102 lines
3.9 KiB
Python
102 lines
3.9 KiB
Python
# -*- coding: utf-8 -*-
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# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright (C) 2012-2013 Yahoo! Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import logging
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import os
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import sys
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logging.basicConfig(level=logging.ERROR)
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top_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
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os.pardir,
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os.pardir))
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sys.path.insert(0, top_dir)
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import taskflow.engines
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from taskflow.patterns import linear_flow as lf
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from taskflow import task
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# INTRO: In this example we create three tasks, each of which ~calls~ a given
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# number (provided as a function input), one of those tasks fails calling a
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# given number (the suzzie calling); this causes the workflow to enter the
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# reverting process, which activates the revert methods of the previous two
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# phone ~calls~.
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#
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# This simulated calling makes it appear like all three calls occur or all
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# three don't occur (transactional like capabilities). No persistence layer is
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# used here so reverting and executing will not handle process failure.
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#
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# This example shows a basic usage of the taskflow structures without involving
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# the complexity of persistence. Using the structures that taskflow provides
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# via tasks and flows makes it possible for you to easily at a later time
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# hook in a persistence layer (and then gain the functionality that offers)
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# when you decide the complexity of adding that layer in is 'worth it' for your
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# applications usage pattern (which some applications may not need).
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class CallJim(task.Task):
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def execute(self, jim_number, *args, **kwargs):
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print("Calling jim %s." % jim_number)
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def revert(self, jim_number, *args, **kwargs):
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print("Calling %s and apologizing." % jim_number)
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class CallJoe(task.Task):
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def execute(self, joe_number, *args, **kwargs):
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print("Calling joe %s." % joe_number)
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def revert(self, joe_number, *args, **kwargs):
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print("Calling %s and apologizing." % joe_number)
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class CallSuzzie(task.Task):
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def execute(self, suzzie_number, *args, **kwargs):
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raise IOError("Suzzie not home right now.")
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# Create your flow and associated tasks (the work to be done).
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flow = lf.Flow('simple-linear').add(
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CallJim(),
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CallJoe(),
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CallSuzzie()
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)
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try:
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# Now run that flow using the provided initial data (store below).
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taskflow.engines.run(flow, store=dict(joe_number=444,
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jim_number=555,
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suzzie_number=666))
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except Exception as e:
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# NOTE(harlowja): This exception will be the exception that came out of the
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# 'CallSuzzie' task instead of a different exception, this is useful since
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# typically surrounding code wants to handle the original exception and not
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# a wrapped or altered one.
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#
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# *WARNING* If this flow was multi-threaded and multiple active tasks threw
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# exceptions then the above exception would be wrapped into a combined
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# exception (the object has methods to iterate over the contained
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# exceptions). See: exceptions.py and the class 'WrappedFailure' to look at
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# how to deal with multiple tasks failing while running.
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#
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# You will also note that this is not a problem in this case since no
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# parallelism is involved; this is ensured by the usage of a linear flow,
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# which runs serially as well as the default engine type which is 'serial'.
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print("Flow failed: %s" % e)
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