在python中使用grpc和protobuf

简介

在python中使用grpc和protobuf，比java和c#中使用要简单一些。只需要先安装grpcio包，然后就可以应用了。

安装

使用pip安装grpcio依赖包；

$ pip install grpcioCollecting grpcio  Downloading grpcio-1.7.0-cp27-cp27m-macosx_10_10_intel.whl (1.5MB)    100% |████████████████████████████████| 1.5MB 18kB/s Requirement already satisfied: enum34>=1.0.4 in /Users/David/anaconda2/lib/python2.7/site-packages (from grpcio)Requirement already satisfied: futures>=2.2.0 in /Users/David/anaconda2/lib/python2.7/site-packages (from grpcio)Requirement already satisfied: six>=1.5.2 in /Users/David/anaconda2/lib/python2.7/site-packages (from grpcio)Collecting protobuf>=3.3.0 (from grpcio)  Downloading protobuf-3.5.0-py2.py3-none-any.whl (388kB)    100% |████████████████████████████████| 389kB 32kB/s Requirement already satisfied: setuptools in /Users/David/anaconda2/lib/python2.7/site-packages (from protobuf>=3.3.0->grpcio)Installing collected packages: protobuf, grpcioSuccessfully installed grpcio-1.7.0 protobuf-3.5.0

安装时，自动地安装了protobuf工具包。

定义protobuf

下面定义一个简单的protobuf文件，在其中声明一个grpc服务。
创建一个proto目录，并在其中创建grpchello.proto文件，如下内容。

syntax = "proto3";package grpcDemo;message HelloRequest {   string name = 1;}message HelloReply {   string message = 1;}service gRPC {  rpc SayHello (HelloRequest) returns (HelloReply) {}}

Note：
- 其实这个protobuf定义文件，在我们的java、c#版本示例中使用了，而且各版本的服务和客户端可以正常通行调用。

编译protobuf

使用protobuf的编译器，为我们生成python版本的Message定义和服务的架手脚。

python -m grpc_tools.protoc -I./proto --python_out=. --grpc_python_out=. grpchello.proto 

在当前目录下，生成2个文件：
- grpchello_pb2.py
- grpchello_pb2_grpc.py

可以看看这2个文件：

首先消息定义文件：

# Generated by the protocol buffer compiler.  DO NOT EDIT!# source: grpchello.protoimport sys_b=sys.version_info[0]<3 and (lambda x:x) or (lambda x:x.encode('latin1'))from google.protobuf import descriptor as _descriptorfrom google.protobuf import message as _messagefrom google.protobuf import reflection as _reflectionfrom google.protobuf import symbol_database as _symbol_databasefrom google.protobuf import descriptor_pb2# @@protoc_insertion_point(imports)_sym_db = _symbol_database.Default()DESCRIPTOR = _descriptor.FileDescriptor(  name='grpchello.proto',  package='grpcDemo',  syntax='proto3',  serialized_pb=_b('\n\x0fgrpchello.proto\x12\x08grpcDemo\"\x1c\n\x0cHelloRequest\x12\x0c\n\x04name\x18\x01 \x01(\t\"\x1d\n\nHelloReply\x12\x0f\n\x07message\x18\x01 \x01(\t2B\n\x04gRPC\x12:\n\x08SayHello\x12\x16.grpcDemo.HelloRequest\x1a\x14.grpcDemo.HelloReply\"\x00\x62\x06proto3'))_HELLOREQUEST = _descriptor.Descriptor(  name='HelloRequest',  full_name='grpcDemo.HelloRequest',  filename=None,  file=DESCRIPTOR,  containing_type=None,  fields=[    _descriptor.FieldDescriptor(      name='name', full_name='grpcDemo.HelloRequest.name', index=0,      number=1, type=9, cpp_type=9, label=1,      has_default_value=False, default_value=_b("").decode('utf-8'),      message_type=None, enum_type=None, containing_type=None,      is_extension=False, extension_scope=None,      options=None),  ],  extensions=[  ],  nested_types=[],  enum_types=[  ],  options=None,  is_extendable=False,  syntax='proto3',  extension_ranges=[],  oneofs=[  ],  serialized_start=29,  serialized_end=57,)_HELLOREPLY = _descriptor.Descriptor(  name='HelloReply',  full_name='grpcDemo.HelloReply',  filename=None,  file=DESCRIPTOR,  containing_type=None,  fields=[    _descriptor.FieldDescriptor(      name='message', full_name='grpcDemo.HelloReply.message', index=0,      number=1, type=9, cpp_type=9, label=1,      has_default_value=False, default_value=_b("").decode('utf-8'),      message_type=None, enum_type=None, containing_type=None,      is_extension=False, extension_scope=None,      options=None),  ],  extensions=[  ],  nested_types=[],  enum_types=[  ],  options=None,  is_extendable=False,  syntax='proto3',  extension_ranges=[],  oneofs=[  ],  serialized_start=59,  serialized_end=88,)DESCRIPTOR.message_types_by_name['HelloRequest'] = _HELLOREQUESTDESCRIPTOR.message_types_by_name['HelloReply'] = _HELLOREPLY_sym_db.RegisterFileDescriptor(DESCRIPTOR)HelloRequest = _reflection.GeneratedProtocolMessageType('HelloRequest', (_message.Message,), dict(  DESCRIPTOR = _HELLOREQUEST,  __module__ = 'grpchello_pb2'  # @@protoc_insertion_point(class_scope:grpcDemo.HelloRequest)  ))_sym_db.RegisterMessage(HelloRequest)HelloReply = _reflection.GeneratedProtocolMessageType('HelloReply', (_message.Message,), dict(  DESCRIPTOR = _HELLOREPLY,  __module__ = 'grpchello_pb2'  # @@protoc_insertion_point(class_scope:grpcDemo.HelloReply)  ))_sym_db.RegisterMessage(HelloReply)_GRPC = _descriptor.ServiceDescriptor(  name='gRPC',  full_name='grpcDemo.gRPC',  file=DESCRIPTOR,  index=0,  options=None,  serialized_start=90,  serialized_end=156,  methods=[  _descriptor.MethodDescriptor(    name='SayHello',    full_name='grpcDemo.gRPC.SayHello',    index=0,    containing_service=None,    input_type=_HELLOREQUEST,    output_type=_HELLOREPLY,    options=None,  ),])_sym_db.RegisterServiceDescriptor(_GRPC)DESCRIPTOR.services_by_name['gRPC'] = _GRPC# @@protoc_insertion_point(module_scope)

