path: root/heat/engine/stack.py

#
#    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 copy
import eventlet
import functools
import re
import warnings

from oslo_config import cfg
from oslo_log import log as logging
from oslo_utils import excutils
from oslo_utils import timeutils as oslo_timeutils
from oslo_utils import uuidutils
from osprofiler import profiler
import six

from heat.common import context as common_context
from heat.common import environment_format as env_fmt
from heat.common import exception
from heat.common.i18n import _
from heat.common import identifier
from heat.common import lifecycle_plugin_utils
from heat.engine import dependencies
from heat.engine import environment
from heat.engine import event
from heat.engine.notification import stack as notification
from heat.engine import parameter_groups as param_groups
from heat.engine import parent_rsrc
from heat.engine import resource
from heat.engine import resources
from heat.engine import scheduler
from heat.engine import stk_defn
from heat.engine import sync_point
from heat.engine import template as tmpl
from heat.engine import update
from heat.objects import raw_template as raw_template_object
from heat.objects import resource as resource_objects
from heat.objects import snapshot as snapshot_object
from heat.objects import stack as stack_object
from heat.objects import stack_tag as stack_tag_object
from heat.objects import user_creds as ucreds_object
from heat.rpc import api as rpc_api
from heat.rpc import worker_client as rpc_worker_client

LOG = logging.getLogger(__name__)


class ForcedCancel(Exception):
    """Exception raised to cancel task execution."""

    def __init__(self, with_rollback=True):
        self.with_rollback = with_rollback

    def __str__(self):
        return "Operation cancelled"


def reset_state_on_error(func):
    @six.wraps(func)
    def handle_exceptions(stack, *args, **kwargs):
        errmsg = None
        try:
            return func(stack, *args, **kwargs)
        except Exception as exc:
            with excutils.save_and_reraise_exception():
                errmsg = six.text_type(exc)
                LOG.error('Unexpected exception in %(func)s: %(msg)s',
                          {'func': func.__name__, 'msg': errmsg})
        except BaseException as exc:
            with excutils.save_and_reraise_exception():
                exc_type = type(exc).__name__
                errmsg = '%s(%s)' % (exc_type, six.text_type(exc))
                LOG.info('Stopped due to %(msg)s in %(func)s',
                         {'func': func.__name__, 'msg': errmsg})
        finally:
            if stack.status == stack.IN_PROGRESS:
                rtnmsg = _("Unexpected exit while IN_PROGRESS.")
                stack.state_set(stack.action, stack.FAILED,
                                errmsg if errmsg is not None else rtnmsg)
                assert errmsg is not None, "Returned while IN_PROGRESS."

    return handle_exceptions


@six.python_2_unicode_compatible
class Stack(collections.Mapping):

    ACTIONS = (
        CREATE, DELETE, UPDATE, ROLLBACK, SUSPEND, RESUME, ADOPT,
        SNAPSHOT, CHECK, RESTORE
    ) = (
        'CREATE', 'DELETE', 'UPDATE', 'ROLLBACK', 'SUSPEND', 'RESUME', 'ADOPT',
        'SNAPSHOT', 'CHECK', 'RESTORE'
    )

    STATUSES = (IN_PROGRESS, FAILED, COMPLETE
                ) = ('IN_PROGRESS', 'FAILED', 'COMPLETE')

    _zones = None

    def __init__(self, context, stack_name, tmpl,
                 stack_id=None, action=None, status=None,
                 status_reason='', timeout_mins=None,
                 disable_rollback=True, parent_resource=None, owner_id=None,
                 adopt_stack_data=None, stack_user_project_id=None,
                 created_time=None, updated_time=None,
                 user_creds_id=None, tenant_id=None,
                 use_stored_context=False, username=None,
                 nested_depth=0, strict_validate=True, convergence=False,
                 current_traversal=None, tags=None, prev_raw_template_id=None,
                 current_deps=None, cache_data=None,
                 deleted_time=None, converge=False):

        """Initialise the Stack.

        Initialise from a context, name, Template object and (optionally)
        Environment object. The database ID may also be initialised, if the
        stack is already in the database.

        Creating a stack with cache_data creates a lightweight stack which
        will not load any resources from the database and resolve the
        functions from the cache_data specified.
        """

        def _validate_stack_name(name):
            try:
                if not re.match("[a-zA-Z][a-zA-Z0-9_.-]{0,254}$", name):
                    message = _('Invalid stack name %s must contain '
                                'only alphanumeric or \"_-.\" characters, '
                                'must start with alpha and must be 255 '
                                'characters or less.') % name
                    raise exception.StackValidationFailed(message=message)
            except TypeError:
                message = _('Invalid stack name %s, must be a string') % name
                raise exception.StackValidationFailed(message=message)

        if owner_id is None:
            _validate_stack_name(stack_name)

        self.id = stack_id
        self.owner_id = owner_id
        self.context = context
        self.name = stack_name
        self.action = (self.ADOPT if adopt_stack_data else
                       self.CREATE if action is None else action)
        self.status = self.IN_PROGRESS if status is None else status
        self.status_reason = status_reason
        self.timeout_mins = timeout_mins
        self.disable_rollback = disable_rollback
        self._outputs = None
        self._resources = None
        self._dependencies = None
        self._implicit_deps_loaded = False
        self._access_allowed_handlers = {}
        self._db_resources = None
        self._tags = tags
        self.adopt_stack_data = adopt_stack_data
        self.stack_user_project_id = stack_user_project_id
        self.created_time = created_time
        self.updated_time = updated_time
        self.deleted_time = deleted_time
        self.user_creds_id = user_creds_id
        self.nested_depth = nested_depth
        self.convergence = convergence
        self.current_traversal = current_traversal
        self.tags = tags
        self.prev_raw_template_id = prev_raw_template_id
        self.current_deps = current_deps
        self._worker_client = None
        self._convg_deps = None
        self.thread_group_mgr = None
        self.converge = converge

        # strict_validate can be used to disable value validation
        # in the resource properties schema, this is useful when
        # performing validation when properties reference attributes
        # for not-yet-created resources (which return None)
        self.strict_validate = strict_validate

        self.in_convergence_check = cache_data is not None

        if use_stored_context:
            self.context = self.stored_context()

        self.clients = self.context.clients

        # This will use the provided tenant ID when loading the stack
        # from the DB or get it from the context for new stacks.
        self.tenant_id = tenant_id or self.context.tenant_id
        self.username = username or self.context.username

        resources.initialise()

        parent_info = parent_rsrc.ParentResourceProxy(context,
                                                      parent_resource,
                                                      owner_id)
        if tmpl is not None:
            self.defn = stk_defn.StackDefinition(context, tmpl,
                                                 self.identifier(),
                                                 cache_data or {},
                                                 parent_info)
        else:
            self.defn = None

    @property
    def tags(self):
        if self._tags is None:
            tags = stack_tag_object.StackTagList.get(
                self.context, self.id)
            if tags:
                self._tags = [t.tag for t in tags]
        return self._tags

    @tags.setter
    def tags(self, value):
        self._tags = value

    @property
    def worker_client(self):
        """Return a client for making engine RPC calls."""
        if not self._worker_client:
            self._worker_client = rpc_worker_client.WorkerClient()
        return self._worker_client

    @property
    def t(self):
        """The stack template."""
        if self.defn is None:
            return None
        return self.defn.t

    @t.setter
    def t(self, tmpl):
        """Set the stack template."""
        self.defn = self.defn.clone_with_new_template(tmpl, self.identifier())

    @property
    def parameters(self):
        return self.defn.parameters

    @property
    def env(self):
        """The stack environment"""
        return self.defn.env

    @property
    def parent_resource_name(self):
        parent_info = self.defn.parent_resource
        return parent_info and parent_info.name

    @property
    def parent_resource(self):
        """Dynamically load up the parent_resource.

