Move the code over for now

27 files changed, 1370 insertions, 0 deletions

diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..c332405
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,176 @@
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+
diff --git a/setup.py b/setup.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/setup.py
diff --git a/taskflow/__init__.py b/taskflow/__init__.py
new file mode 100644
index 0000000..cd51019
--- /dev/null
+++ b/taskflow/__init__.py
@@ -0,0 +1,37 @@
+# -*- 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.
+
+
+# Useful to know when other tasks are being activated and finishing.
+STARTING = 'STARTING'
+COMPLETED = 'COMPLETED'
+ERRORED = 'ERRORED'
+
+
+class Failure(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, task, name, workflow, exception):
+        self.task = task
+        self.name = name
+        self.workflow = workflow
+        self.exception = exception
+
+
+
diff --git a/taskflow/job.py b/taskflow/job.py
new file mode 100644
index 0000000..8873083
--- /dev/null
+++ b/taskflow/job.py
@@ -0,0 +1,59 @@
+# -*- 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
+
+CLAIMED = 'claimed'
+UNCLAIMED = 'unclaimed'
+
+
+class Job(object):
+    __metaclass__ = abc.ABCMeta
+
+    def __init__(self, name, type, reservation):
+        self.name = name
+        # A link back to the reservation which
+        # can be used to query information about
+        # this job (and its subsequent
+        # workflows and tasks).
+        self.reservation = reservation
+        # TBD - likely more details about this job
+        self.details = None
+        self.state = UNCLAIMED
+        self.owner = None
+
+    @abc.abstractproperty
+    def type(self):
+        # Returns which type of job this is.
+        #
+        # For example, a 'run_instance' job, or a 'delete_instance' job could
+        # be possible types.
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def claim(self, owner):
+        # This can be used to transition this job from unclaimed to claimed.
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def consume(self):
+        # This can be used to transition this job from active to finished.
+        #
+        # During said transition the job and any details of it may be removed
+        # from some backing storage (if applicable).
+        raise NotImplementedError()
diff --git a/taskflow/jobboard/__init__.py b/taskflow/jobboard/__init__.py
new file mode 100644
index 0000000..8ae8604
--- /dev/null
+++ b/taskflow/jobboard/__init__.py
@@ -0,0 +1,26 @@
+# -*- 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.
+
+"""
+The jobboard service for Nova. Different implementations can be plugged
+according to the Nova configuration.
+"""
+
+from nova.workflow.jobboard import api
+
+API = api.API
diff --git a/taskflow/jobboard/api.py b/taskflow/jobboard/api.py
new file mode 100644
index 0000000..f5ff742
--- /dev/null
+++ b/taskflow/jobboard/api.py
@@ -0,0 +1,95 @@
+# -*- 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 contextlib
+
+from oslo.config import cfg
+
+from nova.openstack.common import importutils
+from nova.openstack.common import log as logging
+
+LOG = logging.getLogger(__name__)
+jobboard_driver_opt = cfg.StrOpt('job_board_driver',
+                                 default='memory',
+                                 help='The driver that satisfies the '
+                                      'job providing service ( '
+                                      'valid options are: db, mq, zk, memory)')
+
+CONF = cfg.CONF
+CONF.register_opts([jobboard_driver_opt])
+
+
+class API(object):
+
+    _driver = None
+    _driver_name_class_mapping = {
+        # TBD
+    }
+
+    def __new__(cls, *args, **kwargs):
+        '''Create an instance of the lock provider API.
+
+        args and kwargs are passed down to the job board driver when it gets
+        created.
+        '''
+        if not cls._driver:
+            LOG.debug(_('Job board driver defined as an instance of %s'),
+                      str(CONF.job_board_driver))
+            driver_name = CONF.job_board_driver
+            try:
+                driver_class = cls._driver_name_class_mapping[driver_name]
+            except KeyError:
+                raise TypeError(_("Unknown job board driver name: %s")
+                                % driver_name)
+            cls._driver = importutils.import_object(driver_class,
+                                                    *args, **kwargs)
+            utils.check_isinstance(cls._driver, JobBoardDriver)
+        return super(API, cls).__new__(cls)
+
+
+class JobBoardDriver(object):
+    """Base class for job board drivers."""
