Change consecutive build failure limit to a weigher

There is concern over the ability for compute nodes to reasonably
determine which events should count against its consecutive build
failures. Since the compute may erronenously disable itself in
response to mundane or otherwise intentional user-triggered events,
this patch adds a scheduler weigher that considers the build failure
counter and can negatively weigh hosts with recent failures. This
avoids taking computes fully out of rotation, rather treating them as
less likely to be picked for a subsequent scheduling
operation.

This introduces a new conf option to control this weight. The default
is set high to maintain the existing behavior of picking nodes that
are not experiencing high failure rates, and resetting the counter as
soon as a single successful build occurs. This is minimal visible
change from the existing behavior with default configuration.

The rationale behind the default value for this weigher comes from the
values likely to be generated by its peer weighers. The RAM and Disk
weighers will increase the score by number of available megabytes of
memory (range in thousands) and disk (range in millions). The default
value of 1000000 for the build failure weigher will cause competing
nodes with similar amounts of available disk and a small (less than ten)
number of failures to become less desirable than those without, even
with many terabytes of available disk.

Change-Id: I71c56fe770f8c3f66db97fa542fdfdf2b9865fb8
Related-Bug: #1742102
This commit is contained in:
Dan Smith 2018-06-04 10:21:37 -07:00
parent f902e0d5d8
commit 91e29079a0
16 changed files with 277 additions and 73 deletions

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@ -822,6 +822,11 @@ Hosts and cells are weighted based on the following options in the
- Multiplier used for weighing hosts for group soft-anti-affinity. Only a
positive value is meaningful. Negative means that the behavior will
change to the opposite, which is soft-affinity.
* - [filter_scheduler]
- ``build_failure_weight_multiplier``
- Multiplier used for weighing hosts which have recent build failures. A
positive value increases the significance of build falures reported by
the host recently, making them less likely to be chosen.
* - [metrics]
- ``weight_multiplier``
- Multiplier for weighting meters. Use a floating-point value.

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@ -525,7 +525,6 @@ class ComputeManager(manager.Manager):
CONF.max_concurrent_live_migrations)
else:
self._live_migration_semaphore = compute_utils.UnlimitedSemaphore()
self._failed_builds = 0
super(ComputeManager, self).__init__(service_name="compute",
*args, **kwargs)
@ -1677,29 +1676,15 @@ class ComputeManager(manager.Manager):
return block_device_info
def _build_failed(self):
self._failed_builds += 1
limit = CONF.compute.consecutive_build_service_disable_threshold
if limit and self._failed_builds >= limit:
# NOTE(danms): If we're doing a bunch of parallel builds,
# it is possible (although not likely) that we have already
# failed N-1 builds before this and we race with a successful
# build and disable ourselves here when we might've otherwise
# not.
LOG.error('Disabling service due to %(fails)i '
'consecutive build failures',
{'fails': self._failed_builds})
ctx = nova.context.get_admin_context()
service = objects.Service.get_by_compute_host(ctx, CONF.host)
service.disabled = True
service.disabled_reason = (
'Auto-disabled due to %i build failures' % self._failed_builds)
service.save()
# NOTE(danms): Reset our counter now so that when the admin
# re-enables us we can start fresh
self._failed_builds = 0
elif self._failed_builds > 1:
LOG.warning('%(fails)i consecutive build failures',
{'fails': self._failed_builds})
if CONF.compute.consecutive_build_service_disable_threshold:
rt = self._get_resource_tracker()
# NOTE(danms): Update our counter, but wait for the next
# update_available_resource() periodic to flush it to the DB
rt.stats.build_failed()
def _build_succeeded(self):
rt = self._get_resource_tracker()
rt.stats.build_succeeded()
@wrap_exception()
@reverts_task_state
@ -1751,7 +1736,7 @@ class ComputeManager(manager.Manager):
build_results.RESCHEDULED):
self._build_failed()
else:
self._failed_builds = 0
self._build_succeeded()
# NOTE(danms): We spawn here to return the RPC worker thread back to
# the pool. Since what follows could take a really long time, we don't

