gRPC instrumentation fails when server uses unix socket

[diurnalist]

Describe your environment

OS: Ubuntu (did not test others)
Python version: Python 3.9+
Package version: 0.44b0+
grpc version: <=1.50.0

What happened?

When using the gRPC instrumentation with a server that is exposed over a unix socket, we get the following error:

ValueError: not enough values to unpack (expected 2, got 1)

This seems to be because the context.peer() name is "unix://path/to/socket.sock", not simply "unix:". The instrumentation thinks that it is a host:port address and fails to parse it properly.

Note that the grpc project has at times tried to improve the communication of the socket path: grpc/grpc#18556. It seems that this changed after version 1.50.0 (versions 1.51 and 1.52 were yanked for other issues, 1.53.0 is the first version that does not have this problem.) However, I think that we should be handling the case when there is a path defined, as it seems like that's more correct.

Steps to Reproduce

requirements.txt

grpcio==1.50.0
grpcio-tools
opentelemetry-instrumentation-grpc

proto/helloworld.proto

syntax = "proto3";

package helloworld;

service Greeter {
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

message HelloRequest {
  string name = 1;
}

message HelloReply {
  string message = 1;
}

src/server.py

import logging
from concurrent import futures

import grpc
from opentelemetry.instrumentation.grpc import GrpcInstrumentorServer

import helloworld_pb2_grpc
import helloworld_pb2

logger = logging.getLogger(__name__)

class MyGreeter:
    def SayHello(self, request, context):
        return helloworld_pb2.HelloReply(message=":wave: " + request.name)

def serve():
    grpc_server_instrumentor = GrpcInstrumentorServer()
    grpc_server_instrumentor.instrument()

    server = grpc.server(futures.ThreadPoolExecutor())
    helloworld_pb2_grpc.add_GreeterServicer_to_server(MyGreeter(), server)
    server.add_insecure_port('unix:///tmp/grpc.sock')
    server.start()
    server.wait_for_termination()

if __name__ == '__main__':
    logging.basicConfig(level=logging.INFO)
    serve()

src/client.py

import grpc

import helloworld_pb2_grpc
import helloworld_pb2


def run():
    with grpc.insecure_channel("unix:///tmp/grpc.sock") as channel:
        stub = helloworld_pb2_grpc.GreeterStub(channel)
        stub.SayHello(helloworld_pb2.HelloRequest(name="world"))

if __name__ == "__main__":
    run()

How to reproduce:

• uv venv --seed
• uv run pip install -r requirements.txt
• uv run python -m grpc_tools.protoc -I./proto --python_out=./src --grpc_python_out=./src ./proto/helloworld.proto
• uv run python src/server.py
• (in another terminal) uv run python src/client.py

Expected Result

gRPC call should return without error.

Actual Result

Traceback (most recent call last):
  File "/home/jason.anderson/workspaces/grpc-unix-socket-server/src/client.py", line 13, in <module>
    run()
  File "/home/jason.anderson/workspaces/grpc-unix-socket-server/src/client.py", line 10, in run
    stub.SayHello(helloworld_pb2.HelloRequest(name="world"))
  File "/home/jason.anderson/workspaces/grpc-unix-socket-server/.venv/lib/python3.11/site-packages/grpc/_channel.py", line 946, in __call__
    return _end_unary_response_blocking(state, call, False, None)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jason.anderson/workspaces/grpc-unix-socket-server/.venv/lib/python3.11/site-packages/grpc/_channel.py", line 849, in _end_unary_response_blocking
    raise _InactiveRpcError(state)
grpc._channel._InactiveRpcError: <_InactiveRpcError of RPC that terminated with:
        status = StatusCode.UNKNOWN
        details = "Exception calling application: not enough values to unpack (expected 2, got 1)"
        debug_error_string = "UNKNOWN:Error received from peer unix:/tmp/grpc.sock {grpc_message:"Exception calling application: not enough values to unpack (expected 2, got 1)", grpc_status:2, created_time:"2025-03-28T13:48:37.018497876-07:00"}"

Additional context

No response

Would you like to implement a fix?

Yes