+
+    __metaclass__ = abc.ABCMeta
+
+    def __init__(self):
+        self._listeners = []
+
+    @abc.abstractmethod
+    def post(self, job):
+        raise NotImplementedError()
+
+    def _notify_posted(self, job):
+        for i in self._listeners:
+            i.notify_posted(job)
+
+    @abc.abstractmethod
+    def await(self, blocking=True):
+        raise NotImplementedError()
+
+    def subscribe(self, listener):
+        self._listeners.append(listener)
+
+    def unsubscribe(self, listener):
+        if listener in self._listeners:
+            self._listeners.remove(listener)
+
+    def close(self):
+        """Allows the job board provider to free any resources that it has."""
+        pass
diff --git a/taskflow/jobboard/drivers/__init__.py b/taskflow/jobboard/drivers/__init__.py
new file mode 100644
index 0000000..830dd2e
--- /dev/null
+++ b/taskflow/jobboard/drivers/__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.
diff --git a/taskflow/jobboard/drivers/db.py b/taskflow/jobboard/drivers/db.py
new file mode 100644
index 0000000..27ef755
--- /dev/null
+++ b/taskflow/jobboard/drivers/db.py
@@ -0,0 +1,18 @@
+# -*- 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.
+
diff --git a/taskflow/jobboard/drivers/memory.py b/taskflow/jobboard/drivers/memory.py
new file mode 100644
index 0000000..27ef755
--- /dev/null
+++ b/taskflow/jobboard/drivers/memory.py
@@ -0,0 +1,18 @@
+# -*- 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.
+
diff --git a/taskflow/jobboard/drivers/mq.py b/taskflow/jobboard/drivers/mq.py
new file mode 100644
index 0000000..27ef755
--- /dev/null
+++ b/taskflow/jobboard/drivers/mq.py
@@ -0,0 +1,18 @@
+# -*- 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.
+
diff --git a/taskflow/jobboard/drivers/zk.py b/taskflow/jobboard/drivers/zk.py
new file mode 100644
index 0000000..afb3466
--- /dev/null
+++ b/taskflow/jobboard/drivers/zk.py
@@ -0,0 +1,39 @@
+# -*- 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.
+
+from kazoo import client as kazoo_client
+
+from nova.workflow.jobboard import api
+
+from oslo.config import cfg
+
+
+CONF = cfg.CONF
+CONF.import_opt('address', 'nova.servicegroup.zk', group='zookeeper')
+CONF.import_opt('recv_timeout', 'nova.servicegroup.zk', group='zookeeper')
+
+
+class JobBoard(api.JobBoardDriver):
+    def __init__(self):
+        super(JobBoard, self).__init__()
+        self._client = kazoo_client.KazooClient(hosts=CONF.address,
+                                                timeout=CONF.recv_timeout)
+        self._client.start()
+
+    def post(self, job):
+        
diff --git a/taskflow/locks/__init__.py b/taskflow/locks/__init__.py
new file mode 100644
index 0000000..f869bbc
--- /dev/null
+++ b/taskflow/locks/__init__.py
@@ -0,0 +1,26 @@
+# -*- 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.
+
+"""
+The lock provider service for Nova. Different implementations can be plugged
+according to the Nova configuration.
+"""
+
+from nova.workflow.locks import api
+
+API = api.API
diff --git a/taskflow/locks/api.py b/taskflow/locks/api.py
new file mode 100644
index 0000000..335767a
--- /dev/null
+++ b/taskflow/locks/api.py
@@ -0,0 +1,128 @@
+# -*- 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 contextlib
+
+from oslo.config import cfg
+
+from nova.openstack.common import importutils
+from nova.openstack.common import log as logging
+from nova import utils
+
+
+LOG = logging.getLogger(__name__)
+lockprovider_driver_opt = cfg.StrOpt('lock_provider_driver',
+                                     default='memory',
+                                     help='The driver that satisfies the '
+                                          'lock providing service ('
+                                          'valid options are: db, file, '
+                                          'memory, zk)')
+
+CONF = cfg.CONF
+CONF.register_opts([lockprovider_driver_opt])
+
+
+class API(object):
+
+    _driver = None
+    _driver_name_class_mapping = {
+        # This can attempt to provide a distributed lock but extreme! care
+        # has to be taken to know when to expire a database lock, as well as
+        # extreme! care has to be taken when acquiring said lock. It is likely
+        # not possible to guarantee locking consistently and correctness when
+        # using a database to do locking.