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@ -604,7 +604,13 @@ class ResourceTracker(object):
def _copy_resources(self, compute_node, resources):
"""Copy resource values to supplied compute_node."""
# purge old stats and init with anything passed in by the driver
# NOTE(danms): Preserve 'failed_builds' across the stats clearing,
# as that is not part of resources
# TODO(danms): Stop doing this when we get a column to store this
# directly
prev_failed_builds = self.stats.get('failed_builds', 0)
self.stats.clear()
self.stats['failed_builds'] = prev_failed_builds
self.stats.digest_stats(resources.get('stats'))
compute_node.stats = copy.deepcopy(self.stats)

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@ -138,3 +138,11 @@ class Stats(dict):
os_type=os_type, project_id=project_id)
return (vm_state, task_state, os_type, project_id)
def build_failed(self):
self['failed_builds'] = self.get('failed_builds', 0) + 1
def build_succeeded(self):
# FIXME(danms): Make this more graceful, either by time-based aging or
# a fixed decline upon success
self['failed_builds'] = 0

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@ -609,20 +609,20 @@ compute_group_opts = [
cfg.IntOpt('consecutive_build_service_disable_threshold',
default=10,
help="""
Number of consecutive failed builds that result in disabling a compute service.
Enables reporting of build failures to the scheduler.
This option will cause nova-compute to set itself to a disabled state
if a certain number of consecutive build failures occur. This will
prevent the scheduler from continuing to send builds to a compute node that is
consistently failing. Note that all failures qualify and count towards this
score, including reschedules that may have been due to racy scheduler behavior.
Since the failures must be consecutive, it is unlikely that occasional expected
reschedules will actually disable a compute node.
Any nonzero value will enable sending build failure statistics to the
scheduler for use by the BuildFailureWeigher.
Possible values:
* Any positive integer representing a build failure count.
* Zero to never auto-disable.
* Any positive integer enables reporting build failures.
* Zero to disable reporting build failures.
Related options:
* [filter_scheduler]/build_failure_weight_multiplier
"""),
cfg.IntOpt("shutdown_retry_interval",
default=10,

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@ -493,6 +493,34 @@ Possible values:
for hosts with group soft anti-affinity. Only a positive value are
meaningful, as negative values would make this behave as a soft affinity
weigher.
"""),
cfg.FloatOpt(
"build_failure_weight_multiplier",
default=1000000.0,
help="""
Multiplier used for weighing hosts that have had recent build failures.
This option determines how much weight is placed on a compute node with
recent build failures. Build failures may indicate a failing, misconfigured,
or otherwise ailing compute node, and avoiding it during scheduling may be
beneficial. The weight is inversely proportional to the number of recent
build failures the compute node has experienced. This value should be
set to some high value to offset weight given by other enabled weighers
due to available resources. To disable weighing compute hosts by the
number of recent failures, set this to zero.
This option is only used by the FilterScheduler and its subclasses; if you use
a different scheduler, this option has no effect.
Possible values:
* An integer or float value, where the value corresponds to the multiplier
ratio for this weigher.
Related options:
* [compute]/consecutive_build_service_disable_threshold - Must be nonzero
for a compute to report data considered by this weigher.
"""),
cfg.BoolOpt(
"shuffle_best_same_weighed_hosts",

View File

@ -256,6 +256,9 @@ class HostState(object):
self.ram_allocation_ratio = compute.ram_allocation_ratio
self.disk_allocation_ratio = compute.disk_allocation_ratio
# update failed_builds counter reported by the compute
self.failed_builds = int(self.stats.get('failed_builds', 0))
def consume_from_request(self, spec_obj):
"""Incrementally update host state from a RequestSpec object."""

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@ -0,0 +1,33 @@
#
# 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.
"""
BuildFailure Weigher. Weigh hosts by the number of recent failed boot attempts.
"""
import nova.conf
from nova.scheduler import weights
CONF = nova.conf.CONF
class BuildFailureWeigher(weights.BaseHostWeigher):
def weight_multiplier(self):
"""Override the weight multiplier. Note this is negated."""
return -1 * CONF.filter_scheduler.build_failure_weight_multiplier
def _weigh_object(self, host_state, weight_properties):
"""Higher weights win. Our multiplier is negative, so reduce our
weight by number of failed builds.
"""
return host_state.failed_builds

View File

@ -335,6 +335,11 @@ class TestCase(testtools.TestCase):
self.useFixture(nova_fixtures.PrivsepNoHelperFixture())
self.useFixture(mock_fixture.MockAutospecFixture())
# FIXME(danms): Disable this for all tests by default to avoid breaking
# any that depend on default/previous ordering
self.flags(build_failure_weight_multiplier=0.0,
group='filter_scheduler')
def _setup_cells(self):
"""Setup a normal cellsv2 environment.

