planetstack/observer/syncstep.py

   1 import os
   2 import base64
   3 from planetstack.config import Config
   4
   5 class FailedDependency(Exception):
   6         pass
   7
   8 class SyncStep:
   9         """ A PlanetStack Sync step.
  10
  11         Attributes:
  12                 psmodel         Model name the step synchronizes
  13                 dependencies    list of names of models that must be synchronized first if the current model depends on them
  14         """
  15         slow=False
  16         def get_prop(prop):
  17                 try:
  18                         sync_config_dir = Config().sync_config_dir
  19                 except:
  20                         sync_config_dir = '/etc/planetstack/sync'
  21                 prop_config_path = '/'.join(sync_config_dir,self.name,prop)
  22                 return open(prop_config_path).read().rstrip()
  23
  24         def __init__(self, **args):
  25                 """Initialize a sync step
  26                    Keyword arguments:
  27                                 name -- Name of the step
  28                                 provides -- PlanetStack models sync'd by this step
  29                 """
  30                 dependencies = []
  31                 try:
  32                         self.soft_deadline = int(self.get_prop('soft_deadline_seconds'))
  33                 except:
  34                         self.soft_deadline = 5 # 5 seconds
  35
  36                 return
  37
  38         def fetch_pending(self):
  39                 return Sliver.objects.filter(ip=None)
  40
  41         def check_dependencies(self, obj):
  42                 for dep in self.dependencies:
  43                         peer_object = getattr(obj, dep.name.lowercase())
  44                         if (peer_object.pk==dep.pk):
  45                                 raise DependencyFailed
  46
  47         def call(self, failed=[]):
  48                 pending = self.fetch_pending()
  49                 for o in pending:
  50                         if (not self.depends_on(o, failed)):
  51                                 try:
  52                                         check_dependencies(o) # Raises exception if failed
  53                                         self.sync_record(o)
  54                                         o.enacted = datetime.now() # Is this the same timezone? XXX
  55                                         o.save(update_fields=['enacted'])
  56                                 except:
  57                                         failed.append(o)
  58                 return failed
  59
  60         def __call__(self):
  61                 return self.call()