        Note: this should only be used by "Fn::ResourceFacade"
        """
        return self.defn.parent_resource

    def set_parent_stack(self, parent_stack):
        parent_info = self.defn.parent_resource
        if parent_info is not None:
            parent_rsrc.use_parent_stack(parent_info, parent_stack)

    def stored_context(self):
        if self.user_creds_id:
            creds_obj = ucreds_object.UserCreds.get_by_id(
                self.context, self.user_creds_id)
            # Maintain request_id from self.context so we retain traceability
            # in situations where servicing a request requires switching from
            # the request context to the stored context
            creds = creds_obj.obj_to_primitive()["versioned_object.data"]
            creds['request_id'] = self.context.request_id
            # We don't store roles in the user_creds table, so disable the
            # policy check for admin by setting is_admin=False.
            creds['is_admin'] = False
            creds['overwrite'] = False

            return common_context.StoredContext.from_dict(creds)
        else:
            msg = _("Attempt to use stored_context with no user_creds")
            raise exception.Error(msg)

    @property
    def outputs(self):
        return {n: self.defn.output_definition(n)
                for n in self.defn.enabled_output_names()}

    @property
    def resources(self):
        if self._resources is None:
            self._resources = {
                name: resource.Resource(name,
                                        self.defn.resource_definition(name),
                                        self)
                for name in self.defn.enabled_rsrc_names()
            }

        return self._resources

    def _update_all_resource_data(self, for_resources, for_outputs):
        for rsrc in self._explicit_dependencies():
            node_data = rsrc.node_data(for_resources=for_resources,
                                       for_outputs=for_outputs)
            stk_defn.update_resource_data(self.defn, rsrc.name, node_data)

    def _find_filtered_resources(self, filters=None):
        if filters:
            assert not self.in_convergence_check, \
                "Resources should not be loaded from the DB"
            resources = resource_objects.Resource.get_all_by_stack(
                self.context, self.id, filters)
        else:
            resources = self._db_resources_get()

        stk_def_cache = {}
        for rsc in six.itervalues(resources):
            loaded_res = self._resource_from_db_resource(rsc, stk_def_cache)
            if loaded_res is not None:
                yield loaded_res

    def iter_resources(self, nested_depth=0, filters=None):
        """Iterates over all the resources in a stack.

        Iterating includes nested stacks up to `nested_depth` levels below.
        """
        for res in self._find_filtered_resources(filters):
            yield res

        resources = self._find_filtered_resources()
        for res in resources:
            if not res.has_nested() or nested_depth == 0:
                continue

            nested_stack = res.nested()
            if nested_stack is None:
                continue
            for nested_res in nested_stack.iter_resources(nested_depth - 1,
                                                          filters):
                yield nested_res

    def db_active_resources_get(self):
        resources = resource_objects.Resource.get_all_active_by_stack(
            self.context, self.id)
        return resources or None

    def db_resource_get(self, name):
        if self.id is None:
            return None
        return self._db_resources_get().get(name)

    def _db_resources_get(self):
        if self._db_resources is None:
            assert not self.in_convergence_check, \
                "Resources should not be loaded from the DB"
            _db_resources = resource_objects.Resource.get_all_by_stack(
                self.context, self.id)
            if not _db_resources:
                return {}
            self._db_resources = _db_resources
        return self._db_resources

    def _resource_from_db_resource(self, db_res, stk_def_cache=None):
        tid = db_res.current_template_id
        if tid is None:
            tid = self.t.id

        if tid == self.t.id:
            cur_res = self.resources.get(db_res.name)
            if cur_res is not None and (cur_res.id == db_res.id):
                return cur_res

            stk_def = self.defn
        elif stk_def_cache and tid in stk_def_cache:
            stk_def = stk_def_cache[tid]
        else:
            t = tmpl.Template.load(self.context, tid)
            stk_def = self.defn.clone_with_new_template(t,
                                                        self.identifier())
            if stk_def_cache is not None:
                stk_def_cache[tid] = stk_def

        try:
            defn = stk_def.resource_definition(db_res.name)
        except KeyError:
            return None

        return resource.Resource(db_res.name, defn, self)

    def resource_get(self, name):
        """Return a stack resource, even if not in the current template."""
        res = self.resources.get(name)
        if res:
            return res

        # fall back to getting the resource from the database
        db_res = self.db_resource_get(name)
        if db_res:
            return self._resource_from_db_resource(db_res)

        return None

    @property
    def dependencies(self):
        if not self._implicit_deps_loaded:
            self._explicit_dependencies()
            self._add_implicit_dependencies(self._dependencies,
                                            ignore_errors=self.id is not None)
            self._implicit_deps_loaded = True
        return self._dependencies

    def reset_dependencies(self):
        self._implicit_deps_loaded = False
        self._dependencies = None

    def root_stack_id(self):
        if not self.owner_id:
            return self.id
        return stack_object.Stack.get_root_id(self.context, self.owner_id)

    def object_path_in_stack(self):
        """Return stack resources and stacks in path from the root stack.

        If this is not nested return (None, self), else return stack resources
        and stacks in path from the root stack and including this stack.

        Note that this is horribly inefficient, as it requires us to load every
        stack in the chain back to the root in memory at the same time.

        :returns: a list of (stack_resource, stack) tuples.
        """
        if self.parent_resource:
            parent_stack = self.parent_resource._stack()
            if parent_stack is not None:
                path = parent_stack.object_path_in_stack()
                path.extend([(self.parent_resource, self)])
                return path
        return [(None, self)]

    def path_in_stack(self):
        """Return tuples of names in path from the root stack.

        If this is not nested return (None, self.name), else return tuples of
        names (stack_resource.name, stack.name) in path from the root stack and
        including this stack.

        :returns: a list of (string, string) tuples.

        """
        opis = self.object_path_in_stack()
        return [(stckres.name if stckres else None,
                 stck.name if stck else None) for stckres, stck in opis]

    def total_resources(self, stack_id=None):
        """Return the total number of resources in a stack.

        Includes nested stacks below.
        """
        if not stack_id:
            if self.id is None:
                # We're not stored yet, so we don't have anything to count
                return 0
            stack_id = self.id
        return stack_object.Stack.count_total_resources(self.context, stack_id)

    def _set_param_stackid(self):
        """Update self.parameters with the current ARN.

        The ARN is then provided via the Parameters class as the StackId pseudo
        parameter.
        """
        if not self.parameters.set_stack_id(self.identifier()):
            LOG.warning("Unable to set parameters StackId identifier")

    def _explicit_dependencies(self):
        """Return dependencies without making any resource plugin calls.

        This includes at least all of the dependencies that are explicitly
        expressed in the template (via depends_on or an intrinsic function). It
        may include implicit dependencies defined by resource plugins, but only
        if they have already been calculated.
        """
        if self._dependencies is None:
            deps = dependencies.Dependencies()
            for res in six.itervalues(self.resources):
                res.add_explicit_dependencies(deps)
            self._dependencies = deps
        return self._dependencies

    def _add_implicit_dependencies(self, deps, ignore_errors=True):
        """Augment the given dependencies with implicit ones from plugins."""
        for res in six.itervalues(self.resources):
            try:
                res.add_dependencies(deps)
            except Exception as exc:
                if not ignore_errors:
                    raise
                else:
                    LOG.warning('Ignoring error adding implicit '
                                'dependencies for %(res)s: %(err)s',
                                {'res': six.text_type(res),
                                 'err': six.text_type(exc)})

    @classmethod
    def load(cls, context, stack_id=None, stack=None, show_deleted=True,
             use_stored_context=False, force_reload=False, cache_data=None,
             load_template=True):
        """Retrieve a Stack from the database."""
        if stack is None:
            stack = stack_object.Stack.get_by_id(
                context,
                stack_id,
                show_deleted=show_deleted)
        if stack is None:
            message = _('No stack exists with id "%s"') % str(stack_id)
            raise exception.NotFound(message)

        if force_reload:
            stack.refresh()

        return cls._from_db(context, stack,
                            use_stored_context=use_stored_context,
                            cache_data=cache_data,
                            load_template=load_template)

    @classmethod
    def load_all(cls, context, limit=None, marker=None, sort_keys=None,
                 sort_dir=None, filters=None,
                 show_deleted=False,
                 show_nested=False, show_hidden=False, tags=None,
                 tags_any=None, not_tags=None, not_tags_any=None):
        stacks = stack_object.Stack.get_all(
            context,
            limit=limit,
            sort_keys=sort_keys,
            marker=marker,
            sort_dir=sort_dir,
            filters=filters,
            show_deleted=show_deleted,
            show_nested=show_nested,
            show_hidden=show_hidden,
            tags=tags,
            tags_any=tags_any,
            not_tags=not_tags,
            not_tags_any=not_tags_any,
            eager_load=True)
        for stack in stacks:
            try:
                yield cls._from_db(context, stack)
            except exception.NotFound:
                # We're in a different transaction than the get_all, so a stack
                # returned above can be deleted by the time we try to load it.
                pass

    @classmethod
    def _from_db(cls, context, stack,
                 use_stored_context=False, cache_data=None,
                 load_template=True):
        if load_template:
            template = tmpl.Template.load(
                context, stack.raw_template_id, stack.raw_template)
        else:
            template = None
        return cls(context, stack.name, template,
                   stack_id=stack.id,
                   action=stack.action, status=stack.status,
                   status_reason=stack.status_reason,
                   timeout_mins=stack.timeout,
                   disable_rollback=stack.disable_rollback,
                   parent_resource=stack.parent_resource_name,
                   owner_id=stack.owner_id,
                   stack_user_project_id=stack.stack_user_project_id,
                   created_time=stack.created_at,
                   updated_time=stack.updated_at,
                   user_creds_id=stack.user_creds_id, tenant_id=stack.tenant,
                   use_stored_context=use_stored_context,
                   username=stack.username, convergence=stack.convergence,
                   current_traversal=stack.current_traversal,
                   prev_raw_template_id=stack.prev_raw_template_id,
                   current_deps=stack.current_deps, cache_data=cache_data,
                   nested_depth=stack.nested_depth,
                   deleted_time=stack.deleted_at)

    def get_kwargs_for_cloning(self, keep_status=False, only_db=False,
                               keep_tags=False):
        """Get common kwargs for calling Stack() for cloning.

