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Posted to dev@ariatosca.apache.org by mx...@apache.org on 2016/11/06 08:51:22 UTC

[2/2] incubator-ariatosca git commit: Intorduced task_graph tasks, smarter workflow context, and tests.

Intorduced task_graph tasks, smarter workflow context, and tests.


Project: http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/repo
Commit: http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/commit/9002019e
Tree: http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/tree/9002019e
Diff: http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/diff/9002019e

Branch: refs/heads/ARIA-3-api-for-creating-workflows
Commit: 9002019e8d8198745142b00a1ea872d02e54b40b
Parents: 3d1c8b1
Author: mxmrlv <mx...@gmail.com>
Authored: Mon Oct 31 15:29:16 2016 +0200
Committer: mxmrlv <mx...@gmail.com>
Committed: Sun Nov 6 10:46:05 2016 +0200

----------------------------------------------------------------------
 aria/.pylintrc                                  |   2 +-
 aria/__init__.py                                |   2 +-
 aria/cli/commands.py                            |   2 +-
 aria/context/__init__.py                        |  20 ++
 aria/context/operation.py                       |  68 ++++++
 aria/context/workflow.py                        | 188 +++++++++++++++++
 aria/contexts.py                                | 211 -------------------
 aria/decorators.py                              |  47 ++---
 aria/storage/drivers.py                         |   2 +-
 aria/storage/models.py                          |  58 ++---
 aria/workflows/api/__init__.py                  |   2 +
 aria/workflows/api/task.py                      |  90 ++++++++
 aria/workflows/api/task_graph.py                |  29 ++-
 aria/workflows/builtin/execute_operation.py     |  27 +--
 aria/workflows/builtin/heal.py                  |  91 +++++---
 aria/workflows/builtin/install.py               |  12 +-
 aria/workflows/builtin/uninstall.py             |  10 +-
 aria/workflows/builtin/workflows.py             |  85 ++++----
 aria/workflows/core/__init__.py                 |   2 +
 aria/workflows/core/executor.py                 |   5 +-
 aria/workflows/core/task.py                     | 106 ++++++++++
 aria/workflows/core/tasks.py                    | 104 ---------
 aria/workflows/core/translation.py              |  36 ++--
 tests/.pylintrc                                 |   6 +-
 tests/mock/__init__.py                          |  16 ++
 tests/mock/context.py                           |  36 ++++
 tests/mock/models.py                            | 132 ++++++++++++
 tests/mock/operations.py                        |  33 +++
 tests/test_logger.py                            |   2 +-
 tests/workflows/__init__.py                     |   2 +
 tests/workflows/api/test_task.py                | 120 +++++++++++
 tests/workflows/api/test_task_graph.py          |   9 +-
 tests/workflows/builtin/__init__.py             | 130 +-----------
 .../workflows/builtin/test_execute_operation.py |  61 ++++--
 tests/workflows/builtin/test_heal.py            |  43 +++-
 tests/workflows/builtin/test_install.py         |  38 +++-
 tests/workflows/builtin/test_uninstall.py       |  38 +++-
 tests/workflows/core/test_executor.py           |  13 +-
 .../test_task_graph_into_exececution_graph.py   |  56 ++---
 tox.ini                                         |   4 +-
 40 files changed, 1226 insertions(+), 712 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/.pylintrc
----------------------------------------------------------------------
diff --git a/aria/.pylintrc b/aria/.pylintrc
index eb188a0..ee27fdb 100644
--- a/aria/.pylintrc
+++ b/aria/.pylintrc
@@ -62,7 +62,7 @@ confidence=
 # --enable=similarities". If you want to run only the classes checker, but have
 # no Warning level messages displayed, use"--disable=all --enable=classes
 # --disable=W"
-disable=import-star-module-level,old-octal-literal,oct-method,print-statement,unpacking-in-except,parameter-unpacking,backtick,old-raise-syntax,old-ne-operator,long-suffix,dict-view-method,dict-iter-method,metaclass-assignment,next-method-called,raising-string,indexing-exception,raw_input-builtin,long-builtin,file-builtin,execfile-builtin,coerce-builtin,cmp-builtin,buffer-builtin,basestring-builtin,apply-builtin,filter-builtin-not-iterating,using-cmp-argument,useless-suppression,range-builtin-not-iterating,suppressed-message,no-absolute-import,old-division,cmp-method,reload-builtin,zip-builtin-not-iterating,intern-builtin,unichr-builtin,reduce-builtin,standarderror-builtin,unicode-builtin,xrange-builtin,coerce-method,delslice-method,getslice-method,setslice-method,input-builtin,round-builtin,hex-method,nonzero-method,map-builtin-not-iterating,redefined-builtin,logging-format-interpolation
+disable=import-star-module-level,old-octal-literal,oct-method,print-statement,unpacking-in-except,parameter-unpacking,backtick,old-raise-syntax,old-ne-operator,long-suffix,dict-view-method,dict-iter-method,metaclass-assignment,next-method-called,raising-string,indexing-exception,raw_input-builtin,long-builtin,file-builtin,execfile-builtin,coerce-builtin,cmp-builtin,buffer-builtin,basestring-builtin,apply-builtin,filter-builtin-not-iterating,using-cmp-argument,useless-suppression,range-builtin-not-iterating,suppressed-message,no-absolute-import,old-division,cmp-method,reload-builtin,zip-builtin-not-iterating,intern-builtin,unichr-builtin,reduce-builtin,standarderror-builtin,unicode-builtin,xrange-builtin,coerce-method,delslice-method,getslice-method,setslice-method,input-builtin,round-builtin,hex-method,nonzero-method,map-builtin-not-iterating,redefined-builtin,logging-format-interpolation,import-error
 
 [REPORTS]
 

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/__init__.py
----------------------------------------------------------------------
diff --git a/aria/__init__.py b/aria/__init__.py
index 4d9b0f4..eca7b9b 100644
--- a/aria/__init__.py
+++ b/aria/__init__.py
@@ -56,7 +56,7 @@ def application_model_storage(driver):
                 models.DeploymentModification,
                 models.Execution,
                 models.ProviderContext,
-                models.Operation,
+                models.Task,
             ])
     return _model_storage[driver]
 

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/cli/commands.py
----------------------------------------------------------------------
diff --git a/aria/cli/commands.py b/aria/cli/commands.py
index a38229d..f909a1e 100644
--- a/aria/cli/commands.py
+++ b/aria/cli/commands.py
@@ -29,7 +29,7 @@ from aria import application_model_storage, application_resource_storage
 from aria.logger import LoggerMixin
 from aria.storage import FileSystemModelDriver, FileSystemResourceDriver
 from aria.tools.application import StorageManager
-from aria.contexts import WorkflowContext
+from aria.context.workflow import WorkflowContext
 from aria.workflows.core.engine import Engine
 from aria.workflows.core.executor import ThreadExecutor
 

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/context/__init__.py
----------------------------------------------------------------------
diff --git a/aria/context/__init__.py b/aria/context/__init__.py
new file mode 100644
index 0000000..20e19db
--- /dev/null
+++ b/aria/context/__init__.py
@@ -0,0 +1,20 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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.
+
+"""
+Provides contexts to workflow and operation
+"""
+
+from . import workflow, operation

