Source Code for Module virtualization.batching_log_notifier

  1  # 
  2  # Copyright (c) 2008--2013 Red Hat, Inc. 
  3  # 
  4  # This software is licensed to you under the GNU General Public License, 
  5  # version 2 (GPLv2). There is NO WARRANTY for this software, express or 
  6  # implied, including the implied warranties of MERCHANTABILITY or FITNESS 
  7  # FOR A PARTICULAR PURPOSE. You should have received a copy of GPLv2 
  8  # along with this software; if not, see 
  9  # http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt. 
 10  # 
 11  # Red Hat trademarks are not licensed under GPLv2. No permission is 
 12  # granted to use or replicate Red Hat trademarks that are incorporated 
 13  # in this software or its documentation. 
 14  # 
 15   
 16  # 
 17  # This module provides the BatchingLogNotifier class, which has the ability to 
 18  # queue up log messages and periodically forward them in a batch to the server. 
 19  # 
 20   
 21  from threading import Thread, Event, Lock 
 22   
 23  ############################################################################### 
 24  # Constants 
 25  ############################################################################### 
 26   
 27  POLL_INTERVAL = 5  # Seconds 
 28   
 29  ############################################################################### 
 30  # BatchingLogNotifier Class 
 31  ############################################################################### 
 32   
 33 -class BatchingLogNotifier: 
 34   
 35 -    def __init__(self, batch_notify_handler): 
 36          self.__log_message_queue = LockableLogMessageQueue() 
 37          self.__notify_thread = NotifyThread(self.__log_message_queue, 
 38                                              batch_notify_handler) 
 39   
 40 -    def add_log_message(self, log_message): 
 41          self.__log_message_queue.lock() 
 42          try: 
 43              self.__log_message_queue.add(log_message) 
 44          finally: 
 45              self.__log_message_queue.unlock() 
 46   
 47 -    def start(self): 
 48          self.__notify_thread.start() 
 49   
 50 -    def stop(self): 
 51          self.__notify_thread.stop() 
 52          if self.__notify_thread.isAlive(): 
 53              self.__notify_thread.join() 
 54   
 55  ############################################################################### 
 56  # LogQueue Class 
 57  ############################################################################### 
 58   
 59 -class LockableLogMessageQueue: 
 60   
 61 -    def __init__(self): 
 62          self.__log_message_queue = [] 
 63          self.__queue_lock = Lock() 
 64   
 65 -    def lock(self): 
 66          self.__queue_lock.acquire() 
 67   
 68 -    def unlock(self): 
 69          self.__queue_lock.release() 
 70   
 71 -    def add(self, log_message): 
 72          self.__log_message_queue.append(log_message) 
 73   
 74 -    def pop(self): 
 75          first_item = self.__log_message_queue[0] 
 76          self.__log_message_queue.remove(first_item) 
 77          return first_item 
 78   
 79 -    def is_empty(self): 
 80          return len(self.__log_message_queue) == 0 
 81   
 82  ############################################################################### 
 83  # BatchNotifyHandler Class 
 84  ############################################################################### 
 85   
 86 -class BatchNotifyHandler: 
 87      """ 
 88      This class provides a generic mechanism for processing logging callbacks. 
 89      This is just a stub class, which should be inherited by anyone who wants 
 90      to respond to logging events. 
 91      """ 
 92   
 93 -    def __init__(self): 
 94          pass 
 95   
 96 -    def batch_began(): 
 97          pass 
 98   
 99 -    def log_message_discovered(log_message): 
100          pass 
101   
102 -    def batch_ended(): 
103          pass 
104   
105  ############################################################################### 
106  # NotifyThread Class 
107  ############################################################################### 
108   
109 -class NotifyThread(Thread): 
110   
111      ########################################################################### 
112      # Public Interface 
113      ########################################################################### 
114   
115 -    def __init__(self, log_message_queue, batch_notify_handler): 
116          Thread.__init__(self) 
117          self.__log_message_queue = log_message_queue 
118          self.__batch_notify_handler = batch_notify_handler 
119          self.__stop_event = Event() 
120   
121 -    def run(self): 
122          # First, clear the stop event in case it was already set. 
123          self.__stop_event.clear() 
124   
125          # Enter the main loop, flushing the queue every interval. 
126          while not self.__stop_event.isSet(): 
127              self.__flush_log_message_queue() 
128              self.__stop_event.wait(POLL_INTERVAL) 
129   
130          # We've been signaled to stop, but flush the queue one more time before 
131          # exiting. 
132          self.__flush_log_message_queue() 
133   
134 -    def stop(self): 
135          self.__stop_event.set() 
136   
137      ########################################################################### 
138      # Helper Methods 
139      ########################################################################### 
140   
141 -    def __flush_log_message_queue(self): 
142          self.__log_message_queue.lock() 
143          try: 
144              if not self.__log_message_queue.is_empty(): 
145                  self.__batch_notify_handler.batch_began() 
146                  while not self.__log_message_queue.is_empty(): 
147                      log_message = self.__log_message_queue.pop() 
148                      self.__batch_notify_handler.log_message_discovered( 
149                          log_message) 
150                  self.__batch_notify_handler.batch_ended() 
151          finally: 
152              self.__log_message_queue.unlock() 
153   
154  if __name__ == "__main__": 
155      notifier = BatchingLogNotifier() 
156      notifier.start() 
157