S058 · gRPC & Protobuf — When RPC Wins

syntax = "proto3";
package demo;
 
// Request/response messages
message SayHelloRequest {
  string name = 1;
  int32 shouts = 2;   // how many replies to stream back
}
 
message SayHelloResponse {
  string greeting = 1;
  int32 sequence = 2;
}
 
// Service definition
service Greeter {
  // Unary RPC: one request, one response
  rpc SayHello (SayHelloRequest) returns (SayHelloResponse);
 
  // Server-streaming: one request, many responses
  rpc SayHelloStream (SayHelloRequest) returns (stream SayHelloResponse);
}

python -m pip install grpcio grpcio-tools
 
python -m grpc_tools.protoc \
  --proto_path=. \
  --python_out=. \
  --grpc_python_out=. \
  demo.proto

"""server.py — implement Greeter over the generated interface."""
import time
from concurrent import futures
 
import grpc
import demo_pb2
import demo_pb2_grpc
 
 
class GreeterServicer(demo_pb2_grpc.GreeterServicer):
    def SayHello(self, request, context):
        # unary: return one response
        return demo_pb2.SayHelloResponse(
            greeting=f"Hello, {request.name}!",
            sequence=0,
        )
 
    def SayHelloStream(self, request, context):
        # server-streaming: yield multiple responses on the same call
        for i in range(max(1, request.shouts)):
            yield demo_pb2.SayHelloResponse(
                greeting=f"Hello, {request.name}!",
                sequence=i,
            )
            time.sleep(0.2)
 
 
def serve() -> None:
    server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
    demo_pb2_grpc.add_GreeterServicer_to_server(GreeterServicer(), server)
    server.add_insecure_port("127.0.0.1:50051")
    server.start()
    print("gRPC server listening on 127.0.0.1:50051")
    server.wait_for_termination()
 
 
if __name__ == "__main__":
    serve()

"""client.py — call both RPCs, print responses + wire sizes."""
import grpc
import demo_pb2
import demo_pb2_grpc
 
 
def main() -> None:
    with grpc.insecure_channel("127.0.0.1:50051") as channel:
        stub = demo_pb2_grpc.GreeterStub(channel)
 
        # Unary
        req = demo_pb2.SayHelloRequest(name="Dinesh", shouts=1)
        print(f"[wire] request serialized bytes: {len(req.SerializeToString())}")
        resp = stub.SayHello(req)
        print(f"[unary]   {resp.greeting} (seq={resp.sequence})")
        print(f"[wire]    response serialized bytes: {len(resp.SerializeToString())}")
 
        # Server-streaming
        req = demo_pb2.SayHelloRequest(name="Dinesh", shouts=3)
        print("\n[stream]  server-streaming responses:")
        for msg in stub.SayHelloStream(req):
            print(f"  #{msg.sequence}: {msg.greeting}")
 
 
if __name__ == "__main__":
    main()

# terminal 1
python server.py
 
# terminal 2
python client.py