# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
# 
#   http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.    

import logging
import threading
import time

from tashi.rpycservices import rpycservices	     
from tashi.rpycservices.rpyctypes import Errors, InstanceState, HostState, TashiException
from tashi import boolean, ConnectionManager, vmStates, version, scrubString

class ClusterManagerService(object):
	"""RPC service for the ClusterManager"""
	
	def __init__(self, config, data, dfs):
		self.config = config
		self.data = data
		self.authAndEncrypt = boolean(config.get('Security', 'authAndEncrypt'))
		if self.authAndEncrypt:
			self.username = config.get('AccessNodeManager', 'username')
			self.password = config.get('AccessNodeManager', 'password')
		else:
			self.username = None
			self.password = None
		self.proxy = ConnectionManager(self.username, self.password, int(self.config.get('ClusterManager', 'nodeManagerPort')), authAndEncrypt=self.authAndEncrypt)
		self.dfs = dfs
		self.convertExceptions = boolean(config.get('ClusterManagerService', 'convertExceptions'))
		self.log = logging.getLogger(__name__)
		self.log.setLevel(logging.ERROR)
		self.hostLastContactTime = {}
		#self.hostLastUpdateTime = {}
		self.instanceLastContactTime = {}
		self.expireHostTime = float(self.config.get('ClusterManagerService', 'expireHostTime'))
		self.allowDecayed = float(self.config.get('ClusterManagerService', 'allowDecayed'))
		self.allowMismatchedVersions = boolean(self.config.get('ClusterManagerService', 'allowMismatchedVersions'))
		self.maxMemory = int(self.config.get('ClusterManagerService', 'maxMemory'))
		self.maxCores = int(self.config.get('ClusterManagerService', 'maxCores'))
		self.allowDuplicateNames = boolean(self.config.get('ClusterManagerService', 'allowDuplicateNames'))

		self.accountingHost = None
		self.accountingPort = None
		try:
			self.accountingHost = self.config.get('ClusterManagerService', 'accountingHost')
			self.accountingPort = self.config.getint('ClusterManagerService', 'accountingPort')
		except:
			pass

		self.__initAccounting()
		self.__initCluster()

		threading.Thread(target=self.__monitorCluster).start()

	def __initAccounting(self):
		self.accountBuffer = []
		self.accountLines = 0
		self.accountingClient = None
		try:
			if (self.accountingHost is not None) and \
				    (self.accountingPort is not None):
				self.accountingClient = ConnectionManager(self.username, self.password, self.accountingPort)[self.accountingHost]
		except:
			self.log.exception("Could not init accounting")

	def __initCluster(self):
		# initialize state of VMs if restarting
		for instance in self.data.getInstances().itervalues():
			instanceId = instance.id
			instance = self.data.acquireInstance(instanceId)
			instance.decayed = False

			if instance.hostId is None:
				self.__stateTransition(instance, None, InstanceState.Pending)
			else:
				self.__stateTransition(instance, None, InstanceState.Orphaned)

			self.data.releaseInstance(instance)

		# initialize state of hosts if restarting
		for host in self.data.getHosts().itervalues():
			hostId = host.id
			host = self.data.acquireHost(hostId)
			host.up = False
			host.decayed = False
			self.data.releaseHost(host)


	def __ACCOUNTFLUSH(self):
		try:
			if (self.accountingClient is not None):
				self.accountingClient.record(self.accountBuffer)
			self.accountLines = 0
			self.accountBuffer = []
		except:
			self.log.exception("Failed to flush accounting data")


	def __ACCOUNT(self, text, instance=None, host=None):
		now = self.__now()
		instanceText = None
		hostText = None

		if instance is not None:
			try:
				instanceText = 'Instance(%s)' % (instance)
			except:
				self.log.exception("Invalid instance data")

		if host is not None:
			try:
				hostText = "Host(%s)" % (host)
			except:
				self.log.exception("Invalid host data")

