Refactoring of create_volume to use taskflow.

Move the create_volume workflow to using taskflow and
split that workflow into three major pieces (each with
there own workflow) and create tasks that perform the
individual required actions to accomplish the pieces
desired outcome.

1. An api workflow composed of the following tasks:
  - Extracting volume request (which checks types, values) and creates a
    standard output for other tasks to work on (allowing further tasks to be
    plugged in the chain without having to worry about other tasks output
    formats).
  - Quota reservation (rolled back on failure).
  - Database entry creation.
  - Quota committing.
  - Volume RPC casting to volume scheduler or to targeted volume manager.
2. A scheduler workflow composed of the following tasks:
  - Extracting scheduler request specification for further tasks to use.
  - Change status & notify (activated only on failure).
  - Create volume scheduler driver call (which will itself RPC cast to a
    targeted volume manager).
3. A manager workflow composed of the following tasks:
  - Extract volume request specification from incoming request for
    further tasks to use. This also breaks up the incoming request into the 4
    volume types that can be created later.
  - Change status & notify on failure or reschedule on failure, this is
    dependent on if rescheduling is enabled *and* which exception types are
    thrown from the volume creation code.
  - Create volume from specification
    - This contains the code to create from image, create raw volume, create
      from source volume, create from snapshot using the extracted volume
      specification.
  - Change status & notify success.

Key benefits:
  - Handled exceptions in a easier to understand, easier to review and more
    reliable way than they are currently being handled.
  - Rescheduling is now easier to understand.
  - Easier to understand structure with tasks that consume inputs, take some
    action on them and produce outputs and revert on subsequent failure using
    whatever they produced to know how to revert.
  - Ability to add new unit tests that can test individual task actions by
    providing mock task inputs and validating expected task outputs.

Future additions:
  - Eventual addition of resumption logic to recover from operations stopped
    halfway through.
  - Ability to centrally orchestrate the tasks and pick and choice how
    reconciliation of failures based on code or policies.

Part of bp: cinder-state-machine

Change-Id: I96b688511b35014a8c006e4d30b875dcaf409d93

cinder/exception.py

@@ -580,6 +580,22 @@ class GlanceMetadataExists(Invalid):
                 " exists for volume id %(volume_id)s")
 
 
+class ExportFailure(Invalid):
+    message = _("Failed to export for volume: %(reason)s")
+
+
+class MetadataCreateFailure(Invalid):
+    message = _("Failed to create metadata for volume: %(reason)s")
+
+
+class MetadataUpdateFailure(Invalid):
+    message = _("Failed to update metadata for volume: %(reason)s")
+
+
+class MetadataCopyFailure(Invalid):
+    message = _("Failed to copy metadata to volume: %(reason)s")
+
+
 class ImageCopyFailure(Invalid):
     message = _("Failed to copy image to volume: %(reason)s")
 

cinder/policy.py

@@ -62,6 +62,20 @@ def _set_brain(data):
     policy.set_brain(policy.Brain.load_json(data, default_rule))
 
 
+def enforce_action(context, action):
+    """Checks that the action can be done by the given context.
+
+    Applies a check to ensure the context's project_id and user_id can be
+    applied to the given action using the policy enforcement api.
+    """
+
+    target = {
+        'project_id': context.project_id,
+        'user_id': context.user_id,
+    }
+    enforce(context, action, target)
+
+
 def enforce(context, action, target):
     """Verifies that the action is valid on the target in this context.
 

cinder/scheduler/manager.py

@@ -31,8 +31,10 @@ from cinder.openstack.common import excutils
 from cinder.openstack.common import importutils
 from cinder.openstack.common import log as logging
 from cinder.openstack.common.notifier import api as notifier
+from cinder.volume.flows import create_volume
 from cinder.volume import rpcapi as volume_rpcapi
 
+from cinder.taskflow import states
 
 scheduler_driver_opt = cfg.StrOpt('scheduler_driver',
                                   default='cinder.scheduler.filter_scheduler.'
@@ -81,61 +83,18 @@ class SchedulerManager(manager.Manager):
     def create_volume(self, context, topic, volume_id, snapshot_id=None,
                       image_id=None, request_spec=None,
                       filter_properties=None):
-        try:
-            if request_spec is None:
-                # For RPC version < 1.2 backward compatibility
-                request_spec = {}
-                volume_ref = db.volume_get(context, volume_id)
-                size = volume_ref.get('size')
-                availability_zone = volume_ref.get('availability_zone')
-                volume_type_id = volume_ref.get('volume_type_id')
-                vol_type = db.volume_type_get(context, volume_type_id)
-                volume_properties = {'size': size,
-                                     'availability_zone': availability_zone,
-                                     'volume_type_id': volume_type_id}
-                request_spec.update(
-                    {'volume_id': volume_id,
-                     'snapshot_id': snapshot_id,
-                     'image_id': image_id,
-                     'volume_properties': volume_properties,
-                     'volume_type': dict(vol_type).iteritems()})
 
-            self.driver.schedule_create_volume(context, request_spec,
-                                               filter_properties)
-        except exception.NoValidHost as ex:
-            volume_state = {'volume_state': {'status': 'error'}}
-            self._set_volume_state_and_notify('create_volume',
-                                              volume_state,
-                                              context, ex, request_spec)
-        except Exception as ex:
-            with excutils.save_and_reraise_exception():
-                volume_state = {'volume_state': {'status': 'error'}}
-                self._set_volume_state_and_notify('create_volume',
-                                                  volume_state,
-                                                  context, ex, request_spec)
+        flow = create_volume.get_scheduler_flow(db, self.driver,
+                                                request_spec,
+                                                filter_properties,
+                                                volume_id, snapshot_id,
+                                                image_id)
+        assert flow, _('Schedule volume flow not retrieved')
 
-    def _set_volume_state_and_notify(self, method, updates, context, ex,
-                                     request_spec):
-        LOG.error(_("Failed to schedule_%(method)s: %(ex)s") %
-                  {'method': method, 'ex': ex})
-
-        volume_state = updates['volume_state']
-        properties = request_spec.get('volume_properties', {})
-
-        volume_id = request_spec.get('volume_id', None)
-
-        if volume_id:
-            db.volume_update(context, volume_id, volume_state)
-
-        payload = dict(request_spec=request_spec,
-                       volume_properties=properties,
-                       volume_id=volume_id,
-                       state=volume_state,
-                       method=method,
-                       reason=ex)
-
-        notifier.notify(context, notifier.publisher_id("scheduler"),
-                        'scheduler.' + method, notifier.ERROR, payload)
+        flow.run(context)
+        if flow.state != states.SUCCESS:
+            LOG.warn(_("Failed to successfully complete"
+                       " schedule volume using flow: %s"), flow)
 
     def request_service_capabilities(self, context):
         volume_rpcapi.VolumeAPI().publish_service_capabilities(context)
@@ -164,3 +123,28 @@ class SchedulerManager(manager.Manager):
             volume_rpcapi.VolumeAPI().migrate_volume(context, volume_ref,
                                                      tgt_host,
                                                      force_host_copy)
+
+    def _set_volume_state_and_notify(self, method, updates, context, ex,
+                                     request_spec):
+        # TODO(harlowja): move into a task that just does this later.
+
+        LOG.error(_("Failed to schedule_%(method)s: %(ex)s") %
+                  {'method': method, 'ex': ex})
+
+        volume_state = updates['volume_state']
+        properties = request_spec.get('volume_properties', {})
+
+        volume_id = request_spec.get('volume_id', None)
+
+        if volume_id:
+            db.volume_update(context, volume_id, volume_state)
+
+        payload = dict(request_spec=request_spec,
+                       volume_properties=properties,
+                       volume_id=volume_id,
+                       state=volume_state,
+                       method=method,
+                       reason=ex)
+
+        notifier.notify(context, notifier.publisher_id("scheduler"),
+                        'scheduler.' + method, notifier.ERROR, payload)

