subscription_modifiers.py
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32 
33 from collections import deque
34 from threading import Thread, Condition
35 from time import time
36 import traceback
37 import sys
38 
39 """ Sits between incoming messages from a subscription, and the outgoing
40 publish method. Provides throttling / buffering capabilities.
41 
42 When the parameters change, the handler may transition to a different kind
43 of handler
44 """
45 
46 
48  def __init__(self, previous_handler=None, publish=None):
49  if previous_handler:
50  self.last_publish = previous_handler.last_publish
51  self.throttle_rate = previous_handler.throttle_rate
52  self.queue_length = previous_handler.queue_length
53  self.publish = previous_handler.publish
54  else:
55  self.last_publish = 0
56  self.throttle_rate = 0
57  self.queue_length = 0
58  self.publish = publish
59 
60  def set_throttle_rate(self, throttle_rate):
61  self.throttle_rate = throttle_rate / 1000.0
62  return self.transition()
63 
64  def set_queue_length(self, queue_length):
65  self.queue_length = queue_length
66  return self.transition()
67 
68  def time_remaining(self):
69  return max((self.last_publish + self.throttle_rate) - time(), 0)
70 
71  def handle_message(self, msg):
72  self.last_publish = time()
73  self.publish(msg)
74 
75  def transition(self):
76  if self.throttle_rate == 0 and self.queue_length == 0:
77  return self
78  elif self.queue_length == 0:
79  return ThrottleMessageHandler(self)
80  else:
81  return QueueMessageHandler(self)
82 
83  def finish(self, block=True):
84  pass
85 
86 
87 class ThrottleMessageHandler(MessageHandler):
88 
89  def handle_message(self, msg):
90  if self.time_remaining() == 0:
91  MessageHandler.handle_message(self, msg)
92 
93  def transition(self):
94  if self.throttle_rate == 0 and self.queue_length == 0:
95  return MessageHandler(self)
96  elif self.queue_length == 0:
97  return self
98  else:
99  return QueueMessageHandler(self)
100 
101  def finish(self, block=True):
102  pass
103 
104 
105 class QueueMessageHandler(MessageHandler, Thread):
106 
107  def __init__(self, previous_handler):
108  Thread.__init__(self)
109  MessageHandler.__init__(self, previous_handler)
110  self.daemon = True
111  self.queue = deque(maxlen=self.queue_length)
112  self.c = Condition()
113  self.alive = True
114  self.start()
115 
116  def handle_message(self, msg):
117  with self.c:
118  if not self.alive:
119  return
120 
121  should_notify = len(self.queue) == 0
122  self.queue.append(msg)
123  if should_notify:
124  self.c.notify()
125 
126  def transition(self):
127  if self.throttle_rate == 0 and self.queue_length == 0:
128  self.finish()
129  return MessageHandler(self)
130  elif self.queue_length == 0:
131  self.finish()
132  return ThrottleMessageHandler(self)
133  else:
134  with self.c:
135  old_queue = self.queue
136  self.queue = deque(maxlen=self.queue_length)
137  while len(old_queue) > 0:
138  self.queue.append(old_queue.popleft())
139  self.c.notify()
140  return self
141 
142  def finish(self, block=True):
143  """ If throttle was set to 0, this pushes all buffered messages """
144  # Notify the thread to finish
145  with self.c:
146  self.alive = False
147  self.c.notify()
148 
149  if block:
150  self.join()
151 
152  def run(self):
153  while self.alive:
154  msg = None
155  with self.c:
156  if len(self.queue) == 0:
157  self.c.wait()
158  else:
159  self.c.wait(self.time_remaining())
160  if self.alive and self.time_remaining() == 0 and len(self.queue) > 0:
161  msg = self.queue.popleft()
162  if msg is not None:
163  try:
164  MessageHandler.handle_message(self, msg)
165  except:
166  traceback.print_exc(file=sys.stderr)
167  while self.time_remaining() == 0 and len(self.queue) > 0:
168  try:
169  MessageHandler.handle_message(self, self.queue.popleft())
170  except:
171  traceback.print_exc(file=sys.stderr)


rosbridge_library
Author(s): Jonathan Mace
autogenerated on Fri Oct 21 2022 02:45:18