Dockerfile doesn't seem to run while debugging in Visual Studio 2019 - visual-studio

Question

The past few weeks i've been working on a project which is built in C# .NET Core in Visual Studio 2019. I enabled Docker support and am using docker-compose to spin up 2 containers (it starts an identityserver4 and webapi). I've created dockerfiles for both projects and created a docker-compose file for starting up the service stack.
The issue i'm running into is that when i run the docker-compose in Visual Studio Debugging mode, it doesnt seem to run my Dockerfile. In the lasts steps in my Dockerfile, I copy some files around and execute a command. These do not get run. However when I use docker build in my commandline, it DOES execute those Dockerfile commands.
Attached my 2 docker files & docker compose.
Web API Dockerfile:
FROM mcr.microsoft.com/dotnet/core/aspnet:2.2-stretch-slim AS base
WORKDIR /app
EXPOSE 80
FROM mcr.microsoft.com/dotnet/core/sdk:2.2-stretch AS build
WORKDIR /src
COPY ["Api/MyApp.Api.Core/MyApp.Api.Core.csproj", "Api/MyApp.Api.Core/"]
COPY ["Api/MyApp.Api.Base/MyApp.Api.Base.csproj", "Api/MyApp.Api.Base/"]
COPY ["Base/MyApp.Base.Contracts/MyApp.Base.Contracts.csproj", "Base/MyApp.Base.Contracts/"]
COPY ["Base/MyApp.Base.Model/MyApp.Base.Model.csproj", "Base/MyApp.Base.Model/"]
COPY ["Data/MyApp.Data.EntityFramework/MyApp.Data.EntityFramework.csproj", "Data/MyApp.Data.EntityFramework/"]
COPY ["ContactpersoonService.cs/MyApp.Services.csproj", "ContactpersoonService.cs/"]
COPY ["Apps/MyApp.Apps.Settings/MyApp.Apps.Settings.csproj", "Apps/MyApp.Apps.Settings/"]
RUN dotnet restore "Api/MyApp.Api.Core/MyApp.Api.Core.csproj"
COPY . .
WORKDIR "/src/Api/MyApp.Api.Core"
RUN dotnet build "MyApp.Api.Core.csproj" -c Release -o /app
FROM build AS publish
RUN dotnet publish "MyApp.Api.Core.csproj" -c Release -o /app
FROM base AS final
WORKDIR /app
COPY --from=publish /app .
COPY Api/MyApp.Api.Core/Security/Certificates /app/Security/Certificates
RUN mkdir -p /usr/local/share/ca-certificates/identityserver
RUN chmod -R 777 /usr/local/share/ca-certificates/identityserver
RUN cp /app/Security/Certificates/* /usr/local/share/ca-certificates/identityserver
RUN update-ca-certificates
ENTRYPOINT ["dotnet", "MyApp.Api.Core.dll"]
IdentityServer Dockerfile:
FROM mcr.microsoft.com/dotnet/core/aspnet:2.2-stretch-slim AS base
WORKDIR /app
EXPOSE 80
FROM mcr.microsoft.com/dotnet/core/sdk:2.2-stretch AS build
WORKDIR /src
COPY ["Api/MyApp.Api.IdentityServer/MyApp.Api.IdentityServer.csproj", "Api/MyApp.Api.IdentityServer/"]
COPY ["Api/MyApp.Api.Base/MyApp.Api.Base.csproj", "Api/MyApp.Api.Base/"]
COPY ["Base/MyApp.Base.Contracts/MyApp.Base.Contracts.csproj", "Base/MyApp.Base.Contracts/"]
COPY ["Base/MyApp.Base.Model/MyApp.Base.Model.csproj", "Base/MyApp.Base.Model/"]
COPY ["Data/MyApp.Data.EntityFramework/MyApp.Data.EntityFramework.csproj", "Data/MyApp.Data.EntityFramework/"]
COPY ["Apps/MyApp.Apps.Settings/MyApp.Apps.Settings.csproj", "Apps/MyApp.Apps.Settings/"]
RUN dotnet restore "Api/MyApp.Api.IdentityServer/MyApp.Api.IdentityServer.csproj"
COPY . .
WORKDIR "/src/Api/MyApp.Api.IdentityServer"
RUN dotnet build "MyApp.Api.IdentityServer.csproj" -c Release -o /app
FROM build AS publish
RUN dotnet publish "MyApp.Api.IdentityServer.csproj" -c Release -o /app
FROM base AS final
WORKDIR /app
COPY --from=publish /app .
COPY Api/MyApp.Api.Core/Security/Certificates /app/Security/Certificates
RUN mkdir -p /usr/local/share/ca-certificates/identityserver
RUN chmod -R 777 /usr/local/share/ca-certificates/identityserver
RUN cp /app/Security/Certificates/* /usr/local/share/ca-certificates/identityserver
RUN update-ca-certificates
ENTRYPOINT ["dotnet", "MyApp.Api.IdentityServer.dll"]
docker-compose.yaml:
version: '3.4'
services:
myapp.api.core:
image: ${DOCKER_REGISTRY-}myappapicore
build:
context: .
dockerfile: Api/MyApp.Api.Core/Dockerfile
links:
- myapp.identity.api:identityserver
ports:
- "52008:80"
volumes:
- "C:/Projects/User/MyApp.Api/Api/MyApp.Api.Core/Security/Certificates/ca.crt:/usr/local/share/ca-certificates/identityserver/identityserver.crt:ro"
networks:
app_net:
ipv4_address: 192.168.1.200
myapp.identity.api:
image: ${DOCKER_REGISTRY-}myappapiidentityserver
build:
context: .
dockerfile: Identity/MyApp.Identity.Api/Dockerfile
ports:
- "5000:80"
- "5001:443"
volumes:
- "C:/Projects/User/MyApp.Api/Api/MyApp.Api.IdentityServer/Security/Certificates/ca.crt:/usr/local/share/ca-certificates/identityserver/identityserver.crt:ro"
networks:
app_net:
ipv4_address: 192.168.1.201
networks:
app_net:
external: true
I'm using Visual Studio 2019 (16.3.4)