+        'db': 'nova.locks.drivers.db.LockProvider',
+        # This can provide per system level locks but can not provide across
+        # system level locks.
+        'file': 'nova.locks.drivers.file.LockProvider',
+        # Note this driver can be used for distributed locking of resources.
+        'zk': 'nova.locks.drivers.zk.LockProvider',
+        # This driver is pretty much only useful for testing since it can
+        # only provide per-process locking using greenlet/thread level locking.
+        'memory': 'nova.locks.drivers.memory.LockProvider',
+    }
+
+    def __new__(cls, *args, **kwargs):
+        '''Create an instance of the lock provider API.
+
+        args and kwargs are passed down to the lock provider driver when it
+        gets created (if applicable).
+        '''
+        if not cls._driver:
+            LOG.debug(_('Lock provider driver defined as an instance of %s'),
+                      str(CONF.lock_provider_driver))
+            driver_name = CONF.lock_provider_driver
+            try:
+                driver_class = cls._driver_name_class_mapping[driver_name]
+            except KeyError:
+                raise TypeError(_("Unknown lock provider driver name: %s")
+                                % driver_name)
+            cls._driver = importutils.import_object(driver_class,
+                                                    *args, **kwargs)
+            utils.check_isinstance(cls._driver, LockProvider)
+        return super(API, cls).__new__(cls)
+
+
+class Lock(object):
+    """Base class for what a lock (distributed or local or in-between) should
+    provide"""
+
+    __metaclass__ = abc.ABCMeta
+
+    def __init__(self, resource_uri, blocking=True):
+        self.uri = resource_uri
+        self.blocking = blocking
+
+    @abc.abstractmethod
+    def acquire(self):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def release(self):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def is_locked(self):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def cancel(self):
+        raise NotImplementedError()
+
+    def __enter__(self):
+        self.acquire()
+
+    def __exit__(self, type, value, traceback):
+        self.release()
+
+
+class LockProvider(object):
+    """Base class for lock provider drivers."""
+
+    __metaclass__ = abc.ABCMeta
+
+    @abc.abstractmethod
+    def provide(self, resource_uri, blocking=True):
+        """Returns a single lock object which can be used to acquire the lock
+        on the given resource uri"""
+        raise NotImplementedError()
+
+    def close(self):
+        """Allows the lock provider to free any resources that it has."""
+        pass
diff --git a/taskflow/locks/drivers/__init__.py b/taskflow/locks/drivers/__init__.py
new file mode 100644
index 0000000..830dd2e
--- /dev/null
+++ b/taskflow/locks/drivers/__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.
diff --git a/taskflow/locks/drivers/db.py b/taskflow/locks/drivers/db.py
new file mode 100644
index 0000000..214332b
--- /dev/null
+++ b/taskflow/locks/drivers/db.py
@@ -0,0 +1,28 @@
+# -*- 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.
+
+from nova.workflow.locks import api
+
+
+class Lock(api.Lock):
+    pass
+
+
+class LockProvider(api.LockProvider):
+    def provide(self, resource_uri, blocking=True):
+        return Lock(resource_uri, blocking)
diff --git a/taskflow/locks/drivers/file.py b/taskflow/locks/drivers/file.py
new file mode 100644
index 0000000..214332b
--- /dev/null
+++ b/taskflow/locks/drivers/file.py
@@ -0,0 +1,28 @@
+# -*- 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.
