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# coding=utf-8
# Copyright 2013 Hewlett-Packard Development Company, L.P.
# All Rights Reserved.
# 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
# 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.
A context manager to perform a series of tasks on a set of resources.
:class:`TaskManager` is a context manager, created on-demand to allow
synchronized access to a node and its resources.
The :class:`TaskManager` will, by default, acquire an exclusive lock on
a node for the duration that the TaskManager instance exists. You may
create a TaskManager instance without locking by passing "shared=True"
when creating it, but certain operations on the resources held by such
an instance of TaskManager will not be possible. Requiring this exclusive
lock guards against parallel operations interfering with each other.
A shared lock is useful when performing non-interfering operations,
such as validating the driver interfaces.
An exclusive lock is stored in the database to coordinate between
:class:`ironic.conductor.manager` instances, that are typically deployed on
different hosts.
:class:`TaskManager` methods, as well as driver methods, may be decorated to
determine whether their invocation requires an exclusive lock.
The TaskManager instance exposes certain node resources and properties as
attributes that you may access:
The context passed to TaskManager()
False if Node is locked, True if it is not locked. (The
'shared' kwarg arg of TaskManager())
The Node object
Ports belonging to the Node
Portgroups belonging to the Node
Storage connectors belonging to the Node
Storage targets assigned to the Node
The Driver for the Node, or the Driver based on the
'driver_name' kwarg of TaskManager().
Example usage:
with task_manager.acquire(context, node_id, purpose='power on') as task:
If you need to execute task-requiring code in a background thread, the
TaskManager instance provides an interface to handle this for you, making
sure to release resources when the thread finishes (successfully or if
an exception occurs). Common use of this is within the Manager like so:
with task_manager.acquire(context, node_id, purpose='some work') as task:
<do some work>
utils.node_power_action, task, new_state)
All exceptions that occur in the current GreenThread as part of the
spawn handling are re-raised. You can specify a hook to execute custom
code when such exceptions occur. For example, the hook is a more elegant
solution than wrapping the "with task_manager.acquire()" with a
try..exception block. (Note that this hook does not handle exceptions
raised in the background thread.):
def on_error(e):
if isinstance(e, Exception):
with task_manager.acquire(context, node_id, purpose='some work') as task:
<do some work>
utils.node_power_action, task, new_state)
import copy
import futurist
from oslo_config import cfg
from oslo_log import log as logging
from oslo_utils import excutils
from oslo_utils import timeutils
import retrying
import six
from ironic.common import driver_factory
from ironic.common import exception
from ironic.common.i18n import _
from ironic.common import states
from ironic.conductor import notification_utils as notify
from ironic import objects
from ironic.objects import fields
LOG = logging.getLogger(__name__)
def require_exclusive_lock(f):
"""Decorator to require an exclusive lock.
Decorated functions must take a :class:`TaskManager` as the first
parameter. Decorated class methods should take a :class:`TaskManager`
as the first parameter after "self".
def wrapper(*args, **kwargs):
# NOTE(dtantsur): this code could be written simpler, but then unit
# testing decorated functions is pretty hard, as we usually pass a Mock
# object instead of TaskManager there.
if len(args) > 1:
task = args[1] if isinstance(args[1], TaskManager) else args[0]
task = args[0]
if task.shared:
raise exception.ExclusiveLockRequired()
# NOTE(lintan): This is a workaround to set the context of async tasks,
# which should contain an exclusive lock.
return f(*args, **kwargs)
return wrapper
def acquire(context, node_id, shared=False, driver_name=None,
purpose='unspecified action'):
"""Shortcut for acquiring a lock on a Node.
:param context: Request context.
:param node_id: ID or UUID of node to lock.
:param shared: Boolean indicating whether to take a shared or exclusive
lock. Default: False.
:param driver_name: Name of Driver. Default: None.
:param purpose: human-readable purpose to put to debug logs.
:returns: An instance of :class:`TaskManager`.
# NOTE(lintan): This is a workaround to set the context of periodic tasks.
return TaskManager(context, node_id, shared=shared,
driver_name=driver_name, purpose=purpose)
class TaskManager(object):
"""Context manager for tasks.
This class wraps the locking, driver loading, and acquisition
of related resources (eg, Node and Ports) when beginning a unit of work.
def __init__(self, context, node_id, shared=False, driver_name=None,
purpose='unspecified action'):
"""Create a new TaskManager.
Acquire a lock on a node. The lock can be either shared or
exclusive. Shared locks may be used for read-only or
non-disruptive actions only, and must be considerate to what
other threads may be doing on the same node at the same time.
:param context: request context
:param node_id: ID or UUID of node to lock.
:param shared: Boolean indicating whether to take a shared or exclusive
lock. Default: False.
:param driver_name: The name of the driver to load, if different
from the Node's current driver.