        The point of this method is to reduce the number of places that we
        need to update when a kwarg to Stack.__init__() is modified. It
        is otherwise easy to forget an option and cause some unexpected
        error if this option is lost.

        Note:
        - This doesn't return the args(name, template) but only the kwargs.
        - We often want to start 'fresh' so don't want to maintain the old
          status, action and status_reason.
        - We sometimes only want the DB attributes.
        """
        stack = {
            'owner_id': self.owner_id,
            'username': self.username,
            'disable_rollback': self.disable_rollback,
            'stack_user_project_id': self.stack_user_project_id,
            'user_creds_id': self.user_creds_id,
            'nested_depth': self.nested_depth,
            'convergence': self.convergence,
            'current_traversal': self.current_traversal,
            'prev_raw_template_id': self.prev_raw_template_id,
            'current_deps': self.current_deps
        }
        if keep_status:
            stack.update({
                'action': self.action,
                'status': self.status,
                'status_reason': six.text_type(self.status_reason)})

        if only_db:
            stack['parent_resource_name'] = self.parent_resource_name
            stack['tenant'] = self.tenant_id
            stack['timeout'] = self.timeout_mins
        else:
            stack['parent_resource'] = self.parent_resource_name
            stack['tenant_id'] = self.tenant_id
            stack['timeout_mins'] = self.timeout_mins
            stack['strict_validate'] = self.strict_validate
            if keep_tags:
                stack['tags'] = self.tags

        return stack

    @profiler.trace('Stack.store', hide_args=False)
    def store(self, backup=False, exp_trvsl=None,
              ignore_traversal_check=False):
        """Store the stack in the database and return its ID.

        If self.id is set, we update the existing stack.
        """
        s = self.get_kwargs_for_cloning(keep_status=True, only_db=True)
        s['name'] = self.name
        s['backup'] = backup
        s['updated_at'] = self.updated_time
        if self.t.id is None:
            stack_object.Stack.encrypt_hidden_parameters(self.t)
            s['raw_template_id'] = self.t.store(self.context)
        else:
            s['raw_template_id'] = self.t.id

        if self.id is not None:
            if exp_trvsl is None and not ignore_traversal_check:
                exp_trvsl = self.current_traversal

            if self.convergence:
                # do things differently for convergence
                updated = stack_object.Stack.select_and_update(
                    self.context, self.id, s, exp_trvsl=exp_trvsl)

                if not updated:
                    return None
            else:
                stack_object.Stack.update_by_id(self.context, self.id, s)

        else:
            if not self.user_creds_id:
                # Create a context containing a trust_id and trustor_user_id
                # if trusts are enabled
                if cfg.CONF.deferred_auth_method == 'trusts':
                    keystone = self.clients.client('keystone')
                    trust_ctx = keystone.create_trust_context()
                    new_creds = ucreds_object.UserCreds.create(trust_ctx)
                else:
                    new_creds = ucreds_object.UserCreds.create(self.context)
                s['user_creds_id'] = new_creds.id
                self.user_creds_id = new_creds.id

            if self.convergence:
                    # create a traversal ID
                    self.current_traversal = uuidutils.generate_uuid()
                    s['current_traversal'] = self.current_traversal

            new_s = stack_object.Stack.create(self.context, s)
            self.id = new_s.id
            self.created_time = new_s.created_at

        if self.tags:
            stack_tag_object.StackTagList.set(self.context, self.id, self.tags)

        self._set_param_stackid()

        return self.id

    def _backup_name(self):
        return '%s*' % self.name

    def identifier(self):
        """Return an identifier for this stack."""
        return identifier.HeatIdentifier(self.tenant_id, self.name, self.id)

    def __iter__(self):
        """Return an iterator over the resource names."""
        return iter(self.resources)

    def __len__(self):
        """Return the number of resources."""
        return len(self.resources)

    def __getitem__(self, key):
        """Get the resource with the specified name."""
        return self.resources[key]

    def add_resource(self, resource):
        """Insert the given resource into the stack."""
        template = resource.stack.t
        resource.stack = self
        definition = resource.t.reparse(self.defn, template)
        resource.t = definition
        resource.reparse()
        self.resources[resource.name] = resource
        stk_defn.add_resource(self.defn, definition)
        if self.t.id is not None:
            self.t.store(self.context)
        resource.store()

    def remove_resource(self, resource_name):
        """Remove the resource with the specified name."""
        del self.resources[resource_name]
        stk_defn.remove_resource(self.defn, resource_name)
        if self.t.id is not None:
            self.t.store(self.context)

    def __contains__(self, key):
        """Determine whether the stack contains the specified resource."""
        if self._resources is not None:
            return key in self.resources
        else:
            return key in self.t[self.t.RESOURCES]

    def __eq__(self, other):
        """Compare two Stacks for equality.

        Stacks are considered equal only if they are identical.
        """
        return self is other

    def __ne__(self, other):
        return not self.__eq__(other)

    def __str__(self):
        """Return a human-readable string representation of the stack."""
        text = 'Stack "%s" [%s]' % (self.name, self.id)
        return six.text_type(text)

    def resource_by_refid(self, refid):
        """Return the resource in this stack with the specified refid.

        :returns: resource in this stack with the specified refid, or None if
                  not found.
        """
        for r in six.itervalues(self):
            if r.state not in ((r.INIT, r.COMPLETE),
                               (r.CREATE, r.IN_PROGRESS),
                               (r.CREATE, r.COMPLETE),
                               (r.RESUME, r.IN_PROGRESS),
                               (r.RESUME, r.COMPLETE),
                               (r.UPDATE, r.IN_PROGRESS),
                               (r.UPDATE, r.COMPLETE),
                               (r.CHECK, r.COMPLETE)):
                continue

            proxy = self.defn[r.name]
            if proxy._resource_data is None:
                matches = r.FnGetRefId() == refid or r.name == refid
            else:
                matches = proxy.FnGetRefId() == refid

            if matches:
                if self.in_convergence_check and r.id is not None:
                    # We don't have resources loaded from the database at this
                    # point, so load the data for just this one from the DB.
                    db_res = resource_objects.Resource.get_obj(self.context,
                                                               r.id)
                    if db_res is not None:
                        r._load_data(db_res)
                return r

    def register_access_allowed_handler(self, credential_id, handler):
        """Register an authorization handler function.

        Register a function which determines whether the credentials with a
        given ID can have access to a named resource.
        """
        assert callable(handler), 'Handler is not callable'
        self._access_allowed_handlers[credential_id] = handler

    def access_allowed(self, credential_id, resource_name):
        """Is credential_id authorised to access resource by resource_name."""
        if not self.resources:
            # this also triggers lazy-loading of resources
            # so is required for register_access_allowed_handler
            # to be called
            return False

        handler = self._access_allowed_handlers.get(credential_id)
        return handler and handler(resource_name)

    @profiler.trace('Stack.validate', hide_args=False)
    def validate(self, ignorable_errors=None, validate_res_tmpl_only=False):
        """Validates the stack."""
        # TODO(sdake) Should return line number of invalid reference

        # validate overall template (top-level structure)
        self.t.validate()

        # Validate parameters
        self.parameters.validate(context=self.context,
                                 validate_value=self.strict_validate)

        # Validate Parameter Groups
        parameter_groups = param_groups.ParameterGroups(self.t)
        parameter_groups.validate()

        # Continue to call this function, since old third-party Template
        # plugins may depend on it being called to validate the resource
        # definitions before actually generating them.
        if (type(self.t).validate_resource_definitions !=
                tmpl.Template.validate_resource_definitions):
            warnings.warn("The Template.validate_resource_definitions() "
                          "method is deprecated and will no longer be called "
                          "in future versions of Heat. Template subclasses "
                          "should validate resource definitions in the "
                          "resource_definitions() method.",
                          DeprecationWarning)
        self.t.validate_resource_definitions(self)

        self.t.conditions(self).validate()

        # Load the resources definitions (success of which implies the
        # definitions are valid)
        resources = self.resources

