Rewrote toposort to handle loops in Step graph. Simpler implementation
diff --git a/planetstack/observer/event_loop.py b/planetstack/observer/event_loop.py
index bdf5ce3..6b77236 100644
--- a/planetstack/observer/event_loop.py
+++ b/planetstack/observer/event_loop.py
@@ -18,303 +18,259 @@
 from planetstack.config import Config
 from observer.steps import *
 from syncstep import SyncStep
+from toposort import toposort
 
 debug_mode = False
 
 logger = Logger(level=logging.INFO)
 
 class StepNotReady(Exception):
-    pass
-
-def toposort(g, steps=None):
-    if (not steps):
-        keys = set(g.keys())
-        values = set({})
-        for v in g.values():
-            values=values | set(v)
-        
-        steps=list(keys|values)
-    reverse = {}
-
-    for k,v in g.items():
-        for rk in v:
-            try:
-                reverse[rk].append(k)
-            except:
-                reverse[rk]=k
-
-    sources = []
-    for k,v in g.items():
-        if not reverse.has_key(k):
-            sources.append(k)
-
-
-    for k,v in reverse.iteritems():
-        if (not v):
-            sources.append(k)
-
-    order = []
-    marked = []
-
-    while sources:
-        n = sources.pop()
-        try:
-            for m in g[n]:
-                if m not in marked:
-                    sources.append(m)
-                    marked.append(m)
-        except KeyError:
-            pass
-        if (n in steps):
-            order.append(n)
-
-    order.reverse()
-    order.extend(set(steps)-set(order))
-    return order
+	pass
 
 class NoOpDriver:
-    def __init__(self):
-         self.enabled = True
+	def __init__(self):
+		 self.enabled = True
 
 class PlanetStackObserver:
-    #sync_steps = [SyncNetworks,SyncNetworkSlivers,SyncSites,SyncSitePrivileges,SyncSlices,SyncSliceMemberships,SyncSlivers,SyncSliverIps,SyncExternalRoutes,SyncUsers,SyncRoles,SyncNodes,SyncImages,GarbageCollector]
-    sync_steps = []
+	#sync_steps = [SyncNetworks,SyncNetworkSlivers,SyncSites,SyncSitePrivileges,SyncSlices,SyncSliceMemberships,SyncSlivers,SyncSliverIps,SyncExternalRoutes,SyncUsers,SyncRoles,SyncNodes,SyncImages,GarbageCollector]
+	sync_steps = []
 
-    def __init__(self):
-        # The Condition object that gets signalled by Feefie events
-        self.step_lookup = {}
-        self.load_sync_step_modules()
-        self.load_sync_steps()
-        self.event_cond = threading.Condition()
+	def __init__(self):
+		# The Condition object that gets signalled by Feefie events
+		self.step_lookup = {}
+		self.load_sync_step_modules()
+		self.load_sync_steps()
+		self.event_cond = threading.Condition()
 
 
-        self.driver_kind = getattr(Config(), "observer_driver", "openstack")
-        if self.driver_kind=="openstack":
-            self.driver = OpenStackDriver()
-        else:
-            self.driver = NoOpDriver()
+		self.driver_kind = getattr(Config(), "observer_driver", "openstack")
+		if self.driver_kind=="openstack":
+			self.driver = OpenStackDriver()
+		else:
+			self.driver = NoOpDriver()
 
-    def wait_for_event(self, timeout):
-        self.event_cond.acquire()
-        self.event_cond.wait(timeout)
-        self.event_cond.release()
+	def wait_for_event(self, timeout):
+		self.event_cond.acquire()
+		self.event_cond.wait(timeout)
+		self.event_cond.release()
 
-    def wake_up(self):
-        logger.info('Wake up routine called. Event cond %r'%self.event_cond)
-        self.event_cond.acquire()
-        self.event_cond.notify()
-        self.event_cond.release()
+	def wake_up(self):
+		logger.info('Wake up routine called. Event cond %r'%self.event_cond)
+		self.event_cond.acquire()
+		self.event_cond.notify()
+		self.event_cond.release()
 
-    def load_sync_step_modules(self, step_dir=None):
-        if step_dir is None:
-            if hasattr(Config(), "observer_steps_dir"):
-                step_dir = Config().observer_steps_dir
-            else:
-                step_dir = "/opt/planetstack/observer/steps"
+	def load_sync_step_modules(self, step_dir=None):
+		if step_dir is None:
+			if hasattr(Config(), "observer_steps_dir"):
+				step_dir = Config().observer_steps_dir
+			else:
+				step_dir = "/opt/planetstack/observer/steps"
 
