subscription_modifiers.py
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00001 # Software License Agreement (BSD License)
00002 #
00003 # Copyright (c) 2012, Willow Garage, Inc.
00004 # All rights reserved.
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00006 # Redistribution and use in source and binary forms, with or without
00007 # modification, are permitted provided that the following conditions
00008 # are met:
00009 #
00010 #  * Redistributions of source code must retain the above copyright
00011 #    notice, this list of conditions and the following disclaimer.
00012 #  * Redistributions in binary form must reproduce the above
00013 #    copyright notice, this list of conditions and the following
00014 #    disclaimer in the documentation and/or other materials provided
00015 #    with the distribution.
00016 #  * Neither the name of Willow Garage, Inc. nor the names of its
00017 #    contributors may be used to endorse or promote products derived
00018 #    from this software without specific prior written permission.
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00020 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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00031 # POSSIBILITY OF SUCH DAMAGE.
00032 
00033 from threading import Thread, Condition
00034 from time import time
00035 
00036 """ Sits between incoming messages from a subscription, and the outgoing
00037 publish method.  Provides throttling / buffering capabilities.
00038 
00039 When the parameters change, the handler may transition to a different kind
00040 of handler
00041 """
00042 
00043 
00044 class MessageHandler():
00045     def __init__(self, previous_handler=None, publish=None):
00046         if previous_handler:
00047             self.last_publish = previous_handler.last_publish
00048             self.throttle_rate = previous_handler.throttle_rate
00049             self.queue_length = previous_handler.queue_length
00050             self.publish = previous_handler.publish
00051         else:
00052             self.last_publish = 0
00053             self.throttle_rate = 0
00054             self.queue_length = 0
00055             self.publish = publish
00056 
00057     def set_throttle_rate(self, throttle_rate):
00058         self.throttle_rate = throttle_rate / 1000.0
00059         return self.transition()
00060 
00061     def set_queue_length(self, queue_length):
00062         self.queue_length = queue_length
00063         return self.transition()
00064 
00065     def time_remaining(self):
00066         return max((self.last_publish + self.throttle_rate) - time(), 0)
00067 
00068     def handle_message(self, msg):
00069         self.last_publish = time()
00070         self.publish(msg)
00071 
00072     def transition(self):
00073         if self.throttle_rate == 0:
00074             return self
00075         elif self.queue_length == 0:
00076             return ThrottleMessageHandler(self)
00077         else:
00078             return QueueMessageHandler(self)
00079 
00080     def finish(self):
00081         pass
00082 
00083 
00084 class ThrottleMessageHandler(MessageHandler):
00085 
00086     def handle_message(self, msg):
00087         if self.time_remaining() == 0:
00088             MessageHandler.handle_message(self, msg)
00089 
00090     def transition(self):
00091         if self.throttle_rate == 0:
00092             return MessageHandler(self)
00093         elif self.queue_length == 0:
00094             return self
00095         else:
00096             return QueueMessageHandler(self)
00097 
00098     def finish(self):
00099         pass
00100 
00101 
00102 class QueueMessageHandler(MessageHandler, Thread):
00103 
00104     def __init__(self, previous_handler):
00105         Thread.__init__(self)
00106         MessageHandler.__init__(self, previous_handler)
00107         self.daemon = True
00108         self.queue = []
00109         self.c = Condition()
00110         self.alive = True
00111         self.start()
00112 
00113     def handle_message(self, msg):
00114         with self.c:
00115             should_notify = len(self.queue) == 0
00116             self.queue.append(msg)
00117             if len(self.queue) > self.queue_length:
00118                 del self.queue[0:len(self.queue) - self.queue_length]
00119             if should_notify:
00120                 self.c.notify()
00121 
00122     def transition(self):
00123         if self.throttle_rate == 0:
00124             self.finish()
00125             return MessageHandler(self)
00126         elif self.queue_length == 0:
00127             self.finish()
00128             return ThrottleMessageHandler(self)
00129         else:
00130             with self.c:
00131                 if len(self.queue) > self.queue_length:
00132                     del self.queue[0:len(self.queue) - self.queue_length]
00133                 self.c.notify()
00134             return self
00135 
00136     def finish(self):
00137         """ If throttle was set to 0, this pushes all buffered messages """
00138         # Notify the thread to finish
00139         with self.c:
00140             self.alive = False
00141             self.c.notify()
00142 
00143         self.join()
00144 
00145     def run(self):
00146         while self.alive:
00147             with self.c:
00148                 while self.alive and (self.time_remaining() > 0 or len(self.queue) == 0):
00149                     if len(self.queue) == 0:
00150                         self.c.wait()
00151                     else:
00152                         self.c.wait(self.time_remaining())
00153                 if self.alive and self.time_remaining() == 0 and len(self.queue) > 0:
00154                     try:
00155                         MessageHandler.handle_message(self, self.queue[0])
00156                     except:
00157                         pass
00158                     del self.queue[0]
00159         while self.time_remaining() == 0 and len(self.queue) > 0:
00160             try:
00161                 MessageHandler.handle_message(self, self.queue[0])
00162             except:
00163                 pass
00164             del self.queue[0]


rosbridge_library
Author(s): Jonathan Mace
autogenerated on Mon Oct 6 2014 06:58:09