cinder/taskflow/__init__.py

@@ -0,0 +1 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4

cinder/taskflow/decorators.py

@@ -0,0 +1,276 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. 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.
+
+import collections
+import functools
+import inspect
+import types
+
+# These arguments are ones that we will skip when parsing for requirements
+# for a function to operate (when used as a task).
+AUTO_ARGS = ('self', 'context', 'cls')
+
+
+def is_decorated(functor):
+    if not isinstance(functor, (types.MethodType, types.FunctionType)):
+        return False
+    return getattr(extract(functor), '__task__', False)
+
+
+def extract(functor):
+    # Extract the underlying functor if its a method since we can not set
+    # attributes on instance methods, this is supposedly fixed in python 3
+    # and later.
+    #
+    # TODO(harlowja): add link to this fix.
+    assert isinstance(functor, (types.MethodType, types.FunctionType))
+    if isinstance(functor, types.MethodType):
+        return functor.__func__
+    else:
+        return functor
+
+
+def _mark_as_task(functor):
+    setattr(functor, '__task__', True)
+
+
+def _get_wrapped(function):
+    """Get the method at the bottom of a stack of decorators."""
+
+    if hasattr(function, '__wrapped__'):
+        return getattr(function, '__wrapped__')
+
+    if not hasattr(function, 'func_closure') or not function.func_closure:
+        return function
+
+    def _get_wrapped_function(function):
+        if not hasattr(function, 'func_closure') or not function.func_closure:
+            return None
+
+        for closure in function.func_closure:
+            func = closure.cell_contents
+
+            deeper_func = _get_wrapped_function(func)
+            if deeper_func:
+                return deeper_func
+            elif hasattr(closure.cell_contents, '__call__'):
+                return closure.cell_contents
+
+    return _get_wrapped_function(function)
+
+
+def _take_arg(a):
+    if a in AUTO_ARGS:
+        return False
+    # In certain decorator cases it seems like we get the function to be
+    # decorated as an argument, we don't want to take that as a real argument.
+    if isinstance(a, collections.Callable):
+        return False
+    return True
+
+
+def wraps(fn):
+    """This will not be needed in python 3.2 or greater which already has this
+    built-in to its functools.wraps method.
+    """
+
+    def wrapper(f):
+        f = functools.wraps(fn)(f)
+        f.__wrapped__ = getattr(fn, '__wrapped__', fn)
+        return f
+
+    return wrapper
+
+
+def locked(f):
+
+    @wraps(f)
+    def wrapper(self, *args, **kwargs):
+        with self._lock:
+            return f(self, *args, **kwargs)
+
+    return wrapper
+
+
+def task(*args, **kwargs):
+    """Decorates a given function and ensures that all needed attributes of
+    that function are set so that the function can be used as a task.
+    """
+
+    def decorator(f):
+        w_f = extract(f)
+
+        def noop(*args, **kwargs):
+            pass
+
+        # Mark as being a task
+        _mark_as_task(w_f)
+
+        # By default don't revert this.
+        w_f.revert = kwargs.pop('revert_with', noop)
+
+        # Associate a name of this task that is the module + function name.
+        w_f.name = "%s.%s" % (f.__module__, f.__name__)
+
+        # Sets the version of the task.
+        version = kwargs.pop('version', (1, 0))
+        f = _versionize(*version)(f)
+
+        # Attach any requirements this function needs for running.
+        requires_what = kwargs.pop('requires', [])
+        f = _requires(*requires_what, **kwargs)(f)
+
+        # Attach any optional requirements this function needs for running.
+        optional_what = kwargs.pop('optional', [])
+        f = _optional(*optional_what, **kwargs)(f)
+
+        # Attach any items this function provides as output
+        provides_what = kwargs.pop('provides', [])
+        f = _provides(*provides_what, **kwargs)(f)
+
+        @wraps(f)
+        def wrapper(*args, **kwargs):
+            return f(*args, **kwargs)
+
+        return wrapper
+
+    # This is needed to handle when the decorator has args or the decorator
+    # doesn't have args, python is rather weird here...
+    if kwargs or not args:
+        return decorator
+    else:
+        if isinstance(args[0], collections.Callable):
+            return decorator(args[0])
+        else:
+            return decorator
+
+
+def _versionize(major, minor=None):
+    """A decorator that marks the wrapped function with a major & minor version
+    number.
+    """
+
+    if minor is None:
+        minor = 0
+
+    def decorator(f):
+        w_f = extract(f)
+        w_f.version = (major, minor)
+
+        @wraps(f)
+        def wrapper(*args, **kwargs):
+            return f(*args, **kwargs)
+
+        return wrapper
+
+    return decorator
+
+
+def _optional(*args, **kwargs):
+    """Attaches a set of items that the decorated function would like as input
+    to the functions underlying dictionary.
+    """
+
+    def decorator(f):
+        w_f = extract(f)
+
+        if not hasattr(w_f, 'optional'):
+            w_f.optional = set()
+
+        w_f.optional.update([a for a in args if _take_arg(a)])
+
+        @wraps(f)
+        def wrapper(*args, **kwargs):
+            return f(*args, **kwargs)
+
+        return wrapper
+
+    # This is needed to handle when the decorator has args or the decorator
+    # doesn't have args, python is rather weird here...
+    if kwargs or not args:
+        return decorator
+    else:
+        if isinstance(args[0], collections.Callable):
+            return decorator(args[0])
+        else:
+            return decorator
+
+
+def _requires(*args, **kwargs):
+    """Attaches a set of items that the decorated function requires as input
+    to the functions underlying dictionary.
+    """
+
+    def decorator(f):
+        w_f = extract(f)
+
+        if not hasattr(w_f, 'requires'):
+            w_f.requires = set()
+
+        if kwargs.pop('auto_extract', True):
+            inspect_what = _get_wrapped(f)
+            f_args = inspect.getargspec(inspect_what).args
+            w_f.requires.update([a for a in f_args if _take_arg(a)])
+
+        w_f.requires.update([a for a in args if _take_arg(a)])
+
+        @wraps(f)
+        def wrapper(*args, **kwargs):
+            return f(*args, **kwargs)
+
+        return wrapper
+
+    # This is needed to handle when the decorator has args or the decorator
+    # doesn't have args, python is rather weird here...
+    if kwargs or not args:
+        return decorator
+    else:
+        if isinstance(args[0], collections.Callable):
+            return decorator(args[0])
+        else:
+            return decorator
+
+
+def _provides(*args, **kwargs):
+    """Attaches a set of items that the decorated function provides as output
+    to the functions underlying dictionary.
+    """
+
+    def decorator(f):
+        w_f = extract(f)
+
+        if not hasattr(f, 'provides'):
+            w_f.provides = set()
+
+        w_f.provides.update([a for a in args if _take_arg(a)])
+
+        @wraps(f)
+        def wrapper(*args, **kwargs):
+            return f(*args, **kwargs)
+
+        return wrapper
+
+    # This is needed to handle when the decorator has args or the decorator
+    # doesn't have args, python is rather weird here...
+    if kwargs or not args:
+        return decorator
+    else:
+        if isinstance(args[0], collections.Callable):
+            return decorator(args[0])
+        else:
+            return decorator

cinder/taskflow/exceptions.py

@@ -0,0 +1,69 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. 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.
+
+
+class TaskFlowException(Exception):
+    """Base class for exceptions emitted from this library."""
+    pass
+
+
+class Duplicate(TaskFlowException):
+    """Raised when a duplicate entry is found."""
+    pass
+
+
+class NotFound(TaskFlowException):
+    """Raised when some entry in some object doesn't exist."""
+    pass
+
+
+class AlreadyExists(TaskFlowException):
+    """Raised when some entry in some object already exists."""
+    pass
+
+
+class ClosedException(TaskFlowException):
+    """Raised when an access on a closed object occurs."""
+    pass
+
+
+class InvalidStateException(TaskFlowException):
+    """Raised when a task/job/workflow is in an invalid state when an
+    operation is attempting to apply to said task/job/workflow.
+    """
+    pass
+
+
+class UnclaimableJobException(TaskFlowException):
+    """Raised when a job can not be claimed."""
+    pass
+
+
+class JobNotFound(TaskFlowException):
+    """Raised when a job entry can not be found."""
+    pass
+
+
+class MissingDependencies(InvalidStateException):
+    """Raised when a task has dependencies that can not be satisified."""
+    message = ("%(task)s requires %(requirements)s but no other task produces"
+               " said requirements")
+
+    def __init__(self, task, requirements):
+        message = self.message % {'task': task, 'requirements': requirements}
+        super(MissingDependencies, self).__init__(message)