        # Check duplicate names between parameters and resources
        dup_names = set(self.parameters) & set(resources)

        if dup_names:
            LOG.debug("Duplicate names %s" % dup_names)
            raise exception.StackValidationFailed(
                message=_("Duplicate names %s") % dup_names)

        self._update_all_resource_data(for_resources=True, for_outputs=True)

        if self.strict_validate:
            iter_rsc = self.dependencies
        else:
            iter_rsc = self._explicit_dependencies()

        unique_defns = set(res.t for res in six.itervalues(resources))
        unique_defn_names = set(defn.name for defn in unique_defns)

        for res in iter_rsc:
            # Don't validate identical definitions multiple times
            if res.name not in unique_defn_names:
                continue
            result = None
            try:
                if not validate_res_tmpl_only:
                    if res.external_id is not None:
                        res.validate_external()
                        continue
                    result = res.validate()
                elif res.external_id is None:
                    result = res.validate_template()
            except exception.HeatException as ex:
                LOG.debug('%s', ex)
                if ignorable_errors and ex.error_code in ignorable_errors:
                    result = None
                else:
                    raise
            except AssertionError:
                raise
            except Exception as ex:
                LOG.info("Exception in stack validation",
                         exc_info=True)
                raise exception.StackValidationFailed(error=ex,
                                                      resource=res)
            if result:
                raise exception.StackValidationFailed(message=result)
            eventlet.sleep(0)

        for op_name, output in six.iteritems(self.outputs):
            try:
                path = '.'.join([self.t.OUTPUTS, op_name,
                                 self.t.OUTPUT_VALUE])
                output.validate(path)
            except exception.StackValidationFailed:
                raise
            except AssertionError:
                raise

    def requires_deferred_auth(self):
        """Determine whether to perform API requests with deferred auth.

        Returns whether this stack may need to perform API requests
        during its lifecycle using the configured deferred authentication
        method.
        """
        return any(res.requires_deferred_auth for res in six.itervalues(self))

    def _add_event(self, action, status, reason):
        """Add a state change event to the database."""
        ev = event.Event(self.context, self, action, status, reason,
                         self.id, None,
                         self.name, 'OS::Heat::Stack')

        ev.store()
        self.dispatch_event(ev)

    def dispatch_event(self, ev):
        def _dispatch(ctx, sinks, ev):
            try:
                for sink in sinks:
                    sink.consume(ctx, ev)
            except Exception as e:
                LOG.debug('Got error sending events %s', e)
        if self.thread_group_mgr is not None:
            self.thread_group_mgr.start(self.id, _dispatch,
                                        self.context,
                                        self.env.get_event_sinks(),
                                        ev.as_dict())

    @profiler.trace('Stack.state_set', hide_args=False)
    def state_set(self, action, status, reason):
        """Update the stack state."""
        if action not in self.ACTIONS:
            raise ValueError(_("Invalid action %s") % action)

        if status not in self.STATUSES:
            raise ValueError(_("Invalid status %s") % status)

        self.action = action
        self.status = status
        self.status_reason = reason
        self._log_status()

        if self.convergence and action in (
                self.UPDATE, self.DELETE, self.CREATE,
                self.ADOPT, self.ROLLBACK, self.RESTORE):
            # if convergence and stack operation is create/update/rollback/
            # delete, stack lock is not used, hence persist state
            updated = self._persist_state()
            if not updated:
                # Possibly failed concurrent update
                LOG.warning("Failed to set state of stack %(name)s with"
                            " traversal ID %(trvsl_id)s, to"
                            " %(action)s_%(status)s",
                            {'name': self.name,
                             'trvsl_id': self.current_traversal,
                             'action': action, 'status': status})
            return updated

        # Persist state to db only if status == IN_PROGRESS
        # or action == UPDATE/DELETE/ROLLBACK. Else, it would
        # be done before releasing the stack lock.
        if status == self.IN_PROGRESS or action in (
                self.UPDATE, self.DELETE, self.ROLLBACK, self.RESTORE):
            self._persist_state()

    def _log_status(self):
        LOG.info('Stack %(action)s %(status)s (%(name)s): %(reason)s',
                 {'action': self.action,
                  'status': self.status,
                  'name': self.name,
                  'reason': self.status_reason})

    def _persist_state(self):
        """Persist stack state to database"""
        if self.id is None:
            return
        stack = stack_object.Stack.get_by_id(self.context, self.id,
                                             eager_load=False)
        if stack is not None:
            values = {'action': self.action,
                      'status': self.status,
                      'status_reason': six.text_type(self.status_reason)}
            self._send_notification_and_add_event()
            if self.convergence:
                # do things differently for convergence
                updated = stack_object.Stack.select_and_update(
                    self.context, self.id, values,
                    exp_trvsl=self.current_traversal)

                return updated

            else:
                stack.update_and_save(values)

    def _send_notification_and_add_event(self):
        LOG.debug('Persisting stack %(name)s status %(action)s %(status)s',
                  {'action': self.action,
                   'status': self.status,
                   'name': self.name})
        notification.send(self)
        self._add_event(self.action, self.status, self.status_reason)

    def persist_state_and_release_lock(self, engine_id):
        """Persist stack state to database and release stack lock"""
        if self.id is None:
            return
        stack = stack_object.Stack.get_by_id(self.context, self.id,
                                             eager_load=False)
        if stack is not None:
            values = {'action': self.action,
                      'status': self.status,
                      'status_reason': six.text_type(self.status_reason)}
            self._send_notification_and_add_event()
            stack.persist_state_and_release_lock(self.context, self.id,
                                                 engine_id, values)

    @property
    def state(self):
        """Returns state, tuple of action, status."""
        return (self.action, self.status)

    def timeout_secs(self):
        """Return the stack action timeout in seconds."""
        if self.timeout_mins is None:
            return cfg.CONF.stack_action_timeout

        return self.timeout_mins * 60

    def preview_resources(self):
        """Preview the stack with all of the resources."""
        return [resource.preview()
                for resource in six.itervalues(self.resources)]

    def _store_resources(self):
        for r in reversed(self.dependencies):
            if r.action == r.INIT:
                r.store()

    @profiler.trace('Stack.create', hide_args=False)
    @reset_state_on_error
    def create(self, msg_queue=None):
        """Create the stack and all of the resources."""
        def rollback():
            if not self.disable_rollback and self.state == (self.CREATE,
                                                            self.FAILED):
                self.delete(action=self.ROLLBACK)

        self._store_resources()

        check_message = functools.partial(self._check_for_message, msg_queue)

        creator = scheduler.TaskRunner(
            self.stack_task, action=self.CREATE,
            reverse=False, post_func=rollback)
        creator(timeout=self.timeout_secs(), progress_callback=check_message)

    def _adopt_kwargs(self, resource):
        data = self.adopt_stack_data
        if not data or not data.get('resources'):
            return {'resource_data': None}

        return {'resource_data': data['resources'].get(resource.name)}

    @scheduler.wrappertask
    def stack_task(self, action, reverse=False, post_func=None,
                   aggregate_exceptions=False, pre_completion_func=None):
        """A task to perform an action on the stack.

        All of the resources are traversed in forward or reverse dependency
        order.

        :param action: action that should be executed with stack resources
        :param reverse: define if action on the resources need to be executed
         in reverse order (resources - first and then res dependencies )
        :param post_func: function that need to be executed after
        action complete on the stack
        :param aggregate_exceptions: define if exceptions should be aggregated
        :param pre_completion_func: function that need to be executed right
        before action completion. Uses stack ,action, status and reason as
        input parameters
        """
        try:
            lifecycle_plugin_utils.do_pre_ops(self.context, self,
                                              None, action)
        except Exception as e:
            self.state_set(action, self.FAILED, e.args[0] if e.args else
                           'Failed stack pre-ops: %s' % six.text_type(e))
            if callable(post_func):
                post_func()
            return
        self.state_set(action, self.IN_PROGRESS,
                       'Stack %s started' % action)

        stack_status = self.COMPLETE
        reason = 'Stack %s completed successfully' % action

        action_method = action.lower()
        # If a local _$action_kwargs function exists, call it to get the
        # action specific argument list, otherwise an empty arg list
        handle_kwargs = getattr(self,
                                '_%s_kwargs' % action_method,
                                lambda x: {})

        @functools.wraps(getattr(resource.Resource, action_method))
        @scheduler.wrappertask
        def resource_action(r):
            # Find e.g resource.create and call it
            handle = getattr(r, action_method)

            yield handle(**handle_kwargs(r))

            if action == self.CREATE:
                stk_defn.update_resource_data(self.defn, r.name, r.node_data())

        def get_error_wait_time(resource):
            return resource.cancel_grace_period()

        action_task = scheduler.DependencyTaskGroup(
            self.dependencies,
            resource_action,
            reverse,
            error_wait_time=get_error_wait_time,
            aggregate_exceptions=aggregate_exceptions)

        try:
            yield action_task()
        except scheduler.Timeout:
            stack_status = self.FAILED
            reason = '%s timed out' % action.title()
        except Exception as ex:
            # We use a catch-all here to ensure any raised exceptions
            # make the stack fail. This is necessary for when
            # aggregate_exceptions is false, as in that case we don't get
            # ExceptionGroup, but the raw exception.
            # see scheduler.py line 395-399
            stack_status = self.FAILED
            reason = 'Resource %s failed: %s' % (action, six.text_type(ex))

        if pre_completion_func:
            pre_completion_func(self, action, stack_status, reason)

        self.state_set(action, stack_status, reason)

        if callable(post_func):
            post_func()
        lifecycle_plugin_utils.do_post_ops(self.context, self, None, action,
                                           (self.status == self.FAILED))

