imcsdk/imceventhandler.py
# Copyright 2013 Cisco Systems, Inc.
#
# Licensed 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.
"""
This module is responsible for event handling of the events exposed by
IMC server.
"""
import datetime
import logging
import time
from threading import Condition, Lock, Thread
from six.moves import queue
from . import imcmo
from . import imccoreutils
from . import imcxmlcodec as xc
from .imcexception import ImcWarning
from .imcexception import ImcValidationException
log = logging.getLogger('imc')
class MoChangeEvent(object):
"""
This class provides structure to save an event generated for any change,
its associated managed object and property change list.
This functionality is used during add_event_handler.
"""
def __init__(self, event_id=None, mo=None, change_list=None):
self.event_id = event_id
self.mo = mo
self.change_list = change_list
class WatchBlock(object):
"""
This class handles the functionality about the Event Handling/Watch block.
enqueue/dequeue fuctionality of events is handled by this class.
This functionality is used during add_event_handler.
"""
def __init__(self, params, fmce, capacity, callback):
self.fmce = fmce
self.callback = callback
self.capacity = capacity
self.params = params
self.overflow = False
self.error_code = 0 # TODO:error_code to call notify as per PowerTool
self.event_q = queue.Queue() # infinite size Queue
def dequeue(self, miliseconds_timeout):
"""Internal method to dequeue the events."""
while True:
if self.error_code != 0:
log.debug("queue error:" + str(self.error_code))
return None
if not self.event_q.empty():
mo_chg_event = self.event_q.get()
return mo_chg_event
else:
return None
def enqueue(self, cmce):
"""Internal method to enqueue the events."""
if self.event_q.maxsize < self.capacity:
self.event_q.put(cmce)
else:
self.overflow = True
def dequeue_default_callback(self, mce):
"""Default callback method."""
tab_size = 8
print("\n")
print(('EventId'.ljust(tab_size * 2) + ':' + str(mce.event_id)))
print(('ChangeList'.ljust(tab_size * 2) + ':' + str(mce.change_list)))
print(('ClassId'.ljust(tab_size * 2) + ':' + str(mce.mo.get_class_id())))
print(('MoDn'.ljust(tab_size * 2) + ':' + str(mce.mo.dn)))
class ImcEventHandle(object):
"""This class provides api to add and remove event handler."""
def __init__(self, handle):
self.__handle = handle
self.__lock_object = None
self.__wbs = []
self.__wbs_lock = Lock()
self.__enqueue_thread = None
self.__condition = Condition()
self.__event_chan_resp = None
self.__dequeue_thread = None
self.__lowest_timeout = None
self.__wb_to_remove = []
def __get_mo_elem(self, xml_str):
"""
Internal method to extract mo elements from xml string
"""
root = xc.extract_root_elem(xml_str)
mo_elems = []
if root.tag == "methodVessel":
for in_stimuli in root:
for cmce in in_stimuli:
for in_config in cmce:
for mo_elem in in_config:
mo_elems.append(
(mo_elem, cmce.attrib.get('inEid')))
elif root.tag == "configMoChangeEvent":
for in_config in root:
for mo_elem in in_config:
mo_elems.append(mo_elem)
return mo_elems
def __enqueue_function(self):
"""
Internal method used by add_event_handler.
Provides functionality of enqueue/dequeue of the events and
triggering callbacks.