+
+from nova.workflow.locks import api
+
+
+class Lock(api.Lock):
+    pass
+
+
+class LockProvider(api.LockProvider):
+    def provide(self, resource_uri, blocking=True):
+        return Lock(resource_uri, blocking)
diff --git a/taskflow/locks/drivers/memory.py b/taskflow/locks/drivers/memory.py
new file mode 100644
index 0000000..214332b
--- /dev/null
+++ b/taskflow/locks/drivers/memory.py
@@ -0,0 +1,28 @@
+# -*- 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.
+
+from nova.workflow.locks import api
+
+
+class Lock(api.Lock):
+    pass
+
+
+class LockProvider(api.LockProvider):
+    def provide(self, resource_uri, blocking=True):
+        return Lock(resource_uri, blocking)
diff --git a/taskflow/locks/drivers/zk.py b/taskflow/locks/drivers/zk.py
new file mode 100644
index 0000000..e4eaac2
--- /dev/null
+++ b/taskflow/locks/drivers/zk.py
@@ -0,0 +1,62 @@
+# -*- 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.
+
+from kazoo import client as kazoo_client
+from kazoo.recipe import lock as kazoo_lock
+
+from nova.workflow.locks import api
+
+from oslo.config import cfg
+
+
+CONF = cfg.CONF
+CONF.import_opt('address', 'nova.servicegroup.zk', group='zookeeper')
+CONF.import_opt('recv_timeout', 'nova.servicegroup.zk', group='zookeeper')
+
+
+class Lock(api.Lock):
+    def __init__(self, resource_uri, blocking, client):
+        super(Lock, self).__init__(resource_uri, blocking)
+        self._client = client
+        self._lock = kazoo_lock.Lock(client, resource_uri)
+
+    def acquire(self):
+        return self._lock.acquire(self._blocking)
+
+    def is_locked(self):
+        return self._lock.is_acquired
+
+    def release(self):
+        return self._lock.release()
+
+    def cancel(self):
+        return self._lock.cancel()
+
+
+class LockProvider(api.LockProvider):
+    def __init__(self, *args, **kwargs):
+        self._client = kazoo_client.KazooClient(hosts=CONF.address,
+                                                timeout=CONF.recv_timeout)
+        self._client.start()
+
+    def provide(self, resource_uri, blocking=True):
+        return Lock(self._client, resource_uri, blocking)
+
+    def close(self):
+        if self._client:
+            self._client.stop()
diff --git a/taskflow/logbook/__init__.py b/taskflow/logbook/__init__.py
new file mode 100644
index 0000000..ed33d8e
--- /dev/null
+++ b/taskflow/logbook/__init__.py
@@ -0,0 +1,26 @@
+# -*- 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.
+
+"""
+The logbook provider service for Nova. Different implementations can be plugged
+according to the Nova configuration.
+"""
+
+from nova.workflow.logbook import api
+
+API = api.API
diff --git a/taskflow/logbook/api.py b/taskflow/logbook/api.py
new file mode 100644
index 0000000..d130afa
--- /dev/null
+++ b/taskflow/logbook/api.py
@@ -0,0 +1,151 @@
+# -*- 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.
+
+# -*- 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 oslo.config import cfg
+
+"""Define APIs for the logbook providers."""
+
+from nova.openstack.common import importutils
+from nova.openstack.common import log as logging
+
+LOG = logging.getLogger(__name__)
+logprovider_driver_opt = cfg.StrOpt('logbook_provider_driver',
+                                    default='memory',
+                                    help='The driver for that satisfies the '
+                                         'remote lock providing service ( '
+                                         'valid options are: db, memory, zk)')
+
+CONF = cfg.CONF
+CONF.register_opts([logprovider_driver_opt])
+
+
+class API(object):
+
+    _driver = None
+    _driver_name_class_mapping = {
+         # Note these drivers can be used for persistant logging.
+         'zk': 'nova.logbook.drivers.zk.ZooKeeperProviderDriver',
+         'db': 'nova.logbook.drivers.db.DBProviderDriver',
+
+         # This driver is pretty much only useful for testing.