cinder/taskflow/patterns/__init__.py

@@ -0,0 +1 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4

cinder/taskflow/patterns/base.py

@@ -0,0 +1,214 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. 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.
+
+import abc
+import threading
+
+from cinder.openstack.common import uuidutils
+
+from cinder.taskflow import decorators
+from cinder.taskflow import exceptions as exc
+from cinder.taskflow import states
+from cinder.taskflow import utils
+
+
+class Flow(object):
+    """The base abstract class of all flow implementations.
+
+    It provides a set of parents to flows that have a concept of parent flows
+    as well as a state and state utility functions to the deriving classes. It
+    also provides a name and an identifier (uuid or other) to the flow so that
+    it can be uniquely identifed among many flows.
+
+    Flows are expected to provide (if desired) the following methods:
+    - add
+    - add_many
+    - interrupt
+    - reset
+    - rollback
+    - run
+    - soft_reset
+    """
+
+    __metaclass__ = abc.ABCMeta
+
+    # Common states that certain actions can be performed in. If the flow
+    # is not in these sets of states then it is likely that the flow operation
+    # can not succeed.
+    RESETTABLE_STATES = set([
+        states.INTERRUPTED,
+        states.SUCCESS,
+        states.PENDING,
+        states.FAILURE,
+    ])
+    SOFT_RESETTABLE_STATES = set([
+        states.INTERRUPTED,
+    ])
+    UNINTERRUPTIBLE_STATES = set([
+        states.FAILURE,
+        states.SUCCESS,
+        states.PENDING,
+    ])
+    RUNNABLE_STATES = set([
+        states.PENDING,
+    ])
+
+    def __init__(self, name, parents=None, uuid=None):
+        self._name = str(name)
+        # The state of this flow.
+        self._state = states.PENDING
+        # If this flow has a parent flow/s which need to be reverted if
+        # this flow fails then please include them here to allow this child
+        # to call the parents...
+        if parents:
+            self.parents = tuple(parents)
+        else:
+            self.parents = ()
+        # Any objects that want to listen when a wf/task starts/stops/completes
+        # or errors should be registered here. This can be used to monitor
+        # progress and record tasks finishing (so that it becomes possible to
+        # store the result of a task in some persistent or semi-persistent
+        # storage backend).
+        self.notifier = utils.TransitionNotifier()
+        self.task_notifier = utils.TransitionNotifier()
+        # Ensure that modifications and/or multiple runs aren't happening
+        # at the same time in the same flow at the same time.
+        self._lock = threading.RLock()
+        # Assign this flow a unique identifer.
+        if uuid:
+            self._id = str(uuid)
+        else:
+            self._id = uuidutils.generate_uuid()
+
+    @property
+    def name(self):
+        """A non-unique name for this flow (human readable)"""
+        return self._name
+
+    @property
+    def uuid(self):
+        """Uniquely identifies this flow"""
+        return "f-%s" % (self._id)
+
+    @property
+    def state(self):
+        """Provides a read-only view of the flow state."""
+        return self._state
+
+    def _change_state(self, context, new_state):
+        was_changed = False
+        old_state = self.state
+        with self._lock:
+            if self.state != new_state:
+                old_state = self.state
+                self._state = new_state
+                was_changed = True
+        if was_changed:
+            # Don't notify while holding the lock.
+            self.notifier.notify(self.state, details={
+                'context': context,
+                'flow': self,
+                'old_state': old_state,
+            })
+
+    def __str__(self):
+        lines = ["Flow: %s" % (self.name)]
+        lines.append("%s" % (self.uuid))
+        lines.append("%s" % (len(self.parents)))
+        lines.append("%s" % (self.state))
+        return "; ".join(lines)
+
+    @abc.abstractmethod
+    def add(self, task):
+        """Adds a given task to this flow.
+
+        Returns the uuid that is associated with the task for later operations
+        before and after it is ran.
+        """
+        raise NotImplementedError()
+
+    @decorators.locked
+    def add_many(self, tasks):
+        """Adds many tasks to this flow.
+
+        Returns a list of uuids (one for each task added).
+        """
+        uuids = []
+        for t in tasks:
+            uuids.append(self.add(t))
+        return uuids
+
+    def interrupt(self):
+        """Attempts to interrupt the current flow and any tasks that are
+        currently not running in the flow.
+
+        Returns how many tasks were interrupted (if any).
+        """
+        if self.state in self.UNINTERRUPTIBLE_STATES:
+            raise exc.InvalidStateException(("Can not interrupt when"
+                                             " in state %s") % (self.state))
+        # Note(harlowja): Do *not* acquire the lock here so that the flow may
+        # be interrupted while running. This does mean the the above check may
+        # not be valid but we can worry about that if it becomes an issue.
+        old_state = self.state
+        if old_state != states.INTERRUPTED:
+            self._state = states.INTERRUPTED
+            self.notifier.notify(self.state, details={
+                'context': None,
+                'flow': self,
+                'old_state': old_state,
+            })
+        return 0
+
+    @decorators.locked
+    def reset(self):
+        """Fully resets the internal state of this flow, allowing for the flow
+        to be ran again.
+
+        Note: Listeners are also reset.
+        """
+        if self.state not in self.RESETTABLE_STATES:
+            raise exc.InvalidStateException(("Can not reset when"
+                                             " in state %s") % (self.state))
+        self.notifier.reset()
+        self.task_notifier.reset()
+        self._change_state(None, states.PENDING)
+
+    @decorators.locked
+    def soft_reset(self):
+        """Partially resets the internal state of this flow, allowing for the
+        flow to be ran again from an interrupted state only.
+        """
+        if self.state not in self.SOFT_RESETTABLE_STATES:
+            raise exc.InvalidStateException(("Can not soft reset when"
+                                             " in state %s") % (self.state))
+        self._change_state(None, states.PENDING)
+
+    @decorators.locked
+    def run(self, context, *args, **kwargs):
+        """Executes the workflow."""
+        if self.state not in self.RUNNABLE_STATES:
+            raise exc.InvalidStateException("Unable to run flow when "
+                                            "in state %s" % (self.state))
+
+    @decorators.locked
+    def rollback(self, context, cause):
+        """Performs rollback of this workflow and any attached parent workflows
+        if present.
+        """
+        pass

cinder/taskflow/patterns/linear_flow.py

@@ -0,0 +1,271 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. 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.
+
+import collections
+import logging
+
+from cinder.openstack.common import excutils
+
+from cinder.taskflow import decorators
+from cinder.taskflow import exceptions as exc
+from cinder.taskflow import states
+from cinder.taskflow import utils
+
+from cinder.taskflow.patterns import base
+
+LOG = logging.getLogger(__name__)
+
+
+class Flow(base.Flow):
+    """"A linear chain of tasks that can be applied in order as one unit and
+    rolled back as one unit using the reverse order that the tasks have
+    been applied in.
+
+    Note(harlowja): Each task in the chain must have requirements
+    which are satisfied by the previous task/s in the chain.
+    """
+
+    def __init__(self, name, parents=None, uuid=None):
+        super(Flow, self).__init__(name, parents, uuid)
+        # The tasks which have been applied will be collected here so that they
+        # can be reverted in the correct order on failure.
+        self._accumulator = utils.RollbackAccumulator()
+        # Tasks results are stored here. Lookup is by the uuid that was
+        # returned from the add function.
+        self.results = {}
+        # The previously left off iterator that can be used to resume from
+        # the last task (if interrupted and soft-reset).
+        self._leftoff_at = None
+        # All runners to run are collected here.
+        self._runners = []
+        self._connected = False
+        # The resumption strategy to use.
+        self.resumer = None
+
+    @decorators.locked
+    def add(self, task):
+        """Adds a given task to this flow."""
+        assert isinstance(task, collections.Callable)
+        r = utils.Runner(task)
+        r.runs_before = list(reversed(self._runners))
+        self._runners.append(r)
+        self._reset_internals()
+        return r.uuid
+
+    def _reset_internals(self):
+        self._connected = False
+        self._leftoff_at = None
+
+    def _associate_providers(self, runner):
+        # Ensure that some previous task provides this input.
+        who_provides = {}
+        task_requires = runner.requires
+        for r in task_requires:
+            provider = None
+            for before_me in runner.runs_before:
+                if r in before_me.provides:
+                    provider = before_me
+                    break
+            if provider:
+                who_provides[r] = provider
+        # Ensure that the last task provides all the needed input for this
+        # task to run correctly.
+        missing_requires = task_requires - set(who_provides.keys())
+        if missing_requires:
+            raise exc.MissingDependencies(runner, sorted(missing_requires))
+        runner.providers.update(who_provides)
+
+    def __str__(self):
+        lines = ["LinearFlow: %s" % (self.name)]
+        lines.append("%s" % (self.uuid))
+        lines.append("%s" % (len(self._runners)))
+        lines.append("%s" % (len(self.parents)))
+        lines.append("%s" % (self.state))
+        return "; ".join(lines)
+
+    @decorators.locked
+    def remove(self, uuid):
+        index_removed = -1
+        for (i, r) in enumerate(self._runners):
+            if r.uuid == uuid:
+                index_removed = i
+                break
+        if index_removed == -1:
+            raise ValueError("No runner found with uuid %s" % (uuid))
+        else:
+            removed = self._runners.pop(index_removed)
+            self._reset_internals()
+            # Go and remove it from any runner after the removed runner since
+            # those runners may have had an attachment to it.
+            for r in self._runners[index_removed:]:
+                try:
+                    r.runs_before.remove(removed)
+                except (IndexError, ValueError):
+                    pass
+
+    def __len__(self):
+        return len(self._runners)
+
+    def _connect(self):
+        if self._connected:
+            return self._runners
+        for r in self._runners:
+            r.providers = {}
+        for r in reversed(self._runners):
+            self._associate_providers(r)
+        self._connected = True
+        return self._runners
+
+    def _ordering(self):
+        return iter(self._connect())
+
+    @decorators.locked
+    def run(self, context, *args, **kwargs):
+        super(Flow, self).run(context, *args, **kwargs)
+
+        def resume_it():
+            if self._leftoff_at is not None:
+                return ([], self._leftoff_at)
+            if self.resumer:
+                (finished, leftover) = self.resumer.resume(self,
+                                                           self._ordering())
+            else:
+                finished = []
+                leftover = self._ordering()
+            return (finished, leftover)
+
+        self._change_state(context, states.STARTED)
+        try:
+            those_finished, leftover = resume_it()
+        except Exception:
+            with excutils.save_and_reraise_exception():
+                self._change_state(context, states.FAILURE)
+
+        def run_it(runner, failed=False, result=None, simulate_run=False):
+            try:
+                # Add the task to be rolled back *immediately* so that even if
+                # the task fails while producing results it will be given a
+                # chance to rollback.
+                rb = utils.RollbackTask(context, runner.task, result=None)
+                self._accumulator.add(rb)
+                self.task_notifier.notify(states.STARTED, details={
+                    'context': context,
+                    'flow': self,
+                    'runner': runner,
+                })
+                if not simulate_run:
+                    result = runner(context, *args, **kwargs)
+                else:
+                    if failed:
+                        # TODO(harlowja): make this configurable??
+                        # If we previously failed, we want to fail again at
+                        # the same place.
+                        if not result:
+                            # If no exception or exception message was provided
+                            # or captured from the previous run then we need to
+                            # form one for this task.
+                            result = "%s failed running." % (runner.task)
+                        if isinstance(result, basestring):
+                            result = exc.InvalidStateException(result)
+                        if not isinstance(result, Exception):
+                            LOG.warn("Can not raise a non-exception"
+                                     " object: %s", result)
+                            result = exc.InvalidStateException()
+                        raise result
+                # Adjust the task result in the accumulator before
+                # notifying others that the task has finished to
+                # avoid the case where a listener might throw an
+                # exception.
+                rb.result = result
+                runner.result = result
+                self.results[runner.uuid] = result
+                self.task_notifier.notify(states.SUCCESS, details={
+                    'context': context,
+                    'flow': self,
+                    'runner': runner,
+                })
+            except Exception as e:
+                runner.result = e
+                cause = utils.FlowFailure(runner, self, e)
+                with excutils.save_and_reraise_exception():
+                    # Notify any listeners that the task has errored.
+                    self.task_notifier.notify(states.FAILURE, details={
+                        'context': context,
+                        'flow': self,
+                        'runner': runner,
+                    })
+                    self.rollback(context, cause)
+
+        if len(those_finished):
+            self._change_state(context, states.RESUMING)
+            for (r, details) in those_finished:
+                # Fake running the task so that we trigger the same
+                # notifications and state changes (and rollback that
+                # would have happened in a normal flow).
+                failed = states.FAILURE in details.get('states', [])
+                result = details.get('result')
+                run_it(r, failed=failed, result=result, simulate_run=True)
+
+        self._leftoff_at = leftover
+        self._change_state(context, states.RUNNING)
+        if self.state == states.INTERRUPTED:
+            return
+
+        was_interrupted = False
+        for r in leftover:
+            r.reset()
+            run_it(r)
+            if self.state == states.INTERRUPTED:
+                was_interrupted = True
+                break
+
+        if not was_interrupted:
+            # Only gets here if everything went successfully.
+            self._change_state(context, states.SUCCESS)
+            self._leftoff_at = None
+
+    @decorators.locked
+    def reset(self):
+        super(Flow, self).reset()
+        self.results = {}
+        self.resumer = None
+        self._accumulator.reset()
+        self._reset_internals()
+
+    @decorators.locked
+    def rollback(self, context, cause):
+        # Performs basic task by task rollback by going through the reverse
+        # order that tasks have finished and asking said task to undo whatever
+        # it has done. If this flow has any parent flows then they will
+        # also be called to rollback any tasks said parents contain.
+        #
+        # Note(harlowja): if a flow can more simply revert a whole set of
+        # tasks via a simpler command then it can override this method to
+        # accomplish that.
+        #
+        # For example, if each task was creating a file in a directory, then
+        # it's easier to just remove the directory than to ask each task to
+        # delete its file individually.
+        self._change_state(context, states.REVERTING)
+        try:
+            self._accumulator.rollback(cause)
+        finally:
+            self._change_state(context, states.FAILURE)
+        # Rollback any parents flows if they exist...
+        for p in self.parents:
+            p.rollback(context, cause)

