[ZODB-Dev] Deferred notifing from one thread to another.

[Victor Safronovich]

Hello Tim Peters,

Friday, December 9, 2005, 9:18:26 PM, you wrote:

TP> [Victor Safronovich]
>> ...
>> Of course i may write time.sleep( SLEEP_CONSTANT ) before
>> app._p_jar.sync(), but is this a good solution?

TP> I can't make time to understand your problem (sorry!)
   Tim, thank you for your answer.
   
TP> , but I can make time
TP> to tell you that a bare time.sleep() is almost never a good solution to
TP> thread problems.  time.sleep() in a _loop_ can be reliable, provided you can
TP> write code to recognize when what you're waiting for has happened; this
TP> approach is called "polling".

TP>     while what I'm waiting for hasn't happened:
TP>         time.sleep(WHATEVER)

TP> For example, when you change a persistent object, its ._p_changed attribute
TP> gets set to a true value.  When the change gets committed, ._p_changed is
TP> reset to a false value.  So _perhaps_ (I'm not sure -- being sure would
TP> require understanding all of your problem) you could poll waiting for some
TP> specific object's _p_changed to become false.

  Supper, I do the next

  def reset_hook( scheduler ):
      while scheduler._p_changed:
         time.sleep(0.05) # again time sleep :))
      ResetEvent.set()

  and
  
  def addSchedulerElement(self, **options):
        self._setObject(self.generateId(), ScheduleElement(**options))
        Thread(target=reset_hook, args=(self,))

  Tommorow, i`ll check how this works :).


-- 
Best regards,
 Victor Safronovich
 NauMen.NauDoc.SoftwareDeveloper  http://www.naumen.ru