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/context/operation.py
----------------------------------------------------------------------
diff --git a/aria/context/operation.py b/aria/context/operation.py
new file mode 100644
index 0000000..d4d229a
--- /dev/null
+++ b/aria/context/operation.py
@@ -0,0 +1,68 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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.
+
+"""
+Workflow and operation contexts
+"""
+
+from uuid import uuid4
+
+from aria.logger import LoggerMixin
+
+class OperationContext(LoggerMixin):
+    """
+    Context object used during operation creation and execution
+    """
+
+    def __init__(
+            self,
+            name,
+            operation_details,
+            workflow_context,
+            node_instance,
+            inputs=None):
+        super(OperationContext, self).__init__()
+        self.name = name
+        self.id = str(uuid4())
+        self.operation_details = operation_details
+        self.workflow_context = workflow_context
+        self.node_instance = node_instance
+        self.inputs = inputs or {}
+
+    def __repr__(self):
+        details = ', '.join(
+            '{0}={1}'.format(key, value)
+            for key, value in self.operation_details.items())
+        return '{name}({0})'.format(details, name=self.name)
+
+    def __getattr__(self, attr):
+        try:
+            return getattr(self.workflow_context, attr)
+        except AttributeError:
+            return super(OperationContext, self).__getattribute__(attr)
+
+    @property
+    def operation(self):
+        """
+        The model operation
+        """
+        return self.storage.operation.get(self.id)
+
+    @operation.setter
+    def operation(self, value):
+        """
+        Store the operation in the model storage
+        """
+        self.storage.operation.store(value)

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/context/workflow.py
----------------------------------------------------------------------
diff --git a/aria/context/workflow.py b/aria/context/workflow.py
new file mode 100644
index 0000000..b5b4e4b
--- /dev/null
+++ b/aria/context/workflow.py
@@ -0,0 +1,188 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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.
+
+"""
+Workflow and operation contexts
+"""
+
+import threading
+from uuid import uuid4
+from contextlib import contextmanager
+
+from ..logger import LoggerMixin
+from ..tools.lru_cache import lru_cache
+
+
+class WorkflowContext(LoggerMixin):
+    """
+    Context object used during workflow creation and execution
+    """
+
+    def __init__(
+            self,
+            model_storage,
+            resource_storage,
+            deployment_id,
+            workflow_id,
+            # TODO: this should be changed when we decide where the execution is created
+            execution_id=None,
+            parameters=None,
+            **kwargs):
+        super(WorkflowContext, self).__init__(**kwargs)
+        self.id = str(uuid4())
+        self.model = model_storage
+        self.resource = resource_storage
+        self.deployment_id = deployment_id
+        self.workflow_id = workflow_id
+        self.execution_id = execution_id
+        self.parameters = parameters or {}
+
+    def __repr__(self):
+        return (
+            '{name}(deployment_id={self.deployment_id}, '
+            'workflow_id={self.workflow_id}, '
+            'execution_id={self.execution_id})'.format(
+                name=self.__class__.__name__, self=self))
+
+    @property
+    def blueprint_id(self):
+        """
+        The blueprint id
+        """
+        return self.deployment.blueprint_id
+
+    @property
+    @lru_cache()
+    def blueprint(self):
+        """
+        The blueprint model
+        """
+        return self.model.blueprint.get(self.blueprint_id)
+
+    @property
+    @lru_cache()
+    def deployment(self):
+        """
+        The deployment model
+        """
+        return self.model.deployment.get(self.deployment_id)
+
+    @property
+    def nodes(self):
+        """
+        Iterator over nodes
+        """
+        return self.model.node.iter(
+            filters={'blueprint_id': self.blueprint_id})
+
+    @property
+    def node_instances(self):
+        """
+        Iterator over node instances
+        """
+        return self.model.node_instance.iter(filters={'deployment_id': self.deployment_id})
+
+    @property
+    def execution(self):
+        """
+        The execution model
+        """
+        return self.model.execution.get(self.execution_id)
+
+    @execution.setter
+    def execution(self, value):
+        """
+        Store the execution in the model storage
+        """
+        self.model.execution.store(value)
+
+    def download_blueprint_resource(self, destination, path=None):
+        """
+        Download a blueprint resource from the resource storage
+        """
+        return self.resource.blueprint.download(
+            entry_id=self.blueprint_id,
+            destination=destination,
+            path=path)
+
+    def download_deployment_resource(self, destination, path=None):
+        """
+        Download a deployment resource from the resource storage
+        """
+        return self.resource.deployment.download(
+            entry_id=self.deployment_id,
+            destination=destination,
+            path=path)
+
+    @lru_cache()
+    def get_deployment_resource_data(self, path=None):
+        """
+        Read a deployment resource as string from the resource storage
+        """
+        return self.resource.deployment.data(entry_id=self.deployment_id, path=path)
+
+    @lru_cache()
+    def get_blueprint_resource_data(self, path=None):
+        """
+        Read a blueprint resource as string from the resource storage
+        """
+        return self.resource.blueprint.data(entry_id=self.blueprint_id, path=path)
+
+
+class _CurrentContext(threading.local):
+    """
+    Provides thread-level context, which sugarcoats the task api.
+    """
+
+    def _set(self, value):
+        setattr(self, '_workflow_context', value)
+
+    def get(self):
+        """
+        Retrieves the current workflow context
+        :return: the workflow context
+        :rtype: WorkflowContext
+        """
+        try:
+            return getattr(self, '_workflow_context')
+        except AttributeError:
+            return None
+
+    def clear(self):
+        """
+        Clears the current context
+        """
+        if hasattr(self, '_workflow_context'):
+            delattr(self, '_workflow_context')
+
+    @contextmanager
+    def push(self, workflow_context):
+        """
+        Switches the current context to the provides context
+        :param workflow_context: the context to switch to.
+        :yields: the current context
+        """
+        if hasattr(self, '_workflow_context'):
+            prev_workflow_context = getattr(self, '_workflow_context')
+        else:
+            prev_workflow_context = None
+        self._set(workflow_context)
+        try:
+            yield self
+        finally:
+            self._set(prev_workflow_context)
+
+current = _CurrentContext()
+

