pysawsim/manager/thread.py

   1 # Copyright (C) 2010  W. Trevor King <wking@drexel.edu>
   2 #
   3 # This program is free software: you can redistribute it and/or modify
   4 # it under the terms of the GNU General Public License as published by
   5 # the Free Software Foundation, either version 3 of the License, or
   6 # (at your option) any later version.
   7 #
   8 # This program is distributed in the hope that it will be useful,
   9 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 # GNU General Public License for more details.
  12 #
  13 # You should have received a copy of the GNU General Public License
  14 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  15 #
  16 # The author may be contacted at <wking@drexel.edu> on the Internet, or
  17 # write to Trevor King, Drexel University, Physics Dept., 3141 Chestnut St.,
  18 # Philadelphia PA 19104, USA.
  19
  20 """Functions for running external commands on other hosts.
  21 """
  22
  23 import copy
  24 from Queue import Queue, Empty
  25 import threading
  26
  27 from .. import log
  28 from . import Job, JobManager
  29
  30
  31 CLOSE_MESSAGE = "close"
  32
  33
  34 class WorkerThread (threading.Thread):
  35     def __init__(self, spawn_queue, receive_queue, *args, **kwargs):
  36         super(WorkerThread, self).__init__(*args, **kwargs)
  37         self.spawn_queue = spawn_queue
  38         self.receive_queue = receive_queue
  39         self.name = self.getName()  # work around Pythons < 2.6
  40
  41     def run(self):
  42         while True:
  43             msg = self.spawn_queue.get()
  44             if msg == CLOSE_MESSAGE:
  45                 log().debug('%s closing' % self.name)
  46                 break
  47             assert isinstance(msg, Job), msg
  48             log().debug('%s running job %s' % (self.name, msg))
  49             msg.run()
  50             self.receive_queue.put(msg)
  51
  52
  53 class ThreadManager (JobManager):
  54     """Manage asynchronous `Job` execution via :mod:`threading`.
  55
  56     >>> from time import sleep
  57     >>> from math import sqrt
  58     >>> m = ThreadManager()
  59     >>> group_A = []
  60     >>> for i in range(10):
  61     ...     t = max(0, 5-i)
  62     ...     group_A.append(m.async_invoke(Job(target=sleep, args=[t])))
  63     >>> group_B = []
  64     >>> for i in range(10):
  65     ...     group_B.append(m.async_invoke(Job(target=sqrt, args=[i],
  66     ...                 blocks_on=[j.id for j in group_A])))
  67     >>> jobs = m.wait(ids=[j.id for j in group_A[5:8]])
  68     >>> print sorted(jobs.values(), key=lambda j: j.id)
  69     [<Job 5>, <Job 6>, <Job 7>]
  70     >>> jobs = m.wait()
  71     >>> print sorted(jobs.values(), key=lambda j: j.id)
  72     ... # doctest: +NORMALIZE_WHITESPACE
  73     [<Job 0>, <Job 1>, <Job 2>, <Job 3>, <Job 4>, <Job 8>, <Job 9>, <Job 10>,
  74      <Job 11>, <Job 12>, <Job 13>, <Job 14>, <Job 15>, <Job 16>, <Job 17>,
  75      <Job 18>, <Job 19>]
  76     >>> m.teardown()
  77
  78     Note that Python's Global Interpreter Lock (GIL) currently limits
  79     threads to a single core.  See the following discussions:
  80
  81     * http://smoothspan.wordpress.com/2007/09/14/guido-is-right-to-leave-the-gil-in-python-not-for-multicore-but-for-utility-computing/
  82     * http://docs.python.org/faq/library#id18
  83     * http://www.artima.com/weblogs/viewpost.jsp?thread=214235
  84     * http://www.snaplogic.com/blog/?p=94
  85     * http://stackoverflow.com/questions/31340/
  86
  87     Increasing `worker_pool` will only help you get around IO blockin
  88     at the cost increased time-slicing overhead.
  89     """
  90     def __init__(self, worker_pool=2):
  91         super(ThreadManager, self).__init__()
  92         self._blocked = []
  93         self._spawn_queue = Queue()
  94         self._receive_queue = Queue()
  95         self._workers = []
  96         for i in range(worker_pool):
  97             worker = WorkerThread(spawn_queue=self._spawn_queue,
  98                                   receive_queue=self._receive_queue,
  99                                   name='worker-%d' % i)
 100             log().debug('start thread %s' % worker.name)
 101             worker.start()
 102             self._workers.append(worker)
 103
 104     def teardown(self):
 105         for worker in self._workers:
 106             self._spawn_queue.put(CLOSE_MESSAGE)
 107         for worker in self._workers:
 108             log().debug('join thread %s' % worker.name)
 109             worker.join()
 110         super(ThreadManager, self).teardown()
 111
 112     def _job_is_blocked(self, job, ignore_id=None):
 113         for id in job.blocks_on:
 114             if id == ignore_id:
 115                 continue
 116             elif id in self._jobs and self._jobs[id].status == None:
 117                 return True
 118         return False
 119
 120     def _spawn_job(self, job):
 121         self._receive_job(block=False)
 122         if self._job_is_blocked(job):
 123             log().debug('block job %s' % job)
 124             self._blocked.append(job)
 125             return
 126         self._spawn_queue.put(copy.deepcopy(job))  # protect from shared memory
 127
 128     def _receive_job(self, block=True):
 129         try:
 130             job = self._receive_queue.get(block=block)
 131         except Empty:
 132             return
 133         for j in list(self._blocked):
 134             if job.id in j.blocks_on:
 135                 if not self._job_is_blocked(j, ignore_id=job.id):
 136                     log().debug('unblock job %s' % j)
 137                     self._blocked.remove(j)
 138                     self._spawn_queue.put(j)
 139         return job