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c#grpc.net-5

.NET 5 GRPC client call throws exception: Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while HTTP/2 is not enabled

This is my first gRPC application. I'm attempting to invoke a server-streaming RPC call from a .NET 5 gRPC client (Grpc.Net.Client 2.35.0) which results in the following exception in my local development environment:

Grpc.Core.RpcException: Status(StatusCode="Internal", Detail="Error starting gRPC call. HttpRequestException: Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while HTTP/2 is not enabled."

This occurs whether or not the server application is running. Here is the code I'm using to make the call:

using var channel = GrpcChannel.ForAddress(@"http://localhost:5000");
var client = new AlgorithmRunner.AlgorithmRunnerClient(channel);
using var call = client.RunAlgorithm(new RunAlgorithmRequest());

while (await call.ResponseStream.MoveNext())
{

}

My understanding is that .NET 5 gRPC is supposed to have HTTP/2 enabled by default: why does the exception indicate that HTTP/2 is not enabled and how do I resolve it?

Solution

  • I faced the same problem sitting behind a corporate proxy and receiving this error message

    An exception of type 'Grpc.Core.RpcException' occurred in System.Private.CoreLib.dll but was not handled in user code: 'Status(StatusCode="Unavailable", Detail="Error starting gRPC call. HttpRequestException: Connection refused SocketException: Connection refused", DebugException="System.Net.Http.HttpRequestException: Connection refused

    I fully agree that your suggested workaround with bypassing all proxy settings by overwriting the DefaultProxy is legit and functional.

    A slightly better approach would be not to hard code a 'bypass all proxy statement' in your code and use instead the no_proxy environment variable. The purpose of this environment variable is to define a rule for excluding traffic destined to certain hosts

    Solution

    Activate the env. variable no_proxy for your development setup like

    For linux

    export no_proxy=localhost,127.0.0.1

    For Dockerfile

    ENV no_proxy=localhost,127.0.0.1

    For a deep dive session about proxy environment variables

    It is important when you start your gRPC client application, that you check what the value of the read in environment variables is, because gRPC uses the HttpClient class under the hood, which considers all proxy environment variables. If the no_proxy value is not set, it has not effect.

    var noProxy = Environment.GetEnvironmentVariable("no_proxy");