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/contexts.py
----------------------------------------------------------------------
diff --git a/aria/contexts.py b/aria/contexts.py
deleted file mode 100644
index 3bda9be..0000000
--- a/aria/contexts.py
+++ /dev/null
@@ -1,211 +0,0 @@
-# Licensed to the Apache Software Foundation (ASF) under one or more
-# contributor license agreements.  See the NOTICE file distributed with
-# this work for additional information regarding copyright ownership.
-# The ASF licenses this file to You 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.
-
-"""
-Workflow and operation contexts
-"""
-
-from uuid import uuid4
-
-from aria.logger import LoggerMixin
-from aria.tools.lru_cache import lru_cache
-from aria.workflows.api.task_graph import TaskGraph
-
-
-class WorkflowContext(LoggerMixin):
-    """
-    Context object used during workflow creation and execution
-    """
-
-    def __init__(
-            self,
-            name,
-            model_storage,
-            resource_storage,
-            deployment_id,
-            workflow_id,
-            parameters=None,
-            **kwargs):
-        super(WorkflowContext, self).__init__(**kwargs)
-        self.name = name
-        self.id = str(uuid4())
-        self.model = model_storage
-        self.resource = resource_storage
-        self.deployment_id = deployment_id
-        self.workflow_id = workflow_id
-        self.execution_id = str(uuid4())
-        self.parameters = parameters or {}
-
-    def __repr__(self):
-        return (
-            '{name}(deployment_id={self.deployment_id}, '
-            'workflow_id={self.workflow_id}, '
-            'execution_id={self.execution_id})'.format(
-                name=self.__class__.__name__, self=self))
-
-    def operation(
-            self,
-            name,
-            operation_details,
-            node_instance,
-            inputs=None):
-        """
-        Called during workflow creation, return an operation context. This object should be added to
-        the task graph.
-        """
-        return OperationContext(
-            name=name,
-            operation_details=operation_details,
-            workflow_context=self,
-            node_instance=node_instance,
-            inputs=inputs or {})
-
-    @property
-    def task_graph(self):
-        """
-        The task graph class
-        """
-        return TaskGraph
-
-    @property
-    def blueprint_id(self):
-        """
-        The blueprint id
-        """
-        return self.deployment.blueprint_id
-
-    @property
-    @lru_cache()
-    def blueprint(self):
-        """
-        The blueprint model
-        """
-        return self.model.blueprint.get(self.blueprint_id)
-
-    @property
-    @lru_cache()
-    def deployment(self):
-        """
-        The deployment model
-        """
-        return self.model.deployment.get(self.deployment_id)
-
-    @property
-    def nodes(self):
-        """
-        Iterator over nodes
-        """
-        return self.model.node.iter(
-            filters={'blueprint_id': self.blueprint_id})
-
-    @property
-    def node_instances(self):
-        """
-        Iterator over node instances
-        """
-        return self.model.node_instance.iter(filters={'deployment_id': self.deployment_id})
-
-    @property
-    def execution(self):
-        """
-        The execution model
-        """
-        return self.model.execution.get(self.execution_id)
-
-    @execution.setter
-    def execution(self, value):
-        """
-        Store the execution in the model storage
-        """
-        self.model.execution.store(value)
-
-    def download_blueprint_resource(self, destination, path=None):
-        """
-        Download a blueprint resource from the resource storage
-        """
-        return self.resource.blueprint.download(
-            entry_id=self.blueprint_id,
-            destination=destination,
-            path=path)
-
-    def download_deployment_resource(self, destination, path=None):
-        """
-        Download a deployment resource from the resource storage
-        """
-        return self.resource.deployment.download(
-            entry_id=self.deployment_id,
-            destination=destination,
-            path=path)
-
-    @lru_cache()
-    def get_deployment_resource_data(self, path=None):
-        """
-        Read a deployment resource as string from the resource storage
-        """
-        return self.resource.deployment.data(entry_id=self.deployment_id, path=path)
-
-    @lru_cache()
-    def get_blueprint_resource_data(self, path=None):
-        """
-        Read a blueprint resource as string from the resource storage
-        """
-        return self.resource.blueprint.data(entry_id=self.blueprint_id, path=path)
-
-
-class OperationContext(LoggerMixin):
-    """
-    Context object used during operation creation and execution
-    """
-
-    def __init__(
-            self,
-            name,
-            operation_details,
-            workflow_context,
-            node_instance,
-            inputs=None):
-        super(OperationContext, self).__init__()
-        self.name = name
-        self.id = str(uuid4())
-        self.operation_details = operation_details
-        self.workflow_context = workflow_context
-        self.node_instance = node_instance
-        self.inputs = inputs or {}
-
-    def __repr__(self):
-        details = ', '.join(
-            '{0}={1}'.format(key, value)
-            for key, value in self.operation_details.items())
-        return '{name}({0})'.format(details, name=self.name)
-
-    def __getattr__(self, attr):
-        try:
-            return getattr(self.workflow_context, attr)
-        except AttributeError:
-            return super(OperationContext, self).__getattribute__(attr)
-
-    @property
-    def operation(self):
-        """
-        The model operation
-        """
-        return self.storage.operation.get(self.id)
-
-    @operation.setter
-    def operation(self, value):
-        """
-        Store the operation in the model storage
-        """
-        self.storage.operation.store(value)

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/decorators.py
----------------------------------------------------------------------
diff --git a/aria/decorators.py b/aria/decorators.py
index 7bc41b3..5713246 100644
--- a/aria/decorators.py
+++ b/aria/decorators.py
@@ -20,12 +20,13 @@ Workflow and operation decorators
 from uuid import uuid4
 from functools import partial, wraps
 
-from aria.tools.validation import validate_function_arguments
+from . import context
+from .workflows.api import task_graph
+from .tools.validation import validate_function_arguments
 
 
 def workflow(
         func=None,
-        workflow_context=True,
         simple_workflow=True,
         suffix_template=''):
     """
@@ -34,31 +35,29 @@ def workflow(
     if func is None:
         return partial(
             workflow,
-            workflow_context=workflow_context,
             simple_workflow=simple_workflow,
             suffix_template=suffix_template)
 
     @wraps(func)
-    def _wrapper(context, **custom_kwargs):
+    def _wrapper(ctx, **custom_kwargs):
+
         workflow_name = _generate_workflow_name(
             func_name=func.__name__,
             suffix_template=suffix_template,
-            context=context,
+            ctx=ctx,
             **custom_kwargs)
-        func_kwargs = _create_func_kwargs(
-            custom_kwargs,
-            context,
-            add_context=workflow_context,
-            workflow_name=workflow_name)
-        validate_function_arguments(func, func_kwargs)
-        func(**func_kwargs)
-        return func_kwargs['graph']
+
+        custom_kwargs.setdefault('ctx', ctx)
+        custom_kwargs.setdefault('graph', task_graph.TaskGraph(workflow_name))
+        validate_function_arguments(func, custom_kwargs)
+        with context.workflow.current.push(ctx):
+            func(**custom_kwargs)
+        return custom_kwargs['graph']
     return _wrapper
 
 
 def operation(
-        func=None,
-        operation_context=True):
+        func=None):
     """
     Operation decorator
     """
@@ -66,29 +65,25 @@ def operation(
         return partial(operation)
 
     @wraps(func)
-    def _wrapper(context, **custom_kwargs):
+    def _wrapper(ctx, **custom_kwargs):
         func_kwargs = _create_func_kwargs(
             custom_kwargs,
-            context,
-            add_context=operation_context)
+            ctx)
         validate_function_arguments(func, func_kwargs)
-        context.description = func.__doc__
+        ctx.description = func.__doc__
         return func(**func_kwargs)
     return _wrapper
 
 
-def _generate_workflow_name(func_name, context, suffix_template, **custom_kwargs):
+def _generate_workflow_name(func_name, ctx, suffix_template, **custom_kwargs):
     return '{func_name}.{suffix}'.format(
         func_name=func_name,
-        suffix=suffix_template.format(context=context, **custom_kwargs) or str(uuid4()))
+        suffix=suffix_template.format(ctx=ctx, **custom_kwargs) or str(uuid4()))
 
 
 def _create_func_kwargs(
         kwargs,
-        context,
-        add_context=True,
+        ctx,
         workflow_name=None):
-    if add_context:
-        kwargs['context'] = context
-    kwargs.setdefault('graph', context.task_graph(workflow_name))
+    kwargs.setdefault('graph', ctx.task_graph(workflow_name))
     return kwargs

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/storage/drivers.py
----------------------------------------------------------------------
diff --git a/aria/storage/drivers.py b/aria/storage/drivers.py
index 33b7c00..0ad2f49 100644
--- a/aria/storage/drivers.py
+++ b/aria/storage/drivers.py
@@ -32,7 +32,7 @@ import shutil
 # pylint has an issue with distutils and virtualenvs: https://github.com/PyCQA/pylint/issues/73
 import distutils.dir_util                                                                           # pylint: disable=no-name-in-module, import-error
 from functools import partial
-from billiard import RLock
+from multiprocessing import RLock
 
 import jsonpickle
 

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/storage/models.py
----------------------------------------------------------------------
diff --git a/aria/storage/models.py b/aria/storage/models.py
index 32403ed..64c00bc 100644
--- a/aria/storage/models.py
+++ b/aria/storage/models.py
@@ -216,32 +216,6 @@ class Execution(Model):
     is_system_workflow = Field(type=bool, default=False)
 
