text: # Copyright 2012 Red Hat, Inc.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  import threading
  
  import eventlet
  from eventlet import greenpool
  
  from designate.openstack.common import log as logging
  from designate.openstack.common import loopingcall
  
  
  LOG = logging.getLogger(__name__)
  
  
  def _thread_done(gt, *args, **kwargs):
      """Callback function to be passed to GreenThread.link() when we spawn()
      Calls the :class:`ThreadGroup` to notify if.
  
      """
      kwargs['group'].thread_done(kwargs['thread'])
  
  
  class Thread(object):
      """Wrapper around a greenthread, that holds a reference to the
      :class:`ThreadGroup`. The Thread will notify the :class:`ThreadGroup` when
      it has done so it can be removed from the threads list.
      """
      def __init__(self, thread, group):
          self.thread = thread
          self.thread.link(_thread_done, group=group, thread=self)
  
      def stop(self):
          self.thread.kill()
  
      def wait(self):
          return self.thread.wait()
  
      def link(self, func, *args, **kwargs):
          self.thread.link(func, *args, **kwargs)
  
  
  class ThreadGroup(object):
      """The point of the ThreadGroup class is to:
  
      * keep track of timers and greenthreads (making it easier to stop them
        when need be).
      * provide an easy API to add timers.
      """
      def __init__(self, thread_pool_size=10):
          self.pool = greenpool.GreenPool(thread_pool_size)
          self.threads = []
          self.timers = []
  
      def add_dynamic_timer(self, callback, initial_delay=None,
                            periodic_interval_max=None, *args, **kwargs):
          timer = loopingcall.DynamicLoopingCall(callback, *args, **kwargs)
          timer.start(initial_delay=initial_delay,
                      periodic_interval_max=periodic_interval_max)
          self.timers.append(timer)
  
      def add_timer(self, interval, callback, initial_delay=None,
                    *args, **kwargs):
          pulse = loopingcall.FixedIntervalLoopingCall(callback, *args, **kwargs)
          pulse.start(interval=interval,
                      initial_delay=initial_delay)
          self.timers.append(pulse)
  
      def add_thread(self, callback, *args, **kwargs):
          gt = self.pool.spawn(callback, *args, **kwargs)
          th = Thread(gt, self)
          self.threads.append(th)
          return th
  
      def thread_done(self, thread):
          self.threads.remove(thread)
  
      def _stop_threads(self):
          current = threading.current_thread()
  
          # Iterate over a copy of self.threads so thread_done doesn't
          # modify the list while we're iterating
          for x in self.threads[:]:
              if x is current:
                  # don't kill the current thread.
                  continue
              try:
                  x.stop()
              except Exception as ex:
                  LOG.exception(ex)
  
      def stop_timers(self):
          for x in self.timers:
              try:
                  x.stop()
              except Exception as ex:
                  LOG.exception(ex)
          self.timers = []
  
      def stop(self, graceful=False):
          """stop function has the option of graceful=True/False.
  
          * In case of graceful=True, wait for all threads to be finished.
            Never kill threads.
          * In case of graceful=False, kill threads immediately.
          """
          self.stop_timers()
          if graceful:
              # In case of graceful=True, wait for all threads to be
              # finished, never kill threads
              self.wait()
          else:
              # In case of graceful=False(Default), kill threads
              # immediately
              self._stop_threads()
  
      def wait(self):
          for x in self.timers:
              try:
                  x.wait()
              except eventlet.greenlet.GreenletExit:
                  pass
              except Exception as ex:
                  LOG.exception(ex)
          current = threading.current_thread()
  
          # Iterate over a copy of self.threads so thread_done doesn't
          # modify the list while we're iterating
          for x in self.threads[:]:
              if x is current:
                  continue
              try:
                  x.wait()
              except eventlet.greenlet.GreenletExit:
                  pass
              except Exception as ex:
                  LOG.exception(ex)
  