"""
try:
xml_query = '<eventSubscribe cookie="%s"/>' % self.__handle.cookie
self.__event_chan_resp = self.__handle.post_xml(
xml_str=xml_query.encode(), read=False)
except Exception:
raise
try:
while self.__event_chan_resp and len(self.__wbs):
if self.__handle.cookie is None or \
self.__event_chan_resp is None:
break
resp = self.__event_chan_resp.readline()
resp = self.__event_chan_resp.read(int(resp))
for mo_elem in self.__get_mo_elem(resp):
gmo = imcmo.generic_mo_from_xml_elem(mo_elem[0])
mce = MoChangeEvent(event_id=mo_elem[1],
mo=gmo.to_mo(),
change_list=list(gmo.properties.keys()))
for watch_block in self.__wbs:
if watch_block.fmce(mce):
watch_block.enqueue(mce)
with self.__condition:
self.__condition.notify()
if len(self.__wbs) == 0:
self.__condition.acquire()
self.__condition.notify()
self.__condition.release()
except:
raise
def __thread_enqueue_start(self):
"""
Internal method to start the enqueue thread which adds the events in
an internal queue.
"""
self.__enqueue_thread = Thread(name="enqueue_thread",
target=self.__enqueue_function)
self.__enqueue_thread.daemon = True
self.__enqueue_thread.start()
def __time_left(self, watch_block):
timeout_sec = watch_block.params["timeout_sec"]
start_time = watch_block.params["start_time"]
time_diff = datetime.datetime.now() - start_time
if time_diff.seconds < timeout_sec:
return timeout_sec - time_diff.seconds
else:
return 0
# return 2147483647
def __dequeue_mce(self, time_left, watch_block):
if time_left and time_left > 0:
if self.__lowest_timeout is None or \
self.__lowest_timeout > time_left:
self.__lowest_timeout = time_left
mce = watch_block.dequeue(time_left)
else:
mce = watch_block.dequeue(2147483647)
return mce
def __prop_val_exist(self, mo, prop, success_value,
failure_value, transient_value,
change_list=None):
if isinstance(mo, imcmo.GenericMo):
n_prop = prop
n_prop_val = mo.properties[n_prop]
elif prop not in mo.prop_meta:
n_prop = prop
n_prop_val = getattr(mo, n_prop)
else:
n_prop = mo.prop_meta[prop].xml_attribute
n_prop_val = getattr(mo, n_prop)
if change_list and n_prop not in change_list:
return False
if (len(success_value) > 0 and n_prop_val in success_value) or \
(len(failure_value) > 0 and n_prop_val in failure_value) or \
(len(transient_value) > 0 and n_prop_val in transient_value):
return True
return False
def __dequeue_mo_prop_poll(self, mo, prop, poll_sec, watch_block,
timeout_sec=None, time_left=None):
success_value = watch_block.params["success_value"]
failure_value = watch_block.params["failure_value"]
transient_value = watch_block.params["transient_value"]
if not success_value or len(success_value) < 1:
raise ValueError("success_value is missing.")
pmo = self.__handle.query_dn(mo.dn)
if pmo is None:
ImcWarning('Mo ' + pmo.dn + ' not found.')
return
if timeout_sec and time_left and time_left > 0:
if time_left < poll_sec:
poll_sec = timeout_sec - time_left
if self.__lowest_timeout is None or self.__lowest_timeout > poll_sec:
self.__lowest_timeout = poll_sec
if self.__prop_val_exist(pmo, prop, success_value,
failure_value, transient_value):
log.info("Successful")
self.__wb_to_remove.append(watch_block)
def __dequeue_mo_prop_event(self, prop, watch_block, time_left=None):
success_value = watch_block.params["success_value"]
failure_value = watch_block.params["failure_value"]
transient_value = watch_block.params["transient_value"]
if not success_value or len(success_value) < 1:
raise ValueError("success_value is missing.")