 
-class Operation(Model):
-    """
-    A Model which represents an operation
-    """
-    PENDING = 'pending'
-    STARTED = 'started'
-    SUCCESS = 'success'
-    FAILED = 'failed'
-    STATES = (
-        PENDING,
-        STARTED,
-        SUCCESS,
-        FAILED,
-    )
-    END_STATES = [SUCCESS, FAILED]
-
-    id = Field(type=basestring, default=uuid_generator)
-    status = Field(type=basestring, choices=STATES, default=STARTED)
-    execution_id = Field(type=basestring)
-    eta = Field(type=datetime, default=0)
-    started_at = Field(type=datetime, default=None)
-    ended_at = Field(type=datetime, default=None)
-    max_retries = Field(type=int, default=0)
-    retry_count = Field(type=int, default=0)
-
-
 class Relationship(Model):
     """
     A Model which represents a relationship
@@ -395,3 +369,35 @@ class Plugin(Model):
     excluded_wheels = Field()
     supported_py_versions = Field(type=list)
     uploaded_at = Field(type=datetime)
+
+
+class Task(Model):
+    """
+    A Model which represents an task
+    """
+    PENDING = 'pending'
+    STARTED = 'started'
+    SUCCESS = 'success'
+    FAILED = 'failed'
+    STATES = (
+        PENDING,
+        STARTED,
+        SUCCESS,
+        FAILED,
+    )
+    END_STATES = [SUCCESS, FAILED]
+
+    id = Field(type=basestring, default=uuid_generator)
+    status = Field(type=basestring, choices=STATES, default=STARTED)
+    execution_id = Field(type=basestring)
+    eta = Field(type=datetime, default=0)
+    started_at = Field(type=datetime, default=None)
+    ended_at = Field(type=datetime, default=None)
+    max_retries = Field(type=int, default=0)
+    retry_count = Field(type=int, default=0)
+
+    # Operation specific fields
+    name = Field(type=basestring)
+    operation_details = Field(type=dict)
+    node_instance = PointerField(type=NodeInstance)
+    inputs = Field(type=dict, default=lambda: {})

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/api/__init__.py
----------------------------------------------------------------------
diff --git a/aria/workflows/api/__init__.py b/aria/workflows/api/__init__.py
index ae1e83e..b7f4b0c 100644
--- a/aria/workflows/api/__init__.py
+++ b/aria/workflows/api/__init__.py
@@ -12,3 +12,5 @@
 # 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 . import task, task_graph

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/api/task.py
----------------------------------------------------------------------
diff --git a/aria/workflows/api/task.py b/aria/workflows/api/task.py
new file mode 100644
index 0000000..a24fdc4
--- /dev/null
+++ b/aria/workflows/api/task.py
@@ -0,0 +1,90 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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.
+
+"""
+Provides the tasks to be enterd into the task graph
+"""
+from uuid import uuid4
+
+from aria import context
+
+
+class BaseTask(object):
+    """
+    Abstract task_graph task
+    """
+    pass
+
+
+class OperationTask(BaseTask):
+    """
+    Represents an operation task in the task_graph
+    """
+
+    def __init__(self,
+                 name,
+                 operation_details,
+                 node_instance,
+                 **operation_kwargs):
+        """
+        Creates an operation task using the name, details, node instance and any additional kwargs.
+        :param name: the operation of the name.
+        :param operation_details: the details for the operation.
+        :param node_instance: the node instnace on which this operation is registered.
+        :param operation_kwargs: any additional kwargs for the operation.
+        """
+        self.id = uuid4()
+        self.workflow_context = context.workflow.current.get()
+        self.name = name
+        self.operation_details = operation_details
+        self.node_instance = node_instance
+        self.operation_kwargs = operation_kwargs
+
+    def __getattr__(self, item):
+        try:
+            return self.__getattribute__(item)
+        except AttributeError:
+            return getattr(self._workflow_context.model.task.get(self._task_model.id), item)
+
+
+class WorkflowTask(BaseTask):
+    """
+    Represents an workflow task in the task_graph
+    """
+    def __init__(self, workflow_func, **kwargs):
+        """
+        Creates a workflow task using the workflow_func provided and its kwargs
+        :param workflow_func: the function to run
+        :param kwargs: the kwargs that would be passed to the workflow_func
+        """
+        kwargs.setdefault('ctx', context.workflow.current.get())
+        self._graph = workflow_func(**kwargs)
+
+    @property
+    def graph(self):
+        """
+        The graph constructed by the sub workflow
+        :return:
+        """
+        return self._graph
+
+    def __getattr__(self, item):
+        try:
+            return self.__getattribute__(item)
+        except AttributeError:
+            try:
+                return getattr(self._graph, item)
+            except AttributeError:
+                return getattr(context.workflow.current.get(), item)

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/api/task_graph.py
----------------------------------------------------------------------
diff --git a/aria/workflows/api/task_graph.py b/aria/workflows/api/task_graph.py
index 20b0a50..42cf8b6 100644
--- a/aria/workflows/api/task_graph.py
+++ b/aria/workflows/api/task_graph.py
@@ -22,6 +22,8 @@ from collections import Iterable
 
 from networkx import DiGraph, topological_sort
 
+from . import task
+
 
 class TaskNotInGraphError(Exception):
     """
@@ -130,14 +132,15 @@ class TaskGraph(object):
         :return: A list of added tasks
         :rtype: list
         """
+        # assert all([isinstance(t, (task.BaseTask, Iterable)) for t in tasks])
         return_tasks = []
 
-        for task in tasks:
-            if isinstance(task, Iterable):
-                return_tasks += self.add_tasks(*task)
-            elif not self.has_tasks(task):
-                self._graph.add_node(task.id, task=task)
-                return_tasks.append(task)
+        for t in tasks:
+            if isinstance(t, Iterable):
+                return_tasks += self.add_tasks(*t)
+            elif not self.has_tasks(t):
+                self._graph.add_node(t.id, task=t)
+                return_tasks.append(t)
 
         return return_tasks
 
@@ -168,13 +171,14 @@ class TaskGraph(object):
         :return: True if all tasks are in the graph, otherwise True
         :rtype: list
         """
+        # assert all(isinstance(t, (task.BaseTask, Iterable)) for t in tasks)
         return_value = True
 
-        for task in tasks:
-            if isinstance(task, Iterable):
-                return_value &= self.has_tasks(*task)
+        for t in tasks:
+            if isinstance(t, Iterable):
+                return_value &= self.has_tasks(*t)
             else:
-                return_value &= self._graph.has_node(task.id)
+                return_value &= self._graph.has_node(t.id)
 
         return return_value
 
@@ -276,6 +280,11 @@ class TaskGraph(object):
 
     @_filter_out_empty_tasks
     def sequence(self, *tasks):
+        """
+        Create and insert a sequence into the graph, effectively each task i depends on i-1
+        :param tasks: an iterable of dependencies
+        :return: the provided tasks
+        """
         if tasks:
             self.add_tasks(*tasks)
 

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/builtin/execute_operation.py
----------------------------------------------------------------------
diff --git a/aria/workflows/builtin/execute_operation.py b/aria/workflows/builtin/execute_operation.py
index 2843375..ddbb8e7 100644
--- a/aria/workflows/builtin/execute_operation.py
+++ b/aria/workflows/builtin/execute_operation.py
@@ -24,7 +24,7 @@ from .workflows import execute_operation_on_instance
 
 @workflow
 def execute_operation(
-        context,
+        ctx,
         graph,
         operation,
         operation_kwargs,
@@ -37,7 +37,7 @@ def execute_operation(
     """
     The execute_operation workflow
 
