一个简单的Server
~~~~~~~~~~~~~~~~~~~~~~ server.py ~~~~~~~~~~~~~~~~~~~~~~
from SimpleXMLRPCServer import SimpleXMLRPCServer
import logging
import os
# Set up logging
logging.basicConfig(level=logging.DEBUG)
server = SimpleXMLRPCServer((’localhost’, 9000), logRequests=True)
# Expose a function
def list_contents(dir_name):
logging.debug(’list_contents(%s)’, dir_name)
return os.listdir(dir_name)
server.register_function(list_contents)
try:
print ’Use Control-C to exit’
server.serve_forever()
except KeyboardInterrupt:
print ’Exiting’
~~~~~~~~~~~~~~~~~~~~~~ client.py ~~~~~~~~~~~~~~~~~~~~~~
proxy = xmlrpclib.ServerProxy(’http://localhost:9000’)
print proxy.list_contents(’/tmp’)
别名
from SimpleXMLRPCServer import SimpleXMLRPCServer
import os
server = SimpleXMLRPCServer((’localhost’, 9000))
# Expose a function with an alternate name
def list_contents(dir_name):
return os.listdir(dir_name)
server.register_function(list_contents, ’dir’)
try:
print ’Use Control-C to exit’
server.serve_forever()
except KeyboardInterrupt:
print ’Exiting’
~~~~~~~~~~~~~~~~~~~~~~ client.py ~~~~~~~~~~~~~~~~~~~~~~
proxy = xmlrpclib.ServerProxy(’http://localhost:9000’)
print ’dir():’, proxy.dir(’/tmp’)
print ’list_contents():’, proxy.list_contents(’/tmp’)
Dotted Names
from SimpleXMLRPCServer import SimpleXMLRPCServer
import os
server = SimpleXMLRPCServer((’localhost’, 9000), allow_none=True)
server.register_function(os.listdir, ’dir.list’)
server.register_function(os.mkdir, ’dir.create’)
server.register_function(os.rmdir, ’dir.remove’)
try:
print ’Use Control-C to exit’
server.serve_forever()
except KeyboardInterrupt:
print ’Exiting’
~~~~~~~~~~~~~~~~~~~~~~ client.py ~~~~~~~~~~~~~~~~~~~~~~
import xmlrpclib
proxy = xmlrpclib.ServerProxy(’http://localhost:9000’)
print ’BEFORE :’, ’EXAMPLE’ in proxy.dir.list(’/tmp’)
print ’CREATE :’, proxy.dir.create(’/tmp/EXAMPLE’)
print ’SHOULD EXIST :’, ’EXAMPLE’ in proxy.dir.list(’/tmp’)
print ’REMOVE :’, proxy.dir.remove(’/tmp/EXAMPLE’)
print ’AFTER :’, ’EXAMPLE’ in proxy.dir.list(’/tmp’)
任意的名字
from SimpleXMLRPCServer import SimpleXMLRPCServer
server = SimpleXMLRPCServer((’localhost’, 9000))
def my_function(a, b):
return a * b
server.register_function(my_function, ’multiply args’)
try:
print ’Use Control-C to exit’
server.serve_forever()
except KeyboardInterrupt:
print ’Exiting’
~~~~~~~~~~~~~~~~~~~~~~ client.py ~~~~~~~~~~~~~~~~~~~~~~
import xmlrpclib
proxy = xmlrpclib.ServerProxy(’http://localhost:9000’)
print getattr(proxy, ’multiply args’)(5, 5)
暴露对象的方法
By default, register_instance() finds all callable attributes of the instance with names not starting with ‘_‘and registers them with their name.
from SimpleXMLRPCServer import SimpleXMLRPCServer
import os
import inspect
server = SimpleXMLRPCServer((’localhost’, 9000), logRequests=True)
class DirectoryService:
def list(self, dir_name):
return os.listdir(dir_name)
server.register_instance(DirectoryService())
try:
print ’Use Control-C to exit’
server.serve_forever()
except KeyboardInterrupt:
print ’Exiting’
~~~~~~~~~~~~~~~~~~~~~~ client.py ~~~~~~~~~~~~~~~~~~~~~~
import xmlrpclib
proxy = xmlrpclib.ServerProxy(’http://localhost:9000’)
print proxy.list(’/tmp’)
暴露对象的方法 + Dotted Names
from SimpleXMLRPCServer import SimpleXMLRPCServer
import os
import inspect
server = SimpleXMLRPCServer((’localhost’, 9000), logRequests=True)
class ServiceRoot:
pass
class DirectoryService:
def list(self, dir_name):
return os.listdir(dir_name)
root = ServiceRoot()
root.dir = DirectoryService()
server.register_instance(DirectoryService())
try:
print ’Use Control-C to exit’
server.serve_forever()
except KeyboardInterrupt:
print ’Exiting’
~~~~~~~~~~~~~~~~~~~~~~ client.py ~~~~~~~~~~~~~~~~~~~~~~
import xmlrpclib
proxy = xmlrpclib.ServerProxy(’http://localhost:9000’)
print proxy.dir.list(’/tmp’)
自定义转发调用
在客户端尝试调用MyService的一个方法时 _dispatch()方法会被调用。在这个方法里，我们加了一个方法的前缀限定，并且要求这个方法必须有一个叫exposed的属性并且值为True。当然你可以随意设计_dispatch的逻辑来满足你的转发需求。
from SimpleXMLRPCServer import SimpleXMLRPCServer
import os
import inspect
server = SimpleXMLRPCServer((’localhost’, 9000), logRequests=True)
def expose(f):
"Decorator to set exposed flag on a function."