-        for fn in os.listdir(step_dir):
-            pathname = os.path.join(step_dir,fn)
-            if os.path.isfile(pathname) and fn.endswith(".py") and (fn!="__init__.py"):
-                module = imp.load_source(fn[:-3],pathname)
-                for classname in dir(module):
-                    c = getattr(module, classname, None)
+		for fn in os.listdir(step_dir):
+			pathname = os.path.join(step_dir,fn)
+			if os.path.isfile(pathname) and fn.endswith(".py") and (fn!="__init__.py"):
+				module = imp.load_source(fn[:-3],pathname)
+				for classname in dir(module):
+					c = getattr(module, classname, None)
 
-                    # make sure 'c' is a descendent of SyncStep and has a
-                    # provides field (this eliminates the abstract base classes
-                    # since they don't have a provides)
+					# make sure 'c' is a descendent of SyncStep and has a
+					# provides field (this eliminates the abstract base classes
+					# since they don't have a provides)
 
-                    if inspect.isclass(c) and issubclass(c, SyncStep) and hasattr(c,"provides") and (c not in self.sync_steps):
-                        self.sync_steps.append(c)
-        logger.info('loaded sync steps: %s' % ",".join([x.__name__ for x in self.sync_steps]))
-        # print 'loaded sync steps: %s' % ",".join([x.__name__ for x in self.sync_steps])
+					if inspect.isclass(c) and issubclass(c, SyncStep) and hasattr(c,"provides") and (c not in self.sync_steps):
+						self.sync_steps.append(c)
+		logger.info('loaded sync steps: %s' % ",".join([x.__name__ for x in self.sync_steps]))
+		# print 'loaded sync steps: %s' % ",".join([x.__name__ for x in self.sync_steps])
 
-    def load_sync_steps(self):
-        dep_path = Config().observer_dependency_graph
-        logger.info('Loading model dependency graph from %s' % dep_path)
-        try:
-            # This contains dependencies between records, not sync steps
-            self.model_dependency_graph = json.loads(open(dep_path).read())
-        except Exception,e:
-            raise e
+	def load_sync_steps(self):
+		dep_path = Config().observer_dependency_graph
+		logger.info('Loading model dependency graph from %s' % dep_path)
+		try:
+			# This contains dependencies between records, not sync steps
+			self.model_dependency_graph = json.loads(open(dep_path).read())
+		except Exception,e:
+			raise e
 
-        try:
-            backend_path = Config().observer_pl_dependency_graph
-            logger.info('Loading backend dependency graph from %s' % backend_path)
-            # This contains dependencies between backend records
-            self.backend_dependency_graph = json.loads(open(backend_path).read())
-        except Exception,e:
-            logger.info('Backend dependency graph not loaded')
-            # We can work without a backend graph
-            self.backend_dependency_graph = {}
+		try:
+			backend_path = Config().observer_pl_dependency_graph
+			logger.info('Loading backend dependency graph from %s' % backend_path)
+			# This contains dependencies between backend records
+			self.backend_dependency_graph = json.loads(open(backend_path).read())
+		except Exception,e:
+			logger.info('Backend dependency graph not loaded')
+			# We can work without a backend graph
+			self.backend_dependency_graph = {}
 
-        provides_dict = {}
-        for s in self.sync_steps:
-            self.step_lookup[s.__name__] = s 
-            for m in s.provides:
-                try:
-                    provides_dict[m.__name__].append(s.__name__)
-                except KeyError:
-                    provides_dict[m.__name__]=[s.__name__]
+		provides_dict = {}
+		for s in self.sync_steps:
+			self.step_lookup[s.__name__] = s 
+			for m in s.provides:
+				try:
+					provides_dict[m.__name__].append(s.__name__)
+				except KeyError:
+					provides_dict[m.__name__]=[s.__name__]
 
