85 lines
2.8 KiB
Python
85 lines
2.8 KiB
Python
# -*- coding: utf-8 -*-
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# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright (C) 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 os
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import subprocess
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import sys
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import tempfile
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# INTRO: In this example we create a common persistence database (sqlite based)
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# and then we run a few set of processes which themselves use this persistence
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# database, those processes 'crash' (in a simulated way) by exiting with a
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# system error exception. After this occurs a few times we then activate a
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# script which doesn't 'crash' and it will resume all the given engines flows
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# that did not complete and run them to completion (instead of crashing).
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#
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# This shows how a set of tasks can be finished even after repeatingly being
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# crashed, *crash resistance* if you may call it, due to the engine concept as
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# well as the persistence layer which keeps track of the state a flow
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# transitions through and persists the intermediary inputs and outputs and
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# overall flow state.
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def _exec(cmd, add_env=None):
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env = None
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if add_env:
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env = os.environ.copy()
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env.update(add_env)
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proc = subprocess.Popen(cmd, env=env, stdin=None,
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stdout=subprocess.PIPE,
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stderr=sys.stderr)
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stdout, stderr = proc.communicate()
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rc = proc.returncode
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if rc != 0:
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raise RuntimeError("Could not run %s [%s]", cmd, rc)
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print(stdout.decode())
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def _path_to(name):
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return os.path.abspath(os.path.join(os.path.dirname(__file__),
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'resume_many_flows', name))
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def main():
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try:
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fd, db_path = tempfile.mkstemp(prefix='tf-resume-example')
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os.close(fd)
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backend_uri = 'sqlite:///%s' % db_path
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def run_example(name, add_env=None):
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_exec([sys.executable, _path_to(name), backend_uri], add_env)
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print('Run flow:')
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run_example('run_flow.py')
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print('\nRun flow, something happens:')
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run_example('run_flow.py', {'BOOM': 'exit please'})
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print('\nRun flow, something happens again:')
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run_example('run_flow.py', {'BOOM': 'exit please'})
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print('\nResuming all failed flows')
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run_example('resume_all.py')
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finally:
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os.unlink(db_path)
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if __name__ == '__main__':
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main()
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