Source code for ironic.conductor.task_manager

# 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
#
#         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.

"""
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:

    task.context
        The context passed to TaskManager()
    task.shared
        False if Node is locked, True if it is not locked. (The
        'shared' kwarg arg of TaskManager())
    task.node
        The Node object
    task.ports
        Ports belonging to the Node
    task.portgroups
        Portgroups belonging to the Node
    task.volume_connectors
        Storage connectors belonging to the Node
    task.volume_targets
        Storage targets assigned to the Node
    task.driver
        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:
        task.driver.power.power_on(task.node)

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>
        task.spawn_after(self._spawn_worker,
                         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>
        task.set_spawn_error_hook(on_error)
        task.spawn_after(self._spawn_worker,
                         utils.node_power_action, task, new_state)

"""

import copy
import functools

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

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__)

CONF = cfg.CONF


[docs]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". """ @functools.wraps(f) 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] else: 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. task.context.ensure_thread_contain_context() return f(*args, **kwargs) return wrapper
[docs]def acquire(context, *args, **kwargs): """Shortcut for acquiring a lock on a Node. :param context: Request context. :returns: An instance of :class:`TaskManager`. """ # NOTE(lintan): This is a workaround to set the context of periodic tasks. context.ensure_thread_contain_context() return TaskManager(context, *args, **kwargs)
[docs]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, purpose='unspecified action', retry=True, load_driver=True): """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 purpose: human-readable purpose to put to debug logs. :param retry: whether to retry locking if it fails. Default: True. :param load_driver: whether to load the ``driver`` object. Set this to False if loading the driver is undesired or impossible. :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._retry = retry 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 try: node = objects.Node.get(context, node_id) LOG.debug("Attempting to get %(type)s lock on node %(node)s (for " "%(purpose)s)", {'type': 'shared' if shared else 'exclusive', 'node': node.uuid, 'purpose': purpose}) if not self.shared: self._lock() else: self._debug_timer.restart() self.node = node self.ports = objects.Port.list_by_node_id(context, self.node.id) self.portgroups = objects.Portgroup.list_by_node_id(context, self.node.id) self.volume_connectors = objects.VolumeConnector.list_by_node_id( context, self.node.id) self.volume_targets = objects.VolumeTarget.list_by_node_id( context, self.node.id) if load_driver: self.driver = driver_factory.build_driver_for_task(self) else: self.driver = None except Exception: with excutils.save_and_reraise_exception(): self.release_resources() @property def node(self): return self._node @node.setter def node(self, node): self._node = node if node is not None: self.fsm.initialize(start_state=self.node.provision_state, target_state=self.node.target_provision_state) def _lock(self): self._debug_timer.restart() if self._retry: attempts = CONF.conductor.node_locked_retry_attempts else: attempts = 1 # 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. @retrying.retry( retry_on_exception=lambda e: isinstance(e, exception.NodeLocked), stop_max_attempt_number=attempts, wait_fixed=CONF.conductor.node_locked_retry_interval * 1000) def reserve_node(): self.node = objects.Node.reserve(self.context, CONF.host, self.node_id) 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()}) self._debug_timer.restart() reserve_node()
[docs] 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 "node_locked_retry_attempts" """ 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 ' 'seconds)', {'uuid': self.node.uuid, 'purpose': self._purpose, 'time': self._debug_timer.elapsed()}) self._lock() self.shared = False
[docs] 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 exits. :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
[docs] 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
[docs] 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: try: if self.node: objects.Node.release(self.context, CONF.host, self.node.id) except exception.NodeNotFound: # squelch the exception if the node was deleted # within the task's context. pass 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__ try: exc = future.exception() except futurist.CancelledError: LOG.exception("Execution of %(method)s for node %(node)s " "was canceled.", {'method': method, 'node': node.uuid}) else: if exc is not None: msg = _("Async execution of %(method)s failed with error: " "%(error)s") % {'method': method, 'error': str(exc)} node.last_error = msg try: node.save() except exception.NodeNotFound: pass def _notify_provision_state_change(self): """Emit notification about change of the node provision state.""" if self._event is None: return 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 else: 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 else: status = fields.NotificationStatus.SUCCESS notify.emit_provision_set_notification( 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.""" try: self._write_exception(fut) finally: self.release_resources()
[docs] 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 prev_target_state) :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.node.target_provision_state) 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 else: 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 self.node.save() log_message = ('Node %(node)s moved to provision state "%(state)s" ' 'from state "%(previous)s"; target provision state is ' '"%(target)s"' % {'node': self.node.uuid, 'state': self.node.provision_state, 'target': self.node.target_provision_state, 'previous': self._prev_provision_state}) if (self.node.provision_state.endswith('failed') or self.node.provision_state == 'error'): LOG.error(log_message) else: LOG.info(log_message) if callback is None: self._notify_provision_state_change() else: # 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 try: fut = self._spawn_method(*self._spawn_args, **self._spawn_kwargs) # NOTE(comstud): Trying to use a lambda here causes # the callback to not occur for some reason. This # also makes it easier to test. fut.add_done_callback(self._thread_release_resources) # 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. self._notify_provision_state_change() return except Exception as e: with excutils.save_and_reraise_exception(): try: # Execute the on_error hook if set if self._on_error_method: self._on_error_method(e, *self._on_error_args, **self._on_error_kwargs) 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. fut.cancel() self.release_resources() self.release_resources()