def handle_exception(self, exception, decision_context):
"""
Handles exceptions from the event loop.
The default behavior is to log it, fail the workflow, and continue. This method only gets used when in
distributed mode.
:param exception:
:return: True if we want to exit, False otherwise
"""
self.logger.exception('Exception caught while running the event loop.')
# Reset the decisions that we want to make; we can't schedule new activities and fail a workflow in the same
# call
decision_context.decisions = Layer1Decisions()
decision_context.decisions.fail_workflow_execution(
reason='Decider exception', details=exception.message[:3000])
return False
def handle_nextPageToken(self):
# Quick test for nextPageToken
try:
if self.decision["nextPageToken"]:
# nextPageToken should be paging if the decider is configured properly
# If there is a nextPageToken
# something has gone wrong and terminate the workflow execution with
# extreme prejudice
d = Layer1Decisions()
reason="nextPageToken found, maximum_page_size of " + str(self.maximum_page_size) + " exceeded"
d.fail_workflow_execution(reason)
out = self.conn.respond_decision_task_completed(self.token,d._data)
self.logger.info(reason)
self.logger.info('respond_decision_task_completed returned %s' % out)
self.token = None
return False
except KeyError:
# No nextPageToken, so we did not exceed the maximum_page_size, continue
pass
def run_decider(self):
"""
run one iteration of a simple decision engine
"""
# Poll for a decision task.
tries = 0
while True:
dtask = self.conn.poll_for_decision_task(self._domain,
self._task_list,
reverse_order=True)
if dtask.get('taskToken') is not None:
# This means a real decision task has arrived.
break
time.sleep(2)
tries += 1
if tries > 10:
# Give up if it's taking too long. Probably
# means something is broken somewhere else.
assert False, 'no decision task occurred'
# Get the most recent interesting event.
ignorable = (
'DecisionTaskScheduled',
'DecisionTaskStarted',
'DecisionTaskTimedOut',
)
event = None
for tevent in dtask['events']:
if tevent['eventType'] not in ignorable:
event = tevent
break
# Construct the decision response.
decisions = Layer1Decisions()
if event['eventType'] == 'WorkflowExecutionStarted':
activity_id = str(uuid.uuid1())
decisions.schedule_activity_task(
activity_id,
self._activity_type_name,
self._activity_type_version,
task_list=self._task_list,
input=event['workflowExecutionStartedEventAttributes']
['input'])
elif event['eventType'] == 'ActivityTaskCompleted':
decisions.complete_workflow_execution(
result=event['activityTaskCompletedEventAttributes']['result'])
elif event['eventType'] == 'ActivityTaskFailed':
decisions.fail_workflow_execution(
reason=event['activityTaskFailedEventAttributes']['reason'],
details=event['activityTaskFailedEventAttributes']['details'])
else:
decisions.fail_workflow_execution(
reason='unhandled decision task type; %r' %
(event['eventType'], ))
# Send the decision response.
r = self.conn.respond_decision_task_completed(
dtask['taskToken'],
decisions=decisions._data,
execution_context=None)
assert r is None
def complete(self, result):
decisions = self._decisions = Layer1Decisions()
decisions.complete_workflow_execution(result)
return self.flush()
def fail(self, reason):
decisions = self._decisions = Layer1Decisions()
decisions.fail_workflow_execution(reason=str(reason)[:256])
return self.flush()
def restart(self, spec, input, tags):
decisions = self._decisions = Layer1Decisions()
spec.restart(decisions, input, tags)
return self.flush()
def __init__(self, swf_client, token, rate_limit=64):
self._swf_client = swf_client
self._token = token
self._rate_limit = rate_limit
self._decisions = Layer1Decisions()
self._closed = False
def get_decision_manager():
return Layer1Decisions()
def start(self):
"""
Starts the event loop
This method blocks and runs infinitely. Call this method to start a decisioner in distributed mode after
construction.
:return:
"""
while True:
self.logger.debug('Polling')
try:
decision_task = self._swf.poll_for_decision_task(
domain=self._swf_domain, task_list=self._swf_task_list)
# No-op if we got no events
if 'events' not in decision_task:
self.logger.debug('Calling the no-op handler')
self.handle_no_op(decision_task)
continue
self.logger.debug('Received an decision task')
# Get full event history
history = decision_task['events']
next_page_token = decision_task.get('nextPageToken')
while next_page_token:
self.logger.debug('Polling for additional history...')
additional_history = self._swf.poll_for_decision_task(
domain=self._swf_domain,
task_list=self._swf_task_list,
next_page_token=next_page_token)
if 'events' in additional_history:
history.extend(additional_history['events'])
decision_task['events'] = list()
next_page_token = additional_history.get('nextPageToken')
except Exception as e:
self.logger.exception(
'Exception while polling for a task and/or history')
raise e
# Populate the context
try:
decision_context = self._populate_decision_context(
decision_task, history)
# Here's where we make the context available to the decorated function
self._scanner.decision_context = decision_context
# Make sure that timers get them, too
PTimer.decision_context = decision_context
PMarker.decision_context = decision_context
# And markers
except Exception as e:
self.logger.exception(
'Exception while parsing a workflow history')
message = str(e)
if message:
message = message[:3000]
decision_context.decisions = Layer1Decisions()
decision_context.decisions.fail_workflow_execution(
reason='Failed to parse workflow history', details=message)
self._swf.respond_decision_task_completed(
decision_task['taskToken'],
decision_context.decisions._data)
return
# get the args and run the handle function in a thread
args = (list(), dict())
if decision_context.workflow.input:
self.logger.debug('Unpacking input arguments')
serialized_args = self._input_data_store.get(
decision_context.workflow.input)
args = self._input_serializer.deserialize_input(
serialized_args)
# Do we have a self that we need to pass in?
if self._decision_object:
args[0].insert(0, self._decision_object)
try:
finished = False
result = self._decision_function(*args[0], **args[1])
finished = True
except UnfulfilledPromiseException:
finished = False
except Exception as e:
self.logger.debug('Calling the exception handler')
should_exit = self.handle_exception(e, decision_context)
if should_exit:
self.logger.debug(
'Exiting due to return value from handle_exception()')
return
# Is our workflow finished?
if finished is True:
swf_result = None
if result:
self.logger.debug('Packing workflow results')
serialized_result = self._result_serializer.serialize_result(
result)
key = '{}-result'.format(decision_context.workflow.run_id)
swf_result = self._result_data_store.put(
serialized_result, key)
decision_context.decisions.complete_workflow_execution(
result=swf_result)
self.logger.debug('Returning decisions to SWF.')
try:
self._swf.respond_decision_task_completed(
decision_task['taskToken'],
decision_context.decisions._data)
except Exception:
self.logger.exception(
'Error when responding with decision tasks')