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@ -73,6 +73,7 @@ class ServersTestBase(integrated_helpers._IntegratedTestBase):
_min_count_parameter = 'min_count'
def setUp(self):
self.computes = {}
super(ServersTestBase, self).setUp()
# The network service is called as part of server creates but no
# networks have been populated in the db, so stub the methods.
@ -133,6 +134,30 @@ class ServersTest(ServersTestBase):
for server in servers:
LOG.debug("server: %s", server)
def _get_node_build_failures(self):
ctxt = context.get_admin_context()
computes = objects.ComputeNodeList.get_all(ctxt)
return {
node.hypervisor_hostname: int(node.stats.get('failed_builds', 0))
for node in computes}
def _run_periodics(self):
"""Run the update_available_resource task on every compute manager
This runs periodics on the computes in an undefined order; some child
class redefined this function to force a specific order.
"""
if self.compute.host not in self.computes:
self.computes[self.compute.host] = self.compute
ctx = context.get_admin_context()
for compute in self.computes.values():
LOG.info('Running periodic for compute (%s)',
compute.manager.host)
compute.manager.update_available_resource(ctx)
LOG.info('Finished with periodics')
def test_create_server_with_error(self):
# Create a server which will enter error state.
@ -154,6 +179,12 @@ class ServersTest(ServersTestBase):
self.assertEqual('ERROR', found_server['status'])
self._delete_server(created_server_id)
# We should have no (persisted) build failures until we update
# resources, after which we should have one
self.assertEqual([0], list(self._get_node_build_failures().values()))
self._run_periodics()
self.assertEqual([1], list(self._get_node_build_failures().values()))
def _test_create_server_with_error_with_retries(self):
# Create a server which will enter error state.
@ -161,6 +192,7 @@ class ServersTest(ServersTestBase):
self.addCleanup(fake.restore_nodes)
self.flags(host='host2')
self.compute2 = self.start_service('compute', host='host2')
self.computes['compute2'] = self.compute2
fails = []
@ -188,11 +220,17 @@ class ServersTest(ServersTestBase):
self.flags(max_attempts=2, group='scheduler')
fails = self._test_create_server_with_error_with_retries()
self.assertEqual(2, fails)
self._run_periodics()
self.assertEqual(
[1, 1], list(self._get_node_build_failures().values()))
def test_create_server_with_error_with_no_retries(self):
self.flags(max_attempts=1, group='scheduler')
fails = self._test_create_server_with_error_with_retries()
self.assertEqual(1, fails)
self._run_periodics()
self.assertEqual(
[0, 1], list(sorted(self._get_node_build_failures().values())))
def test_create_and_delete_server(self):
# Creates and deletes a server.

