修改Python的pyxmpp2中的主循环使其提高性能

引子

之前clubot使用的pyxmpp2的默认mainloop也就是一个poll的主循环,但是clubot上线后资源占用非常厉害,使用strace跟踪发现clubot在不停的poll,查看pyxmpp2代码发现pyxmpp2的poll在使用超时阻塞时使用最小超时时间,而最小超时时间一直是0,所以会变成一个没有超时的非阻塞poll很浪费资源,不打算更改库代码,所以自己仿照poll的mainloop写了一个更加高效的epoll的mainloop
实现

#!/usr/bin/env python
# -*- coding:utf-8 -*-
#
#  Author :  cold
#  E-mail :  wh_linux@126.com
#  Date  :  13/01/06 10:41:31
#  Desc  :  Clubot epoll mainloop
#
from __future__ import absolute_import, division

import select

from pyxmpp2.mainloop.interfaces import HandlerReady, PrepareAgain
from pyxmpp2.mainloop.base import MainLoopBase

from plugin.util import get_logger

class EpollMainLoop(MainLoopBase):
 """ Main event loop based on the epoll() syscall on Linux system """
 READ_ONLY = (select.EPOLLIN | select.EPOLLPRI | select.EPOLLHUP |
        select.EPOLLERR |select.EPOLLET)
 READ_WRITE = READ_ONLY | select.EPOLLOUT
 def __init__(self, settings = None, handlers= None):
   self.epoll = select.epoll()
   self._handlers = {}
   self._unprepared_handlers = {}
   self._timeout = None
   self._exists_fd = {}
   self.logger = get_logger()
   MainLoopBase.__init__(self, settings, handlers)

return

def _add_io_handler(self, handler):
   self._unprepared_handlers[handler] = None
   self._configure_io_handler(handler)

def _configure_io_handler(self, handler):
   if self.check_events():
     return
   if handler in self._unprepared_handlers:
     old_fileno = self._unprepared_handlers[handler]
     prepared = self._prepare_io_handler(handler)
   else:
     old_fileno = None
     prepared = True
   fileno = handler.fileno()
   if old_fileno is not None and fileno != old_fileno:
     del self._handlers[old_fileno]
     self._exists.pop(old_fileno, None)
     self.epoll.unregister(old_fileno)
   if not prepared:
     self._unprepared_handlers[handler] = fileno

if not fileno:
     return

self._handlers[fileno] = handler
   events = 0
   if handler.is_readable():
     events |= self.READ_ONLY
   if handler.is_writable():
     events |= self.READ_WRITE

if events:
     if fileno in self._exists_fd:
       self.epoll.modify(fileno, events)
     else:
       self._exists_fd.update({fileno:1})
       self.epoll.register(fileno, events)

def _prepare_io_handler(self, handler):
   ret = handler.prepare()
   if isinstance(ret, HandlerReady):
     del self._unprepared_handlers[handler]
     prepared = True
   elif isinstance(ret, PrepareAgain):
     if ret.timeout is not None:
       if self._timeout is not None:
         self._timeout = min(self._timeout, ret.timeout)
       else:
         self._timeout = ret.timeout
     prepared = False
   else:
     raise TypeError("Unexpected result from prepare()")

return prepared

def _remove_io_handler(self, handler):
   if handler in self._unprepared_handlers:
     old_fileno = self._unprepared_handlers[handler]
     del self._unprepared_handlers[handler]
   else:
     old_fileno = handler.fileno()
   if old_fileno is not None:
     try:
       del self._handlers[old_fileno]
       self._exists.pop(old_fileno, None)
       self.epoll.unregister(old_fileno)
     except KeyError:
       pass

def loop_iteration(self, timeout = 60):
   next_timeout, sources_handled = self._call_timeout_handlers()
   if self.check_events():
     return
   if self._quit:
     return sources_handled
   for handler in list(self._unprepared_handlers):
     self._configure_io_handler(handler)
   if self._timeout is not None:
     timeout = min(timeout, self._timeout)
   if next_timeout is not None:
     timeout = min(next_timeout, timeout)

if timeout == 0:
     timeout += 1  # 带有超时的非阻塞,解约资源
   events = self.epoll.poll(timeout)
   for fd, flag in events:
     if flag & (select.EPOLLIN | select.EPOLLPRI | select.EPOLLET):
       self._handlers[fd].handle_read()
     if flag & (select.EPOLLOUT|select.EPOLLET):
       self._handlers[fd].handle_write()
     if flag & (select.EPOLLERR | select.EPOLLET):
       self._handlers[fd].handle_err()
     if flag & (select.EPOLLHUP | select.EPOLLET):
       self._handlers[fd].handle_hup()
     #if flag & select.EPOLLNVAL:
       #self._handlers[fd].handle_nval()

sources_handled += 1
     self._configure_io_handler(self._handlers[fd])

return sources_handled

使用

如何使用新的mainloop?只需在实例化Client时传入

mainloop = EpollMainLoop(settings)
client = Client(my_jid, [self, version_provider], settings, mainloop)

这样就会使用epoll作为mainloop
注意

epoll仅仅在Linux下支持