Docker and ASP.NET Core 2.1 preview 1

Question

I have installed ASP.NET Core 2.1 preview 1 from here and the latest preview of Visual Studio.

Then I follow the steps: File > New Project > ASP.NET Core Web Application > Choose API, check Enable Docker Support (Os: Linux) and No Authentication.

This nicely generates project template, as well as a Docker project with docker compose files. This builds fine, and pulls all the required images. However, when I try to run it with Docker, from within Visual Studio, it doesn't seem to work.

In the logs I see the following:

Content root path: /app
Now listening on: http://[::]:80
...
Request starting HTTP/1.1 GET http://localhost:32778/ Microsoft.AspNetCore.Hosting.Internal.WebHost:Information: Request starting HTTP/1.1 GET http://localhost:32778/

Now, when I try to do a GET to http://localhost:32778/api/values (using Postman), no response is seen:

Could not get any response There was an error connecting to http://localhost:32778/api/values.

BUT! The Docker logs show that the request is being made:

Microsoft.AspNetCore.Hosting.Internal.WebHost:Information: Request starting HTTP/1.1 GET http://localhost:32778/api/values
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[1] Request starting HTTP/1.1 GET http://localhost:32778/api/values
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[2] Request finished in 14.4873ms 307 Microsoft.AspNetCore.Hosting.Internal.WebHost:Information: Request finished in 14.4873ms 307

What am I missing here? If I run the default project with IIS Express, everything works as expected.

EDIT: I've just tested this on ASP.NET Core 2.0, and everything works just fine.

Answer 1

As @andrewbadera pointed out, the repositories changed:

SDK

Old : microsoft/aspnetcore-build:2.0

New: microsoft/dotnet:2.1-sdk

ASP NET

Old : microsoft/aspnetcore:2.0

New: microsoft/dotnet:2.1-aspnetcore-runtime

I don't know why the template from visual studio is not using it already, but soon they probably will fix this.

Visual Studio template is generating:

SDK => microsoft/aspnetcore:2.1

ASP NET => microsoft/aspnetcore-build:2.1

Answer 2

I'm also struggling with netcoreapp2.1 on Docker. Are you sure that docker images are pulled down successfully? Because when I'm creating a new project, the created Dockerfile has:

FROM microsoft/aspnetcore:2.1 AS base
//...
//...
FROM microsoft/aspnetcore-build:2.1 AS build

and from what I can see in the microsoft docker repo, those images simply do not exist (!).

The output in VS shows:

========== Pulling Images ==========
Pulling missing Docker images. To cancel this download, close the command prompt window. To disable image auto-pull, see Tools > Options > Container Tools.
docker pull microsoft/aspnetcore:2.1
docker pull failed

The closest images I found are:

microsoft/aspnetcore:2.1.0-preview1
microsoft/aspnetcore-build:2.1.300-preview1

and the app works, BUT there is another problem: while debugging in VS, the debugger doesn't hit any breakpoints (because PDB symbols are not loaded, I don't know why that happens).

Everything I just described, works when creating a new ASP.NET Core 2.0 project.