View File

@ -5258,24 +5258,19 @@ class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
nil_out_host_and_node=True)
@mock.patch.object(manager.ComputeManager, '_do_build_and_run_instance')
@mock.patch('nova.objects.Service.get_by_compute_host')
def test_build_failures_disable_service(self, mock_service, mock_dbari):
@mock.patch('nova.compute.stats.Stats.build_failed')
def test_build_failures_reported(self, mock_failed, mock_dbari):
mock_dbari.return_value = build_results.FAILED
instance = objects.Instance(uuid=uuids.instance)
for i in range(0, 10):
self.compute.build_and_run_instance(self.context, instance, None,
None, None)
service = mock_service.return_value
self.assertTrue(service.disabled)
self.assertEqual('Auto-disabled due to 10 build failures',
service.disabled_reason)
service.save.assert_called_once_with()
self.assertEqual(0, self.compute._failed_builds)
self.assertEqual(10, mock_failed.call_count)
@mock.patch.object(manager.ComputeManager, '_do_build_and_run_instance')
@mock.patch('nova.objects.Service.get_by_compute_host')
def test_build_failures_not_disable_service(self, mock_service,
mock_dbari):
@mock.patch('nova.compute.stats.Stats.build_failed')
def test_build_failures_not_reported(self, mock_failed, mock_dbari):
self.flags(consecutive_build_service_disable_threshold=0,
group='compute')
mock_dbari.return_value = build_results.FAILED
@ -5283,13 +5278,14 @@ class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
for i in range(0, 10):
self.compute.build_and_run_instance(self.context, instance, None,
None, None)
service = mock_service.return_value
self.assertFalse(service.save.called)
self.assertEqual(10, self.compute._failed_builds)
mock_failed.assert_not_called()
@mock.patch.object(manager.ComputeManager, '_do_build_and_run_instance')
@mock.patch('nova.objects.Service.get_by_compute_host')
def test_transient_build_failures_no_disable_service(self, mock_service,
@mock.patch.object(manager.ComputeManager, '_build_failed')
@mock.patch.object(manager.ComputeManager, '_build_succeeded')
def test_transient_build_failures_no_report(self, mock_succeeded,
mock_failed,
mock_dbari):
results = [build_results.FAILED,
build_results.ACTIVE,
@ -5306,31 +5302,34 @@ class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
for i in range(0, 10):
self.compute.build_and_run_instance(self.context, instance, None,
None, None)
service = mock_service.return_value
self.assertFalse(service.save.called)
self.assertEqual(0, self.compute._failed_builds)
self.assertEqual(2, mock_failed.call_count)
self.assertEqual(8, mock_succeeded.call_count)
@mock.patch.object(manager.ComputeManager, '_do_build_and_run_instance')
@mock.patch('nova.objects.Service.get_by_compute_host')
def test_build_reschedules_disable_service(self, mock_service, mock_dbari):
@mock.patch.object(manager.ComputeManager, '_build_failed')
@mock.patch.object(manager.ComputeManager, '_build_succeeded')
def test_build_reschedules_reported(self, mock_succeeded,
mock_failed,
mock_dbari):
mock_dbari.return_value = build_results.RESCHEDULED
instance = objects.Instance(uuid=uuids.instance)
for i in range(0, 10):
self.compute.build_and_run_instance(self.context, instance, None,
None, None)
service = mock_service.return_value
self.assertTrue(service.disabled)
self.assertEqual('Auto-disabled due to 10 build failures',
service.disabled_reason)
service.save.assert_called_once_with()
self.assertEqual(0, self.compute._failed_builds)
self.assertEqual(10, mock_failed.call_count)
mock_succeeded.assert_not_called()
@mock.patch.object(manager.ComputeManager, '_do_build_and_run_instance')
@mock.patch('nova.objects.Service.get_by_compute_host')
@mock.patch('nova.exception_wrapper._emit_exception_notification')
@mock.patch('nova.compute.utils.add_instance_fault_from_exc')
def test_build_exceptions_disable_service(self, mock_if, mock_notify,
mock_service, mock_dbari):
@mock.patch.object(manager.ComputeManager, '_build_failed')
@mock.patch.object(manager.ComputeManager, '_build_succeeded')
def test_build_exceptions_reported(self, mock_succeeded,
mock_failed,
mock_if, mock_notify,
mock_dbari):
mock_dbari.side_effect = test.TestingException()
instance = objects.Instance(uuid=uuids.instance,
task_state=None)
@ -5339,12 +5338,9 @@ class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
self.compute.build_and_run_instance,
self.context, instance, None,
None, None)
service = mock_service.return_value
self.assertTrue(service.disabled)
self.assertEqual('Auto-disabled due to 10 build failures',
service.disabled_reason)
service.save.assert_called_once_with()
self.assertEqual(0, self.compute._failed_builds)
self.assertEqual(10, mock_failed.call_count)
mock_succeeded.assert_not_called()
@mock.patch.object(manager.ComputeManager, '_shutdown_instance')
@mock.patch.object(manager.ComputeManager, '_build_networks_for_instance')

