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(' x0fgrpchello.protox12x08grpcDemo"x1c x0cHelloRequestx12x0c x04namex18x01 x01( "x1d HelloReplyx12x0f x07messagex18x01 x01( 2B x04gRPCx12: x08SayHellox12x16.grpcDemo.HelloRequestx1ax14.grpcDemo.HelloReply"x00x62x06proto3')
)

_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。