-                
-        step_graph = {}
-        for k,v in self.model_dependency_graph.iteritems():
-            try:
-                for source in provides_dict[k]:
-                    for m in v:
-                        try:
-                            for dest in provides_dict[m]:
-                                # no deps, pass
-                                try:
-                                    step_graph[source].append(dest)
-                                except:
-                                    step_graph[source]=[dest]
-                        except KeyError:
-                            pass
-                    
-            except KeyError:
-                pass
-                # no dependencies, pass
-        
-        #import pdb
-        #pdb.set_trace()
-        if (self.backend_dependency_graph):
-            backend_dict = {}
-            for s in self.sync_steps:
-                for m in s.serves:
-                    backend_dict[m]=s.__name__
-                    
-            for k,v in backend_dependency_graph.iteritems():
-                try:
-                    source = backend_dict[k]
-                    for m in v:
-                        try:
-                            dest = backend_dict[m]
-                        except KeyError:
-                            # no deps, pass
-                            pass
-                        step_graph[source]=dest
-                        
-                except KeyError:
-                    pass
-                    # no dependencies, pass
+				
+		step_graph = {}
+		for k,v in self.model_dependency_graph.iteritems():
+			try:
+				for source in provides_dict[k]:
+					for m in v:
+						try:
+							for dest in provides_dict[m]:
+								# no deps, pass
+								try:
+									if (dest not in step_graph[source]):
+										step_graph[source].append(dest)
+								except:
+									step_graph[source]=[dest]
+						except KeyError:
+							pass
+					
+			except KeyError:
+				pass
+				# no dependencies, pass
+		
+		#import pdb
+		#pdb.set_trace()
+		if (self.backend_dependency_graph):
+			backend_dict = {}
+			for s in self.sync_steps:
+				for m in s.serves:
+					backend_dict[m]=s.__name__
+					
+			for k,v in backend_dependency_graph.iteritems():
+				try:
+					source = backend_dict[k]
+					for m in v:
+						try:
+							dest = backend_dict[m]
+						except KeyError:
+							# no deps, pass
+							pass
+						step_graph[source]=dest
+						
+				except KeyError:
+					pass
+					# no dependencies, pass
 
-        dependency_graph = step_graph
+		dependency_graph = step_graph
 
-        self.ordered_steps = toposort(dependency_graph, map(lambda s:s.__name__,self.sync_steps))
-        print "Order of steps=",self.ordered_steps
-        self.load_run_times()
-        
+		self.ordered_steps = toposort(dependency_graph, map(lambda s:s.__name__,self.sync_steps))
+		print "Order of steps=",self.ordered_steps
+		self.load_run_times()
+		
 
-    def check_duration(self, step, duration):
-        try:
-            if (duration > step.deadline):
-                logger.info('Sync step %s missed deadline, took %.2f seconds'%(step.name,duration))
-        except AttributeError:
-            # S doesn't have a deadline
-            pass
+	def check_duration(self, step, duration):
+		try:
+			if (duration > step.deadline):
+				logger.info('Sync step %s missed deadline, took %.2f seconds'%(step.name,duration))
+		except AttributeError:
+			# S doesn't have a deadline
+			pass
 
-    def update_run_time(self, step):
-        self.last_run_times[step.__name__]=time.time()
+	def update_run_time(self, step):
+		self.last_run_times[step.__name__]=time.time()
 
-    def check_schedule(self, step):
-        time_since_last_run = time.time() - self.last_run_times.get(step.__name__, 0)
-        try:
-            if (time_since_last_run < step.requested_interval):
-                raise StepNotReady
-        except AttributeError:
-            logger.info('Step %s does not have requested_interval set'%step.__name__)
-            raise StepNotReady
-    
-    def load_run_times(self):
-        try:
-            jrun_times = open('/tmp/observer_run_times').read()
-            self.last_run_times = json.loads(jrun_times)
-        except:
-            self.last_run_times={}
-            for e in self.ordered_steps:
-                self.last_run_times[e]=0
+	def check_schedule(self, step):
+		time_since_last_run = time.time() - self.last_run_times.get(step.__name__, 0)
+		try:
+			if (time_since_last_run < step.requested_interval):
+				raise StepNotReady
+		except AttributeError:
+			logger.info('Step %s does not have requested_interval set'%step.__name__)
+			raise StepNotReady
+	
+	def load_run_times(self):
+		try:
+			jrun_times = open('/tmp/observer_run_times').read()
+			self.last_run_times = json.loads(jrun_times)
+		except:
+			self.last_run_times={}
+			for e in self.ordered_steps:
+				self.last_run_times[e]=0
 
 
-    def save_run_times(self):
-        run_times = json.dumps(self.last_run_times)
-        open('/tmp/observer_run_times','w').write(run_times)
+	def save_run_times(self):
+		run_times = json.dumps(self.last_run_times)
+		open('/tmp/observer_run_times','w').write(run_times)
 
-    def check_class_dependency(self, step, failed_steps):
-        step.dependenices = []
-        for obj in step.provides:
-            step.dependenices.extend(self.model_dependency_graph.get(obj.__name__, []))
-        for failed_step in failed_steps:
-            if (failed_step in step.dependencies):
-                raise StepNotReady
+	def check_class_dependency(self, step, failed_steps):
+		step.dependenices = []
+		for obj in step.provides:
+			step.dependenices.extend(self.model_dependency_graph.get(obj.__name__, []))
+		for failed_step in failed_steps:
+			if (failed_step in step.dependencies):
+				raise StepNotReady
 