cinder/taskflow/states.py

@@ -0,0 +1,40 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. 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.
+
+# Job states.
+CLAIMED = 'CLAIMED'
+FAILURE = 'FAILURE'
+PENDING = 'PENDING'
+RUNNING = 'RUNNING'
+SUCCESS = 'SUCCESS'
+UNCLAIMED = 'UNCLAIMED'
+
+# Flow states.
+FAILURE = FAILURE
+INTERRUPTED = 'INTERRUPTED'
+PENDING = 'PENDING'
+RESUMING = 'RESUMING'
+REVERTING = 'REVERTING'
+RUNNING = RUNNING
+STARTED = 'STARTED'
+SUCCESS = SUCCESS
+
+# Task states.
+FAILURE = FAILURE
+STARTED = STARTED
+SUCCESS = SUCCESS

cinder/taskflow/task.py

@@ -0,0 +1,66 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. 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.
+
+import abc
+
+from cinder.taskflow import utils
+
+
+class Task(object):
+    """An abstraction that defines a potential piece of work that can be
+    applied and can be reverted to undo the work as a single unit.
+    """
+    __metaclass__ = abc.ABCMeta
+
+    def __init__(self, name):
+        self.name = name
+        # An *immutable* input 'resource' name set this task depends
+        # on existing before this task can be applied.
+        self.requires = set()
+        # An *immutable* input 'resource' name set this task would like to
+        # depends on existing before this task can be applied (but does not
+        # strongly depend on existing).
+        self.optional = set()
+        # An *immutable* output 'resource' name set this task
+        # produces that other tasks may depend on this task providing.
+        self.provides = set()
+        # This identifies the version of the task to be ran which
+        # can be useful in resuming older versions of tasks. Standard
+        # major, minor version semantics apply.
+        self.version = (1, 0)
+
+    def __str__(self):
+        return "%s==%s" % (self.name, utils.join(self.version, with_what="."))
+
+    @abc.abstractmethod
+    def __call__(self, context, *args, **kwargs):
+        """Activate a given task which will perform some operation and return.
+
+           This method can be used to apply some given context and given set
+           of args and kwargs to accomplish some goal. Note that the result
+           that is returned needs to be serializable so that it can be passed
+           back into this task if reverting is triggered.
+        """
+        raise NotImplementedError()
+
+    def revert(self, context, result, cause):
+        """Revert this task using the given context, result that the apply
+           provided as well as any information which may have caused
+           said reversion.
+        """
+        pass

