gRPC 在 Python中的应用

python -m grpc_tools.protoc --proto_path=. --python_out=. --grpc_python_out=. hello.proto

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 grpcio

Collecting 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, grpcio

Successfully 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

1

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.proto

import sys

_b=sys.version_info[0]❤️ and (lambda x:x) or (lambda x:x.encode('latin1'))

from google.protobuf import descriptor as _descriptor

from google.protobuf import message as _message

from google.protobuf import reflection as _reflection

from google.protobuf import symbol_database as _symbol_database

from 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'] = _HELLOREQUEST

DESCRIPTOR.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 grpc

import grpchello_pb2 as grpchello__pb2

class 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 grpc

import time

from concurrent import futures

import grpchello_pb2, grpchello_pb2_grpc

_HOST = 'localhost'

_PORT = '8188'

_ONE_DAY_IN_SECONDS = 60 * 60 * 24

class 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_function

import grpc

from grpchello_pb2 import * ## or import grpchello_pb2

from 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。