    @profiler.trace('Stack.check', hide_args=False)
    @reset_state_on_error
    def check(self):
        self.updated_time = oslo_timeutils.utcnow()
        checker = scheduler.TaskRunner(
            self.stack_task, self.CHECK,
            post_func=self.supports_check_action,
            aggregate_exceptions=True)
        checker()

    def supports_check_action(self):
        def is_supported(res):
            if res.has_nested() and res.nested():
                return res.nested().supports_check_action()
            else:
                return hasattr(res, 'handle_%s' % res.CHECK.lower())

        all_supported = all(is_supported(res)
                            for res in six.itervalues(self.resources))

        if not all_supported:
            msg = ". '%s' not fully supported (see resources)" % self.CHECK
            reason = self.status_reason + msg
            self.state_set(self.CHECK, self.status, reason)

        return all_supported

    @profiler.trace('Stack._backup_stack', hide_args=False)
    def _backup_stack(self, create_if_missing=True):
        """Backup the stack.

        Get a Stack containing any in-progress resources from the previous
        stack state prior to an update.
        """
        s = stack_object.Stack.get_by_name_and_owner_id(
            self.context,
            self._backup_name(),
            owner_id=self.id)
        if s is not None:
            LOG.debug('Loaded existing backup stack')
            return self.load(self.context, stack=s)
        elif create_if_missing:
            kwargs = self.get_kwargs_for_cloning(keep_tags=True)
            kwargs['owner_id'] = self.id
            del(kwargs['prev_raw_template_id'])
            prev = type(self)(self.context, self._backup_name(),
                              copy.deepcopy(self.t),
                              **kwargs)
            prev.store(backup=True)
            LOG.debug('Created new backup stack')
            return prev
        else:
            return None

    @profiler.trace('Stack.adopt', hide_args=False)
    @reset_state_on_error
    def adopt(self):
        """Adopt existing resources into a new stack."""
        def rollback():
            if not self.disable_rollback and self.state == (self.ADOPT,
                                                            self.FAILED):
                # enter the same flow as abandon and just delete the stack
                for res in six.itervalues(self.resources):
                    res.abandon_in_progress = True
                self.delete(action=self.ROLLBACK, abandon=True)

        creator = scheduler.TaskRunner(
            self.stack_task,
            action=self.ADOPT,
            reverse=False,
            post_func=rollback)
        creator(timeout=self.timeout_secs())

    @profiler.trace('Stack.update', hide_args=False)
    @reset_state_on_error
    def update(self, newstack, msg_queue=None):
        """Update the stack.

        Compare the current stack with newstack,
        and where necessary create/update/delete the resources until
        this stack aligns with newstack.

        Note update of existing stack resources depends on update
        being implemented in the underlying resource types

        Update will fail if it exceeds the specified timeout. The default is
        60 minutes, set in the constructor
        """
        self.updated_time = oslo_timeutils.utcnow()
        updater = scheduler.TaskRunner(self.update_task, newstack,
                                       msg_queue=msg_queue)
        updater()

    @profiler.trace('Stack.converge_stack', hide_args=False)
    def converge_stack(self, template, action=UPDATE, new_stack=None):
        """Update the stack template and trigger convergence for resources."""
        if action not in [self.CREATE, self.ADOPT]:
            # no back-up template for create action
            self.prev_raw_template_id = getattr(self.t, 'id', None)

        # switch template and reset dependencies
        self.defn = self.defn.clone_with_new_template(template,
                                                      self.identifier(),
                                                      clear_resource_data=True)
        self.reset_dependencies()
        self._resources = None

        if action is not self.CREATE:
            self.updated_time = oslo_timeutils.utcnow()

        if new_stack is not None:
            self.disable_rollback = new_stack.disable_rollback
            self.timeout_mins = new_stack.timeout_mins
            self.converge = new_stack.converge

            self.defn = new_stack.defn
            self._set_param_stackid()

            self.tags = new_stack.tags
            if new_stack.tags:
                stack_tag_object.StackTagList.set(self.context, self.id,
                                                  new_stack.tags)
            else:
                stack_tag_object.StackTagList.delete(self.context, self.id)

        self.action = action
        self.status = self.IN_PROGRESS
        self.status_reason = 'Stack %s started' % self.action

        # generate new traversal and store
        previous_traversal = self.current_traversal
        self.current_traversal = uuidutils.generate_uuid()
        # we expect to update the stack having previous traversal ID
        stack_id = self.store(exp_trvsl=previous_traversal)
        if stack_id is None:
            LOG.warning("Failed to store stack %(name)s with traversal "
                        "ID %(trvsl_id)s, aborting stack %(action)s",
                        {'name': self.name, 'trvsl_id': previous_traversal,
                         'action': self.action})
            return
        self._send_notification_and_add_event()

        # delete the prev traversal sync_points
        if previous_traversal:
            sync_point.delete_all(self.context, self.id, previous_traversal)

        # TODO(later): lifecycle_plugin_utils.do_pre_ops

        self.thread_group_mgr.start(self.id, self._converge_create_or_update)

    def _converge_create_or_update(self):
        current_resources = self._update_or_store_resources()
        self._compute_convg_dependencies(self.ext_rsrcs_db, self.dependencies,
                                         current_resources)
        # Store list of edges
        self.current_deps = {
            'edges': [[rqr, rqd] for rqr, rqd in
                      self.convergence_dependencies.graph().edges()]}
        stack_id = self.store()
        if stack_id is None:
            # Failed concurrent update
            LOG.warning("Failed to store stack %(name)s with traversal "
                        "ID %(trvsl_id)s, aborting stack %(action)s",
                        {'name': self.name, 'trvsl_id': self.current_traversal,
                         'action': self.action})
            return

        LOG.info('convergence_dependencies: %s',
                 self.convergence_dependencies)

        # create sync_points for resources in DB
        for rsrc_id, is_update in self.convergence_dependencies:
            sync_point.create(self.context, rsrc_id,
                              self.current_traversal, is_update,
                              self.id)
        # create sync_point entry for stack
        sync_point.create(
            self.context, self.id, self.current_traversal, True, self.id)

        leaves = set(self.convergence_dependencies.leaves())
        if not any(leaves):
            self.mark_complete()
        else:
            for rsrc_id, is_update in self.convergence_dependencies.leaves():
                if is_update:
                    LOG.info("Triggering resource %s for update", rsrc_id)
                else:
                    LOG.info("Triggering resource %s for cleanup",
                             rsrc_id)
                input_data = sync_point.serialize_input_data({})
                self.worker_client.check_resource(self.context, rsrc_id,
                                                  self.current_traversal,
                                                  input_data, is_update,
                                                  self.adopt_stack_data,
                                                  self.converge)
                if scheduler.ENABLE_SLEEP:
                    eventlet.sleep(1)

    def rollback(self):
        old_tmpl_id = self.prev_raw_template_id
        if old_tmpl_id is None:
            rollback_tmpl = tmpl.Template.create_empty_template(
                version=self.t.version)
        else:
            rollback_tmpl = tmpl.Template.load(self.context, old_tmpl_id)
            self.prev_raw_template_id = None
            stack_id = self.store()
            if stack_id is None:
                # Failed concurrent update
                LOG.warning("Failed to store stack %(name)s with traversal"
                            " ID %(trvsl_id)s, not triggering rollback.",
                            {'name': self.name,
                             'trvsl_id': self.current_traversal})
                return

        self.converge_stack(rollback_tmpl, action=self.ROLLBACK)

    def _get_best_existing_rsrc_db(self, rsrc_name):
        candidate = None
        if self.ext_rsrcs_db:
            for id, ext_rsrc in self.ext_rsrcs_db.items():
                if ext_rsrc.name != rsrc_name:
                    continue
                if ext_rsrc.current_template_id == self.t.id:
                    # Rollback where the previous resource still exists
                    candidate = ext_rsrc
                    break
                elif (ext_rsrc.current_template_id ==
                        self.prev_raw_template_id):
                    # Current resource is otherwise a good candidate
                    candidate = ext_rsrc
                elif candidate is None:
                    # In multiple concurrent updates, if candidate is not
                    # found in current/previous template, it could be found
                    # in old tmpl.
                    candidate = ext_rsrc

