如何在 docker 容器中运行 .net 核心 grpc？

Question

Hi I have created GRPC project using.Net 5. Below is my Docker file.

FROM mcr.microsoft.com/dotnet/aspnet:5.0-buster-slim AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443

FROM mcr.microsoft.com/dotnet/sdk:5.0-buster-slim AS build
WORKDIR /src
COPY ./*.sln ./
COPY */*.csproj ./
RUN for file in $(ls *.csproj); do mkdir -p ${file%.*} && mv $file ${file%.*}; done
RUN dotnet restore
COPY . .
WORKDIR "/src/Geography"
RUN dotnet build "Geography.csproj" -c Release -o /app/build

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

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

I tried to run solution in visual studio using Docker and I see container up and running. I see below ports exposed.

 0.0.0.0:32775->80/tcp, 0.0.0.0:32774->443/tcp

I created client application and tried to hit grpc end points as below.

using var channel = GrpcChannel.ForAddress("http://localhost:32774");
var client = new Geographys.GeographysClient(channel);

Here I am getting below error

Status(StatusCode="Internal", Detail="Error starting gRPC call. HttpRequestException: An error occurred while sending the request. IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.. SocketException: An existing connection was forcibly closed by the remote host.", DebugException="System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.. --->

can someone help me to understand the root cause of this issue? Any help would be greatly appreciated. Thank you

Answer 1

Are you confident that your .NET code is exposing a non-TLS HTTP endpoint on container port 80 and a TLS HTTP endpoint on 443 ?

I suspect it isn't and this would explain why you're unable to access the service through the ports when they're bound to the host (on 32775 and 32774 respectively).

NOTE Your client code tries to access http://localhost:32774 which possibly maps to the container's TLS endpoint ( :443 ) so you'd need to use https:// and configure a certificate.

If you're running Linux on the host, you can try telnet'ing to those ports to see whether you get a response:

telnet localhost 32775
telnet localhost 32774

If you have gRPCurl (and IMO you should for any gRPC dev), you can try listing methods:

grpcurl \
-plaintext \
-proto path/to/your.proto \
localhost:32775 \
list

grpcurl \
-plaintext \
-proto path/to/your.proto \
localhost:32774 \
list

NOTE I think that's the correct grpcurl for both TLS and non-TLS but writing without being able to test

Answer 2

Adding the following code

"Kestrel": {
    "EndpointDefaults": {
      "Protocols": "Http2"
    }
  }

in the appsettings.json file on the gRPC server side and calling 'http' port instead of 'https' on the gRPC client side should do the trick. In your example that would be:

using var channel = GrpcChannel.ForAddress("http://localhost:32775");