# dequeue mce
mce = self.__dequeue_mce(time_left, watch_block)
if mce is None:
return
# checks if prop value exist in success or failure or transient values
attributes = mce.change_list
if self.__prop_val_exist(mce.mo, prop, success_value, failure_value,
transient_value, attributes):
if watch_block.callback:
ctxt = watch_block.params['context']
ctxt["done"] = True
watch_block.callback(mce)
self.__wb_to_remove.append(watch_block)
def __dequeue_mo_until_removed(self, watch_block, time_left=None):
# dequeue mce
mce = self.__dequeue_mce(time_left, watch_block)
if mce is None:
return
if watch_block.callback:
watch_block.callback(mce)
# watch mo until gets deleted
if mce.mo.status == "deleted":
self.__wb_to_remove.append(watch_block)
def __dequeue_all_class_id(self, watch_block, time_left=None):
# dequeue mce
mce = self.__dequeue_mce(time_left, watch_block)
if mce and watch_block.callback:
watch_block.callback(mce)
def __dequeue_function(self):
"""
Internal method to dequeue to events.
"""
while len(self.__wbs):
self.__lowest_timeout = None
self.__wb_to_remove = []
try:
for watch_block in self.__wbs:
mo = watch_block.params["managed_object"]
prop = watch_block.params["prop"]
poll_sec = watch_block.params["poll_sec"]
timeout_sec = watch_block.params["timeout_sec"]
# checks if watch_block is not timed out, else remove
time_left = None
if timeout_sec:
time_left = self.__time_left(watch_block)
if time_left <= 0:
self.__wb_to_remove.append(watch_block)
continue
# poll for mo. Not to monitor event.
if poll_sec and mo:
self.__dequeue_mo_prop_poll(mo, prop, poll_sec,
watch_block, timeout_sec,
time_left)
elif mo:
# watch mo until prop_val changed to desired value
if prop:
self.__dequeue_mo_prop_event(prop, watch_block,
time_left)
# watch mo until it is removed
else:
self.__dequeue_mo_until_removed(watch_block,
time_left)
elif mo is None:
# watch all event or specific to class_id
self.__dequeue_all_class_id(watch_block, time_left)
except Exception as e:
log.info(str(e))
self.__wb_to_remove.append(watch_block)
# removing watch_block
if len(self.__wb_to_remove):
self.__wbs_lock.acquire()
for wb in self.__wb_to_remove:
if "context" in wb.params:
ctxt = wb.params['context']
ctxt["done"] = True
self.watch_block_remove(wb)
self.__wb_to_remove = []
self.__wbs_lock.release()
# wait for more events only if watch_block exists
if len(self.__wbs):
with self.__condition:
self.__condition.wait(self.__lowest_timeout)
return
def __thread_dequeue_start(self):
"""
Internal method to start dequeue thread.
"""
self.__dequeue_thread = Thread(name="dequeue_thread",
target=self.__dequeue_function)
self.__dequeue_thread.daemon = True
self.__dequeue_thread.start()
def watch_block_add(self, params,
filter_callback,
capacity=500,
callback=None):
"""
Internal method to add a watch block for starting event monitoring.
"""
if self.__handle.cookie is None:
return None
self.__wbs_lock.acquire()
watch_block = WatchBlock(params,
filter_callback,
capacity,
callback) # Add a List of Watchers
if watch_block and watch_block.callback is None:
watch_block.callback = watch_block.dequeue_default_callback
self.__wbs.append(watch_block)
self.__wbs_lock.release()
return watch_block
def watch_block_remove(self, watch_block):
"""
Internal method to remove a watch block for
stopping event monitoring.
"""
if watch_block in self.__wbs:
self.__wbs.remove(watch_block)
def _add_class_id_watch(self, class_id):
if imccoreutils.find_class_id_in_mo_meta_ignore_case(class_id) is None:
raise ImcValidationException(
"Invalid ClassId %s specified." % class_id)
def watch__type_filter(mce):
"""
Callback method to work on events with a specific class_id.