-    :param WorkflowContext context: the workflow context
+    :param WorkflowContext workflow_context: the workflow context
     :param TaskGraph graph: the graph which will describe the workflow.
     :param basestring operation: the operation name to execute
     :param dict operation_kwargs:
@@ -52,7 +52,7 @@ def execute_operation(
     subgraphs = {}
     # filtering node instances
     filtered_node_instances = list(_filter_node_instances(
-        context=context,
+        context=ctx,
         node_ids=node_ids,
         node_instance_ids=node_instance_ids,
         type_names=type_names))
@@ -60,27 +60,28 @@ def execute_operation(
     if run_by_dependency_order:
         filtered_node_instances_ids = set(node_instance.id
                                           for node_instance in filtered_node_instances)
-        for node_instance in context.node_instances:
+        for node_instance in ctx.node_instances:
             if node_instance.id not in filtered_node_instances_ids:
-                subgraphs[node_instance.id] = context.task_graph(
+                subgraphs[node_instance.id] = ctx.task_graph(
                     name='execute_operation_stub_{0}'.format(node_instance.id))
 
     # registering actual tasks to sequences
     for node_instance in filtered_node_instances:
-        execute_operation_on_instance(
-            context=context,
-            graph=graph,
-            node_instance=node_instance,
-            operation=operation,
-            operation_kwargs=operation_kwargs,
-            allow_kwargs_override=allow_kwargs_override)
+        graph.add_tasks(
+            execute_operation_on_instance(
+                node_instance=node_instance,
+                operation=operation,
+                operation_kwargs=operation_kwargs,
+                allow_kwargs_override=allow_kwargs_override
+            )
+        )
 
     for _, node_instance_sub_workflow in subgraphs.items():
         graph.add_tasks(node_instance_sub_workflow)
 
     # adding tasks dependencies if required
     if run_by_dependency_order:
-        for node_instance in context.node_instances:
+        for node_instance in ctx.node_instances:
             for relationship_instance in node_instance.relationship_instances:
                 graph.add_dependency(source_task=subgraphs[node_instance.id],
                                      after=[subgraphs[relationship_instance.target_id]])

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/builtin/heal.py
----------------------------------------------------------------------
diff --git a/aria/workflows/builtin/heal.py b/aria/workflows/builtin/heal.py
index efdd7b1..2f3d538 100644
--- a/aria/workflows/builtin/heal.py
+++ b/aria/workflows/builtin/heal.py
@@ -19,36 +19,36 @@ Builtin heal workflow
 
 from aria import workflow
 
-from .uninstall import uninstall
-from .install import install
-from .workflows import relationship_tasks
+from .workflows import relationship_tasks, install_node_instance, uninstall_node_instance
+from ..api import task, task_graph
 
 
 @workflow
-def heal(context, graph, node_instance_id):
+def heal(ctx, graph, node_instance_id):
     """
     The heal workflow
 
-    :param WorkflowContext context: the workflow context
+    :param WorkflowContext ctx: the workflow context
     :param TaskGraph graph: the graph which will describe the workflow.
     :param node_instance_id: the id of the node instance to heal
     :return:
     """
-    failing_node = context.model.node_instance.get(node_instance_id)
-    host_node = context.model.node_instance.get(failing_node.host_id)
-    failed_node_instance_subgraph = _get_contained_subgraph(context, host_node)
+    failing_node = ctx.model.node_instance.get(node_instance_id)
+    host_node = ctx.model.node_instance.get(failing_node.host_id)
+    failed_node_instance_subgraph = _get_contained_subgraph(ctx, host_node)
     failed_node_instance_ids = list(n.id for n in failed_node_instance_subgraph)
 
-    targeted_node_instances = [node_instance for node_instance in context.node_instances
+    targeted_node_instances = [node_instance for node_instance in ctx.node_instances
                                if node_instance.id not in failed_node_instance_ids]
 
-    uninstall_subgraph = heal_uninstall(
-        context=context,
+    uninstall_subgraph = task.WorkflowTask(
+        heal_uninstall,
         failing_node_instances=failed_node_instance_subgraph,
-        targeted_node_instances=targeted_node_instances)
+        targeted_node_instances=targeted_node_instances
+    )
 
-    install_subgraph = heal_install(
-        context=context,
+    install_subgraph = task.WorkflowTask(
+        heal_install,
         failing_node_instances=failed_node_instance_subgraph,
         targeted_node_instances=targeted_node_instances)
 
@@ -58,10 +58,10 @@ def heal(context, graph, node_instance_id):
 
 
 @workflow(suffix_template='{failing_node_instances}')
-def heal_uninstall(context, graph, failing_node_instances, targeted_node_instances):
+def heal_uninstall(ctx, graph, failing_node_instances, targeted_node_instances):
     """
     the uninstall part of the heal mechanism
-    :param WorkflowContext context: the workflow context
+    :param WorkflowContext ctx: the workflow context
     :param TaskGraph graph: the task graph to edit.
     :param failing_node_instances: the failing nodes to heal.
     :param targeted_node_instances: the targets of the relationships where the failing node are
@@ -72,24 +72,34 @@ def heal_uninstall(context, graph, failing_node_instances, targeted_node_instanc
 
     # Create install stub workflow for each unaffected node instance
     for node_instance in targeted_node_instances:
-        node_instance_sub_workflow = context.task_graph(
+        node_instance_sub_workflow = task_graph.TaskGraph(
             name='uninstall_stub_{0}'.format(node_instance.id))
         node_instance_sub_workflows[node_instance.id] = node_instance_sub_workflow
         graph.add_tasks(node_instance_sub_workflow)
 
-    # Create install sub workflow for each failing node
-    uninstall(
-        context=context,
-        graph=graph,
-        node_instances=failing_node_instances,
-        node_instance_sub_workflows=node_instance_sub_workflows)
+    # Create install sub workflow for each failing node on the same graph
+    node_instance_sub_workflows = node_instance_sub_workflows or {}
+
+    # create install sub workflow for every node instance
+    for node_instance in failing_node_instances:
+        node_instance_sub_workflow = task.WorkflowTask(uninstall_node_instance,
+                                                       node_instance=node_instance)
+        node_instance_sub_workflows[node_instance.id] = node_instance_sub_workflow
+        graph.add_tasks(node_instance_sub_workflow)
+
+    # create dependencies between the node instance sub workflow
+    for node_instance in failing_node_instances:
+        node_instance_sub_workflow = node_instance_sub_workflows[node_instance.id]
+        for relationship_instance in reversed(node_instance.relationship_instances):
+            graph.add_dependency(node_instance_sub_workflows[relationship_instance.target_id],
+                                 node_instance_sub_workflow)
 
     # Add operations for intact nodes depending on a node instance belonging to node_instances
     for node_instance in targeted_node_instances:
         node_instance_sub_workflow = node_instance_sub_workflows[node_instance.id]
 
         for relationship_instance in reversed(node_instance.relationship_instances):
-            target_node_instance = context.model.node_instance.get(relationship_instance.target_id)
+            target_node_instance = ctx.model.node_instance.get(relationship_instance.target_id)
             target_node_instance_subgraph = node_instance_sub_workflows[target_node_instance.id]
             graph.add_dependency(target_node_instance_subgraph, node_instance_sub_workflow)
 
@@ -98,17 +108,17 @@ def heal_uninstall(context, graph, failing_node_instances, targeted_node_instanc
                     graph=graph,
                     node_instance=node_instance,
                     relationship_instance=relationship_instance,
-                    context=context,
+                    context=ctx,
                     operation_name='aria.interfaces.relationship_lifecycle.unlink')
 
                 graph.add_dependency(node_instance_sub_workflow, dependency)
 
