Can't run dockerized .NET Core (3.1) API-CodePudding

Dockerfile

# syntax=docker/dockerfile:1
FROM mcr.microsoft.com/dotnet/sdk:3.1 AS build-env
WORKDIR /app

# Copy csproj and restore as distinct layers
COPY *.csproj ./
RUN dotnet restore

# Build
RUN dotnet publish -c Release -o out

# Build runtime image
FROM mcr.microsoft.com/dotnet/aspnet:3.1
WORKDIR /app
COPY --from=build-env /app/out .
ENTRYPOINT ["dotnet", "myapp.dll"]

Building it for the first time, I had this error:

error CS5001: Program does not contain a static 'Main' method suitable for an entry point

And I solved it adding

<OutputType>Library</OutputType>

to my .csproj, then I could build it.

At this point, when trying to run it with

docker run -p 8082:8080 --rm dockerized-app:dev

Docker throws this error:

The library 'libhostpolicy.so' required to execute the application was not found in '/app/'.

Looking for a solution on internet I found that I could solve it adding

<GenerateRuntimeConfigurationFiles>true</GenerateRuntimeConfigurationFiles>

to the .csproj, which I did, built again, and when running I'm getting this error which I can't solve:

Entry point not found in assembly 'myapp, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.

EDIT: Adding the actual code of the API.

Controller.cs:

    [ApiController]
    [Route("api/[controller]")]
    public class MyAppController : ControllerBase
    {
        [EnableCors("AllowOrigin")]
        [HttpGet]
        public string GetText(Request request)
        {
            return request.text;
        }
    }

Program.cs:

public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });

Startup.cs:

public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
            services.AddCors(options =>
            {
                options.AddPolicy("AllowAllHeaders",
                      builder =>
                      {
                          builder.AllowAnyOrigin()
                                 .AllowAnyHeader()
                                 .AllowAnyMethod();
                      });
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseCors(builder =>
            {
                builder
                .AllowAnyOrigin()
                .AllowAnyMethod()
                .AllowAnyHeader();
            });

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }

launchSettings.json:

{
  "$schema": "http://json.schemastore.org/launchsettings.json",
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:58726",
      "sslPort": 0
    }
  },
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "launchUrl": "myapp",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "MyApp": {
      "commandName": "Project",
      "launchUrl": "myapp",
      "applicationUrl": "http://localhost:5000",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  }
}

myapp.csproj (with the changes I mentioned before):

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <OutputType>Library</OutputType>
    <GenerateRuntimeConfigurationFiles>true</GenerateRuntimeConfigurationFiles>
  </PropertyGroup>


  <ItemGroup>
    <None Remove="Newtonsoft.Json" />
    <None Remove="Models\" />
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
  </ItemGroup>
  <ItemGroup>
    <Folder Include="Models\" />
  </ItemGroup>
</Project>

And, just in case someone asks, it works locally, it starts and wait for receiving a request.

CodePudding user response：

You only copy the .csproj file into the image. You're missing the step where you copy the rest of the files.

# syntax=docker/dockerfile:1
FROM mcr.microsoft.com/dotnet/sdk:3.1 AS build-env
WORKDIR /app

# Copy csproj and restore as distinct layers
COPY *.csproj ./
RUN dotnet restore

# vvvv   This is missing
COPY . .

# Build
RUN dotnet publish -c Release -o out

# Build runtime image
FROM mcr.microsoft.com/dotnet/aspnet:3.1
WORKDIR /app
COPY --from=build-env /app/out .
ENTRYPOINT ["dotnet", "myapp.dll"]