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@ -1155,7 +1155,7 @@ class TestInitComputeNode(BaseTestCase):
ram_allocation_ratio=1.0,
cpu_allocation_ratio=1.0,
disk_allocation_ratio=1.0,
stats={},
stats={'failed_builds': 0},
pci_device_pools=objects.PciDevicePoolList(objects=[]),
uuid=uuids.compute_node_uuid
)

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@ -238,3 +238,19 @@ class StatsTestCase(test.NoDBTestCase):
self.assertEqual(0, len(self.stats))
self.assertEqual(0, len(self.stats.states))
def test_build_failed_succeded(self):
self.assertEqual('not-set', self.stats.get('failed_builds', 'not-set'))
self.stats.build_failed()
self.assertEqual(1, self.stats['failed_builds'])
self.stats.build_failed()
self.assertEqual(2, self.stats['failed_builds'])
self.stats.build_succeeded()
self.assertEqual(0, self.stats['failed_builds'])
self.stats.build_succeeded()
self.assertEqual(0, self.stats['failed_builds'])
def test_build_succeeded_first(self):
self.assertEqual('not-set', self.stats.get('failed_builds', 'not-set'))
self.stats.build_succeeded()
self.assertEqual(0, self.stats['failed_builds'])

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@ -163,6 +163,7 @@ class CachingSchedulerTestCase(test_scheduler.SchedulerTestCase):
host_state.ram_allocation_ratio = 1.5
host_state.disk_allocation_ratio = 1.0
host_state.metrics = objects.MonitorMetricList(objects=[])
host_state.failed_builds = 0
return host_state
@mock.patch('nova.db.instance_extra_get_by_instance_uuid',

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@ -0,0 +1,57 @@
#
# 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.
"""
Tests For Scheduler build failure weights.
"""
from nova.scheduler import weights
from nova.scheduler.weights import compute
from nova import test
from nova.tests.unit.scheduler import fakes
class BuildFailureWeigherTestCase(test.NoDBTestCase):
def setUp(self):
super(BuildFailureWeigherTestCase, self).setUp()
self.weight_handler = weights.HostWeightHandler()
self.weighers = [compute.BuildFailureWeigher()]
def _get_weighed_host(self, hosts):
return self.weight_handler.get_weighed_objects(self.weighers,
hosts, {})
def _get_all_hosts(self):
host_values = [
('host1', 'node1', {'failed_builds': 0}),
('host2', 'node2', {'failed_builds': 1}),
('host3', 'node3', {'failed_builds': 10}),
('host4', 'node4', {'failed_builds': 100})
]
return [fakes.FakeHostState(host, node, values)
for host, node, values in host_values]
def test_build_failure_weigher_disabled(self):
self.flags(build_failure_weight_multiplier=0.0,
group='filter_scheduler')
hosts = self._get_all_hosts()
weighed_hosts = self._get_weighed_host(hosts)
self.assertTrue(all([wh.weight == 0.0
for wh in weighed_hosts]))
def test_build_failure_weigher_scaled(self):
self.flags(build_failure_weight_multiplier=1000.0,
group='filter_scheduler')
hosts = self._get_all_hosts()
weighed_hosts = self._get_weighed_host(hosts)
self.assertEqual([0, -10, -100, -1000],
[wh.weight for wh in weighed_hosts])

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@ -0,0 +1,23 @@
---
security:
- |
To mitigate potential issues with compute nodes disabling
themselves in response to failures that were either non-fatal or
user-generated, the consecutive build failure counter
functionality in the compute service has been changed to advise
the scheduler of the count instead of self-disabling the service
upon exceeding the threshold. The
``[compute]/consecutive_build_service_disable_threshold``
configuration option still controls whether the count is tracked,
but the action taken on this value has been changed to a scheduler
weigher. This allows the scheduler to be configured to weigh hosts
with consecutive failures lower than other hosts, configured by the
``[filter_scheduler]/build_failure_weight_multiplier`` option. If
the compute threshold option is nonzero, computes will report their
failure count for the scheduler to consider. If the threshold
value is zero, then computes will not report this value
and the scheduler will assume the number of failures for
non-reporting compute nodes to be zero. By default, the scheduler
weigher is enabled and configured with a very large multiplier to
ensure that hosts with consecutive failures are scored low by
default.