		secondary = ','.join(filter(None, (hostText, instanceText)))

		line = "%s|%s|%s" % (now, text, secondary)

		self.accountBuffer.append(line)
		self.accountLines += 1

		# XXXstroucki think about autoflush by time
		if (self.accountLines > 0):
			self.__ACCOUNTFLUSH()


	def __stateTransition(self, instance, old, cur):
		if (old and instance.state != old):
			raise TashiException(d={'errno':Errors.IncorrectVmState,'msg':"VmState is not %s - it is %s" % (vmStates[old], vmStates[instance.state])})
		if (instance.state == cur):
			# don't do anything if we're already at current state
			return

		instance.state = cur
		# pass something down to the NM?

	def __now(self):
		return time.time()

	def __downHost(self, host):
		self.log.warning('Host %s is down' % (host.name))
		host.up = False
		host.decayed = False

		self.__orphanInstances(host)

	def __upHost(self, host):
		self.log.warning('Host %s is up' % (host.name))
		host.up = True
		host.decayed = True

	def __orphanInstances(self, host):
		# expects lock to be held on host
		instances = [instance.id for instance in self.data.getInstances().itervalues() if instance.hostId == host.id]

		for instanceId in instances:
			instance = self.data.acquireInstance(instanceId)
			if instance.hostId == host.id:
				instance.decayed = True
				self.__stateTransition(instance, None, InstanceState.Orphaned)

			self.data.releaseInstance(instance)

	def __checkHosts(self):
		# Check if hosts have been heard from recently
		# Otherwise, see if it is alive

		for hostId in self.hostLastContactTime.keys():
			if (self.hostLastContactTime[hostId] < (self.__now() - self.expireHostTime)):
				host = self.data.acquireHost(hostId)
				string = None
				try:
					string = self.proxy[host.name].liveCheck()
				except:
					pass

				if string != "alive":
					self.__downHost(host)
					del self.hostLastContactTime[hostId]
				else:
					self.__upHost(host)
					self.hostLastContactTime[hostId] = self.__now()

				self.data.releaseHost(host)

	def __checkInstances(self):
		# Reconcile instances with nodes

		# obtain a list of instances I know about
		myInstancesError = False
		try:
			myInstances = self.data.getInstances()
		except:
			myInstancesError = True
			self.log.warning('Failure communicating with my database')

		if myInstancesError == True:
			return

		# iterate through all hosts I believe are up
		for hostId in self.hostLastContactTime.keys():
			#self.log.warning("iterate %d" % hostId)
			host = self.data.acquireHost(hostId)
			# XXXstroucki: timing has changed with the message
			# buffering in the NM, so this wasn't being run any-
			# more because the time check was passing.
			# I should think a bit more about this, but
			# the "if True" is probably appropriate.
			#if (self.hostLastContactTime[hostId] < (self.__now() - self.allowDecayed)):
			if True:
				host.decayed = True

				self.log.debug('Fetching state from host %s because it is decayed' % (host.name))
				
				myInstancesThisHost = [i for i in myInstances.values() if i.hostId == host.id]

				# get a list of VMs running on host
				try:
					hostProxy = self.proxy[host.name]
					remoteInstances = [hostProxy.getVmInfo(vmId) for vmId in hostProxy.listVms()]
				except:
					self.log.warning('Failure getting instances from host %s' % (host.name))
					self.data.releaseHost(host)
					continue

				# register instances I don't know about
				for instance in remoteInstances:
					if (instance.id not in myInstances):
						instance.hostId = host.id
						instance = self.data.registerInstance(instance)
						self.data.releaseInstance(instance)
				remoteInstanceIds = [i.id for i in remoteInstances]
				# remove instances that shouldn't be running
				for instance in myInstancesThisHost:
					if (instance.id not in remoteInstanceIds):
						# XXXstroucki before 20110902 excepted here with host lock
						try:
							instance = self.data.acquireInstance(instance.id)
						except:
							continue

