instrumentation/next-share/BaseLib/Utilities/TimedTaskQueue.py

   1 # Written by Arno Bakker
   2 # see LICENSE.txt for license information
   3 #
   4 # TimedTaskQueue is a server that executes tasks on behalf of e.g. the GUI that
   5 # are too time consuming to be run by the actual GUI Thread (MainThread). Note
   6 # that you still need to delegate the actual updating of the GUI to the
   7 # MainThread via the wx.CallAfter mechanism.
   8 #
   9 import sys
  10
  11 from threading import Thread,Condition
  12 from traceback import print_exc,print_stack
  13 from time import time
  14
  15 DEBUG = False
  16
  17 class TimedTaskQueue:
  18
  19     __single = None
  20
  21     def __init__(self,nameprefix="TimedTaskQueue",isDaemon=True):
  22         self.cond = Condition()
  23         self.queue = []
  24         self.count = 0.0 # serves to keep task that were scheduled at the same time in FIFO order
  25         self.thread = Thread(target = self.run)
  26         self.thread.setDaemon(isDaemon)
  27         self.thread.setName( nameprefix+self.thread.getName() )
  28         self.thread.start()
  29
  30     def add_task(self,task,t=0,id=None):
  31         """ t parameter is now usable, unlike before.
  32             If id is given, all the existing tasks with the same id will be removed
  33             before inserting this task
  34         """
  35
  36         if task is None:
  37             print_stack()
  38
  39         self.cond.acquire()
  40         when = time()+t
  41         if DEBUG:
  42             print >>sys.stderr,"ttqueue: ADD EVENT",t,task
  43
  44         if id != None:  # remove all redundant tasks
  45             self.queue = filter(lambda item:item[2]!=id, self.queue)
  46         self.queue.append((when,self.count,task,id))
  47         self.count += 1.0
  48         self.cond.notify()
  49         self.cond.release()
  50
  51     def run(self):
  52         """ Run by server thread """
  53         while True:
  54             task = None
  55             timeout = None
  56             flag = False
  57             self.cond.acquire()
  58             while True:
  59                 while len(self.queue) == 0 or flag:
  60                     flag = False
  61                     if timeout is None:
  62                         # Wait until something is queued
  63                         self.cond.wait()
  64                     else:
  65                         # Wait till first event is due
  66                         self.cond.wait(timeout)
  67                 # A new event was added or an event is due
  68                 self.queue.sort()
  69
  70                 (when,count,task,id) = self.queue[0]
  71                 if DEBUG:
  72                     print >>sys.stderr,"ttqueue: EVENT IN QUEUE",when,task
  73                 now = time()
  74                 if now < when:
  75                     # Event not due, wait some more
  76                     if DEBUG:
  77                         print >>sys.stderr,"ttqueue: EVENT NOT TILL",when-now
  78                     timeout = when-now
  79                     flag = True
  80                 else:
  81                     # Event due, execute
  82                     if DEBUG:
  83                         print >>sys.stderr,"ttqueue: EVENT DUE"
  84                     self.queue.pop(0)
  85                     break
  86             self.cond.release()
  87
  88             # Execute task outside lock
  89             try:
  90                 # 'stop' and 'quit' are only used for unit test
  91                 if task == 'stop':
  92                     break
  93                 elif task == 'quit':
  94                     if len(self.queue) == 0:
  95                         break
  96                     else:
  97                         (when,count,task,id) = self.queue[-1]
  98                         t = when-time()+0.001
  99                         self.add_task('quit',t)
 100                 else:
 101                     task()
 102             except:
 103                 print_exc()
 104
 105