Docker: are the build and publish stages required by container tools?

Question

Docker: are the build and publish stages required by container tools?

RdJNL 36

When adding Docker support to a C# project, you'll automatically get a Dockerfile with 4 stages: base, build, publish, final. I know what the base and final stages are for, and I get that the build/publish has to happen in a separate stage in order to not have the full SDK in the final image.

But is there any requirement by VS for the build/publish to be in 2 separate stages?

I think the default Dockerfile's build stage is kinda useless, because the publish will build the project again. I want to change this, but I'm not sure if VS will have issues with that.

2 answers

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Answer 1

Ken Tucker 5,861

This article here gives a good explanation on how the container is built

https://learn.microsoft.com/en-us/visualstudio/containers/container-build?view=vs-2019&WT.mc_id=visualstudio_containers_aka_containerfastmode

Basically build uses the .net sdk to build the project instead of the asp.net sdk. The publish step moves only what is needed for the website to keep the container size smaller.

RdJNL 36 Reputation points

2022-01-16T21:50:05.207+00:00

I understand that, I just wanna know if Visual Studio requires or utilizes the separate "build" and "publish" stages.

Alessandro Piccione 1

The build is done with the SDK image
Then the publish is done again with the same sdk image.
Also the publish does not use --no-restore and not the --no-build, so it is practically repeating the same job.
Then it uses the aspnet image to run it.

I'm talking about this:

FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base  
WORKDIR /app  
  
FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build  
WORKDIR /src    
COPY . .  
WORKDIR "src/TestSite"  
RUN dotnet build "TestSite.csproj" -c Release -o /app/build  
  
FROM build AS publish  
RUN dotnet publish "TestSite.csproj" -c Release -o /app/publish   
  
FROM base  AS final  
WORKDIR /app  
COPY --from=publish /app/publish .  
ENTRYPOINT ["dotnet", "TestSite.dll"]

Answer 2

Bruce (SqlWork.com) 78,161 Volunteer Moderator

for a trivial project you could drop the build step. but if the project references other projects that also need to be built, or you have complex build steps, then you don't want to simplify. you also might want also want to add a unit test step.

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Docker: are the build and publish stages required by container tools?

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