						# XXXstroucki destroy?
						try:
							del self.instanceLastContactTime[instance.id]
						except:
							pass
						self.data.removeInstance(instance)

				self.hostLastContactTime[hostId] = self.__now()
				host.decayed = False

			self.data.releaseHost(host)
			#self.log.warning("iterate %d done" % hostId)
		
		# iterate through all VMs I believe are active
		for instanceId in self.instanceLastContactTime.keys():

			# XXXstroucki should lock instance here?
			try:
				lastContactTime = self.instanceLastContactTime[instanceId]
			except KeyError:
				continue

			if (lastContactTime < (self.__now() - self.allowDecayed)):
				try:
					instance = self.data.acquireInstance(instanceId)
					# Don't query non-running VMs. eg. if a VM
					# is suspended, and has no host, then there's
					# no one to ask
					if instance.state != InstanceState.Running and \
					   instance.state != InstanceState.Activating and \
					   instance.state != InstanceState.Orphaned:
						self.data.releaseInstance(instance)
						continue
				except:
					continue

				instance.decayed = True
				self.log.debug('Fetching state on instance %s because it is decayed' % (instance.name))
				if instance.hostId is None: raise AssertionError

				# XXXstroucki check if host is down?
				host = self.data.getHost(instance.hostId)

				# get updated state on VM
				try:
					hostProxy = self.proxy[host.name]
					newInstance = hostProxy.getVmInfo(instance.vmId)
				except:
					self.log.warning('Failure getting data for instance %s from host %s' % (instance.name, host.name))
					self.data.releaseInstance(instance)
					continue

				# replace existing state with new state
				# XXXstroucki more?
				instance.state = newInstance.state
				self.instanceLastContactTime[instanceId] = self.__now()
				instance.decayed = False
				self.data.releaseInstance(instance)


	def normalize(self, instance):
		instance.id = None
		instance.vmId = None
		instance.hostId = None
		instance.decayed = False
		instance.name = scrubString(instance.name, allowed="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-.")
		instance.state = InstanceState.Pending
		# XXXstroucki At some point, check userId
		if (not self.allowDuplicateNames):
			for i in self.data.getInstances().itervalues():
				if (i.name == instance.name):
					raise TashiException(d={'errno':Errors.InvalidInstance,'msg':"The name %s is already in use" % (instance.name)})
		if (instance.cores < 1):
			raise TashiException(d={'errno':Errors.InvalidInstance,'msg':"Number of cores must be >= 1"})
		if (instance.cores > self.maxCores):
			raise TashiException(d={'errno':Errors.InvalidInstance,'msg':"Number of cores must be <= %d" % (self.maxCores)})
		if (instance.memory < 1):
			raise TashiException(d={'errno':Errors.InvalidInstance,'msg':"Amount of memory must be >= 1"})
		if (instance.memory > self.maxMemory):
			raise TashiException(d={'errno':Errors.InvalidInstance,'msg':"Amount of memory must be <= %d" % (self.maxMemory)})
		# Make sure disk spec is valid
		# Make sure network spec is valid
		# Ignore internal hints
		for hint in instance.hints:
			if (hint.startswith("__")):
				del instance.hints[hint]
		return instance
	
	def createVm(self, instance):
		"""Function to add a VM to the list of pending VMs"""
		# XXXstroucki: check for exception here
		instance = self.normalize(instance)
		instance = self.data.registerInstance(instance)
		self.data.releaseInstance(instance)
		self.__ACCOUNT("CM VM REQUEST", instance=instance)
		return instance
	
	def shutdownVm(self, instanceId):
		instance = self.data.acquireInstance(instanceId)
		self.__stateTransition(instance, None, InstanceState.ShuttingDown)
		self.data.releaseInstance(instance)
		self.__ACCOUNT("CM VM SHUTDOWN", instance=instance)
		hostname = self.data.getHost(instance.hostId).name
		try:
			self.proxy[hostname].shutdownVm(instance.vmId)
		except Exception:
			self.log.exception('shutdownVm failed for host %s vmId %d' % (instance.name, instance.vmId))
			raise
		return
	
