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# Copyright 2020 Catalyst Cloud
#
# 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.
from oslo_service import loopingcall
def build_polling_task(retriever, condition=lambda value: value,
sleep_time=1, time_out=0, initial_delay=0):
"""Run a function in a loop with backoff on error.
The condition function runs based on the retriever function result.
"""
def poll_and_check():
obj = retriever()
if condition(obj):
raise loopingcall.LoopingCallDone(retvalue=obj)
call = loopingcall.BackOffLoopingCall(f=poll_and_check)
return call.start(initial_delay=initial_delay,
starting_interval=sleep_time,
max_interval=30, timeout=time_out)
def poll_until(retriever, condition=lambda value: value,
sleep_time=3, time_out=0, initial_delay=0):
"""Retrieves object until it passes condition, then returns it.
If time_out_limit is passed in, PollTimeOut will be raised once that
amount of time is eclipsed.
"""
task = build_polling_task(retriever, condition=condition,
sleep_time=sleep_time, time_out=time_out,
initial_delay=initial_delay)
return task.wait()
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