        return candidate

    def _update_or_store_resources(self):
        self.ext_rsrcs_db = self.db_active_resources_get()

        curr_name_translated_dep = self.dependencies.translate(lambda res:
                                                               res.name)
        rsrcs = {}

        def update_needed_by(res):
            new_requirers = set(
                rsrcs[rsrc_name].id for rsrc_name in
                curr_name_translated_dep.required_by(res.name)
            )
            old_requirers = set(res.needed_by) if res.needed_by else set()
            needed_by = old_requirers | new_requirers
            res.needed_by = list(needed_by)

        for rsrc in reversed(self.dependencies):
            existing_rsrc_db = self._get_best_existing_rsrc_db(rsrc.name)
            if existing_rsrc_db is None:
                update_needed_by(rsrc)
                rsrc.current_template_id = self.t.id
                rsrc.store()
                rsrcs[rsrc.name] = rsrc
            else:
                update_needed_by(existing_rsrc_db)
                resource.Resource.set_needed_by(
                    existing_rsrc_db, existing_rsrc_db.needed_by
                )
                rsrcs[existing_rsrc_db.name] = existing_rsrc_db
        return rsrcs

    def set_resource_deps(self):
        curr_name_translated_dep = self.dependencies.translate(lambda res:
                                                               res.id)
        ext_rsrcs_db = self.db_active_resources_get()
        for r in self.dependencies:
            r.needed_by = list(curr_name_translated_dep.required_by(r.id))
            r.requires = list(curr_name_translated_dep.requires(r.id))
            resource.Resource.set_needed_by(ext_rsrcs_db[r.id], r.needed_by)
            resource.Resource.set_requires(ext_rsrcs_db[r.id], r.requires)

    def _compute_convg_dependencies(self, existing_resources,
                                    current_template_deps, current_resources):
        def make_graph_key(rsrc):
            return current_resources[rsrc.name].id, True
        dep = current_template_deps.translate(make_graph_key)
        if existing_resources:
            for rsrc_id, rsrc in existing_resources.items():
                dep += (rsrc_id, False), None

                for requirement in rsrc.requires:
                    if requirement in existing_resources:
                        dep += (requirement, False), (rsrc_id, False)
                if rsrc.replaces in existing_resources:
                    dep += (rsrc.replaces, False), (rsrc_id, False)

                if (rsrc.id, True) in dep:
                    dep += (rsrc_id, False), (rsrc_id, True)

        self._convg_deps = dep

    @property
    def convergence_dependencies(self):
        if self._convg_deps is None:
            current_deps = ([tuple(i), (tuple(j) if j is not None else None)]
                            for i, j in self.current_deps['edges'])
            self._convg_deps = dependencies.Dependencies(edges=current_deps)

        return self._convg_deps

    def reset_stack_and_resources_in_progress(self, reason):
        for name, rsrc in six.iteritems(self.resources):
            if rsrc.status == rsrc.IN_PROGRESS:
                rsrc.state_set(rsrc.action,
                               rsrc.FAILED,
                               six.text_type(reason))
        self.state_set(self.action, self.FAILED, six.text_type(reason))

    @scheduler.wrappertask
    def update_task(self, newstack, action=UPDATE, msg_queue=None):
        if action not in (self.UPDATE, self.ROLLBACK, self.RESTORE):
            LOG.error("Unexpected action %s passed to update!", action)
            self.state_set(self.UPDATE, self.FAILED,
                           "Invalid action %s" % action)
            return

        try:
            lifecycle_plugin_utils.do_pre_ops(self.context, self,
                                              newstack, action)
        except Exception as e:
            self.state_set(action, self.FAILED, e.args[0] if e.args else
                           'Failed stack pre-ops: %s' % six.text_type(e))
            return
        if self.status == self.IN_PROGRESS:
            if action == self.ROLLBACK:
                LOG.debug("Starting update rollback for %s", self.name)
            else:
                reason = _('Attempted to %s an IN_PROGRESS '
                           'stack') % action
                self.reset_stack_and_resources_in_progress(reason)
                return

        # Save a copy of the new template.  To avoid two DB writes
        # we store the ID at the same time as the action/status
        prev_tmpl_id = self.prev_raw_template_id
        # newstack.t may have been pre-stored, so save with that one
        bu_tmpl, newstack.t = newstack.t, copy.deepcopy(newstack.t)
        self.prev_raw_template_id = bu_tmpl.store(self.context)
        self.action = action
        self.status = self.IN_PROGRESS
        self.status_reason = 'Stack %s started' % action
        self._send_notification_and_add_event()
        self.store()
        if prev_tmpl_id is not None:
            raw_template_object.RawTemplate.delete(self.context, prev_tmpl_id)

        if action == self.UPDATE:
            # Oldstack is useless when the action is not UPDATE , so we don't
            # need to build it, this can avoid some unexpected errors.
            kwargs = self.get_kwargs_for_cloning(keep_tags=True)
            self._ensure_encrypted_param_names_valid()
            oldstack = Stack(self.context, self.name, copy.deepcopy(self.t),
                             **kwargs)

        backup_stack = self._backup_stack()
        existing_params = environment.Environment({env_fmt.PARAMETERS:
                                                  self.t.env.params})
        previous_template_id = None
        should_rollback = False
        update_task = update.StackUpdate(
            self, newstack, backup_stack,
            rollback=action == self.ROLLBACK)
        try:
            updater = scheduler.TaskRunner(update_task)

            self.defn.parameters = newstack.defn.parameters
            self.defn.t.files = newstack.defn.t.files
            self.defn.t.env = newstack.defn.t.env
            self.disable_rollback = newstack.disable_rollback
            self.timeout_mins = newstack.timeout_mins
            self._set_param_stackid()

            self.tags = newstack.tags
            if newstack.tags:
                stack_tag_object.StackTagList.set(self.context, self.id,
                                                  newstack.tags)
            else:
                stack_tag_object.StackTagList.delete(self.context, self.id)

            check_message = functools.partial(self._check_for_message,
                                              msg_queue)
            try:
                yield updater.as_task(timeout=self.timeout_secs(),
                                      progress_callback=check_message)
            finally:
                self.reset_dependencies()

            if action in (self.UPDATE, self.RESTORE, self.ROLLBACK):
                self.status_reason = 'Stack %s completed successfully' % action
            self.status = self.COMPLETE

        except scheduler.Timeout:
            self.status = self.FAILED
            self.status_reason = 'Timed out'
        except Exception as e:
            # If rollback is enabled when resource failure occurred,
            # we do another update, with the existing template,
            # so we roll back to the original state
            should_rollback = self._update_exception_handler(e, action)
            if should_rollback:
                yield self.update_task(oldstack, action=self.ROLLBACK)
        except BaseException as e:
            with excutils.save_and_reraise_exception():
                self._update_exception_handler(e, action)
        else:
            LOG.debug('Deleting backup stack')
            backup_stack.delete(backup=True)

            # flip the template to the newstack values
            previous_template_id = self.t.id
            self.t = newstack.t
            self._outputs = None
        finally:
            if should_rollback:
                # Already handled in rollback task
                return

            # Don't use state_set to do only one update query and avoid race
            # condition with the COMPLETE status
            self.action = action

            self._log_status()
            self._send_notification_and_add_event()
            if self.status == self.FAILED:
                # Since template was incrementally updated based on existing
                # and new stack resources, we should have user params of both.
                existing_params.load(newstack.t.env.user_env_as_dict())
                self.t.env = existing_params
                # Update the template version, in case new things were used
                self.t.t[newstack.t.version[0]] = max(
                    newstack.t.version[1], self.t.version[1])
                self.t.merge_snippets(newstack.t)
                self.t.store(self.context)
                backup_stack.t.env = existing_params
                backup_stack.t.t[newstack.t.version[0]] = max(
                    newstack.t.version[1], self.t.version[1])
                backup_stack.t.merge_snippets(newstack.t)
                backup_stack.t.store(self.context)
            self.store()

            if previous_template_id is not None:
                raw_template_object.RawTemplate.delete(self.context,
                                                       previous_template_id)

            lifecycle_plugin_utils.do_post_ops(self.context, self,
                                               newstack, action,
                                               (self.status == self.FAILED))

    def _update_exception_handler(self, exc, action):
        """Handle exceptions in update_task.

        Decide if we should cancel tasks or not. Also decide if we should
        rollback or not, depend on disable rollback flag if force rollback flag
        not triggered.

