OpenStack Study: scheduler.py

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# 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

from oslo.config import cfg

from nova.cells import filters

from nova.cells import weights

from nova import compute

from nova.compute import flavors

from nova.compute import instance_actions

from nova.compute import vm_states

from nova import conductor

from nova.db import base

from nova import exception

from nova.objects import base as obj_base

from nova.objects import instance as instance_obj

from nova.objects import instance_action as instance_action_obj

from nova.openstack.common.gettextutils import _

from nova.openstack.common import log as logging

from nova.scheduler import rpcapi as scheduler_rpcapi

from nova.scheduler import utils as scheduler_utils

from nova import utils

cell_scheduler_opts = [

cfg.ListOpt('scheduler_filter_classes',

default=['nova.cells.filters.all_filters'],

help='Filter classes the cells scheduler should use. '

'An entry of "nova.cells.filters.all_filters" '

'maps to all cells filters included with nova.'),

cfg.ListOpt('scheduler_weight_classes',

default=['nova.cells.weights.all_weighers'],

help='Weigher classes the cells scheduler should use. '

'An entry of "nova.cells.weights.all_weighers" '

'maps to all cell weighers included with nova.'),

cfg.IntOpt('scheduler_retries',

default=10,

help='How many retries when no cells are available.'),

cfg.IntOpt('scheduler_retry_delay',

default=2,

help='How often to retry in seconds when no cells are '

'available.')

]

LOG = logging.getLogger(__name__)

CONF = cfg.CONF

CONF.register_opts(cell_scheduler_opts, group='cells')

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class CellsScheduler(base.Base):

"""The cells scheduler."""

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def __init__(self, msg_runner):

super(CellsScheduler, self).__init__()

self.msg_runner = msg_runner

self.state_manager = msg_runner.state_manager

self.compute_api = compute.API()

self.scheduler_rpcapi = scheduler_rpcapi.SchedulerAPI()

self.compute_task_api = conductor.ComputeTaskAPI()

self.filter_handler = filters.CellFilterHandler()

self.filter_classes = self.filter_handler.get_matching_classes(

CONF.cells.scheduler_filter_classes)

self.weight_handler = weights.CellWeightHandler()

self.weigher_classes = self.weight_handler.get_matching_classes(

CONF.cells.scheduler_weight_classes)

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def _create_instances_here(self, ctxt, instance_uuids, instance_properties,

instance_type, image, security_groups, block_device_mapping):

instance_values = copy.copy(instance_properties)

# The parent may pass these metadata values as lists, and the

# create call expects it to be a dict.

instance_values['metadata'] = utils.instance_meta(instance_values)

sys_metadata = utils.instance_sys_meta(instance_values)

# Make sure the flavor info is set. It may not have been passed

# down.

sys_metadata = flavors.save_flavor_info(sys_metadata, instance_type)

instance_values['system_metadata'] = sys_metadata

# Pop out things that will get set properly when re-creating the

# instance record.

instance_values.pop('id')

instance_values.pop('name')

instance_values.pop('info_cache')

instance_values.pop('security_groups')

num_instances = len(instance_uuids)

for i, instance_uuid in enumerate(instance_uuids):

instance = instance_obj.Instance()

instance.update(instance_values)

instance.uuid = instance_uuid

instance = self.compute_api.create_db_entry_for_new_instance(

block_device_mapping,

num_instances, i)

instance = obj_base.obj_to_primitive(instance)

self.msg_runner.instance_update_at_top(ctxt, instance)

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def _create_action_here(self, ctxt, instance_uuids):

for instance_uuid in instance_uuids:

instance_action_obj.InstanceAction.action_start(

ctxt,

instance_uuid,

instance_actions.CREATE,

want_result=False)

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def _get_possible_cells(self):

cells = self.state_manager.get_child_cells()

our_cell = self.state_manager.get_my_state()

# Include our cell in the list, if we have any capacity info

if not cells or our_cell.capacities:

cells.append(our_cell)

return cells

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def _grab_target_cells(self, filter_properties):

cells = self._get_possible_cells()

cells = self.filter_handler.get_filtered_objects(self.filter_classes,

cells,

filter_properties)

# NOTE(comstud): I know this reads weird, but the 'if's are nested

# this way to optimize for the common case where 'cells' is a list

# containing at least 1 entry.

if not cells:

if cells is None:

# None means to bypass further scheduling as a filter

# took care of everything.

return

raise exception.NoCellsAvailable()

weighted_cells = self.weight_handler.get_weighed_objects(

self.weigher_classes, cells, filter_properties)

LOG.debug(_("Weighted cells: %(weighted_cells)s"),

{'weighted_cells': weighted_cells})

target_cells = [cell.obj for cell in weighted_cells]

return target_cells

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def _run_instance(self, message, target_cells, instance_uuids,

host_sched_kwargs):

"""Attempt to schedule instance(s)."""

ctxt = message.ctxt

request_spec = host_sched_kwargs['request_spec']

instance_properties = request_spec['instance_properties']

instance_type = request_spec['instance_type']

image = request_spec['image']

security_groups = request_spec['security_group']

block_device_mapping = request_spec['block_device_mapping']

LOG.debug(_("Scheduling with routing_path=%(routing_path)s"),

{'routing_path': message.routing_path})

for target_cell in target_cells:

try:

if target_cell.is_me:

# Need to create instance DB entries as the host scheduler

# expects that the instance(s) already exists.

self._create_instances_here(ctxt, instance_uuids,

instance_properties, instance_type, image,

security_groups, block_device_mapping)

# Need to record the create action in the db as the

# scheduler expects it to already exist.

self._create_action_here(ctxt, instance_uuids)

self.scheduler_rpcapi.run_instance(ctxt,

**host_sched_kwargs)

return

self.msg_runner.schedule_run_instance(ctxt, target_cell,

host_sched_kwargs)

return

except Exception:

LOG.exception(_("Couldn't communicate with cell '%s'") %

target_cell.name)

# FIXME(comstud): Would be nice to kick this back up so that

# the parent cell could retry, if we had a parent.

msg = _("Couldn't communicate with any cells")

LOG.error(msg)

raise exception.NoCellsAvailable()

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def _build_instances(self, message, target_cells, instance_uuids,

build_inst_kwargs):

"""Attempt to build instance(s) or send msg to child cell."""

ctxt = message.ctxt

instance_properties = build_inst_kwargs['instances'][0]

filter_properties = build_inst_kwargs['filter_properties']

instance_type = filter_properties['instance_type']

image = build_inst_kwargs['image']

security_groups = build_inst_kwargs['security_groups']

block_device_mapping = build_inst_kwargs['block_device_mapping']

LOG.debug(_("Building instances with routing_path=%(routing_path)s"),

{'routing_path': message.routing_path})

for target_cell in target_cells:

try:

if target_cell.is_me:

# Need to create instance DB entries as the conductor

# expects that the instance(s) already exists.

self._create_instances_here(ctxt, instance_uuids,

instance_properties, instance_type, image,

security_groups, block_device_mapping)

# Need to record the create action in the db as the

# conductor expects it to already exist.

self._create_action_here(ctxt, instance_uuids)

self.compute_task_api.build_instances(ctxt,

**build_inst_kwargs)

return

self.msg_runner.build_instances(ctxt, target_cell,

build_inst_kwargs)

return

except Exception:

LOG.exception(_("Couldn't communicate with cell '%s'") %

target_cell.name)

# FIXME(comstud): Would be nice to kick this back up so that

# the parent cell could retry, if we had a parent.

msg = _("Couldn't communicate with any cells")

LOG.error(msg)

raise exception.NoCellsAvailable()

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def build_instances(self, message, build_inst_kwargs):

image = build_inst_kwargs['image']

instance_uuids = [inst['uuid'] for inst in

build_inst_kwargs['instances']]

instances = build_inst_kwargs['instances']

request_spec = scheduler_utils.build_request_spec(message.ctxt,

image, instances)

filter_properties = copy.copy(build_inst_kwargs['filter_properties'])

filter_properties.update({'context': message.ctxt,

'scheduler': self,

'routing_path': message.routing_path,

'host_sched_kwargs': build_inst_kwargs,

'request_spec': request_spec})

# NOTE(belliott) remove when deprecated schedule_run_instance

# code gets removed.

filter_properties['cell_scheduler_method'] = 'build_instances'

self._schedule_build_to_cells(message, instance_uuids,

filter_properties, self._build_instances, build_inst_kwargs)

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def run_instance(self, message, host_sched_kwargs):

request_spec = host_sched_kwargs['request_spec']

instance_uuids = request_spec['instance_uuids']

filter_properties = copy.copy(host_sched_kwargs['filter_properties'])

filter_properties.update({'context': message.ctxt,

'scheduler': self,

'routing_path': message.routing_path,

'host_sched_kwargs': host_sched_kwargs,

'request_spec': request_spec})

# NOTE(belliott) remove when deprecated schedule_run_instance

# code gets removed.

filter_properties['cell_scheduler_method'] = 'schedule_run_instance'

self._schedule_build_to_cells(message, instance_uuids,

filter_properties, self._run_instance, host_sched_kwargs)

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def _schedule_build_to_cells(self, message, instance_uuids,

filter_properties, method, method_kwargs):

"""Pick a cell where we should create a new instance(s)."""

try:

for i in xrange(max(0, CONF.cells.scheduler_retries) + 1):

try:

target_cells = self._grab_target_cells(filter_properties)

if target_cells is None:

# a filter took care of scheduling. skip.

return

return method(message, target_cells, instance_uuids,

method_kwargs)

except exception.NoCellsAvailable:

if i == max(0, CONF.cells.scheduler_retries):

raise

sleep_time = max(1, CONF.cells.scheduler_retry_delay)

LOG.info(_("No cells available when scheduling. Will "

"retry in %(sleep_time)s second(s)"),

{'sleep_time': sleep_time})

time.sleep(sleep_time)

continue

except Exception:

LOG.exception(_("Error scheduling instances %(instance_uuids)s"),

{'instance_uuids': instance_uuids})

ctxt = message.ctxt

for instance_uuid in instance_uuids:

self.msg_runner.instance_update_at_top(ctxt,

{'uuid': instance_uuid,

'vm_state': vm_states.ERROR})

try:

self.db.instance_update(ctxt,

instance_uuid,

{'vm_state': vm_states.ERROR})

except Exception:

pass