+         'memory': 'nova.logbook.drivers.memory.MemoryProviderDriver',
+    }
+
+    def __new__(cls, *args, **kwargs):
+        '''Create an instance of the logbook provider API.
+
+        args and kwargs are passed down to the logbook provider driver when it
+        gets created.
+        '''
+        if not cls._driver:
+            LOG.debug(_('Logbook provider driver defined as an instance of %s'),
+                      str(CONF.logbook_provider_driver))
+            driver_name = CONF.logbook_provider_driver
+            try:
+                driver_class = cls._driver_name_class_mapping[driver_name]
+            except KeyError:
+                raise TypeError(_("Unknown logbook provider driver name: %s")
+                                % driver_name)
+            cls._driver = importutils.import_object(driver_class,
+                                                    *args, **kwargs)
+            utils.check_isinstance(cls._driver, LogBookProviderDriver)
+        return super(API, cls).__new__(cls)
+
+
+class RecordNotFound(Exception):
+    pass
+
+
+class LogBook(object):
+    """Base class for what a logbook (distributed or local or in-between)
+    should provide"""
+
+    __metaclass__ = abc.ABCMeta
+
+    def __init__(self, resource_uri):
+        self.uri = resource_uri
+
+    @abc.abstractmethod
+    def add_record(self, name, metadata=None):
+        """Atomically adds a new entry to the given logbook with the supplied
+        metadata (if any)."""
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def fetch_record(self, name):
+        """Fetchs a record with the given name and returns any metadata about
+        said record."""
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def __contains__(self, name):
+        """Determines if any entry with the given name exists in this
+        logbook."""
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def mark(self, name, metadata, merge_functor=None):
+        """Marks the given logbook entry (which must exist) with the given
+        metadata, if said entry already exists then the provided merge functor
+        or a default function, will be activated to merge the existing metadata
+        with the supplied metadata."""
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def __iter__(self):
+        """Iterates over all names and metadata and provides back both of these
+        via a (name, metadata) tuple. The order will be in the same order that
+        they were added."""
+        raise NotImplementedError()
+
+
+class LogBookProvider(object):
+    """Base class for logbook provider drivers."""
+
+    __metaclass__ = abc.ABCMeta
+
+    @abc.abstractmethod
+    def provide(self, resource_uri):
+        """Returns a new (if not existent) logbook object or used logbook
+        object (if already existent) which can be used to determine the actions
+        performed on a given resource uri"""
+        raise NotImplementedError()
+
+    def close(self):
+        """Allows the log provider to free any resources that it has."""
+        pass
diff --git a/taskflow/logbook/drivers/db.py b/taskflow/logbook/drivers/db.py
new file mode 100644
index 0000000..830dd2e
--- /dev/null
+++ b/taskflow/logbook/drivers/db.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.
diff --git a/taskflow/logbook/drivers/memory.py b/taskflow/logbook/drivers/memory.py
new file mode 100644
index 0000000..830dd2e
--- /dev/null
+++ b/taskflow/logbook/drivers/memory.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.
diff --git a/taskflow/logbook/drivers/zk.py b/taskflow/logbook/drivers/zk.py
new file mode 100644
index 0000000..b65dc38
--- /dev/null
+++ b/taskflow/logbook/drivers/zk.py
@@ -0,0 +1,108 @@
+# -*- 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.
