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