cinder/taskflow/utils.py

@@ -0,0 +1,464 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. 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.
+
+import collections
+import contextlib
+import copy
+import logging
+import re
+import sys
+import threading
+import time
+import types
+
+from cinder.openstack.common import uuidutils
+
+from cinder.taskflow import decorators
+
+LOG = logging.getLogger(__name__)
+
+
+def get_attr(task, field, default=None):
+    if decorators.is_decorated(task):
+        # If its a decorated functor then the attributes will be either
+        # in the underlying function of the instancemethod or the function
+        # itself.
+        task = decorators.extract(task)
+    return getattr(task, field, default)
+
+
+def join(itr, with_what=","):
+    pieces = [str(i) for i in itr]
+    return with_what.join(pieces)
+
+
+def get_many_attr(obj, *attrs):
+    many = []
+    for a in attrs:
+        many.append(get_attr(obj, a, None))
+    return many
+
+
+def get_task_version(task):
+    """Gets a tasks *string* version, whether it is a task object/function."""
+    task_version = get_attr(task, 'version')
+    if isinstance(task_version, (list, tuple)):
+        task_version = join(task_version, with_what=".")
+    if task_version is not None and not isinstance(task_version, basestring):
+        task_version = str(task_version)
+    return task_version
+
+
+def get_task_name(task):
+    """Gets a tasks *string* name, whether it is a task object/function."""
+    task_name = ""
+    if isinstance(task, (types.MethodType, types.FunctionType)):
+        # If its a function look for the attributes that should have been
+        # set using the task() decorator provided in the decorators file. If
+        # those have not been set, then we should at least have enough basic
+        # information (not a version) to form a useful task name.
+        task_name = get_attr(task, 'name')
+        if not task_name:
+            name_pieces = [a for a in get_many_attr(task,
+                                                    '__module__',
+                                                    '__name__')
+                           if a is not None]
+            task_name = join(name_pieces, ".")
+    else:
+        task_name = str(task)
+    return task_name
+
+
+def is_version_compatible(version_1, version_2):
+    """Checks for major version compatibility of two *string" versions."""
+    if version_1 == version_2:
+        # Equivalent exactly, so skip the rest.
+        return True
+
+    def _convert_to_pieces(version):
+        try:
+            pieces = []
+            for p in version.split("."):
+                p = p.strip()
+                if not len(p):
+                    pieces.append(0)
+                    continue
+                # Clean off things like 1alpha, or 2b and just select the
+                # digit that starts that entry instead.
+                p_match = re.match(r"(\d+)([A-Za-z]*)(.*)", p)
+                if p_match:
+                    p = p_match.group(1)
+                pieces.append(int(p))
+        except (AttributeError, TypeError, ValueError):
+            pieces = []
+        return pieces
+
+    version_1_pieces = _convert_to_pieces(version_1)
+    version_2_pieces = _convert_to_pieces(version_2)
+    if len(version_1_pieces) == 0 or len(version_2_pieces) == 0:
+        return False
+
+    # Ensure major version compatibility to start.
+    major1 = version_1_pieces[0]
+    major2 = version_2_pieces[0]
+    if major1 != major2:
+        return False
+    return True
+
+
+def await(check_functor, timeout=None):
+    if timeout is not None:
+        end_time = time.time() + max(0, timeout)
+    else:
+        end_time = None
+    # Use the same/similar scheme that the python condition class uses.
+    delay = 0.0005
+    while not check_functor():
+        time.sleep(delay)
+        if end_time is not None:
+            remaining = end_time - time.time()
+            if remaining <= 0:
+                return False
+            delay = min(delay * 2, remaining, 0.05)
+        else:
+            delay = min(delay * 2, 0.05)
+    return True
+
+
+class LastFedIter(object):
+    """An iterator which yields back the first item and then yields back
+    results from the provided iterator.
+    """
+
+    def __init__(self, first, rest_itr):
+        self.first = first
+        self.rest_itr = rest_itr
+
+    def __iter__(self):
+        yield self.first
+        for i in self.rest_itr:
+            yield i
+
+
+class FlowFailure(object):
+    """When a task failure occurs the following object will be given to revert
+       and can be used to interrogate what caused the failure.
+    """
+
+    def __init__(self, runner, flow, exception):
+        self.runner = runner
+        self.flow = flow
+        self.exc = exception
+        self.exc_info = sys.exc_info()
+
+
+class RollbackTask(object):
+    """A helper task that on being called will call the underlying callable
+    tasks revert method (if said method exists).
+    """
+
+    def __init__(self, context, task, result):
+        self.task = task
+        self.result = result
+        self.context = context
+
+    def __str__(self):
+        return str(self.task)
+
+    def __call__(self, cause):
+        if ((hasattr(self.task, "revert") and
+             isinstance(self.task.revert, collections.Callable))):
+            self.task.revert(self.context, self.result, cause)
+
+
+class Runner(object):
+    """A helper class that wraps a task and can find the needed inputs for
+    the task to run, as well as providing a uuid and other useful functionality
+    for users of the task.
+
+    TODO(harlowja): replace with the task details object or a subclass of
+    that???
+    """
+
+    def __init__(self, task, uuid=None):
+        assert isinstance(task, collections.Callable)
+        self.task = task
+        self.providers = {}
+        self.runs_before = []
+        self.result = None
+        if not uuid:
+            self._id = uuidutils.generate_uuid()
+        else:
+            self._id = str(uuid)
+
+    @property
+    def uuid(self):
+        return "r-%s" % (self._id)
+
+    @property
+    def requires(self):
+        return set(get_attr(self.task, 'requires', []))
+
+    @property
+    def provides(self):
+        return set(get_attr(self.task, 'provides', []))
+
+    @property
+    def optional(self):
+        return set(get_attr(self.task, 'optional', []))
+
+    @property
+    def version(self):
+        return get_task_version(self.task)
+
+    @property
+    def name(self):
+        return get_task_name(self.task)
+
+    def reset(self):
+        self.result = None
+
+    def __str__(self):
+        lines = ["Runner: %s" % (self.name)]
+        lines.append("%s" % (self.uuid))
+        lines.append("%s" % (self.version))
+        return "; ".join(lines)
+
+    def __call__(self, *args, **kwargs):
+        # Find all of our inputs first.
+        kwargs = dict(kwargs)
+        for (k, who_made) in self.providers.iteritems():
+            if who_made.result and k in who_made.result:
+                kwargs[k] = who_made.result[k]
+            else:
+                kwargs[k] = None
+        optional_keys = self.optional
+        optional_missing_keys = optional_keys - set(kwargs.keys())
+        if optional_missing_keys:
+            for k in optional_missing_keys:
+                for r in self.runs_before:
+                    r_provides = r.provides
+                    if k in r_provides and r.result and k in r.result:
+                        kwargs[k] = r.result[k]
+                        break
+        # And now finally run.
+        self.result = self.task(*args, **kwargs)
+        return self.result
+
+
+class TransitionNotifier(object):
+    """A utility helper class that can be used to subscribe to
+    notifications of events occuring as well as allow a entity to post said
+    notifications to subscribers.
+    """
+
+    RESERVED_KEYS = ('details',)
+    ANY = '*'
+
+    def __init__(self):
+        self._listeners = collections.defaultdict(list)
+
+    def reset(self):
+        self._listeners = collections.defaultdict(list)
+
+    def notify(self, state, details):
+        listeners = list(self._listeners.get(self.ANY, []))
+        for i in self._listeners[state]:
+            if i not in listeners:
+                listeners.append(i)
+        if not listeners:
+            return
+        for (callback, args, kwargs) in listeners:
+            if args is None:
+                args = []
+            if kwargs is None:
+                kwargs = {}
+            kwargs['details'] = details
+            try:
+                callback(state, *args, **kwargs)
+            except Exception:
+                LOG.exception(("Failure calling callback %s to notify about"
+                               " state transition %s"), callback, state)
+
+    def register(self, state, callback, args=None, kwargs=None):
+        assert isinstance(callback, collections.Callable)
+        for i, (cb, args, kwargs) in enumerate(self._listeners.get(state, [])):
+            if cb is callback:
+                raise ValueError("Callback %s already registered" % (callback))
+        if kwargs:
+            for k in self.RESERVED_KEYS:
+                if k in kwargs:
+                    raise KeyError(("Reserved key '%s' not allowed in "
+                                    "kwargs") % k)
+            kwargs = copy.copy(kwargs)
+        if args:
+            args = copy.copy(args)
+        self._listeners[state].append((callback, args, kwargs))
+
+    def deregister(self, state, callback):
+        if state not in self._listeners:
+            return
+        for i, (cb, args, kwargs) in enumerate(self._listeners[state]):
+            if cb is callback:
+                self._listeners[state].pop(i)
+                break
+
+
+class RollbackAccumulator(object):
+    """A utility class that can help in organizing 'undo' like code
+    so that said code be rolled back on failure (automatically or manually)
+    by activating rollback callables that were inserted during said codes
+    progression.
+    """
+
+    def __init__(self):
+        self._rollbacks = []
+
+    def add(self, *callables):
+        self._rollbacks.extend(callables)
+
+    def reset(self):
+        self._rollbacks = []
+
+    def __len__(self):
+        return len(self._rollbacks)
+
+    def __iter__(self):
+        # Rollbacks happen in the reverse order that they were added.
+        return reversed(self._rollbacks)
+
+    def __enter__(self):
+        return self
+
+    def rollback(self, cause):
+        LOG.warn("Activating %s rollbacks due to %s.", len(self), cause)
+        for (i, f) in enumerate(self):
+            LOG.debug("Calling rollback %s: %s", i + 1, f)
+            try:
+                f(cause)
+            except Exception:
+                LOG.exception(("Failed rolling back %s: %s due "
+                               "to inner exception."), i + 1, f)
+
+    def __exit__(self, type, value, tb):
+        if any((value, type, tb)):
+            self.rollback(value)
+
+
+class ReaderWriterLock(object):
+    """A simple reader-writer lock.
+
+    Several readers can hold the lock simultaneously, and only one writer.
+    Write locks have priority over reads to prevent write starvation.
+
+    Public domain @ http://majid.info/blog/a-reader-writer-lock-for-python/
+    """
+
+    def __init__(self):
+        self.rwlock = 0
+        self.writers_waiting = 0
+        self.monitor = threading.Lock()
+        self.readers_ok = threading.Condition(self.monitor)
+        self.writers_ok = threading.Condition(self.monitor)
+
+    @contextlib.contextmanager
+    def acquire(self, read=True):
+        """Acquire a read or write lock in a context manager."""
+        try:
+            if read:
+                self.acquire_read()
+            else:
+                self.acquire_write()
+            yield self
+        finally:
+            self.release()
+
+    def acquire_read(self):
+        """Acquire a read lock.
+
+        Several threads can hold this typeof lock.
+        It is exclusive with write locks.
+        """
+
+        self.monitor.acquire()
+        while self.rwlock < 0 or self.writers_waiting:
+            self.readers_ok.wait()
+        self.rwlock += 1
+        self.monitor.release()
+
+    def acquire_write(self):
+        """Acquire a write lock.
+
+        Only one thread can hold this lock, and only when no read locks
+        are also held.
+        """
+
+        self.monitor.acquire()
+        while self.rwlock != 0:
+            self.writers_waiting += 1
+            self.writers_ok.wait()
+            self.writers_waiting -= 1
+        self.rwlock = -1
+        self.monitor.release()
+
+    def release(self):
+        """Release a lock, whether read or write."""
+
+        self.monitor.acquire()
+        if self.rwlock < 0:
+            self.rwlock = 0
+        else:
+            self.rwlock -= 1
+        wake_writers = self.writers_waiting and self.rwlock == 0
+        wake_readers = self.writers_waiting == 0
+        self.monitor.release()
+        if wake_writers:
+            self.writers_ok.acquire()
+            self.writers_ok.notify()
+            self.writers_ok.release()
+        elif wake_readers:
+            self.readers_ok.acquire()
+            self.readers_ok.notifyAll()
+            self.readers_ok.release()
+
+
+class LazyPluggable(object):
+    """A pluggable backend loaded lazily based on some value."""
+
+    def __init__(self, pivot, **backends):
+        self.__backends = backends
+        self.__pivot = pivot
+        self.__backend = None
+
+    def __get_backend(self):
+        if not self.__backend:
+            backend_name = 'sqlalchemy'
+            backend = self.__backends[backend_name]
+            if isinstance(backend, tuple):
+                name = backend[0]
+                fromlist = backend[1]
+            else:
+                name = backend
+                fromlist = backend
+
+            self.__backend = __import__(name, None, None, fromlist)
+        return self.__backend
+
+    def __getattr__(self, key):
+        backend = self.__get_backend()
+        return getattr(backend, key)

cinder/tests/test_volume.py

@@ -49,6 +49,7 @@ from cinder.tests.image import fake as fake_image
 from cinder.volume import configuration as conf
 from cinder.volume import driver
 from cinder.volume.drivers import lvm
+from cinder.volume.flows import create_volume
 from cinder.volume import rpcapi as volume_rpcapi
 from cinder.volume import utils as volutils
 
@@ -151,7 +152,7 @@ class VolumeTestCase(test.TestCase):
             'volume_type': None,
             'snapshot_id': None,
             'user_id': 'fake',
-            'launched_at': '',
+            'launched_at': 'DONTCARE',
             'size': 0,
         }
         self.assertDictMatch(msg['payload'], expected)
@@ -167,7 +168,7 @@ class VolumeTestCase(test.TestCase):
             'volume_type': None,
             'snapshot_id': None,
             'user_id': 'fake',
-            'launched_at': '',
+            'launched_at': 'DONTCARE',
             'size': 0,
         }
         self.assertDictMatch(msg['payload'], expected)
@@ -1376,14 +1377,10 @@ class VolumeTestCase(test.TestCase):
 
     def test_create_volume_from_unelevated_context(self):
         """Test context does't change after volume creation failure."""
-        def fake_create_volume(context, volume_ref, snapshot_ref,
-                               sourcevol_ref, image_service, image_id,
-                               image_location):
+        def fake_create_volume(*args, **kwargs):
             raise exception.CinderException('fake exception')
 