	def destroyVm(self, instanceId):
		instance = self.data.acquireInstance(instanceId)
		if (instance.state is InstanceState.Pending or instance.state is InstanceState.Held):
			self.__ACCOUNT("CM VM DESTROY UNSTARTED", instance=instance)
			self.data.removeInstance(instance)
		elif (instance.state is InstanceState.Activating):
			self.__ACCOUNT("CM VM DESTROY STARTING", instance=instance)
			self.__stateTransition(instance, None, InstanceState.Destroying)
			self.data.releaseInstance(instance)
		else:
			# XXXstroucki: This is a problem with keeping
			# clean state.
			self.__ACCOUNT("CM VM DESTROY", instance=instance)
			self.__stateTransition(instance, None, InstanceState.Destroying)
			if instance.hostId is None:
				self.data.removeInstance(instance)
			else:
				hostname = self.data.getHost(instance.hostId).name
				try:
					if hostname is not None:
						self.proxy[hostname].destroyVm(instance.vmId)
						self.data.releaseInstance(instance)
				except:
					self.log.warning('destroyVm failed on host %s vmId %s' % (hostname, str(instance.vmId)))
					self.data.removeInstance(instance)


		return
	
	def suspendVm(self, instanceId):
		instance = self.data.acquireInstance(instanceId)
		try:
			self.__stateTransition(instance, InstanceState.Running, InstanceState.Suspending)
		except TashiException:
			self.data.releaseInstance(instance)
			raise

		self.data.releaseInstance(instance)
		self.__ACCOUNT("CM VM SUSPEND", instance=instance)
		hostname = self.data.getHost(instance.hostId).name
		destination = "suspend/%d_%s" % (instance.id, instance.name)
		try:
			self.proxy[hostname].suspendVm(instance.vmId, destination)
		except:
			self.log.exception('suspendVm failed for host %s vmId %d' % (hostname, instance.vmId))
			raise TashiException(d={'errno':Errors.UnableToSuspend, 'msg':'Failed to suspend %s' % (instance.name)})
		return
	
	def resumeVm(self, instanceId):
		instance = self.data.acquireInstance(instanceId)
		try:
			self.__stateTransition(instance, InstanceState.Suspended, InstanceState.Pending)
		except TashiException:
			self.data.releaseInstance(instance)
			raise

		source = "suspend/%d_%s" % (instance.id, instance.name)
		instance.hints['__resume_source'] = source
		self.data.releaseInstance(instance)
		self.__ACCOUNT("CM VM RESUME", instance=instance)
		return instance
	
	def migrateVm(self, instanceId, targetHostId):
		instance = self.data.acquireInstance(instanceId)
		self.__ACCOUNT("CM VM MIGRATE", instance=instance)
		try:
			# FIXME: should these be acquire/release host?
			targetHost = self.data.getHost(targetHostId)
			sourceHost = self.data.getHost(instance.hostId)
			# FIXME: Are these the correct state transitions?
		except:
			self.data.releaseInstance(instance)
			raise

		try:
			self.__stateTransition(instance, InstanceState.Running, InstanceState.MigratePrep)
		except TashiException:
			self.data.releaseInstance(instance)
			raise

		self.data.releaseInstance(instance)
		try:
			# Prepare the target
			self.log.info("migrateVm: Calling prepSourceVm on source host %s" % sourceHost.name)
			self.proxy[sourceHost.name].prepSourceVm(instance.vmId)
			self.log.info("migrateVm: Calling prepReceiveVm on target host %s" % targetHost.name)
			cookie = self.proxy[targetHost.name].prepReceiveVm(instance, sourceHost)
		except Exception:
			self.log.exception('prepReceiveVm failed')
			raise
		instance = self.data.acquireInstance(instance.id)
		try:
			self.__stateTransition(instance, InstanceState.MigratePrep, InstanceState.MigrateTrans)
		except TashiException:
			self.data.releaseInstance(instance)
			raise