+
+from kazoo import client as kazoo_client
+
+from nova.openstack.common import jsonutils
+from nova.workflow.logbook import api
+
+from oslo.config import cfg
+
+
+CONF = cfg.CONF
+CONF.import_opt('address', 'nova.servicegroup.zk', group='zookeeper')
+CONF.import_opt('recv_timeout', 'nova.servicegroup.zk', group='zookeeper')
+
+
+class LogBook(api.LogBook):
+    prefix = "entry-"
+
+    def __init__(self, client, resource_uri):
+        super(LogBook, self).__init__(self, "%s/logbook" % (resource_uri))
+        self._client = client
+        self._paths_made = False
+        self._paths = [self.uri]
+
+    def _ensure_paths(self):
+        if self._paths_made:
+            return
+        for p in self._paths:
+            self._client.ensure_path(p)
+        self._paths_made = True
+
+    def add_record(self, name, metadata=None):
+        self._ensure_paths()
+        (path, value) = self._make_storage(name, metadata)
+        self._client.create(path, jsonutils.dumps(value), sequence=True)
+
+    def _make_storage(self, name, metadata):
+        path = "{root}/{prefix}".format(root=self.uri, prefix=self.prefix)
+        value = {
+            'name': name,
+            'metadata': metadata,
+        }
+        return (path, value)
+
+    def __iter__(self):
+        for c in self._client.get_children(self.uri + "/"):
+            if not c.startswith(self.prefix):
+                continue
+            (value, _zk) = self._client.get("%s/%s" % (self.uri, c))
+            value = jsonutils.loads(value)
+            yield (value['name'], value['metadata'])
+
+    def __contains__(self, name):
+        for (n, metadata) in self:
+            if name == n:
+                return True
+        return False
+
+    def mark(self, name, metadata, merge_func=None):
+        if merge_func is None:
+            merge_func = lambda old,new : new
+        for c in self._client.get_children(self.uri + "/"):
+           if not c.startswith(self.prefix):
+               continue
+           (value, _zk) = self._client.get("%s/%s" % (self.uri, c))
+           value = jsonutils.loads(value)
+           if value['name'] == name:
+               value['metadata'] = merge_func(value['metadata'], metadata)
+               self._client.set("%s/%s" % (self.uri, c),
+                                jsonutils.dumps(value))
+               return
+        raise api.RecordNotFound()
+
+    def fetch_record(self, name):
+        for n, metadata in self:
+            if name == n:
+                return metadata
+        raise api.RecordNotFound()
+
+
+class LogBookProvider(api.LogBookProvider):
+    def __init__(self, *args, **kwargs):
+        self._client = kazoo_client.KazooClient(hosts=CONF.address,
+                                                timeout=CONF.recv_timeout)
+        self._client.start()
+
+    def close(self):
+        if self._client:
+            self._client.stop()
+
+    def provide(self, resource_uri):
+        return LogBook(self._client, resource_uri)
diff --git a/taskflow/patterns/__init__.py b/taskflow/patterns/__init__.py
new file mode 100644
index 0000000..830dd2e
--- /dev/null
+++ b/taskflow/patterns/__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.
diff --git a/taskflow/patterns/linear_workflow.py b/taskflow/patterns/linear_workflow.py
new file mode 100644
index 0000000..768b52e
--- /dev/null
+++ b/taskflow/patterns/linear_workflow.py
@@ -0,0 +1,139 @@
+# -*- 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 as dict_provider
+import copy
+
+# OrderedDict is only in 2.7 or greater :-(
+if not hasattr(dict_provider, 'OrderedDict'):
+    import ordereddict as dict_provider
+
+from nova import workflow
+from nova.openstack.common import excutils
+from nova.openstack.common import log as logging
+
+LOG = logging.getLogger(__name__)
+
+
+class Workflow(object):
+    """A linear chain of independent tasks that can be applied as one unit or
+       rolled back as one unit."""
+
+    def __init__(self, name, tolerant=False, parents=None):
+        # The tasks which have been applied will be collected here so that they
+        # can be reverted in the correct order on failure.
+        self.reversions = []
+        self.name = name
+        # If this chain can ignore individual task reversion failure then this
+        # should be set to true, instead of the default value of false.
+        self.tolerant = tolerant
+        # Ordered dicts are used so that we can nicely refer to the tasks by
+        # name and easily fetch there results but also allow for the running
+        # of said tasks to happen in a linear order.
+        self.tasks = dict_provider.OrderedDict()
+        self.results = dict_provider.OrderedDict()
+        # If this workflow has a parent workflow/s which need to be reverted if
+        # this workflow fails then please include them here to allow this child
+        # to call the parents...
+        self.parents = parents
+        # This should be a functor that returns whether a given task has
+        # already ran by returning the return value of the task or returning
+        # 'None' if the task has not ran.
