173 lines
6.0 KiB
Python
173 lines
6.0 KiB
Python
#
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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 random
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from heat.common import exception
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from heat.common.i18n import _
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from heat.engine import constraints
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from heat.engine import properties
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from heat.engine import resource
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from heat.engine import support
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from oslo_utils import timeutils
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class Delay(resource.Resource):
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"""A resource that pauses for a configurable delay.
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By manipulating the dependency relationships between resources in the
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template, a delay can be inserted at an arbitrary point during e.g. stack
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creation or deletion. They delay will occur after any resource that it
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depends on during CREATE or SUSPEND, and before any resource that it
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depends on during DELETE or RESUME. Similarly, it will occur before any
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resource that depends on it during CREATE or SUSPEND, and after any
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resource thet depends on it during DELETE or RESUME.
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If a non-zero maximum jitter is specified, a random amount of jitter -
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chosen with uniform probability in the range from 0 to the product of the
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maximum jitter value and the jitter multiplier (1s by default) - is added
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to the minimum delay time. This can be used, for example, in the scaled
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unit of a large scaling group to prevent 'thundering herd' issues.
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"""
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support_status = support.SupportStatus(version='11.0.0')
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_ALLOWED_ACTIONS = (
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resource.Resource.CREATE,
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resource.Resource.DELETE,
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resource.Resource.SUSPEND,
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resource.Resource.RESUME,
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)
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PROPERTIES = (
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MIN_WAIT_SECS, MAX_JITTER, JITTER_MULTIPLIER_SECS, DELAY_ACTIONS,
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) = (
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'min_wait', 'max_jitter', 'jitter_multiplier', 'actions',
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)
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properties_schema = {
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MIN_WAIT_SECS: properties.Schema(
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properties.Schema.NUMBER,
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_('Minimum time in seconds to wait during the specified actions.'),
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update_allowed=True,
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default=0,
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constraints=[
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constraints.Range(min=0)
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]
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),
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MAX_JITTER: properties.Schema(
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properties.Schema.NUMBER,
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_('Maximum jitter to add to the minimum wait time.'),
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update_allowed=True,
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default=0,
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constraints=[
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constraints.Range(min=0),
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]
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),
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JITTER_MULTIPLIER_SECS: properties.Schema(
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properties.Schema.NUMBER,
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_('Number of seconds to multiply the maximum jitter value by.'),
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update_allowed=True,
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default=1.0,
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constraints=[
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constraints.Range(min=0),
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]
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),
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DELAY_ACTIONS: properties.Schema(
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properties.Schema.LIST,
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_('Actions during which the delay will occur.'),
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update_allowed=True,
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default=[resource.Resource.CREATE],
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constraints=[constraints.AllowedValues(_ALLOWED_ACTIONS)]
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),
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}
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attributes_schema = {}
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def _delay_parameters(self):
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"""Return a tuple of the min delay and max jitter, in seconds."""
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min_wait_secs = self.properties[self.MIN_WAIT_SECS]
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max_jitter_secs = (self.properties[self.MAX_JITTER] *
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self.properties[self.JITTER_MULTIPLIER_SECS])
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return min_wait_secs, max_jitter_secs
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def validate(self):
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result = super(Delay, self).validate()
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if not self.stack.strict_validate:
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return result
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min_wait_secs, max_jitter_secs = self._delay_parameters()
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max_wait = min_wait_secs + max_jitter_secs
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if max_wait > self.stack.timeout_secs():
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raise exception.StackValidationFailed(_('%(res_type)s maximum '
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'delay %(max_wait)ss '
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'exceeds stack timeout.') %
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{'res_type': self.type,
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'max_wait': max_wait})
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return result
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def _wait_secs(self, action):
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"""Return a (randomised) wait time for the specified action."""
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if action not in self.properties[self.DELAY_ACTIONS]:
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return 0
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min_wait_secs, max_jitter_secs = self._delay_parameters()
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return min_wait_secs + (max_jitter_secs * random.random())
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def _handle_action(self):
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"""Return a tuple of the start time in UTC and the time to wait."""
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return timeutils.utcnow(), self._wait_secs(self.action)
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@staticmethod
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def _check_complete(started_at, wait_secs):
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if not wait_secs:
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return True
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elapsed_secs = (timeutils.utcnow() - started_at).total_seconds()
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if elapsed_secs >= wait_secs:
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return True
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remaining = wait_secs - elapsed_secs
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if remaining >= 4:
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raise resource.PollDelay(int(remaining // 2))
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return False
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def handle_create(self):
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return self._handle_action()
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def handle_delete(self):
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return self._handle_action()
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def handle_suspend(self):
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return self._handle_action()
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def handle_resume(self):
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return self._handle_action()
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def check_create_complete(self, cookie):
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return self._check_complete(*cookie)
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def check_delete_complete(self, cookie):
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return self._check_complete(*cookie)
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def check_suspend_complete(self, cookie):
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return self._check_complete(*cookie)
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def check_resume_complete(self, cookie):
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return self._check_status_complete(*cookie)
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def resource_mapping():
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return {
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'OS::Heat::Delay': Delay,
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}
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