-        def fake_reschedule_or_error(context, volume_id, exc_info,
-                                     snapshot_id, image_id, request_spec,
-                                     filter_properties):
+        def fake_reschedule_or_error(self, context, *args, **kwargs):
             self.assertFalse(context.is_admin)
             self.assertFalse('admin' in context.roles)
             #compare context passed in with the context we saved
@@ -1398,10 +1395,9 @@ class VolumeTestCase(test.TestCase):
         #create one copy of context for future comparison
         self.saved_ctxt = ctxt.deepcopy()
 
-        self.stubs.Set(self.volume, '_reschedule_or_error',
+        self.stubs.Set(create_volume.OnFailureRescheduleTask, '_reschedule',
                        fake_reschedule_or_error)
-        self.stubs.Set(self.volume, '_create_volume',
-                       fake_create_volume)
+        self.stubs.Set(self.volume.driver, 'create_volume', fake_create_volume)
 
         volume_src = self._create_volume()
         self.assertRaises(exception.CinderException,
@@ -1490,13 +1486,6 @@ class VolumeTestCase(test.TestCase):
             db.volume_update(self.context, src_vref['id'], {'status': 'error'})
             raise exception.CinderException('fake exception')
 
-        def fake_reschedule_or_error(context, volume_id, exc_info,
-                                     snapshot_id, image_id, request_spec,
-                                     filter_properties):
-            pass
-
-        self.stubs.Set(self.volume, '_reschedule_or_error',
-                       fake_reschedule_or_error)
         self.stubs.Set(self.volume.driver, 'create_cloned_volume',
                        fake_error_create_cloned_volume)
         volume_src = self._create_volume()

cinder/utils.py

@@ -86,6 +86,54 @@ def find_config(config_path):
     raise exception.ConfigNotFound(path=os.path.abspath(config_path))
 
 
+def as_int(obj, quiet=True):
+    # Try "2" -> 2
+    try:
+        return int(obj)
+    except (ValueError, TypeError):
+        pass
+    # Try "2.5" -> 2
+    try:
+        return int(float(obj))
+    except (ValueError, TypeError):
+        pass
+    # Eck, not sure what this is then.
+    if not quiet:
+        raise TypeError(_("Can not translate %s to integer.") % (obj))
+    return obj
+
+
+def check_exclusive_options(**kwargs):
+    """Checks that only one of the provided options is actually not-none.
+
+    Iterates over all the kwargs passed in and checks that only one of said
+    arguments is not-none, if more than one is not-none then an exception will
+    be raised with the names of those arguments who were not-none.
+    """
+
+    if not kwargs:
+        return
+
+    pretty_keys = kwargs.pop("pretty_keys", True)
+    exclusive_options = {}
+    for (k, v) in kwargs.iteritems():
+        if v is not None:
+            exclusive_options[k] = True
+
+    if len(exclusive_options) > 1:
+        # Change the format of the names from pythonic to
+        # something that is more readable.
+        #
+        # Ex: 'the_key' -> 'the key'
+        if pretty_keys:
+            names = [k.replace('_', ' ') for k in kwargs.keys()]
+        else:
+            names = kwargs.keys()
+        names = ", ".join(sorted(names))
+        msg = (_("May specify only one of %s") % (names))
+        raise exception.InvalidInput(reason=msg)
+
+
 def fetchfile(url, target):
     LOG.debug(_('Fetching %s') % url)
     execute('curl', '--fail', url, '-o', target)

cinder/volume/api.py

@@ -37,9 +37,12 @@ from cinder import quota
 from cinder.scheduler import rpcapi as scheduler_rpcapi
 from cinder import units
 from cinder import utils
+from cinder.volume.flows import create_volume
 from cinder.volume import rpcapi as volume_rpcapi
 from cinder.volume import volume_types
 
+from cinder.taskflow import states
+
 
 volume_host_opt = cfg.BoolOpt('snapshot_same_host',
                               default=True,
@@ -56,7 +59,6 @@ CONF.register_opt(volume_same_az_opt)
 CONF.import_opt('storage_availability_zone', 'cinder.volume.manager')
 
 LOG = logging.getLogger(__name__)
-GB = units.GiB
 QUOTAS = quota.QUOTAS
 
 
@@ -95,248 +97,17 @@ class API(base.Base):
         self.availability_zone_names = ()
         super(API, self).__init__(db_driver)
 
-    def create(self, context, size, name, description, snapshot=None,
-               image_id=None, volume_type=None, metadata=None,
-               availability_zone=None, source_volume=None,
-               scheduler_hints=None):
-
-        exclusive_options = (snapshot, image_id, source_volume)
-        exclusive_options_set = sum(1 for option in
-                                    exclusive_options if option is not None)
-        if exclusive_options_set > 1:
-            msg = (_("May specify only one of snapshot, imageRef "
-                     "or source volume"))
-            raise exception.InvalidInput(reason=msg)
-
-        check_policy(context, 'create')
-        if snapshot is not None:
-            if snapshot['status'] != "available":
-                msg = _("status must be available")
-                raise exception.InvalidSnapshot(reason=msg)
-            if not size:
-                size = snapshot['volume_size']
-            elif size < snapshot['volume_size']:
-                msg = _("Volume size cannot be lesser than"
-                        " the Snapshot size")
-                raise exception.InvalidInput(reason=msg)
-            snapshot_id = snapshot['id']
-        else:
-            snapshot_id = None
-
-        if source_volume is not None:
-            if source_volume['status'] == "error":
-                msg = _("Unable to clone volumes that are in an error state")
-                raise exception.InvalidSourceVolume(reason=msg)
-            if not size:
-                size = source_volume['size']
-            else:
-                if size < source_volume['size']:
-                    msg = _("Clones currently must be "
-                            ">= original volume size.")
-                    raise exception.InvalidInput(reason=msg)
-            source_volid = source_volume['id']
-        else:
-            source_volid = None
-
-        def as_int(s):
-            try:
-                return int(s)
-            except (ValueError, TypeError):
-                return s
-
-        # tolerate size as stringified int
-        size = as_int(size)
-
-        if not isinstance(size, int) or size <= 0:
-            msg = (_("Volume size '%s' must be an integer and greater than 0")
-                   % size)
-            raise exception.InvalidInput(reason=msg)
-
-        if (image_id and not (source_volume or snapshot)):
-            # check image existence
-            image_meta = self.image_service.show(context, image_id)
-            image_size_in_gb = (int(image_meta['size']) + GB - 1) / GB
-            #check image size is not larger than volume size.
-            if image_size_in_gb > size:
-                msg = _('Size of specified image is larger than volume size.')
-                raise exception.InvalidInput(reason=msg)
-            # Check image minDisk requirement is met for the particular volume
-            if size < image_meta.get('min_disk', 0):
-                msg = _('Image minDisk size is larger than the volume size.')
-                raise exception.InvalidInput(reason=msg)
-
-        if availability_zone is None:
-            if snapshot is not None:
-                availability_zone = snapshot['volume']['availability_zone']
-            elif source_volume is not None:
-                availability_zone = source_volume['availability_zone']
-            else:
-                availability_zone = CONF.storage_availability_zone
-        else:
-            self._check_availabilty_zone(availability_zone)
-
-        if CONF.cloned_volume_same_az:
-            if (snapshot and
-                snapshot['volume']['availability_zone'] !=
-                    availability_zone):
-                msg = _("Volume must be in the same "
-                        "availability zone as the snapshot")
-                raise exception.InvalidInput(reason=msg)
-            elif source_volume and \
-                    source_volume['availability_zone'] != availability_zone:
-                msg = _("Volume must be in the same "
-                        "availability zone as the source volume")
-                raise exception.InvalidInput(reason=msg)
-
-        if not volume_type and not source_volume:
-            volume_type = volume_types.get_default_volume_type()
-
-        if not volume_type and source_volume:
-            volume_type_id = source_volume['volume_type_id']
-        else:
-            volume_type_id = volume_type.get('id')
-
-        try:
-            reserve_opts = {'volumes': 1, 'gigabytes': size}
-            QUOTAS.add_volume_type_opts(context, reserve_opts, volume_type_id)
-            reservations = QUOTAS.reserve(context, **reserve_opts)
-        except exception.OverQuota as e:
-            overs = e.kwargs['overs']
-            usages = e.kwargs['usages']
-            quotas = e.kwargs['quotas']
-
-            def _consumed(name):
-                return (usages[name]['reserved'] + usages[name]['in_use'])
-
-            for over in overs:
-                if 'gigabytes' in over:
-                    msg = _("Quota exceeded for %(s_pid)s, tried to create "
-                            "%(s_size)sG volume (%(d_consumed)dG of "
-                            "%(d_quota)dG already consumed)")
-                    LOG.warn(msg % {'s_pid': context.project_id,
-                                    's_size': size,
-                                    'd_consumed': _consumed(over),
-                                    'd_quota': quotas[over]})
-                    raise exception.VolumeSizeExceedsAvailableQuota()
-                elif 'volumes' in over:
-                    msg = _("Quota exceeded for %(s_pid)s, tried to create "
-                            "volume (%(d_consumed)d volumes"
-                            "already consumed)")
-                    LOG.warn(msg % {'s_pid': context.project_id,
-                                    'd_consumed': _consumed(over)})
-                    raise exception.VolumeLimitExceeded(allowed=quotas[over])
-
-        self._check_metadata_properties(context, metadata)
-        options = {'size': size,
-                   'user_id': context.user_id,
-                   'project_id': context.project_id,
-                   'snapshot_id': snapshot_id,
-                   'availability_zone': availability_zone,
-                   'status': "creating",
-                   'attach_status': "detached",
-                   'display_name': name,
-                   'display_description': description,
-                   'volume_type_id': volume_type_id,
-                   'metadata': metadata,
-                   'source_volid': source_volid}
-
-        try:
-            volume = self.db.volume_create(context, options)
-            QUOTAS.commit(context, reservations)
-        except Exception:
-            with excutils.save_and_reraise_exception():
-                try:
-                    self.db.volume_destroy(context, volume['id'])
-                finally:
-                    QUOTAS.rollback(context, reservations)
-
-        request_spec = {'volume_properties': options,
-                        'volume_type': volume_type,
-                        'volume_id': volume['id'],
-                        'snapshot_id': volume['snapshot_id'],
-                        'image_id': image_id,
-                        'source_volid': volume['source_volid']}
-
-        if scheduler_hints:
-            filter_properties = {'scheduler_hints': scheduler_hints}
-        else:
-            filter_properties = {}
-
-        self._cast_create_volume(context, request_spec, filter_properties)
-
-        return volume
-
-    def _cast_create_volume(self, context, request_spec, filter_properties):
-
-        # NOTE(Rongze Zhu): It is a simple solution for bug 1008866
-        # If snapshot_id is set, make the call create volume directly to
-        # the volume host where the snapshot resides instead of passing it
-        # through the scheduler. So snapshot can be copy to new volume.
-
-        source_volid = request_spec['source_volid']
-        volume_id = request_spec['volume_id']
-        snapshot_id = request_spec['snapshot_id']
-        image_id = request_spec['image_id']
-
-        if snapshot_id and CONF.snapshot_same_host:
-            snapshot_ref = self.db.snapshot_get(context, snapshot_id)
-            source_volume_ref = self.db.volume_get(context,
-                                                   snapshot_ref['volume_id'])
-            now = timeutils.utcnow()
-            values = {'host': source_volume_ref['host'], 'scheduled_at': now}
-            volume_ref = self.db.volume_update(context, volume_id, values)
-
-            # bypass scheduler and send request directly to volume
-            self.volume_rpcapi.create_volume(
-                context,
-                volume_ref,
-                volume_ref['host'],
-                request_spec=request_spec,
-                filter_properties=filter_properties,
-                allow_reschedule=False,
-                snapshot_id=snapshot_id,
-                image_id=image_id)
-        elif source_volid:
-            source_volume_ref = self.db.volume_get(context,
-                                                   source_volid)
-            now = timeutils.utcnow()
-            values = {'host': source_volume_ref['host'], 'scheduled_at': now}
-            volume_ref = self.db.volume_update(context, volume_id, values)
-
-            # bypass scheduler and send request directly to volume
-            self.volume_rpcapi.create_volume(
-                context,
-                volume_ref,
-                volume_ref['host'],
-                request_spec=request_spec,
-                filter_properties=filter_properties,
-                allow_reschedule=False,
-                snapshot_id=snapshot_id,
-                image_id=image_id,
-                source_volid=source_volid)
-        else:
-            self.scheduler_rpcapi.create_volume(
-                context,
-                CONF.volume_topic,
-                volume_id,
-                snapshot_id,
-                image_id,
-                request_spec=request_spec,
-                filter_properties=filter_properties)
-
-    def _check_availabilty_zone(self, availability_zone):
+    def _valid_availabilty_zone(self, availability_zone):
         #NOTE(bcwaldon): This approach to caching fails to handle the case
         # that an availability zone is disabled/removed.
         if availability_zone in self.availability_zone_names:
-            return
+            return True
+        if CONF.storage_availability_zone == availability_zone:
+            return True
 
