/examples/grpc-interop/README.md

# gRPC Interop Example

This example shows that **any standard gRPC client** can call a go-micro service — no go-micro SDK required on the client side.

The server is a normal go-micro service using the gRPC transport. The client is a plain `google.golang.org/grpc` client with no go-micro imports.

## How it works

go-micro's gRPC server uses a [`grpc.UnknownServiceHandler`](https://pkg.go.dev/google.golang.org/grpc#UnknownServiceHandler) that catches all incoming requests and routes them by parsing the standard gRPC method path (`/package.Service/Method`). This means any language with gRPC support (Python, Java, Rust, etc.) can call go-micro services using generated protobuf stubs.

## Running

Start the server:

```bash
cd examples/grpc-interop
go run ./server/
```

In another terminal, call it with the standard gRPC client:

```bash
cd examples/grpc-interop
go run ./client/ --name Alice
# Response: Hello Alice
```

## Calling from other languages

Generate stubs from `proto/greeter.proto` in your language of choice and point them at `localhost:50051`. For example, with Python:

```bash
pip install grpcio-tools
python -m grpc_tools.protoc -Iproto --python_out=. --grpc_python_out=. proto/greeter.proto
```

```python
import grpc
import greeter_pb2
import greeter_pb2_grpc

channel = grpc.insecure_channel("localhost:50051")
stub = greeter_pb2_grpc.GreeterStub(channel)

response = stub.Hello(greeter_pb2.HelloRequest(name="Alice"))
print(response.message)  # Hello Alice
```

## Key points

- The go-micro server registers handlers via `pb.RegisterGreeterHandler()`
- The standard gRPC client uses stubs generated by `protoc-gen-go-grpc`
- Both share the same `.proto` file — that's the contract
- The server uses protobuf encoding on the wire, same as any gRPC service
- Service discovery (mDNS, consul, etc.) is only needed for go-micro-to-go-micro calls; direct gRPC clients connect by address

## Regenerating proto stubs

```bash
protoc --go_out=. --go_opt=paths=source_relative \
       --go-grpc_out=. --go-grpc_opt=paths=source_relative \
       --micro_out=. --micro_opt=paths=source_relative \
       proto/greeter.proto
```

Requires `protoc-gen-go`, `protoc-gen-go-grpc`, and `protoc-gen-micro`.