How do I send an Image rotate request to gprc server with python?

Question

I am new to grpc. I am having trouble understanding it. Anyway, I am working based on a protobuf file called: image.proto

Below are the contents of my image.proto file:

syntax = "proto3";

option java_multiple_files = true;

message NLImage {
    bool color = 1;
    bytes data = 2;
    int32 width = 3;
    int32 height = 4;
}


message NLImageRotateRequest {
    enum Rotation {
        NONE = 0;
        NINETY_DEG = 1;
        ONE_EIGHTY_DEG = 2;
        TWO_SEVENTY_DEG = 3;
    }

    Rotation rotation = 1;
    NLImage image = 2;
}

service NLImageService {
    rpc RotateImage(NLImageRotateRequest) returns (NLImage);
    rpc MeanFilter(NLImage) returns (NLImage);
}

I was able to create a server.py file, and client.py. I also generated the image_pb2.py from the image.proto file and I generated the image_pb2_grpc.py.

Now, I am stuck into sending an image rotation request from the client to the server, and getting back an appropriate response.

Here is what I have so far tried in my client.py

import grpc
# import the generated files
import image_pb2
import image_pb2_grpc

#.......
#.......SEVERAL LINES OF CODE LATER
#.......

print('Input image path is', inputfile)
print('Output path is', outputfile)
print('Mean  is', mean)
print("Rotate is", rotate)
channel = grpc.insecure_channel('localhost:5000')
stub = image_pb2_grpc.NLImageServiceStub(channel)


# SEND ROTATION REQUEST IF rotate
img_rotate_request = image_pb2.NLImageRotateRequest()
stub.RotateImage(img_rotate_request, inputfile)

I am not sure how to send that RotateImage request properly.

Below is my server.py:

import sys, getopt
from google.protobuf.descriptor import EnumDescriptor
import grpc
from concurrent import futures
import time
import numpy as np

# importing grpc generated classes
import image_pb2
import image_pb2_grpc

class NLImageServiceServicer(image_pb2_grpc.NLImageServiceServicer):
   def RotateImage(self, request, context):
      print("Request to rotate image received")
      return image_pb2._NLIMAGE()

   def MeanFilter(self, request, context):
      print("Request to filter received")
      return image_pb2.NLImage()

   server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
   image_pb2_grpc.add_NLImageServiceServicer_to_server(NLImageServiceServicer, server)
   server.add_insecure_port( host + ":" + str(port))
   server.start()
   print("Server started ...on " + host + ":" + port)
   server.wait_for_termination()

Answer 1

Eyeballing your code, it appears OK; I've not run it.

You're correctly calling the method: stub.RotateImage but you're not correctly creating the message type (NLImageRotateRequest) for it. It will be an instance of the class generated for you by protoc, probably image_pb2.NLImageRotateRequest and this contains rotation and image properties. The image is itself an instance of a class image_pb2.Image etc.

Please see this link for using protobuf with Python because each language is distinct and Python has some quirks in how you create messages.

At some point, you'll need to read in inputfile as bytes in order to populate the data property of image.

If you've not, perhaps run through the Python HelloWorld example on grpc.io. It's basic but it will get you started with gRPC. Then review the link I included above and the protobuf sections on Python.