        :returns: a boolean for require rollback flag.
        """
        self.status_reason = six.text_type(exc)
        self.status = self.FAILED
        if action != self.UPDATE:
            return False
        if isinstance(exc, ForcedCancel):
            return exc.with_rollback or not self.disable_rollback
        elif isinstance(exc, exception.ResourceFailure):
            return not self.disable_rollback
        else:
            return False

    def _ensure_encrypted_param_names_valid(self):
        # If encryption was enabled when the stack was created but
        # then disabled when the stack was updated, env.params and
        # env.encrypted_param_names will be in an inconsistent
        # state
        if not cfg.CONF.encrypt_parameters_and_properties:
            self.t.env.encrypted_param_names = []

    @staticmethod
    def _check_for_message(msg_queue):
        if msg_queue is None:
            return
        try:
            message = msg_queue.get_nowait()
        except eventlet.queue.Empty:
            return

        if message == rpc_api.THREAD_CANCEL:
            raise ForcedCancel(with_rollback=False)
        elif message == rpc_api.THREAD_CANCEL_WITH_ROLLBACK:
            raise ForcedCancel(with_rollback=True)

        LOG.error('Unknown message "%s" received', message)

    def _delete_backup_stack(self, stack):
        # Delete resources in the backup stack referred to by 'stack'

        def failed(child):
            return (child.action == child.CREATE and
                    child.status in (child.FAILED, child.IN_PROGRESS))

        def copy_data(source_res, destination_res):
            if source_res.data():
                for key, val in six.iteritems(source_res.data()):
                    destination_res.data_set(key, val)

        for key, backup_res in stack.resources.items():
            # If UpdateReplace is failed, we must restore backup_res
            # to existing_stack in case of it may have dependencies in
            # these stacks. curr_res is the resource that just
            # created and failed, so put into the stack to delete anyway.
            backup_res_id = backup_res.resource_id
            curr_res = self.resources.get(key)
            if backup_res_id is not None and curr_res is not None:
                curr_res_id = curr_res.resource_id
                if (any(failed(child) for child in
                        self.dependencies[curr_res]) or
                        curr_res.status in
                        (curr_res.FAILED, curr_res.IN_PROGRESS)):
                    # If child resource failed to update, curr_res
                    # should be replaced to resolve dependencies. But this
                    # is not fundamental solution. If there are update
                    # failer and success resources in the children, cannot
                    # delete the stack.
                    # Stack class owns dependencies as set of resource's
                    # objects, so we switch members of the resource that is
                    # needed to delete it.
                    self.resources[key].resource_id = backup_res_id
                    self.resources[key].properties = backup_res.properties
                    copy_data(backup_res, self.resources[key])

                    stack.resources[key].resource_id = curr_res_id
                    stack.resources[key].properties = curr_res.properties
                    copy_data(curr_res, stack.resources[key])

        stack.delete(backup=True)

    def _try_get_user_creds(self):
        # There are cases where the user_creds cannot be returned
        # due to credentials truncated when being saved to DB.
        # Ignore this error instead of blocking stack deletion.
        try:
            return ucreds_object.UserCreds.get_by_id(self.context,
                                                     self.user_creds_id)
        except exception.Error:
            LOG.exception("Failed to retrieve user_creds")
            return None

    def _delete_credentials(self, stack_status, reason, abandon):
        # Cleanup stored user_creds so they aren't accessible via
        # the soft-deleted stack which remains in the DB
        # The stack_status and reason passed in are current values, which
        # may get rewritten and returned from this method
        if self.user_creds_id:
            user_creds = self._try_get_user_creds()
            # If we created a trust, delete it
            if user_creds is not None:
                trust_id = user_creds.get('trust_id')
                if trust_id:
                    try:
                        # If the trustor doesn't match the context user the
                        # we have to use the stored context to cleanup the
                        # trust, as although the user evidently has
                        # permission to delete the stack, they don't have
                        # rights to delete the trust unless an admin
                        trustor_id = user_creds.get('trustor_user_id')
                        if self.context.user_id != trustor_id:
                            LOG.debug("Context user_id doesn't match "
                                      "trustor, using stored context")
                            sc = self.stored_context()
                            sc.clients.client('keystone').delete_trust(
                                trust_id)
                        else:
                            self.clients.client('keystone').delete_trust(
                                trust_id)
                    except Exception as ex:
                        LOG.exception("Error deleting trust")
                        stack_status = self.FAILED
                        reason = ("Error deleting trust: %s" %
                                  six.text_type(ex))

            # Delete the stored credentials
            try:
                ucreds_object.UserCreds.delete(self.context,
                                               self.user_creds_id)
            except exception.NotFound:
                LOG.info("Tried to delete user_creds that do not exist "
                         "(stack=%(stack)s user_creds_id=%(uc)s)",
                         {'stack': self.id, 'uc': self.user_creds_id})

            try:
                self.user_creds_id = None
                self.store()
            except exception.NotFound:
                LOG.info("Tried to store a stack that does not exist %s",
                         self.id)

        # If the stack has a domain project, delete it
        if self.stack_user_project_id and not abandon:
            try:
                keystone = self.clients.client('keystone')
                keystone.delete_stack_domain_project(
                    project_id=self.stack_user_project_id)
            except Exception as ex:
                LOG.exception("Error deleting project")
                stack_status = self.FAILED
                reason = "Error deleting project: %s" % six.text_type(ex)

        return stack_status, reason

    @profiler.trace('Stack.delete', hide_args=False)
    @reset_state_on_error
    def delete(self, action=DELETE, backup=False, abandon=False):
        """Delete all of the resources, and then the stack itself.

        The action parameter is used to differentiate between a user
        initiated delete and an automatic stack rollback after a failed
        create, which amount to the same thing, but the states are recorded
        differently.

        Note abandon is a delete where all resources have been set to a
        RETAIN deletion policy, but we also don't want to delete anything
        required for those resources, e.g the stack_user_project.
        """
        if action not in (self.DELETE, self.ROLLBACK):
            LOG.error("Unexpected action %s passed to delete!", action)
            self.state_set(self.DELETE, self.FAILED,
                           "Invalid action %s" % action)
            return

        stack_status = self.COMPLETE
        reason = 'Stack %s completed successfully' % action
        self.state_set(action, self.IN_PROGRESS, 'Stack %s started' %
                       action)

        backup_stack = self._backup_stack(False)
        if backup_stack:
            self._delete_backup_stack(backup_stack)
            if backup_stack.status != backup_stack.COMPLETE:
                errs = backup_stack.status_reason
                failure = 'Error deleting backup resources: %s' % errs
                self.state_set(action, self.FAILED,
                               'Failed to %s : %s' % (action, failure))
                return

        self.delete_all_snapshots()

        if not backup:
            try:
                lifecycle_plugin_utils.do_pre_ops(self.context, self,
                                                  None, action)
            except Exception as e:
                self.state_set(action, self.FAILED,
                               e.args[0] if e.args else
                               'Failed stack pre-ops: %s' % six.text_type(e))
                return

        action_task = scheduler.DependencyTaskGroup(self.dependencies,
                                                    resource.Resource.destroy,
                                                    reverse=True)
        try:
            scheduler.TaskRunner(action_task)(timeout=self.timeout_secs())
        except exception.ResourceFailure as ex:
            stack_status = self.FAILED
            reason = 'Resource %s failed: %s' % (action, six.text_type(ex))
        except scheduler.Timeout:
            stack_status = self.FAILED
            reason = '%s timed out' % action.title()

        # If the stack delete succeeded, this is not a backup stack and it's
        # not a nested stack, we should delete the credentials
        if stack_status != self.FAILED and not backup and not self.owner_id:
            stack_status, reason = self._delete_credentials(stack_status,
                                                            reason,
                                                            abandon)

        try:
            self.state_set(action, stack_status, reason)
        except exception.NotFound:
            LOG.info("Tried to delete stack that does not exist "
                     "%s ", self.id)

        if not backup:
            lifecycle_plugin_utils.do_post_ops(self.context, self,
                                               None, action,
                                               (self.status == self.FAILED))
        if stack_status != self.FAILED:
            # delete the stack
            try:
                stack_object.Stack.delete(self.context, self.id)
            except exception.NotFound:
                LOG.info("Tried to delete stack that does not exist "
                         "%s ", self.id)
            self.id = None

    @profiler.trace('Stack.suspend', hide_args=False)
    @reset_state_on_error
    def suspend(self):
        """Suspend the stack.

        Invokes handle_suspend for all stack resources.

        Waits for all resources to become SUSPEND_COMPLETE then declares the
        stack SUSPEND_COMPLETE.
        Note the default implementation for all resources is to do nothing
        other than move to SUSPEND_COMPLETE, so the resources must implement
        handle_suspend for this to have any effect.
        """
        # No need to suspend if the stack has been suspended
        if self.state == (self.SUSPEND, self.COMPLETE):
            LOG.info('%s is already suspended', self)
            return

        self.updated_time = oslo_timeutils.utcnow()
        sus_task = scheduler.TaskRunner(
            self.stack_task,
            action=self.SUSPEND,
            reverse=True)
        sus_task(timeout=self.timeout_secs())

    @profiler.trace('Stack.resume', hide_args=False)
    @reset_state_on_error
    def resume(self):
        """Resume the stack.