:param purpose: human-readable purpose to put to debug logs.
:raises: DriverNotFound
:raises: InterfaceNotFoundInEntrypoint
:raises: NodeNotFound
:raises: NodeLocked
self._spawn_method = None
self._on_error_method = None
self.context = context
self._node = None
self.node_id = node_id
self.shared = shared
self.fsm = states.machine.copy()
self._purpose = purpose
self._debug_timer = timeutils.StopWatch()
# states and event for notification
self._prev_provision_state = None
self._prev_target_provision_state = None
self._event = None
self._saved_node = None
node = objects.Node.get(context, node_id)
LOG.debug("Attempting to get %(type)s lock on node %(node)s (for "
{'type': 'shared' if shared else 'exclusive',
'node': node.uuid, 'purpose': purpose})
if not self.shared:
self.node = node
self.ports = objects.Port.list_by_node_id(context,
self.portgroups = objects.Portgroup.list_by_node_id(context,
self.volume_connectors = objects.VolumeConnector.list_by_node_id(
self.volume_targets = objects.VolumeTarget.list_by_node_id(
self.driver = driver_factory.build_driver_for_task(
self, driver_name=driver_name)
except Exception:
with excutils.save_and_reraise_exception():
def node(self):
return self._node
def node(self, node):
self._node = node
if node is not None:
def _lock(self):
# NodeLocked exceptions can be annoying. Let's try to alleviate
# some of that pain by retrying our lock attempts. The retrying
# module expects a wait_fixed value in milliseconds.
retry_on_exception=lambda e: isinstance(e, exception.NodeLocked),
wait_fixed=CONF.conductor.node_locked_retry_interval * 1000)
def reserve_node():
self.node = objects.Node.reserve(self.context,,
LOG.debug("Node %(node)s successfully reserved for %(purpose)s "
"(took %(time).2f seconds)",
{'node': self.node.uuid, 'purpose': self._purpose,
'time': self._debug_timer.elapsed()})
def upgrade_lock(self, purpose=None):
"""Upgrade a shared lock to an exclusive lock.
Also reloads node object from the database.
If lock is already exclusive only changes the lock purpose
when provided with one.
:param purpose: optionally change the purpose of the lock
:raises: NodeLocked if an exclusive lock remains on the node after
if purpose is not None:
self._purpose = purpose
if self.shared:
LOG.debug('Upgrading shared lock on node %(uuid)s for %(purpose)s '
'to an exclusive one (shared lock was held %(time).2f '
{'uuid': self.node.uuid, 'purpose': self._purpose,
'time': self._debug_timer.elapsed()})
self.shared = False
def spawn_after(self, _spawn_method, *args, **kwargs):
"""Call this to spawn a thread to complete the task.
The specified method will be called when the TaskManager instance
:param _spawn_method: a method that returns a GreenThread object
:param args: args passed to the method.
:param kwargs: additional kwargs passed to the method.
self._spawn_method = _spawn_method
self._spawn_args = args
self._spawn_kwargs = kwargs
def set_spawn_error_hook(self, _on_error_method, *args, **kwargs):
"""Create a hook to handle exceptions when spawning a task.
Create a hook that gets called upon an exception being raised
from spawning a background thread to do a task.
:param _on_error_method: a callable object, it's first parameter
should accept the Exception object that was raised.
:param args: additional args passed to the callable object.
:param kwargs: additional kwargs passed to the callable object.
self._on_error_method = _on_error_method
self._on_error_args = args
self._on_error_kwargs = kwargs
def release_resources(self):
"""Unlock a node and release resources.
If an exclusive lock is held, unlock the node. Reset attributes
to make it clear that this instance of TaskManager should no
longer be accessed.
if not self.shared:
if self.node:
except exception.NodeNotFound:
# squelch the exception if the node was deleted
# within the task's context.
if self.node:
LOG.debug("Successfully released %(type)s lock for %(purpose)s "
"on node %(node)s (lock was held %(time).2f sec)",
{'type': 'shared' if self.shared else 'exclusive',
'purpose': self._purpose, 'node': self.node.uuid,
'time': self._debug_timer.elapsed()})
self.node = None
self.driver = None
self.ports = None
self.portgroups = None
self.volume_connectors = None
self.volume_targets = None
self.fsm = None
def _write_exception(self, future):
"""Set node last_error if exception raised in thread."""
node = self.node
# do not rewrite existing error
if node and node.last_error is None:
method = self._spawn_args[0].__name__
exc = future.exception()
except futurist.CancelledError:
LOG.exception("Execution of %(method)s for node %(node)s "
"was canceled.", {'method': method,
'node': node.uuid})
if exc is not None:
msg = _("Async execution of %(method)s failed with error: "
"%(error)s") % {'method': method,
'error': six.text_type(exc)}
node.last_error = msg
except exception.NodeNotFound:
def _notify_provision_state_change(self):
"""Emit notification about change of the node provision state."""