f.exposed = True
return f
def is_exposed(f):
"Test whether another function should be publicly exposed."
return getattr(f, ’exposed’, False)
class MyService:
PREFIX = ’prefix’
def _dispatch(self, method, params):
# Remove our prefix from the method name
if not method.startswith(self.PREFIX + ’.’):
raise Exception(’method "%s" is not supported’ % method)
method_name = method.partition(’.’)[2]
func = getattr(self, method_name)
if not is_exposed(func):
raise Exception(’method "%s" is not supported’ % method)
return func(*params)
@expose
def public(self):
return ’This is public’
def private(self):
return ’This is private’
server.register_instance(MyService())
try:
print ’Use Control-C to exit’
server.serve_forever()
except KeyboardInterrupt:
print ’Exiting’
~~~~~~~~~~~~~~~~~~~~~~ client.py ~~~~~~~~~~~~~~~~~~~~~~
import xmlrpclib
proxy = xmlrpclib.ServerProxy(’http://localhost:9000’)
print ’public():’, proxy.prefix.public()
try:
print ’private():’, proxy.prefix.private()
except Exception, err:
print ’ERROR:’, err
try:
print ’public() without prefix:’, proxy.public()
except Exception, err:
print ’ERROR:’, err
Introspection API
有时候我们需要查询服务器有哪些可以调用的接口，这时候这个API就很有用了。
默认这些功能都是被关闭了。你可以通过 register_introspection_functions() 来打开。
from SimpleXMLRPCServer import SimpleXMLRPCServer, list_public_methods
import os
import inspect
server = SimpleXMLRPCServer((’localhost’, 9000), logRequests=True)
server.register_introspection_functions()
class DirectoryService:
def _listMethods(self):
return list_public_methods(self)
def _methodHelp(self, method):
f = getattr(self, method)
return inspect.getdoc(f)
def list(self, dir_name):
"""list(dir_name) => []
Returns a list containing the contents of the named directory.
"""
return os.listdir(dir_name)
server.register_instance(MyService())
try:
print ’Use Control-C to exit’
server.serve_forever()
except KeyboardInterrupt:
print ’Exiting’
~~~~~~~~~~~~~~~~~~~~~~ client.py ~~~~~~~~~~~~~~~~~~~~~~
import xmlrpclib
proxy = xmlrpclib.ServerProxy(’http://localhost:9000’)
for method_name in proxy.system.listMethods():
print ’=’ * 60
print method_name
print ’-’ * 60
print proxy.system.methodHelp(method_name)
print
多线程
这个SimpleXMLRPCServer是单任务的，即阻塞式。整成非阻塞式也非常方便:
from SimpleXMLRPCServer import SimpleXMLRPCServer
import SocketServer
class AsyncXMLRPCServer(SocketServer.ThreadingMixIn, SimpleXMLRPCServer):
pass
server = AsyncXMLRPCServer(SERVER_URL, allow_none=True)
编码的坑
unicode中ASCII码低于空格的（比如这个黑桃字符♠️），在进行XML中传输时，客户端会抛出解析失败的错误:
xml.parsers.expat.ExpatError: not well-formed (invalid token): line 9004, column 46
所以，要么需要对字符串进行一个safe check（将所有ASCII码低于空格的转成空格），要么转用其他协议传输（比如json）。
RPC的设计原则
一个良好的RPC系统设计主要由以下几个独立的模块组成：
- 数据结构 (requests/response/errors)
- 序列化 (JSON, XML, UI)
- 传输 (Socket, TCP/IP, HTTP)
- 代理/分发器dispatcher (映射函数调用到RPC)
开源选择
Reference:
https://www.simple-is-better.org/rpc/