart: always

environment:

    POSTGRES_USER: "root"

    POSTGRES_PASSWORD: "root"

This docker-compose.yml file works just fine on my local machine. The issue comes when I want to deploy it on the server. Someone online have made a docker-compose file which runs an nginx proxy and containers for automatically retrieving valid SSL certificates using Let's Encrypt (jwilder/nginx-proxy).

It is pretty easy to get it working. When starting a new docker container, you just have to assign it to the correct external docker network (in this case: nginx-proxy), and then give it the following environment variables:

• 
  VIRTUAL_HOST: example.com


• LETSENCRYPT_HOST: example.com


• LETSENCRYPT_EMAIL: myemail@example.com

Furthermore, instead of mapping ports, you just have to expose port 80. Then when the container starts up, the other containers will automatically get the SSL certificates and make a proxy to the newly started container.

The issue here is the way Microsoft's containers works with environment variables. The container for my web api has a few environment variables of itself, such as DB_HOST=mydbhost.com. It then automatically gets imported in the code. That means I can't add the environment variables (i.e. VIRTUAL_HOST: example.com) needed for the proxy containers to work properly.

I tried out with the following docker-compose.yml configuration:

  version: '3'

  services:

    restapi:

      build:

        context: ./EffortlessApi

        dockerfile: Dockerfile

      depends_on:

        - db

      expose:

        - 80

      restart: always

      environment:

        - DB_HOST=db

        - VIRTUAL_HOST: my_domain.com

        - LETSENCRYPT_HOST: my_domain.com

        - LETSENCRYPT_EMAIL: my@email.com

    db:

    image: postgres

    ports:

      - "5432:5432"

    restart: always

    environment:

      POSTGRES_USER: "root"

      POSTGRES_PASSWORD: "root"

  networks:

    default:

      external:

        name: nginx-proxy

But that resolved in the following error when running docker-compose up:

ERROR: The Compose file './docker-compose.yml' is invalid because:
services.restapi.environment contains {"VIRTUAL_HOST":
"api.effortless.dk"}, which is an invalid type, it should be a string

I'm quite lost on how I should solve this issue. I want to easily deploy and manage multiple containers with valid SSL certificates, and this setup is pretty cool, if just it worked with the .NET project as well.

I figured it all out, the solution was luckily pretty simple. I don't know why, but Microsoft for some reason simply chose to format their environment wrong. To fix this, simply use = rather than : without the space:

(...)

environment:

   - DB_HOST=db

   - VIRTUAL_HOST=my_domain.com

   - LETSENCRYPT_HOST=my_domain.com

   - LETSENCRYPT_EMAIL=my@email.com

(...)