		self.data.releaseInstance(instance)
		try:
			# Send the VM
			self.proxy[sourceHost.name].migrateVm(instance.vmId, targetHost, cookie)
		except Exception:
			self.log.exception('migrateVm failed')
			raise
		try:
			instance = self.data.acquireInstance(instance.id)
			instance.hostId = targetHost.id
		finally:
			self.data.releaseInstance(instance)

		try:
			# Notify the target
			vmId = self.proxy[targetHost.name].receiveVm(instance, cookie)
		except Exception:
			self.log.exception('receiveVm failed')
			raise
		return
	
	def pauseVm(self, instanceId):
		instance = self.data.acquireInstance(instanceId)
		try:
			self.__stateTransition(instance, InstanceState.Running, InstanceState.Pausing)
		except TashiException:
			self.data.releaseInstance(instance)
			raise

		self.data.releaseInstance(instance)
		self.__ACCOUNT("CM VM PAUSE", instance=instance)
		hostname = self.data.getHost(instance.hostId).name
		try:
			self.proxy[hostname].pauseVm(instance.vmId)
		except Exception:
			self.log.exception('pauseVm failed on host %s with vmId %d' % (hostname, instance.vmId))
			raise
		instance = self.data.acquireInstance(instanceId)
		try:
			self.__stateTransition(instance, InstanceState.Pausing, InstanceState.Paused)
		except TashiException:
			self.data.releaseInstance(instance)
			raise

		self.data.releaseInstance(instance)
		return

	def unpauseVm(self, instanceId):
		instance = self.data.acquireInstance(instanceId)
		try:
			self.__stateTransition(instance, InstanceState.Paused, InstanceState.Unpausing)
		except TashiException:
			self.data.releaseInstance(instance)
			raise

		self.data.releaseInstance(instance)
		self.__ACCOUNT("CM VM UNPAUSE", instance=instance)
		hostname = self.data.getHost(instance.hostId).name
		try:
			self.proxy[hostname].unpauseVm(instance.vmId)
		except Exception:
			self.log.exception('unpauseVm failed on host %s with vmId %d' % (hostname, instance.vmId))
			raise
		instance = self.data.acquireInstance(instanceId)
		try:
			self.__stateTransition(instance, InstanceState.Unpausing, InstanceState.Running)
		except TashiException:
			self.data.releaseInstance(instance)
			raise

		self.data.releaseInstance(instance)
		return
	
	def getHosts(self):
		return self.data.getHosts().values()
	
	def getNetworks(self):
		return self.data.getNetworks().values()
	
	def getUsers(self):
		return self.data.getUsers().values()
	
	def getInstances(self):
		return self.data.getInstances().values()

	def getImages(self):
		return self.data.getImages()
	
	def copyImage(self, src, dst):
		imageSrc = self.dfs.getLocalHandle("images/" + src)
		imageDst = self.dfs.getLocalHandle("images/" + dst)
		try:
			#  Attempt to restrict to the image directory
			if ".." not in imageSrc and ".." not in imageDst:
				self.dfs.copy(imageSrc, imageDst)
				self.log.info('DFS image copy: %s->%s' % (imageSrc, imageDst))
			else:
				self.log.warning('DFS image copy bad path: %s->%s' % (imageSrc, imageDst))
		except Exception, e:
			self.log.exception('DFS image copy failed: %s (%s->%s)' % (e, imageSrc, imageDst))

	def vmmSpecificCall(self, instanceId, arg):
		instance = self.data.getInstance(instanceId)
		hostname = self.data.getHost(instance.hostId).name
		self.__ACCOUNT("CM VM SPECIFIC CALL", instance=instance)
		try:
			res = self.proxy[hostname].vmmSpecificCall(instance.vmId, arg)
		except Exception:
			self.log.exception('vmmSpecificCall failed on host %s with vmId %d' % (hostname, instance.vmId))
			raise
		return res
	
