Is this dockerfile creating a corrupted image? - docker

Question

I am trying to run a dotnet core Web Api application on a docker container on Windows 10
This is the project structure on the left side of the image. The Dockerfile is one level up the .csproj file, so its something like this.
/WebApi {Root folder}
- WebApi {folder container the WEbApi.csproj and other files folders}
- Dockerfile
- .dockerignore
- WebApi.sln
This the Dockerfile contents
FROM mcr.microsoft.com/dotnet/aspnet:3.1 AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443
# Copy csproj and restore as distinct layers
FROM mcr.microsoft.com/dotnet/sdk:3.1 AS build
COPY WebApi/*.* src/
RUN dotnet restore src/WebApi.csproj
RUN dotnet build "src/WebApi.csproj" -c Release -o /app/build
# publish the project
FROM build AS publish
RUN dotnet publish src/WebApi.csproj -c Release -o /app/out
# Build runtime image
FROM base AS final
WORKDIR /app
COPY --from=publish /app/out .
ENTRYPOINT ["dotnet", "WebApi.dll"]
I build the image using this docker build -t webapi-img . in the same folder that has the Dockerfile.
This is the build log
Then I run the container using docker run -p 8090:8071 --name webpi-cntr webapi-img which gives the following output
info: Microsoft.Hosting.Lifetime[0]
Now listening on: http://[::]:8071
info: Microsoft.Hosting.Lifetime[0]
Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
Hosting environment: Production
info: Microsoft.Hosting.Lifetime[0]
Content root path: /app
The container runs but when I try to access the service on the host machine using http://localhost:8090/WeatherForecast, I get a 404 error.
When I access the container CLI and run the curl command using the port of the application I get no response as you can see in the screenshot below
Back on the host when I telnet localhost 8090, the telnet client connects to the port.
It looks like the container is running correctly and the mapping has also happened correctly. My assumption is that the core dotnet app is not running correctly, but I don't know what could be causing that or any ways to probe this further. Any pointers?
PS: I am using Dockerfile because I want to take this project later to an AWS ECS container via CDK and using a pipeline. Not sure if I can use docker compose there, but thats for later.

Answer 1

You should add EXPOSE 8071 to your Dockerfile so that your container exposes that port.

Answer 2

The problem was in this line
COPY WebApi/*.* src/
This was only copying the files in the root folder and not the folder which had the controllers. This is why on compiling, it was not able to find the path, /WeatherForecast but was standing up the server anyways.
The correction to the line that got everything working was ...
COPY WebApi/** src/