         azs = self.list_availability_zones()
         self.availability_zone_names = [az['name'] for az in azs]
-
-        if availability_zone not in self.availability_zone_names:
-            msg = _("Availability zone is invalid")
-            LOG.warn(msg)
-            raise exception.InvalidInput(reason=msg)
+        return availability_zone in self.availability_zone_names
 
     def list_availability_zones(self):
         """Describe the known availability zones
@@ -358,6 +129,56 @@ class API(base.Base):
 
         return tuple(azs)
 
+    def create(self, context, size, name, description, snapshot=None,
+               image_id=None, volume_type=None, metadata=None,
+               availability_zone=None, source_volume=None,
+               scheduler_hints=None):
+
+        def check_volume_az_zone(availability_zone):
+            try:
+                return self._valid_availabilty_zone(availability_zone)
+            except exception.CinderException:
+                LOG.exception(_("Unable to query if %s is in the "
+                                "availability zone set"), availability_zone)
+                return False
+
+        create_what = {
+            'size': size,
+            'name': name,
+            'description': description,
+            'snapshot': snapshot,
+            'image_id': image_id,
+            'volume_type': volume_type,
+            'metadata': metadata,
+            'availability_zone': availability_zone,
+            'source_volume': source_volume,
+            'scheduler_hints': scheduler_hints,
+        }
+        (flow, uuid) = create_volume.get_api_flow(self.scheduler_rpcapi,
+                                                  self.volume_rpcapi,
+                                                  self.db,
+                                                  self.image_service,
+                                                  check_volume_az_zone,
+                                                  create_what)
+
+        assert flow, _('Create volume flow not retrieved')
+        flow.run(context)
+        if flow.state != states.SUCCESS:
+            raise exception.CinderException(_("Failed to successfully complete"
+                                              " create volume workflow"))
+
+        # Extract the volume information from the task uuid that was specified
+        # to produce said information.
+        volume = None
+        try:
+            volume = flow.results[uuid]['volume']
+        except KeyError:
+            pass
+
+        # Raise an error, nobody provided it??
+        assert volume, _('Expected volume result not found')
+        return volume
+
     @wrap_check_policy
     def delete(self, context, volume, force=False):
         if context.is_admin and context.project_id != volume['project_id']:

cinder/volume/flows/__init__.py

@@ -0,0 +1,17 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. 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.

cinder/volume/manager.py

@@ -58,9 +58,12 @@ from cinder.openstack.common import uuidutils
 from cinder import quota
 from cinder import utils
 from cinder.volume.configuration import Configuration
+from cinder.volume.flows import create_volume
 from cinder.volume import rpcapi as volume_rpcapi
 from cinder.volume import utils as volume_utils
 
+from cinder.taskflow import states
+
 LOG = logging.getLogger(__name__)
 
 QUOTAS = quota.QUOTAS
@@ -167,282 +170,34 @@ class VolumeManager(manager.SchedulerDependentManager):
         # collect and publish service capabilities
         self.publish_service_capabilities(ctxt)
 
-    def _create_volume(self, context, volume_ref, snapshot_ref,
-                       srcvol_ref, image_service, image_id, image_location):
-        cloned = None
-        model_update = False
-
-        if all(x is None for x in(snapshot_ref, image_id, srcvol_ref)):
-            model_update = self.driver.create_volume(volume_ref)
-        elif snapshot_ref is not None:
-            model_update = self.driver.create_volume_from_snapshot(
-                volume_ref,
-                snapshot_ref)
-
-            originating_vref = self.db.volume_get(context,
-                                                  snapshot_ref['volume_id'])
-            if originating_vref.bootable:
-                self.db.volume_update(context,
-                                      volume_ref['id'],
-                                      {'bootable': True})
-        elif srcvol_ref is not None:
-            model_update = self.driver.create_cloned_volume(volume_ref,
-                                                            srcvol_ref)
-            if srcvol_ref.bootable:
-                self.db.volume_update(context,
-                                      volume_ref['id'],
-                                      {'bootable': True})
-        else:
-            # create the volume from an image
-            # NOTE (singn): two params need to be returned
-            # dict containing provider_location for cloned volume
-            # and clone status
-            model_update, cloned = self.driver.clone_image(
-                volume_ref, image_location)
-            if not cloned:
-                model_update = self.driver.create_volume(volume_ref)
-
-                updates = dict(model_update or dict(), status='downloading')
-                volume_ref = self.db.volume_update(context,
-                                                   volume_ref['id'],
-                                                   updates)
-
-                # TODO(jdg): Wrap this in a try block and update status
-                # appropriately if the download image fails
-                self._copy_image_to_volume(context,
-                                           volume_ref,
-                                           image_service,
-                                           image_id)
-                self.db.volume_update(context,
-                                      volume_ref['id'],
-                                      {'bootable': True})
-        return model_update, cloned
-
     def create_volume(self, context, volume_id, request_spec=None,
                       filter_properties=None, allow_reschedule=True,
                       snapshot_id=None, image_id=None, source_volid=None):
         """Creates and exports the volume."""
-        context_saved = context.deepcopy()
-        context = context.elevated()
-        if filter_properties is None:
-            filter_properties = {}
-        volume_ref = self.db.volume_get(context, volume_id)
-        self._notify_about_volume_usage(context, volume_ref, "create.start")
 
-        # NOTE(vish): so we don't have to get volume from db again
-        #             before passing it to the driver.
-        volume_ref['host'] = self.host
+        flow = create_volume.get_manager_flow(
+            self.db,
+            self.driver,
+            self.scheduler_rpcapi,
+            self.host,
+            volume_id,
+            request_spec=request_spec,
+            filter_properties=filter_properties,
+            allow_reschedule=allow_reschedule,
+            snapshot_id=snapshot_id,
+            image_id=image_id,
+            source_volid=source_volid,
+            reschedule_context=context.deepcopy())
 
