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# -*- coding: utf-8 -*-
# Copyright (C) 2012-2013 Yahoo! Inc. All Rights Reserved.
#
# 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.
import logging
import os
import sys
logging.basicConfig(level=logging.ERROR)
top_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
os.pardir,
os.pardir))
sys.path.insert(0, top_dir)
import taskflow.engines
from taskflow.patterns import linear_flow as lf
from taskflow import task
# INTRO: In this example we create three tasks, each of which ~calls~ a given
# number (provided as a function input), one of those tasks *fails* calling a
# given number (the suzzie calling); this causes the workflow to enter the
# reverting process, which activates the revert methods of the previous two
# phone ~calls~.
#
# This simulated calling makes it appear like all three calls occur or all
# three don't occur (transaction-like capabilities). No persistence layer is
# used here so reverting and executing will *not* be tolerant of process
# failure.
class CallJim(task.Task):
def execute(self, jim_number, *args, **kwargs):
print("Calling jim %s." % jim_number)
def revert(self, jim_number, *args, **kwargs):
print("Calling %s and apologizing." % jim_number)
class CallJoe(task.Task):
def execute(self, joe_number, *args, **kwargs):
print("Calling joe %s." % joe_number)
def revert(self, joe_number, *args, **kwargs):
print("Calling %s and apologizing." % joe_number)
class CallSuzzie(task.Task):
def execute(self, suzzie_number, *args, **kwargs):
raise IOError("Suzzie not home right now.")
# Create your flow and associated tasks (the work to be done).
flow = lf.Flow('simple-linear').add(
CallJim(),
CallJoe(),
CallSuzzie()
)
try:
# Now run that flow using the provided initial data (store below).
taskflow.engines.run(flow, store=dict(joe_number=444,
jim_number=555,
suzzie_number=666))
except Exception as e:
# NOTE(harlowja): This exception will be the exception that came out of the
# 'CallSuzzie' task instead of a different exception, this is useful since
# typically surrounding code wants to handle the original exception and not
# a wrapped or altered one.
#
# *WARNING* If this flow was multi-threaded and multiple active tasks threw
# exceptions then the above exception would be wrapped into a combined
# exception (the object has methods to iterate over the contained
# exceptions). See: exceptions.py and the class 'WrappedFailure' to look at
# how to deal with multiple tasks failing while running.
#
# You will also note that this is not a problem in this case since no
# parallelism is involved; this is ensured by the usage of a linear flow
# and the default engine type which is 'serial' vs being 'parallel'.
print("Flow failed: %s" % e)
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