 
 @workflow(suffix_template='{failing_node_instances}')
-def heal_install(context, graph, failing_node_instances, targeted_node_instances):
+def heal_install(ctx, graph, failing_node_instances, targeted_node_instances):
     """
     the install part of the heal mechanism
-    :param WorkflowContext context: the workflow context
+    :param WorkflowContext ctx: the workflow context
     :param TaskGraph graph: the task graph to edit.
     :param failing_node_instances: the failing nodes to heal.
     :param targeted_node_instances: the targets of the relationships where the failing node are
@@ -119,17 +129,28 @@ def heal_install(context, graph, failing_node_instances, targeted_node_instances
 
     # Create install sub workflow for each unaffected
     for node_instance in targeted_node_instances:
-        node_instance_sub_workflow = context.task_graph(
+        node_instance_sub_workflow = task_graph.TaskGraph(
             name='install_stub_{0}'.format(node_instance.id))
         node_instance_sub_workflows[node_instance.id] = node_instance_sub_workflow
         graph.add_tasks(node_instance_sub_workflow)
 
+    # create install sub workflow for each failing node on the same graph
+    node_instance_sub_workflows = node_instance_sub_workflows or {}
+
     # create install sub workflow for every node instance
-    install(
-        context=context,
-        graph=graph,
-        node_instances=failing_node_instances,
-        node_instance_sub_workflows=node_instance_sub_workflows)
+    for node_instance in failing_node_instances:
+        node_instance_sub_workflow = task.WorkflowTask(install_node_instance,
+                                                       node_instance=node_instance)
+        node_instance_sub_workflows[node_instance.id] = node_instance_sub_workflow
+        graph.add_tasks(node_instance_sub_workflow)
+
+    # create dependencies between the node instance sub workflow
+    for node_instance in failing_node_instances:
+        node_instance_sub_workflow = node_instance_sub_workflows[node_instance.id]
+        if node_instance.relationship_instances:
+            dependencies = [node_instance_sub_workflows[relationship_instance.target_id]
+                            for relationship_instance in node_instance.relationship_instances]
+            graph.add_dependency(node_instance_sub_workflow, dependencies)
 
     # Add operations for intact nodes depending on a node instance
     # belonging to node_instances
@@ -137,7 +158,7 @@ def heal_install(context, graph, failing_node_instances, targeted_node_instances
         node_instance_sub_workflow = node_instance_sub_workflows[node_instance.id]
 
         for relationship_instance in node_instance.relationship_instances:
-            target_node_instance = context.model.node_instance.get(relationship_instance.target_id)
+            target_node_instance = ctx.model.node_instance.get(relationship_instance.target_id)
             target_node_instance_subworkflow = node_instance_sub_workflows[target_node_instance.id]
             graph.add_dependency(node_instance_sub_workflow, target_node_instance_subworkflow)
 
@@ -146,7 +167,7 @@ def heal_install(context, graph, failing_node_instances, targeted_node_instances
                     graph=graph,
                     node_instance=node_instance,
                     relationship_instance=relationship_instance,
-                    context=context,
+                    context=ctx,
                     operation_name='aria.interfaces.relationship_lifecycle.establish')
 
                 graph.add_dependency(dependent, node_instance_sub_workflow)

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/builtin/install.py
----------------------------------------------------------------------
diff --git a/aria/workflows/builtin/install.py b/aria/workflows/builtin/install.py
index c6b392f..0ab3ad6 100644
--- a/aria/workflows/builtin/install.py
+++ b/aria/workflows/builtin/install.py
@@ -20,13 +20,14 @@ Builtin install workflow
 from aria import workflow
 
 from .workflows import install_node_instance
+from ..api import task
 
 
 @workflow
-def install(context, graph, node_instances=(), node_instance_sub_workflows=None):
+def install(ctx, graph, node_instances=(), node_instance_sub_workflows=None):
     """
     The install workflow
-    :param WorkflowContext context: the workflow context
+    :param WorkflowContext ctx: the workflow context
     :param TaskGraph graph: the graph which will describe the workflow.
     :param node_instances: the node instances on which to run the workflow
     :param dict node_instance_sub_workflows: a dictionary of subworkflows  with id as key and
@@ -34,13 +35,12 @@ def install(context, graph, node_instances=(), node_instance_sub_workflows=None)
     :return:
     """
     node_instance_sub_workflows = node_instance_sub_workflows or {}
-    node_instances = node_instances or list(context.node_instances)
+    node_instances = node_instances or list(ctx.node_instances)
 
     # create install sub workflow for every node instance
     for node_instance in node_instances:
-        node_instance_sub_workflow = install_node_instance(
-            context=context,
-            node_instance=node_instance)
+        node_instance_sub_workflow = task.WorkflowTask(install_node_instance,
+                                                       node_instance=node_instance)
         node_instance_sub_workflows[node_instance.id] = node_instance_sub_workflow
         graph.add_tasks(node_instance_sub_workflow)
 

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/builtin/uninstall.py
----------------------------------------------------------------------
diff --git a/aria/workflows/builtin/uninstall.py b/aria/workflows/builtin/uninstall.py
index 9557dd8..f4e965c 100644
--- a/aria/workflows/builtin/uninstall.py
+++ b/aria/workflows/builtin/uninstall.py
@@ -20,10 +20,11 @@ Builtin uninstall workflow
 from aria import workflow
 
 from .workflows import uninstall_node_instance
+from ..api import task
 
 
 @workflow
-def uninstall(context, graph, node_instances=(), node_instance_sub_workflows=None):
+def uninstall(ctx, graph, node_instances=(), node_instance_sub_workflows=None):
     """
     The uninstall workflow
     :param WorkflowContext context: the workflow context
@@ -34,13 +35,12 @@ def uninstall(context, graph, node_instances=(), node_instance_sub_workflows=Non
     :return:
     """
     node_instance_sub_workflows = node_instance_sub_workflows or {}
-    node_instances = node_instances or list(context.node_instances)
+    node_instances = node_instances or list(ctx.node_instances)
 
     # create install sub workflow for every node instance
     for node_instance in node_instances:
-        node_instance_sub_workflow = uninstall_node_instance(
-            context=context,
-            node_instance=node_instance)
+        node_instance_sub_workflow = task.WorkflowTask(uninstall_node_instance,
+                                                       node_instance=node_instance)
         node_instance_sub_workflows[node_instance.id] = node_instance_sub_workflow
         graph.add_tasks(node_instance_sub_workflow)
 

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/builtin/workflows.py
----------------------------------------------------------------------
diff --git a/aria/workflows/builtin/workflows.py b/aria/workflows/builtin/workflows.py
index 0119e26..4bff7cd 100644
--- a/aria/workflows/builtin/workflows.py
+++ b/aria/workflows/builtin/workflows.py
@@ -21,6 +21,8 @@ from itertools import groupby
 
 from aria import workflow
 
+from ..api import task
+
 
 __all__ = (
     'install_node_instance',
@@ -32,42 +34,43 @@ __all__ = (
 # Install node instance workflow and sub workflows
 
 @workflow(suffix_template='{node_instance.id}')
-def install_node_instance(context, graph, node_instance):
+def install_node_instance(ctx, graph, node_instance):
     """
     A workflow which installs a node instance.
-    :param WorkflowContext context: the workflow context
+    :param WorkflowContext ctx: the workflow context
     :param TaskGraph graph: the tasks graph of which to edit
     :param node_instance: the node instance to install
     :return:
     """
-    create_node_instance = context.operation(
+    create_node_instance = task.OperationTask(
         name='aria.interfaces.lifecycle.create.{0}'.format(node_instance.id),
-        operation_details=node_instance.node.operations[
-            'aria.interfaces.lifecycle.create'],
+        operation_details=node_instance.node.operations['aria.interfaces.lifecycle.create'],
         node_instance=node_instance
     )
-    configure_node_instance = context.operation(
+    configure_node_instance = task.OperationTask(
         name='aria.interfaces.lifecycle.configure.{0}'.format(node_instance.id),
         operation_details=node_instance.node.operations['aria.interfaces.lifecycle.configure'],
         node_instance=node_instance
         )
-    start_node_instance = context.operation(
+    start_node_instance = task.OperationTask(
         name='aria.interfaces.lifecycle.start.{0}'.format(node_instance.id),
-        operation_details=node_instance.node.operations[
-            'aria.interfaces.lifecycle.start'],
+        operation_details=node_instance.node.operations['aria.interfaces.lifecycle.start'],
         node_instance=node_instance
     )
 