Answer 1

This is apparently by design as a "Fast mode" optimization in Visual Studio 2019. See the documentation for debugging in containers here.
What it states is that "Fast mode" is the default behavior when debugging containers in VS 2019. In this mode, only the first stage (base) of a multi-stage build is built according to the Dockerfile. VS then handles the rest on the host machine, ignoring the Dockerfile, and shares the output to the container by using volume mounting. This means that any custom steps you add to other stages will be ignored when using the Debug configuration in VS 2019. (The reason given for this non-obvious, and therefore potentially frustrating, optimization is that builds are much slower in a container than on the local machine.) Note that this optimization only happens when using the Debug configuration. The Release configuration will use the entire Dockerfile.
Your options are:
Place your custom steps in the first (base) step of the Dockerfile.
or
Disable this optimization by editing the project file like this:
<PropertyGroup>
<ContainerDevelopmentMode>Regular</ContainerDevelopmentMode>
</PropertyGroup>
Also keep in mind that it will try to reuse a previously built container if possible, so you may need to perform a Clean or Rebuild in order to force the build to create a new version of the container.
Good luck!
** EDIT **
It seems that there is an issue when trying to use the ContainerDevelopmentMode flag after Container Orchestration Support (in this case, Docker Compose) is added. See this issue. It is suggested in the issue discussion that this flag could be used on the docker-compose.dcproj file, but there is a bug (still not fixed) that keeps that approach from working.
A third option, hinted at in my previous answer but not made explicit, would be:
Switch your solution configuration from Debug to Release.
This works, but clearly isn't ideal when you're trying to debug your application.