-        if volume_ref['status'] == 'migration_target_creating':
-            status = 'migration_target'
-        else:
-            status = 'available'
-        model_update = False
-        image_meta = None
-        cloned = False
+        assert flow, _('Manager volume flow not retrieved')
 
-        try:
-            LOG.debug(_("volume %(vol_name)s: creating lv of"
-                        " size %(vol_size)sG"),
-                      {'vol_name': volume_ref['name'],
-                       'vol_size': volume_ref['size']})
-            snapshot_ref = None
-            sourcevol_ref = None
-            image_service = None
-            image_location = None
-            image_meta = None
+        flow.run(context.elevated())
+        if flow.state != states.SUCCESS:
+            raise exception.CinderException(_("Failed to successfully complete"
+                                              " manager volume workflow"))
 
-            if snapshot_id is not None:
-                LOG.info(_("volume %s: creating from snapshot"),
-                         volume_ref['name'])
-                snapshot_ref = self.db.snapshot_get(context, snapshot_id)
-            elif source_volid is not None:
-                LOG.info(_("volume %s: creating from existing volume"),
-                         volume_ref['name'])
-                sourcevol_ref = self.db.volume_get(context, source_volid)
-            elif image_id is not None:
-                LOG.info(_("volume %s: creating from image"),
-                         volume_ref['name'])
-                # create the volume from an image
-                image_service, image_id = \
-                    glance.get_remote_image_service(context,
-                                                    image_id)
-                image_location = image_service.get_location(context, image_id)
-                image_meta = image_service.show(context, image_id)
-            else:
-                LOG.info(_("volume %s: creating"), volume_ref['name'])
-
-            try:
-                model_update, cloned = self._create_volume(context,
-                                                           volume_ref,
-                                                           snapshot_ref,
-                                                           sourcevol_ref,
-                                                           image_service,
-                                                           image_id,
-                                                           image_location)
-            except exception.ImageCopyFailure as ex:
-                LOG.error(_('Setting volume: %s status to error '
-                            'after failed image copy.'), volume_ref['id'])
-                self.db.volume_update(context,
-                                      volume_ref['id'],
-                                      {'status': 'error'})
-                return
-            except Exception:
-                exc_info = sys.exc_info()
-                # restore source volume status before reschedule
-                # FIXME(zhiteng) do all the clean-up before reschedule
-                if sourcevol_ref is not None:
-                    self.db.volume_update(context, sourcevol_ref['id'],
-                                          {'status': sourcevol_ref['status']})
-                rescheduled = False
-                # try to re-schedule volume:
-                if allow_reschedule:
-                    rescheduled = self._reschedule_or_error(context_saved,
-                                                            volume_id,
-                                                            exc_info,
-                                                            snapshot_id,
-                                                            image_id,
-                                                            request_spec,
-                                                            filter_properties)
-
-                if rescheduled:
-                    LOG.error(_('Unexpected Error: '), exc_info=exc_info)
-                    msg = (_('Creating %(volume_id)s %(snapshot_id)s '
-                             '%(image_id)s was rescheduled due to '
-                             '%(reason)s')
-                           % {'volume_id': volume_id,
-                              'snapshot_id': snapshot_id,
-                              'image_id': image_id,
-                              'reason': unicode(exc_info[1])})
-                    raise exception.CinderException(msg)
-                else:
-                    # not re-scheduling
-                    raise exc_info[0], exc_info[1], exc_info[2]
-
-            if model_update:
-                volume_ref = self.db.volume_update(
-                    context, volume_ref['id'], model_update)
-            if sourcevol_ref is not None:
-                self.db.volume_glance_metadata_copy_from_volume_to_volume(
-                    context,
-                    source_volid,
-                    volume_id)
-
-            LOG.debug(_("volume %s: creating export"), volume_ref['name'])
-            model_update = self.driver.create_export(context, volume_ref)
-            if model_update:
-                self.db.volume_update(context, volume_ref['id'], model_update)
-        except Exception:
-            with excutils.save_and_reraise_exception():
-                volume_ref['status'] = 'error'
-                self.db.volume_update(context,
-                                      volume_ref['id'],
-                                      {'status': volume_ref['status']})
-                LOG.error(_("volume %s: create failed"), volume_ref['name'])
-                self._notify_about_volume_usage(context, volume_ref,
-                                                "create.end")
-
-        if snapshot_id:
-            # Copy any Glance metadata from the original volume
-            self.db.volume_glance_metadata_copy_to_volume(context,
-                                                          volume_ref['id'],
-                                                          snapshot_id)
-
-        if image_id and image_meta:
-            # Copy all of the Glance image properties to the
-            # volume_glance_metadata table for future reference.
-            self.db.volume_glance_metadata_create(context,
-                                                  volume_ref['id'],
-                                                  'image_id', image_id)
-            name = image_meta.get('name', None)
-            if name:
-                self.db.volume_glance_metadata_create(context,
-                                                      volume_ref['id'],
-                                                      'image_name', name)
-            # Save some more attributes into the volume metadata
-            IMAGE_ATTRIBUTES = ['size', 'disk_format',
-                                'container_format', 'checksum',
-                                'min_disk', 'min_ram']
-            for key in IMAGE_ATTRIBUTES:
-                value = image_meta.get(key, None)
-                if value is not None:
-                    self.db.volume_glance_metadata_create(context,
-                                                          volume_ref['id'],
-                                                          key, value)
-            image_properties = image_meta.get('properties', {})
-            for key, value in image_properties.items():
-                self.db.volume_glance_metadata_create(context,
-                                                      volume_ref['id'],
-                                                      key, value)
-
-        now = timeutils.utcnow()
-        volume_ref['status'] = status
-        self.db.volume_update(context,
-                              volume_ref['id'],
-                              {'status': volume_ref['status'],
-                               'launched_at': now})
-        LOG.info(_("volume %s: created successfully"), volume_ref['name'])
         self._reset_stats()
-
-        self._notify_about_volume_usage(context, volume_ref, "create.end")
-        return volume_ref['id']
-
-    def _reschedule_or_error(self, context, volume_id, exc_info,
-                             snapshot_id, image_id, request_spec,
-                             filter_properties):
-        """Try to re-schedule the request."""
-        rescheduled = False
-        try:
-            method_args = (CONF.volume_topic, volume_id, snapshot_id,
-                           image_id, request_spec, filter_properties)
-
-            rescheduled = self._reschedule(context, request_spec,
-                                           filter_properties, volume_id,
-                                           self.scheduler_rpcapi.create_volume,
-                                           method_args,
-                                           exc_info)
-        except Exception:
-            rescheduled = False
-            LOG.exception(_("volume %s: Error trying to reschedule create"),
-                          volume_id)
-
-        return rescheduled
-
-    def _reschedule(self, context, request_spec, filter_properties,
-                    volume_id, scheduler_method, method_args,
-                    exc_info=None):
-        """Attempt to re-schedule a volume operation."""
-
-        retry = filter_properties.get('retry', None)
-        if not retry:
-            # no retry information, do not reschedule.
-            LOG.debug(_("Retry info not present, will not reschedule"))
-            return
-
-        if not request_spec:
-            LOG.debug(_("No request spec, will not reschedule"))
-            return
-
-        request_spec['volume_id'] = volume_id
-
-        LOG.debug(_("volume %(volume_id)s: re-scheduling %(method)s "
-                    "attempt %(num)d") %
-                  {'volume_id': volume_id,
-                   'method': scheduler_method.func_name,
-                   'num': retry['num_attempts']})
-
-        # reset the volume state:
-        now = timeutils.utcnow()
-        self.db.volume_update(context, volume_id,
-                              {'status': 'creating',
-                               'scheduled_at': now})
-
-        if exc_info:
-            # stringify to avoid circular ref problem in json serialization:
-            retry['exc'] = traceback.format_exception(*exc_info)
-
-        scheduler_method(context, *method_args)
-        return True
+        return volume_id
 
     def delete_volume(self, context, volume_id):
         """Deletes and unexports volume."""
@@ -680,28 +435,6 @@ class VolumeManager(manager.SchedulerDependentManager):
                 volume['name'] not in volume['provider_location']):
             self.driver.ensure_export(context, volume)
 
-    def _copy_image_to_volume(self, context, volume, image_service, image_id):
-        """Downloads Glance image to the specified volume."""
-        volume_id = volume['id']
-        try:
-            self.driver.copy_image_to_volume(context, volume,
-                                             image_service,
-                                             image_id)
-        except exception.ProcessExecutionError as ex:
-            LOG.error(_("Failed to copy image to volume: %(volume_id)s, "
-                        "error: %(error)s") % {'volume_id': volume_id,
-                                               'error': ex.stderr})
-            raise exception.ImageCopyFailure(reason=ex.stderr)
-        except Exception as ex:
-            LOG.error(_("Failed to copy image to volume: %(volume_id)s, "
-                        "error: %(error)s") % {'volume_id': volume_id,
-                                               'error': ex})
-            raise exception.ImageCopyFailure(reason=ex)
-
-        LOG.info(_("Downloaded image %(image_id)s to %(volume_id)s "
-                   "successfully.") % {'image_id': image_id,
-                                       'volume_id': volume_id})
-
     def copy_volume_to_image(self, context, volume_id, image_meta):
         """Uploads the specified volume to Glance.
 

taskflow.conf

@@ -0,0 +1,7 @@
+[DEFAULT]
+
+# The list of primitives to copy from taskflow
+primitives=flow.linear_flow,task
+
+# The base module to hold the copy of taskflow
+base=cinder