47 lines
1.7 KiB
Python
47 lines
1.7 KiB
Python
# Copyright 2020 Catalyst Cloud
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain 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,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from oslo_service import loopingcall
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def build_polling_task(retriever, condition=lambda value: value,
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sleep_time=1, time_out=0, initial_delay=0):
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"""Run a function in a loop with backoff on error.
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The condition function runs based on the retriever function result.
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"""
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def poll_and_check():
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obj = retriever()
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if condition(obj):
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raise loopingcall.LoopingCallDone(retvalue=obj)
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call = loopingcall.BackOffLoopingCall(f=poll_and_check)
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return call.start(initial_delay=initial_delay,
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starting_interval=sleep_time,
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max_interval=30, timeout=time_out)
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def poll_until(retriever, condition=lambda value: value,
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sleep_time=3, time_out=0, initial_delay=0):
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"""Retrieves object until it passes condition, then returns it.
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If time_out_limit is passed in, PollTimeOut will be raised once that
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amount of time is eclipsed.
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"""
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task = build_polling_task(retriever, condition=condition,
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sleep_time=sleep_time, time_out=time_out,
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initial_delay=initial_delay)
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return task.wait()
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