在看看grpc服务定义

# Generated by the gRPC Python protocol compiler plugin. DO NOT EDIT!import grpcimport grpchello_pb2 as grpchello__pb2class gRPCStub(object):  # missing associated documentation comment in .proto file  pass  def __init__(self, channel):    """Constructor.    Args:      channel: A grpc.Channel.    """    self.SayHello = channel.unary_unary(        '/grpcDemo.gRPC/SayHello',        request_serializer=grpchello__pb2.HelloRequest.SerializeToString,        response_deserializer=grpchello__pb2.HelloReply.FromString,        )class gRPCServicer(object):  # missing associated documentation comment in .proto file  pass  def SayHello(self, request, context):    # missing associated documentation comment in .proto file    pass    context.set_code(grpc.StatusCode.UNIMPLEMENTED)    context.set_details('Method not implemented!')    raise NotImplementedError('Method not implemented!')def add_gRPCServicer_to_server(servicer, server):  rpc_method_handlers = {      'SayHello': grpc.unary_unary_rpc_method_handler(          servicer.SayHello,          request_deserializer=grpchello__pb2.HelloRequest.FromString,          response_serializer=grpchello__pb2.HelloReply.SerializeToString,      ),  }  generic_handler = grpc.method_handlers_generic_handler(      'grpcDemo.gRPC', rpc_method_handlers)  server.add_generic_rpc_handlers((generic_handler,))

简单看下：
- 在grpc服务架手脚定义中，定义了gRPCStub，这是给client端使用，调用grpc服务的。
- 定义的服务类gRPCServicer，方法SayHello需要我们在子类中进行实现。定义的add_gRPCServicer_to_server方法，用于把实现的类和grpc API调用注册起来。

这里使用的几个主要方法（类）：
- grpc.server – Creates a Server with which RPCs can be serviced
- grpc.method_handlers_generic_handler – Creates a GenericRpcHandler from RpcMethodHandlers.
- grpc.unary_unary_rpc_method_handler – Creates an RpcMethodHandler for a unary-unary RPC method.

实现服务

在我们的实现服务的类中，使用服务方法，并在网络中暴露出来。

# -*- coding: utf-8 -*-import grpcimport timefrom concurrent import futures import grpchello_pb2, grpchello_pb2_grpc_HOST = 'localhost'_PORT = '8188'_ONE_DAY_IN_SECONDS = 60 * 60 * 24class gRPCServicerImpl(grpchello_pb2_grpc.gRPCServicer):    def SayHello(self, request, context):        print ("called with " + request.name)        return grpchello_pb2.HelloReply(message='Hello, %s!' % request.name)def serve():  server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))  grpchello_pb2_grpc.add_gRPCServicer_to_server(gRPCServicerImpl(), server)  server.add_insecure_port('[::]:'+_PORT)  server.start()  try:    while True:      time.sleep(_ONE_DAY_IN_SECONDS)  except KeyboardInterrupt:    server.stop(0)if __name__ == '__main__':    serve()

这里包括2个实现：
- 1、在grpc的API的实现（服务实现类）gRPCServicerImpl中，实现SayHello方法。
- 2、然后，定义网络服务和端口，把grpc的API注册到网络服务的处理上。这里简单利用了grpc.server类。

使用客户端client

在客户端，调用grpc的服务API。

# -*- coding: utf-8 -*-"""The Python implementation of the gRPC client."""from __future__ import print_functionimport grpcfrom grpchello_pb2  import *    ## or import grpchello_pb2from grpchello_pb2_grpc import *## No grpcDemo!  from grpcDemo import grpchello_pb2, grpchello_pb2_grpc #error!_PORT = '8188'def run():    conn = grpc.insecure_channel(_HOST + ':' + _PORT)    client = gRPCStub(channel=conn)    response = client.SayHello(HelloRequest(name='David'))    print("received: " + response.message)## if __name__ == '__main__':    if len(sys.argv)== 2:        print (sys.argv[1])        _HOST = sys.argv[1]    else:        _HOST = 'localhost'    #        run()

说明：
- 1、 def insecure_channel(target, options=None):
– Creates an insecure Channel to a server.
- 2、 客户端使用服务的Stub，调用API。

测试

分别启动服务，然后再启动客户端，可以看到调用结果。
也可以启动java、c#版本的grpc服务端、客户端，都能调用成功。