-    graph.sequence(create_node_instance,
-                   preconfigure_relationship(graph, context, node_instance),
-                   configure_node_instance,
-                   postconfigure_relationship(graph, context, node_instance),
-                   start_node_instance,
-                   establish_relationship(graph, context, node_instance)
-                   )
+    graph.sequence(
+        create_node_instance,
+        preconfigure_relationship(graph, ctx, node_instance),
+        configure_node_instance,
+        postconfigure_relationship(graph, ctx, node_instance),
+        start_node_instance,
+        establish_relationship(graph, ctx, node_instance)
+    )
+
+    return graph
 
 
-def preconfigure_relationship(graph, context, node_instance):
+def preconfigure_relationship(graph, ctx, node_instance):
     """
 
     :param context:
@@ -78,11 +81,11 @@ def preconfigure_relationship(graph, context, node_instance):
     return relationships_tasks(
         graph=graph,
         operation_name='aria.interfaces.relationship_lifecycle.preconfigure',
-        context=context,
+        context=ctx,
         node_instance=node_instance)
 
 
-def postconfigure_relationship(graph, context, node_instance):
+def postconfigure_relationship(graph, ctx, node_instance):
     """
 
     :param context:
@@ -93,11 +96,11 @@ def postconfigure_relationship(graph, context, node_instance):
     return relationships_tasks(
         graph=graph,
         operation_name='aria.interfaces.relationship_lifecycle.postconfigure',
-        context=context,
+        context=ctx,
         node_instance=node_instance)
 
 
-def establish_relationship(graph, context, node_instance):
+def establish_relationship(graph, ctx, node_instance):
     """
 
     :param context:
@@ -108,14 +111,14 @@ def establish_relationship(graph, context, node_instance):
     return relationships_tasks(
         graph=graph,
         operation_name='aria.interfaces.relationship_lifecycle.establish',
-        context=context,
+        context=ctx,
         node_instance=node_instance)
 
 
 # Uninstall node instance workflow and subworkflows
 
 @workflow(suffix_template='{node_instance.id}')
-def uninstall_node_instance(graph, context, node_instance):
+def uninstall_node_instance(ctx, graph, node_instance):
     """
         A workflow which uninstalls a node instance.
         :param WorkflowContext context: the workflow context
@@ -123,27 +126,25 @@ def uninstall_node_instance(graph, context, node_instance):
         :param node_instance: the node instance to uninstall
         :return:
         """
-    stop_node_instance = context.operation(
+    stop_node_instance = task.OperationTask(
         name='aria.interfaces.lifecycle.stop.{0}'.format(node_instance.id),
-        operation_details=node_instance.node.operations[
-            'aria.interfaces.lifecycle.stop'],
+        operation_details=node_instance.node.operations['aria.interfaces.lifecycle.stop'],
         node_instance=node_instance
     )
-    delete_node_instance = context.operation(
+    delete_node_instance = task.OperationTask(
         name='aria.interfaces.lifecycle.delete.{0}'.format(node_instance.id),
-        operation_details=node_instance.node.operations[
-            'aria.interfaces.lifecycle.delete'],
+        operation_details=node_instance.node.operations['aria.interfaces.lifecycle.delete'],
         node_instance=node_instance
     )
 
     graph.sequence(
         stop_node_instance,
-        unlink_relationship(graph, context, node_instance),
+        unlink_relationship(graph, ctx, node_instance),
         delete_node_instance
     )
 
 
-def unlink_relationship(graph, context, node_instance):
+def unlink_relationship(graph, ctx, node_instance):
     """
 
     :param context:
@@ -154,15 +155,12 @@ def unlink_relationship(graph, context, node_instance):
     return relationships_tasks(
         graph=graph,
         operation_name='aria.interfaces.relationship_lifecycle.unlink',
-        context=context,
+        context=ctx,
         node_instance=node_instance
     )
 
 
-@workflow(suffix_template='{node_instance.id}.{operation}')
 def execute_operation_on_instance(
-        context,
-        graph,
         node_instance,
         operation,
         operation_kwargs,
@@ -185,13 +183,12 @@ def execute_operation_on_instance(
         node_instance=node_instance,
         operation_name=operation)
 
-    graph.add_tasks(
-        context.operation(
-            name=task_name,
-            operation_details=node_instance.node.operations[operation],
-            node_instance=node_instance,
-            inputs=operation_kwargs)
-    )
+    return task.OperationTask(
+        name=task_name,
+        operation_details=node_instance.node.operations[operation],
+        node_instance=node_instance,
+        inputs=operation_kwargs)
+
 
 
 def relationships_tasks(graph,
@@ -246,12 +243,12 @@ def relationship_tasks(graph,
         source_id=node_instance.id,
         target_id=relationship_instance.target_id,
     )
-    source_operation = context.operation(
+    source_operation = task.OperationTask(
         name=operation_name_template.format('source'),
         node_instance=node_instance,
         operation_details=relationship_instance.relationship.source_operations[
             operation_name])
-    target_operation = context.operation(
+    target_operation = task.OperationTask(
         name=operation_name_template.format('target'),
         node_instance=context.model.node_instance.get(relationship_instance.target_id),
         operation_details=relationship_instance.relationship.target_operations[

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/core/__init__.py
----------------------------------------------------------------------
diff --git a/aria/workflows/core/__init__.py b/aria/workflows/core/__init__.py
index ae1e83e..08ccff7 100644
--- a/aria/workflows/core/__init__.py
+++ b/aria/workflows/core/__init__.py
@@ -12,3 +12,5 @@
 # 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 . import translation, task

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/core/executor.py
----------------------------------------------------------------------
diff --git a/aria/workflows/core/executor.py b/aria/workflows/core/executor.py
index 1abecac..0a5cd67 100644
--- a/aria/workflows/core/executor.py
+++ b/aria/workflows/core/executor.py
@@ -18,7 +18,7 @@ Executors for workflow tasks
 """
 
 import threading
-import billiard as multiprocessing
+import multiprocessing
 import Queue
 
 import jsonpickle
@@ -134,8 +134,7 @@ class MultiprocessExecutor(BaseExecutor):
         self._listener_thread = threading.Thread(target=self._listener)
         self._listener_thread.daemon = True
         self._listener_thread.start()
-        self._pool = multiprocessing.Pool(processes=pool_size,
-                                          maxtasksperchild=1)
+        self._pool = multiprocessing.Pool(processes=pool_size)
 