#	@timed
	def registerNodeManager(self, host, instances):
		"""Called by the NM every so often as a keep-alive/state polling -- state changes here are NOT AUTHORITATIVE"""

		# Handle a new registration
		if (host.id == None):
			hostList = [h for h in self.data.getHosts().itervalues() if h.name == host.name]
			if (len(hostList) != 1):
				raise TashiException(d={'errno':Errors.NoSuchHost, 'msg':'A host with name %s is not identifiable' % (host.name)})
			host.id = hostList[0].id

		# Check if remote host information matches mine
		oldHost = self.data.acquireHost(host.id)
		if (oldHost.name != host.name):
			self.data.releaseHost(oldHost)
			raise TashiException(d={'errno':Errors.NoSuchHostId, 'msg':'Host id and hostname mismatch'})

		if oldHost.up == False:
			self.__upHost(oldHost)
		self.hostLastContactTime[host.id] = self.__now()
		oldHost.version = host.version
		oldHost.memory = host.memory
		oldHost.cores = host.cores

		# compare whether CM / NM versions are compatible
		if (host.version != version and not self.allowMismatchedVersions):
			oldHost.state = HostState.VersionMismatch
		if (host.version == version and oldHost.state == HostState.VersionMismatch):
			oldHost.state = HostState.Normal

		# let the host communicate what it is running
		# and note that the information is not stale
		for instance in instances:
			self.instanceLastContactTime.setdefault(instance.id, 0)

		self.data.releaseHost(oldHost)
		return host.id
	
	def vmUpdate(self, instanceId, instance, oldState):
		try:
			oldInstance = self.data.acquireInstance(instanceId)
		except TashiException, e:
			# shouldn't have a lock to clean up after here
			if (e.errno == Errors.NoSuchInstanceId):
				self.log.warning('Got vmUpdate for unknown instanceId %d' % (instanceId))
				return
		except:
			self.log.exception("Could not acquire instance")
			raise

		self.instanceLastContactTime[instanceId] = self.__now()
		oldInstance.decayed = False
		self.__ACCOUNT("CM VM UPDATE", instance=oldInstance)

		if (instance.state == InstanceState.Exited):
			# determine why a VM has exited
			hostname = self.data.getHost(oldInstance.hostId).name
			if (oldInstance.state not in [InstanceState.ShuttingDown, InstanceState.Destroying, InstanceState.Suspending]):
				self.log.warning('Unexpected exit on %s of instance %s (vmId %d)' % (hostname, oldInstance.name, oldInstance.vmId))
			if (oldInstance.state == InstanceState.Suspending):
				self.__stateTransition(oldInstance, InstanceState.Suspending, InstanceState.Suspended)
				oldInstance.hostId = None
				oldInstance.vmId = None
				self.data.releaseInstance(oldInstance)
			else:
				del self.instanceLastContactTime[oldInstance.id]
				self.data.removeInstance(oldInstance)
		else:
			if (instance.state):
				# XXXstroucki does this matter?
				if (oldState and oldInstance.state != oldState):
					self.log.warning('Got vmUpdate of state from %s to %s, but the instance was previously %s' % (vmStates[oldState], vmStates[instance.state], vmStates[oldInstance.state]))
				oldInstance.state = instance.state
			if (instance.vmId):
				oldInstance.vmId = instance.vmId
			if (instance.hostId):
				oldInstance.hostId = instance.hostId
			if (instance.nics):
				for nic in instance.nics:
					if (nic.ip):
						for oldNic in oldInstance.nics:
							if (oldNic.mac == nic.mac):
								oldNic.ip = nic.ip

			self.data.releaseInstance(oldInstance)

		return "success"
	
	def activateVm(self, instanceId, host):
		dataHost = self.data.acquireHost(host.id)

