Missing DLL in docker image after copying published tree inside

Question

I am currently experimenting with using JIB for packaging and deploying a dotnet project not written by me (I am not very familiar with dotnet).

I have the dotnet SDK installed (and visual studio 19) on my windows machine and after invoking "dotnet publish -c Release" on my solution which contain a project X and a test project X_test I end up with a bin/Release/netcoreapp2.1\publish folder.

In here I can run "dotnet X.dll" and the application starts.

Now I want to deploy said published folder to a docker image. My first attempt was using mcr.microsoft.com/dotnet/core/runtime:2.1 which caused

It was not possible to find any compatible framework version
The specified framework 'Microsoft.AspNetCore.App', version '2.1.1' was not found.
  - Check application dependencies and target a framework version installed at:
      /usr/share/dotnet/
  - Installing .NET Core prerequisites might help resolve this problem:
      https://go.microsoft.com/fwlink/?LinkID=798306&clcid=0x409
  - The .NET Core framework and SDK can be installed from:
      https://aka.ms/dotnet-download

I then tried using mcr.microsoft.com/dotnet/core/aspnet:2.1 which gave

C:\Users\m86194\git\microsvc-operational-information>docker run -it  operational-information-ms:0.0.1-SNAPSHOT bash
Error:
  An assembly specified in the application dependencies manifest (Operational_Information.deps.json) was not found:
    package: 'Elasticsearch.Net', version: '6.0.0'
    path: 'lib/netstandard1.3/Elasticsearch.Net.dll'

There is an "Elasticsearch.Net.dll" file in the root of bin\Release\netcoreapp21\publish folder, but not elsewhere.

I believe there is something about the build process I am missing.

Suggestions?

Answer 1

I had the same problem with Asp.Net Core 3 and since I'm neither well versed in Docker nor the .Net build system, I used the default Dockerfile Visual Studio creates.

FROM mcr.microsoft.com/dotnet/core/aspnet:3.1-buster-slim AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443

FROM mcr.microsoft.com/dotnet/core/sdk:3.1-buster AS build
WORKDIR /src
COPY ["Application/Application.csproj", "Application/"]
COPY ["Dependency1/Dependency1.csproj", "Dependency1/"]
RUN dotnet restore "Application/Application.csproj"
COPY . .
WORKDIR "/src/Application"
RUN dotnet build "Application.csproj" -c Release -o /app/build

FROM build AS publish
RUN dotnet publish "Application.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "application.dll"]

By default it only runs dotnet restore for the main application. After adding the same for the dependent projects, it works.

FROM mcr.microsoft.com/dotnet/core/aspnet:3.1-buster-slim AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443

FROM mcr.microsoft.com/dotnet/core/sdk:3.1-buster AS build
WORKDIR /src
COPY ["Application/Application.csproj", "Application/"]
COPY ["Dependency1/Dependency1.csproj", "Dependency1/"]
RUN dotnet restore "Dependency1/Dependency1.csproj" <-- this one is new
RUN dotnet restore "Application/Application.csproj"
COPY . .
WORKDIR "/src/Application"
RUN dotnet build "Application.csproj" -c Release -o /app/build

FROM build AS publish
RUN dotnet publish "Application.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "application.dll"]

Answer 2

Turned out that I had made a mistake when specifying the docker file deployment.

Instead of using bin\Release\netcoreapp21\publish I used bin\Release\netcoreapp21\ which also has an X.dll along the publish folder but gave the error. Changing to use the publish folder instead, solved the problem.

Answer 3

Try doing a dotnet restore before executing the publish command. Alternatively, you can use a multi stage docker build. See https://docs.docker.com/engine/examples/dotnetcore/ (mind the aspnet core version)