+        #
+        # NOTE(harlowja): This allows for resumption by skipping tasks which
+        # have already occurred. The previous return value is needed due to
+        # the contract we have with tasks that they will be given the value
+        # they returned if reversion is triggered.
+        self.result_fetcher = None
+        # Any objects that want to listen when a 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.listeners = []
+
+    def __setitem__(self, name, task):
+        self.tasks[name] = task
+
+    def __getitem__(self, name):
+        return self.results[name]
+
+    def run(self, context, *args, **kwargs):
+        for (name, task) in self.tasks.iteritems():
+            try:
+                self._on_task_start(context, task, name)
+                # See if we have already ran this...
+                result = None
+                if self.result_fetcher:
+                    result = self.result_fetcher(context, name, self)
+                if result is None:
+                    result = task.apply(context, *args, **kwargs)
+                # Keep a pristine copy of the result in the results table
+                # so that if said result is altered by other further states
+                # the one here will not be.
+                self.results[name] = copy.deepcopy(result)
+                self._on_task_finish(context, task, name, result)
+            except Exception as ex:
+                with excutils.save_and_reraise_exception():
+                    try:
+                        self._on_task_error(context, task, name)
+                    except Exception:
+                        LOG.exception(_("Dropping exception catched when"
+                                        " notifying about existing task"
+                                        " exception."))
+                    self.rollback(context,
+                                  workflow.Failure(task, name, self, ex))
+
+    def _on_task_error(self, context, task, name):
+        # Notify any listeners that the task has errored.
+        for i in self.listeners:
+            i.notify(context, workflow.ERRORED, self, task, name)
+
+    def _on_task_start(self, context, task, name):
+        # Notify any listeners that we are about to start the given task.
+        for i in self.listeners:
+            i.notify(context, workflow.STARTING, self, task, name)
+
+    def _on_task_finish(self, context, task, name, result):
+        # Notify any listeners that we are finishing the given task.
+        self.reversions.append((name, task))
+        for i in self.listeners:
+            i.notify(context, workflow.COMPLETED, self, task,
+                     name, result=result)
+
+    def rollback(self, context, cause):
+        for (i, (name, task)) in enumerate(reversed(self.reversions)):
+            try:
+                task.revert(context, self.results[name], cause)
+            except Exception:
+                # Ex: WARN: Failed rolling back stage 1 (validate_request) of
+                #           chain validation due to Y exception.
+                msg = _("Failed rolling back stage %(index)s (%(name)s)"
+                        " of workflow %(workflow)s, due to inner exception.")
+                LOG.warn(msg % {'index': (i + 1), 'stage': name,
+                         'workflow': self.name})
+                if not self.tolerant:
+                    # NOTE(harlowja): LOG a msg AND re-raise the exception if
+                    # the chain does not tolerate exceptions happening in the
+                    # rollback method.
+                    raise
+        if self.parents:
+            # Rollback any parents workflows if they exist...
+            for p in self.parents:
+                p.rollback(context, cause)
+    
diff --git a/taskflow/reservation.py b/taskflow/reservation.py
new file mode 100644
index 0000000..bb0a279
--- /dev/null
+++ b/taskflow/reservation.py
@@ -0,0 +1,30 @@
+# -*- 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 Reservation(object):
+    """This is an abstraction of a promise to complete some type of job which
+    can be returned to a user for later lookup on the progress of said
+    promise"""
+
+    def __init__(self, for_who, id):
+        self.for_who = for_who
+        self.id = id
+
+    def __str__(self):
+        return "Reservation: '%s' for '%s'" % (self.id, self.for_who)
diff --git a/taskflow/task.py b/taskflow/task.py
new file mode 100644
index 0000000..c5133f3
--- /dev/null
+++ b/taskflow/task.py
@@ -0,0 +1,45 @@
+# -*- 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
+
+
+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 __str__(self):
+        return "Task: %s" % (self.__class__.__name__)
+
+    @abc.abstractmethod
+    def apply(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