-    def run(self):
-        if not self.driver.enabled:
-            return
-        if (self.driver_kind=="openstack") and (not self.driver.has_openstack):
-            return
+	def run(self):
+		if not self.driver.enabled:
+			return
+		if (self.driver_kind=="openstack") and (not self.driver.has_openstack):
+			return
 
-        while True:
-            try:
-                logger.info('Waiting for event')
-                tBeforeWait = time.time()
-                self.wait_for_event(timeout=30)
-                logger.info('Observer woke up')
+		while True:
+			try:
+				logger.info('Waiting for event')
+				tBeforeWait = time.time()
+				self.wait_for_event(timeout=30)
+				logger.info('Observer woke up')
 
-                # Set of whole steps that failed
-                failed_steps = []
+				# Set of whole steps that failed
+				failed_steps = []
 
-                # Set of individual objects within steps that failed
-                failed_step_objects = set()
+				# Set of individual objects within steps that failed
+				failed_step_objects = set()
 
-                for S in self.ordered_steps:
-                    step = self.step_lookup[S]
-                    start_time=time.time()
-                    
-                    sync_step = step(driver=self.driver)
-                    sync_step.__name__ = step.__name__
-                    sync_step.dependencies = []
-                    try:
-                        mlist = sync_step.provides
-                        
-                        for m in mlist:
-                            sync_step.dependencies.extend(self.model_dependency_graph[m.__name__])
-                    except KeyError:
-                        pass
-                    sync_step.debug_mode = debug_mode
+				for S in self.ordered_steps:
+					step = self.step_lookup[S]
+					start_time=time.time()
+					
+					sync_step = step(driver=self.driver)
+					sync_step.__name__ = step.__name__
+					sync_step.dependencies = []
+					try:
+						mlist = sync_step.provides
+						
+						for m in mlist:
+							sync_step.dependencies.extend(self.model_dependency_graph[m.__name__])
+					except KeyError:
+						pass
+					sync_step.debug_mode = debug_mode
 
-                    should_run = False
-                    try:
-                        # Various checks that decide whether
-                        # this step runs or not
-                        self.check_class_dependency(sync_step, failed_steps) # dont run Slices if Sites failed
-                        self.check_schedule(sync_step) # dont run sync_network_routes if time since last run < 1 hour
-                        should_run = True
-                    except StepNotReady:
-                        logging.info('Step not ready: %s'%sync_step.__name__)
-                        failed_steps.append(sync_step)
-                    except:
-                        failed_steps.append(sync_step)
+					should_run = False
+					try:
+						# Various checks that decide whether
+						# this step runs or not
+						self.check_class_dependency(sync_step, failed_steps) # dont run Slices if Sites failed
+						self.check_schedule(sync_step) # dont run sync_network_routes if time since last run < 1 hour
+						should_run = True
+					except StepNotReady:
+						logging.info('Step not ready: %s'%sync_step.__name__)
+						failed_steps.append(sync_step)
+					except:
+						failed_steps.append(sync_step)
 
-                    if (should_run):
-                        try:
-                            duration=time.time() - start_time
+					if (should_run):
+						try:
+							duration=time.time() - start_time
 
-                            logger.info('Executing step %s' % sync_step.__name__)
+							logger.info('Executing step %s' % sync_step.__name__)
 
-                            # ********* This is the actual sync step
-                            #import pdb
-                            #pdb.set_trace()
-                            failed_objects = sync_step(failed=list(failed_step_objects))
+							# ********* This is the actual sync step
+							#import pdb
+							#pdb.set_trace()
+							failed_objects = sync_step(failed=list(failed_step_objects))
 
 
-                            self.check_duration(sync_step, duration)
-                            if failed_objects:
-                                failed_step_objects.update(failed_objects)
-                            self.update_run_time(sync_step)
-                        except:
-                            failed_steps.append(S)
-                self.save_run_times()
-            except:
-                logger.log_exc("Exception in observer run loop")
-                traceback.print_exc()
+							self.check_duration(sync_step, duration)
+							if failed_objects:
+								failed_step_objects.update(failed_objects)
+							self.update_run_time(sync_step)
+						except:
+							failed_steps.append(S)
+				self.save_run_times()
+			except:
+				logger.log_exc("Exception in observer run loop")
+				traceback.print_exc()