if self._event is None:
if self.node is None:
# Rare case if resource released before notification
task = copy.copy(self)
task.fsm = states.machine.copy()
task.node = self._saved_node
task = self
node = task.node
state = node.provision_state
prev_state = self._prev_provision_state
new_unstable = state in states.UNSTABLE_STATES
prev_unstable = prev_state in states.UNSTABLE_STATES
level = fields.NotificationLevel.INFO
if self._event in ('fail', 'error'):
status = fields.NotificationStatus.ERROR
level = fields.NotificationLevel.ERROR
elif (prev_unstable, new_unstable) == (False, True):
status = fields.NotificationStatus.START
elif (prev_unstable, new_unstable) == (True, False):
status = fields.NotificationStatus.END
status = fields.NotificationStatus.SUCCESS
task, level, status, self._prev_provision_state,
self._prev_target_provision_state, self._event)
# reset saved event, avoiding duplicate notification
self._event = None
def _thread_release_resources(self, fut):
"""Thread callback to release resources."""
def process_event(self, event, callback=None, call_args=None,
call_kwargs=None, err_handler=None, target_state=None):
"""Process the given event for the task's current state.
:param event: the name of the event to process
:param callback: optional callback to invoke upon event transition
:param call_args: optional \*args to pass to the callback method
:param call_kwargs: optional \**kwargs to pass to the callback method
:param err_handler: optional error handler to invoke if the
callback fails, eg. because there are no workers available
(err_handler should accept arguments node, prev_prov_state, and
:param target_state: if specified, the target provision state for the
node. Otherwise, use the target state from the fsm
:raises: InvalidState if the event is not allowed by the associated
state machine
# save previous states and event
self._prev_provision_state = self.node.provision_state
self._prev_target_provision_state = self.node.target_provision_state
self._event = event
# Advance the state model for the given event. Note that this doesn't
# alter the node in any way. This may raise InvalidState, if this event
# is not allowed in the current state.
self.fsm.process_event(event, target_state=target_state)
# stash current states in the error handler if callback is set,
# in case we fail to get a worker from the pool
if err_handler and callback:
self.set_spawn_error_hook(err_handler, self.node,
self.node.provision_state = self.fsm.current_state
# NOTE(lucasagomes): If there's no extra processing
# (callback) and we've moved to a stable state, make sure the
# target_provision_state is cleared
if not callback and self.fsm.is_stable(self.node.provision_state):
self.node.target_provision_state = states.NOSTATE
self.node.target_provision_state = self.fsm.target_state
# set up the async worker
if callback:
# clear the error if we're going to start work in a callback
self.node.last_error = None
if call_args is None:
call_args = ()
if call_kwargs is None:
call_kwargs = {}
self.spawn_after(callback, *call_args, **call_kwargs)
# publish the state transition by saving the Node'Node %(node)s moved to provision state "%(state)s" from '
'state "%(previous)s"; target provision state is '
{'node': self.node.uuid, 'state': self.node.provision_state,
'target': self.node.target_provision_state,
'previous': self._prev_provision_state})
if callback is None:
# save the node, in case it is released before a notification is
# emitted at __exit__().
self._saved_node = self.node
def __enter__(self):
return self
def __exit__(self, exc_type, exc_val, exc_tb):
if exc_type is None and self._spawn_method is not None:
# Spawn a worker to complete the task
# The linked callback below will be called whenever:
# - background task finished with no errors.
# - background task has crashed with exception.
# - callback was added after the background task has
# finished or crashed. While eventlet currently doesn't
# schedule the new thread until the current thread blocks
# for some reason, this is true.
# All of the above are asserted in tests such that we'll
# catch if eventlet ever changes this behavior.
fut = None
fut = self._spawn_method(*self._spawn_args,
# NOTE(comstud): Trying to use a lambda here causes
# the callback to not occur for some reason. This
# also makes it easier to test.
# Don't unlock! The unlock will occur when the
# thread finishes.
# NOTE(yuriyz): A race condition with process_event()
# in callback is possible here if eventlet changes behavior.
# E.g., if the execution of the new thread (that handles the
# event processing) finishes before we get here, that new
# thread may emit the "end" notification before we emit the
# following "start" notification.
except Exception as e:
with excutils.save_and_reraise_exception():
# Execute the on_error hook if set
if self._on_error_method:
self._on_error_method(e, *self._on_error_args,
except Exception:
LOG.warning("Task's on_error hook failed to "
"call %(method)s on node %(node)s",
{'method': self._on_error_method.__name__,
'node': self.node.uuid})
if fut is not None:
# This means the add_done_callback() failed for some
# reason. Nuke the thread.