"""
if mce.mo.get_class_id().lower() == class_id.lower():
return True
return False
return watch__type_filter
def _add_mo_watch(self, managed_object, prop=None, success_value=[],
poll_sec=None, platform=None):
if imccoreutils.find_class_id_in_mo_meta_ignore_case(
managed_object.get_class_id()) is None:
raise ImcValidationException(
"Unknown ClassId %s provided." %
managed_object.get_class_id())
if prop:
mo_property_meta = imccoreutils.get_mo_property_meta(
managed_object.get_class_id(), prop, platform)
if mo_property_meta is None:
raise ImcValidationException(
"Unknown Property %s provided." % prop)
if not success_value:
raise ImcValidationException(
"success_value parameter is not provided.")
if poll_sec is None:
def watch_mo_filter(mce):
"""
Callback method to work on events specific to respective
managed object.
"""
if mce.mo.dn == managed_object.dn:
return True
return False
return watch_mo_filter
else:
def watch_none_filter(mce):
"""
Callback method to ignore all events.
"""
return False
return watch_none_filter
def add(self,
class_id=None,
managed_object=None,
prop=None,
success_value=[],
failure_value=[],
transient_value=[],
poll_sec=None,
timeout_sec=None,
call_back=None,
context=None,
platform=None):
"""
Adds an event handler.
An event handler can be added using this method where an user can
subscribe for the event channel from IMC and can monitor those events
for any specific success value or failure value for a managed object.
Args:
class_id (str): managed object class id
managed_object (ManagedObject)
prop (str) - property of the managed object to monitor
success_value (list) - success values of a prop
failure_value (list) - failure values of a prop
transient_value (list) - transient values of a prop
poll_sec - specifies the time in seconds for polling event.
timeout_sec - time after which method should stop monitoring.
call_back - call back method
"""
if class_id and managed_object:
raise ImcValidationException(
"Specify either class_id or managedObject, not both")
if class_id:
filter_callback = self._add_class_id_watch(class_id)
elif managed_object:
filter_callback = self._add_mo_watch(managed_object, prop,
success_value, poll_sec,
platform)
else:
def watch_all_filter(mce):
"""
Callback method to work on all events.
"""
return True
filter_callback = watch_all_filter
param_dict = {'class_id': class_id,
'managed_object': managed_object,
'prop': prop,
'success_value': success_value,
'failure_value': failure_value,
'transient_value': transient_value,
'poll_sec': poll_sec,
'timeout_sec': timeout_sec,
'call_back': call_back,
'start_time': datetime.datetime.now(),
'context': context}
if filter_callback is None:
raise ImcValidationException("Error adding WatchBlock...")
watch_block = self.watch_block_add(params=param_dict,
filter_callback=filter_callback,
callback=call_back)
if watch_block and len(self.__wbs) == 1:
if poll_sec is None:
self.__thread_enqueue_start()
self.__thread_dequeue_start()
return watch_block
def remove(self, watch_block):
"""
Removes an event handler.
"""
self.__wbs_lock.acquire()
if watch_block in self.__wbs:
self.watch_block_remove(watch_block)
else:
ImcWarning("Event handler not found")
self.__wbs_lock.release()
def clean(self):
"""
Removes all the watch blocks from the event handler
"""
self.__wbs_lock.acquire()
for each in self.__wbs:
self.watch_block_remove(each)
self.__wbs_lock.release()
def get(self):
"""
Returns the list of event handlers.
"""
return self.__wbs
def wait(handle, mo, prop, value, cb, timeout_sec=None):
"""
Waits for `mo.prop == value`
Args:
handle(ImcHandle): connection handle to the server
mo (Managed Object): managed object to watch
prop (str): property to watch
value (str): property value to wait for
cb(function): callback on success
timeout_sec (int): timeout
Returns:
None
Example:
This method is called from ImcHandle class,
wait_for_event method
"""
# create a new event handler
ueh = ImcEventHandle(handle)
context = {}
context["done"] = False
if isinstance(value, list):
success_value = value
else:
success_value = [value]
# create a watch block
ueh.add(managed_object=mo, prop=prop, success_value=success_value,
call_back=cb, timeout_sec=timeout_sec, context=context)
# wait for the event to occur
while not context["done"]:
time.sleep(1)