		if (dataHost.name != host.name):
			self.data.releaseHost(dataHost)
			raise TashiException(d={'errno':Errors.HostNameMismatch,'msg':"Mismatched target host"})
		if (not dataHost.up):
			self.data.releaseHost(dataHost)
			raise TashiException(d={'errno':Errors.HostNotUp,'msg':"Target host is not up"})
		if (dataHost.state != HostState.Normal):
			self.data.releaseHost(dataHost)
			raise TashiException(d={'errno':Errors.HostStateError,'msg':"Target host state is not normal"})

		self.data.releaseHost(dataHost)
		instance = self.data.acquireInstance(instanceId)
		self.__ACCOUNT("CM VM ACTIVATE", instance=instance)

		if ('__resume_source' in instance.hints):
			self.__stateTransition(instance, None, InstanceState.Resuming)
		else:
			# XXXstroucki should held VMs be continually tried? Or be explicitly set back to pending?
			#self.__stateTransition(instance, InstanceState.Pending, InstanceState.Activating)
			self.__stateTransition(instance, None, InstanceState.Activating)

		instance.hostId = host.id
		self.data.releaseInstance(instance)

		try:
			if ('__resume_source' in instance.hints):
				vmId = self.proxy[host.name].resumeVm(instance, instance.hints['__resume_source'])
			else:
				vmId = self.proxy[host.name].instantiateVm(instance)
		except Exception:
			instance = self.data.acquireInstance(instanceId)
			if (instance.state is InstanceState.Destroying): # Special case for if destroyVm is called during initialization and initialization fails
				self.data.removeInstance(instance)
			else:
				# XXXstroucki what can we do about pending hosts in the scheduler?
				# put them at the end of the queue and keep trying?
				self.__stateTransition(instance, None, InstanceState.Held)
				instance.hostId = None
				self.data.releaseInstance(instance)
			return "failure"

		instance = self.data.acquireInstance(instanceId)
		instance.vmId = vmId

		if (instance.state is InstanceState.Destroying): # Special case for if destroyVm is called during initialization
			try:
				self.proxy[host.name].destroyVm(vmId)
				self.data.removeInstance(instance)
			except Exception:
				self.log.exception('destroyVm failed for host %s vmId %d' % (host.name, instance.vmId))
				self.data.releaseInstance(instance)
				return "failure"
		else:
			if ('__resume_source' not in instance.hints):
				# XXXstroucki should we just wait for NM to update?
				#self.__stateTransition(instance, InstanceState.Activating, InstanceState.Running)
				pass

		self.data.releaseInstance(instance)
		return "success"

	def registerHost(self, hostname, memory, cores, version):
		hostId, alreadyRegistered = self.data.registerHost(hostname, memory, cores, version)
		if alreadyRegistered:
			self.log.info("Host %s is already registered, it was updated now" % hostname)
		else:
			self.log.info("A host was registered - hostname: %s, version: %s, memory: %s, cores: %s" % (hostname, version, memory, cores))

		try:
			host = self.data.getHost(hostId)
			self.__ACCOUNT("CM HOST REGISTER", host=host)
		except:
			self.log.warning("Failed to lookup host %s" % hostId)

		return hostId

	def unregisterHost(self, hostId):
		try:
			host = self.data.getHost(hostId)
			self.__ACCOUNT("CM HOST UNREGISTER", host=host)
		except:
			self.log.warning("Failed to lookup host %s" % hostId)
			return

		self.data.unregisterHost(hostId)
		self.log.info("Host %s was unregistered" % hostId)
		return

	# service thread
	def __monitorCluster(self):
		while True:
			sleepFor = min(self.expireHostTime, self.allowDecayed)

			try:
				self.__checkHosts()
				self.__checkInstances()
			except:
				self.log.exception('monitorCluster iteration failed')
			#  XXXrgass too chatty.  Remove
			# XXXstroucki the risk is that a deadlock in obtaining
			# data could prevent this loop from continuing.
			#self.log.info("Sleeping for %d seconds" % sleepFor)
			time.sleep(sleepFor)