        Invokes handle_resume for all stack resources.

        Waits for all resources to become RESUME_COMPLETE then declares the
        stack RESUME_COMPLETE.
        Note the default implementation for all resources is to do nothing
        other than move to RESUME_COMPLETE, so the resources must implement
        handle_resume for this to have any effect.
        """
        # No need to resume if the stack has been resumed
        if self.state == (self.RESUME, self.COMPLETE):
            LOG.info('%s is already resumed', self)
            return

        self.updated_time = oslo_timeutils.utcnow()
        sus_task = scheduler.TaskRunner(
            self.stack_task,
            action=self.RESUME,
            reverse=False)
        sus_task(timeout=self.timeout_secs())

    @profiler.trace('Stack.snapshot', hide_args=False)
    @reset_state_on_error
    def snapshot(self, save_snapshot_func):
        """Snapshot the stack, invoking handle_snapshot on all resources."""
        self.updated_time = oslo_timeutils.utcnow()
        sus_task = scheduler.TaskRunner(
            self.stack_task,
            action=self.SNAPSHOT,
            reverse=False,
            pre_completion_func=save_snapshot_func)
        sus_task(timeout=self.timeout_secs())

    def delete_all_snapshots(self):
        """Remove all snapshots for this stack."""
        snapshots = snapshot_object.Snapshot.get_all(self.context, self.id)
        for snapshot in snapshots:
            self.delete_snapshot(snapshot)
            snapshot_object.Snapshot.delete(self.context, snapshot.id)

    @profiler.trace('Stack.delete_snapshot', hide_args=False)
    def delete_snapshot(self, snapshot):
        """Remove a snapshot from the backends."""
        for name, rsrc in six.iteritems(self.resources):
            snapshot_data = snapshot.data
            if snapshot_data:
                data = snapshot.data['resources'].get(name)
                if data:
                    scheduler.TaskRunner(rsrc.delete_snapshot, data)()

    def restore_data(self, snapshot):
        env = environment.Environment(snapshot.data['environment'])
        files = snapshot.data['files']
        template = tmpl.Template(snapshot.data['template'],
                                 env=env, files=files)
        newstack = self.__class__(self.context, self.name, template,
                                  timeout_mins=self.timeout_mins,
                                  disable_rollback=self.disable_rollback)

        for name in newstack.defn.enabled_rsrc_names():
            defn = newstack.defn.resource_definition(name)
            rsrc = resource.Resource(name, defn, self)
            data = snapshot.data['resources'].get(name)
            handle_restore = getattr(rsrc, 'handle_restore', None)
            if callable(handle_restore):
                defn = handle_restore(defn, data)
            template.add_resource(defn, name)

        newstack.parameters.set_stack_id(self.identifier())

        return newstack, template

    @reset_state_on_error
    def restore(self, snapshot):
        """Restore the given snapshot.

        Invokes handle_restore on all resources.
        """
        self.updated_time = oslo_timeutils.utcnow()
        newstack = self.restore_data(snapshot)[0]

        updater = scheduler.TaskRunner(self.update_task, newstack,
                                       action=self.RESTORE)
        updater()

    def restart_resource(self, resource_name):
        """Restart the resource specified by resource_name.

        stop resource_name and all that depend on it
        start resource_name and all that depend on it
        """
        warnings.warn("Stack.restart_resource() is horribly broken and will "
                      "never be fixed. If you're using it in a resource type "
                      "other than HARestarter, don't. And don't use "
                      "HARestarter either.",
                      DeprecationWarning)

        deps = self.dependencies[self[resource_name]]
        failed = False

        for res in reversed(deps):
            try:
                scheduler.TaskRunner(res.destroy)()
            except exception.ResourceFailure as ex:
                failed = True
                LOG.info('Resource %(name)s delete failed: %(ex)s',
                         {'name': res.name, 'ex': ex})

        for res in deps:
            if not failed:
                try:
                    res.state_reset()
                    scheduler.TaskRunner(res.create)()
                except exception.ResourceFailure as ex:
                    failed = True
                    LOG.info('Resource %(name)s create failed: '
                             '%(ex)s', {'name': res.name, 'ex': ex})
            else:
                res.state_set(res.CREATE, res.FAILED,
                              'Resource restart aborted')
        # TODO(asalkeld) if any of this fails we Should
        # restart the whole stack

    def get_availability_zones(self):
        nova = self.clients.client('nova')
        if self._zones is None:
            self._zones = [
                zone.zoneName for zone in
                nova.availability_zones.list(detailed=False)]
        return self._zones

    def set_stack_user_project_id(self, project_id):
        self.stack_user_project_id = project_id
        self.store()

    @profiler.trace('Stack.create_stack_user_project_id', hide_args=False)
    def create_stack_user_project_id(self):
        project_id = self.clients.client(
            'keystone').create_stack_domain_project(self.id)
        self.set_stack_user_project_id(project_id)

    @profiler.trace('Stack.prepare_abandon', hide_args=False)
    def prepare_abandon(self):
        return {
            'name': self.name,
            'id': self.id,
            'action': self.action,
            'environment': self.env.user_env_as_dict(),
            'files': self.t.files,
            'status': self.status,
            'template': self.t.t,
            'resources': dict((res.name, res.prepare_abandon())
                              for res in six.itervalues(self.resources)),
            'project_id': self.tenant_id,
            'stack_user_project_id': self.stack_user_project_id,
            'tags': self.tags,
        }

    def mark_complete(self):
        """Mark the update as complete.

        This currently occurs when all resources have been updated; there may
        still be resources being cleaned up, but the Stack should now be in
        service.
        """

        LOG.info('[%(name)s(%(id)s)] update traversal %(tid)s complete',
                 {'name': self.name, 'id': self.id,
                  'tid': self.current_traversal})

        reason = 'Stack %s completed successfully' % self.action
        updated = self.state_set(self.action, self.COMPLETE, reason)
        if not updated:
            return

        self.purge_db()

    def purge_db(self):
        """Cleanup database after stack has completed/failed.

        1. Delete the resources from DB.
        2. If the stack failed, update the current_traversal to empty string
        so that the resource workers bail out.
        3. Delete previous raw template if stack completes successfully.
        4. Deletes all sync points. They are no longer needed after stack
           has completed/failed.
        5. Delete the stack if the action is DELETE.
       """
        resource_objects.Resource.purge_deleted(self.context, self.id)

        exp_trvsl = self.current_traversal
        if self.status == self.FAILED:
            self.current_traversal = ''

        prev_tmpl_id = None
        if (self.prev_raw_template_id is not None and
                self.status != self.FAILED):
            prev_tmpl_id = self.prev_raw_template_id
            self.prev_raw_template_id = None

        stack_id = self.store(exp_trvsl=exp_trvsl)
        if stack_id is None:
            # Failed concurrent update
            LOG.warning("Failed to store stack %(name)s with traversal ID "
                        "%(trvsl_id)s, aborting stack purge",
                        {'name': self.name,
                         'trvsl_id': self.current_traversal})
            return

        if prev_tmpl_id is not None:
            raw_template_object.RawTemplate.delete(self.context, prev_tmpl_id)

        sync_point.delete_all(self.context, self.id, exp_trvsl)

        if (self.action, self.status) == (self.DELETE, self.COMPLETE):
            if not self.owner_id:
                status, reason = self._delete_credentials(
                    self.status,
                    self.status_reason,
                    False)
                if status == self.FAILED:
                    # something wrong when delete credentials, set FAILED
                    self.state_set(self.action, status, reason)
                    return
            try:
                stack_object.Stack.delete(self.context, self.id)
            except exception.NotFound:
                pass

    def time_elapsed(self):
        """Time elapsed in seconds since the stack operation started."""
        start_time = self.updated_time or self.created_time
        return (oslo_timeutils.utcnow() - start_time).total_seconds()

    def time_remaining(self):
        """Time left before stack times out."""
        return self.timeout_secs() - self.time_elapsed()

    def has_timed_out(self):
        """Returns True if this stack has timed-out."""
        if self.status == self.IN_PROGRESS:
            return self.time_elapsed() > self.timeout_secs()

        return False

    def migrate_to_convergence(self):
        values = {'current_template_id': self.t.id}
        db_rsrcs = self.db_active_resources_get()
        if db_rsrcs is not None:
            for res in db_rsrcs.values():
                res.update_and_save(values=values)
        self.set_resource_deps()
        self.current_traversal = uuidutils.generate_uuid()
        self.convergence = True
        prev_raw_template_id = self.prev_raw_template_id
        self.prev_raw_template_id = None
        self.store(ignore_traversal_check=True)
        if prev_raw_template_id:
            raw_template_object.RawTemplate.delete(self.context,
                                                   prev_raw_template_id)