cis/cis_lb/load_balancer/base.py

   1 import threading
   2 import urllib
   3 import json
   4
   5 import config
   6 import logger
   7
   8
   9 class LoadBalancer(threading.Thread):
  10
  11     def __init__(self, id, queue):
  12         """
  13         Initialize Load Balancer,
  14         """
  15
  16         threading.Thread.__init__(self, \
  17                 name = '%s%02d' % (self.__class__.__name__, id))
  18
  19         self.queue = queue
  20
  21     def run(self):
  22
  23         while True:
  24             (request, data) = self.queue.get()
  25             urls = config.CIS_URLS[:]
  26             code = json.loads(data)['code']
  27             success = False
  28
  29             while len(urls) != 0:
  30                 cis = self.choose(urls)
  31
  32                 # Request is forwarded to the chosen CIS.
  33                 try:
  34                     urllib.urlopen(cis + request, data)
  35                 except IOError:
  36                     logger.log_msg('#%s: Failed to forward request to %s' \
  37                             % (code, cis), \
  38                             logger.LOG_LEVEL_ERROR)
  39                     continue
  40
  41                 success = True
  42                 logger.log_msg('#%s: Request forwarded to %s' \
  43                             % (code, cis), \
  44                         logger.LOG_LEVEL_INFO)
  45                 break
  46
  47             if len(urls) == 0 and not success:
  48                 logger.log_msg('#%s: Failed to forward request to any CIS' \
  49                             % code, \
  50                             logger.LOG_LEVEL_FATAL)
  51                 self.notify_error(code)
  52
  53             self.queue.task_done()
  54
  55     def notify_error(self, code):
  56         logger.log_msg('#%s: notifying web server about the error...'\
  57                 % code)
  58
  59         if config.WS_ERROR[len(config.WS_ERROR) - 1] == '/':
  60             url = config.WS_ERROR + code
  61         else:
  62             url = config.WS_ERROR + '/' + code
  63         url = url + '/' + 'unreachable'
  64
  65         f = urllib.urlopen(url)
  66         f.read()
  67
  68     def choose(self, urls):
  69         """
  70         Implement load balancing policy in this method for child classes which
  71         choses a CIS from urls parameter. The chosen URL should be deleted from
  72         urls list.
  73         """
  74         pass