     def execute(self, task):
         self._tasks[task.id] = task

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/core/task.py
----------------------------------------------------------------------
diff --git a/aria/workflows/core/task.py b/aria/workflows/core/task.py
new file mode 100644
index 0000000..de8a561
--- /dev/null
+++ b/aria/workflows/core/task.py
@@ -0,0 +1,106 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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.
+
+"""
+Workflow tasks
+"""
+
+
+class BaseTask(object):
+    """
+    Base class for Task objects
+    """
+
+    def __init__(self, id):
+        self._id = id
+
+    @property
+    def id(self):
+        """
+        :return: the task's id
+        """
+        return self._id
+
+
+class StartWorkflowTask(BaseTask):
+    """
+    Tasks marking a workflow start
+    """
+    pass
+
+
+class EndWorkflowTask(BaseTask):
+    """
+    Tasks marking a workflow end
+    """
+    pass
+
+
+class StartSubWorkflowTask(BaseTask):
+    """
+    Tasks marking a subworkflow start
+    """
+    pass
+
+
+class EndSubWorkflowTask(BaseTask):
+    """
+    Tasks marking a subworkflow end
+    """
+    pass
+
+
+class OperationTask(BaseTask):
+    """
+    Operation tasks
+    """
+
+    def __init__(self, api_task, *args, **kwargs):
+        self._api_task = api_task
+        self._ctx = api_task.workflow_context
+        super(OperationTask, self).__init__(id=api_task.id)
+        self._create_operation_in_storage()
+
+    @property
+    def ctx(self):
+        """
+        :return: the task's name
+        """
+        return self._ctx
+
+    @property
+    def api_task(self):
+        """
+        :return: the task's context
+        """
+        return self._api_task
+
+    def _create_operation_in_storage(self):
+        task = self.ctx.model.task.model_cls(
+            name=self.api_task.name,
+            operation_details=self.api_task.operation_details,
+            node_instance=self.api_task.node_instance,
+            inputs=self.api_task.operation_kwargs,
+
+            execution_id=self.ctx.execution_id,
+            max_retries=self.ctx.parameters.get('max_retries', 1),
+        )
+        self.ctx.model.task.store(task)
+
+    def __getattr__(self, attr):
+        try:
+            return super(OperationTask, self).__getattribute__(attr)
+        except AttributeError:
+            return getattr(self.context, attr)

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/core/tasks.py
----------------------------------------------------------------------
diff --git a/aria/workflows/core/tasks.py b/aria/workflows/core/tasks.py
deleted file mode 100644
index 76ae609..0000000
--- a/aria/workflows/core/tasks.py
+++ /dev/null
@@ -1,104 +0,0 @@
-# Licensed to the Apache Software Foundation (ASF) under one or more
-# contributor license agreements.  See the NOTICE file distributed with
-# this work for additional information regarding copyright ownership.
-# The ASF licenses this file to You 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.
-
-"""
-Workflow tasks
-"""
-
-
-class BaseTask(object):
-    """
-    Base class for Task objects
-    """
-
-    def __init__(self, id, name, context):
-        self._id = id
-        self._name = name
-        self._context = context
-
-    @property
-    def id(self):
-        """
-        :return: the task's id
-        """
-        return self._id
-
-    @property
-    def name(self):
-        """
-        :return: the task's name
-        """
-        return self._name
-
-    @property
-    def context(self):
-        """
-        :return: the task's context
-        """
-        return self._context
-
-
-class StartWorkflowTask(BaseTask):
-    """
-    Tasks marking a workflow start
-    """
-    pass
-
-
-class EndWorkflowTask(BaseTask):
-    """
-    Tasks marking a workflow end
-    """
-    pass
-
-
-class StartSubWorkflowTask(BaseTask):
-    """
-    Tasks marking a subworkflow start
-    """
-    pass
-
-
-class EndSubWorkflowTask(BaseTask):
-    """
-    Tasks marking a subworkflow end
-    """
-    pass
-
-
-class OperationTask(BaseTask):
-    """
-    Operation tasks
-    """
-
-    def __init__(self, *args, **kwargs):
-        super(OperationTask, self).__init__(*args, **kwargs)
-        self._create_operation_in_storage()
-
-    def _create_operation_in_storage(self):
-        operation_cls = self.context.storage.operation.model_cls
-        operation = operation_cls(
-            id=self.context.id,
-            execution_id=self.context.execution_id,
-            max_retries=self.context.parameters.get('max_retries', 1),
-            status=operation_cls.PENDING,
-        )
-        self.context.operation = operation
-
-    def __getattr__(self, attr):
-        try:
-            return getattr(self.context, attr)
-        except AttributeError:
-            return super(OperationTask, self).__getattribute__(attr)

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/aria/workflows/core/translation.py
----------------------------------------------------------------------
diff --git a/aria/workflows/core/translation.py b/aria/workflows/core/translation.py
index f746fb9..ec44f48 100644
--- a/aria/workflows/core/translation.py
+++ b/aria/workflows/core/translation.py
@@ -17,17 +17,15 @@
 Translation of user graph's API to the execution graph
 """
 
-from aria import contexts
-
-from . import tasks
+from . import task
+from .. import api
 
 
 def build_execution_graph(
         task_graph,
-        workflow_context,
         execution_graph,
-        start_cls=tasks.StartWorkflowTask,
-        end_cls=tasks.EndWorkflowTask,
+        start_cls=task.StartWorkflowTask,
+        end_cls=task.EndWorkflowTask,
         depends_on=()):
     """
     Translates the user graph to the execution graph
@@ -39,30 +37,27 @@ def build_execution_graph(
     :param depends_on: internal use
     """
     # Insert start marker
-    start_task = start_cls(id=_start_graph_suffix(task_graph.id),
-                           name=_start_graph_suffix(task_graph.name),
-                           context=workflow_context)
+    start_task = start_cls(id=_start_graph_suffix(task_graph.id))
     _add_task_and_dependencies(execution_graph, start_task, depends_on)
 
-    for task in task_graph.topological_order(reverse=True):
-        dependencies = task_graph.get_dependencies(task)
+    for api_task in task_graph.topological_order(reverse=True):
+        dependencies = task_graph.get_dependencies(api_task)
         operation_dependencies = _get_tasks_from_dependencies(
             execution_graph,
             dependencies,
             default=[start_task])
 
-        if _is_operation(task):
+        if _is_operation(api_task):
             # Add the task an the dependencies
-            operation_task = tasks.OperationTask(id=task.id, name=task.name, context=task)
+            operation_task = task.OperationTask(api_task)
             _add_task_and_dependencies(execution_graph, operation_task, operation_dependencies)
         else:
             # Built the graph recursively while adding start and end markers
             build_execution_graph(
-                task_graph=task,
-                workflow_context=workflow_context,
+                task_graph=api_task,
                 execution_graph=execution_graph,
-                start_cls=tasks.StartSubWorkflowTask,
-                end_cls=tasks.EndSubWorkflowTask,
+                start_cls=task.StartSubWorkflowTask,
+                end_cls=task.EndSubWorkflowTask,
                 depends_on=operation_dependencies
             )
 
@@ -71,10 +66,7 @@ def build_execution_graph(
         execution_graph,
         _get_non_dependency_tasks(task_graph),
         default=[start_task])
-    end_task = end_cls(
-        id=_end_graph_suffix(task_graph.id),
-        name=_end_graph_suffix(task_graph.name),
-        context=workflow_context)
+    end_task = end_cls(id=_end_graph_suffix(task_graph.id))
     _add_task_and_dependencies(execution_graph, end_task, workflow_dependencies)
 
 
@@ -94,7 +86,7 @@ def _get_tasks_from_dependencies(execution_graph, dependencies, default=()):
 
 
 def _is_operation(task):
-    return isinstance(task, contexts.OperationContext)
+    return isinstance(task, api.task.OperationTask)
 
 
 def _start_graph_suffix(id):

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/tests/.pylintrc
----------------------------------------------------------------------
diff --git a/tests/.pylintrc b/tests/.pylintrc
index f6cfd7a..59cca90 100644
--- a/tests/.pylintrc
+++ b/tests/.pylintrc
@@ -62,7 +62,7 @@ confidence=
 # --enable=similarities". If you want to run only the classes checker, but have
 # no Warning level messages displayed, use"--disable=all --enable=classes
 # --disable=W"
-disable=import-star-module-level,old-octal-literal,oct-method,print-statement,unpacking-in-except,parameter-unpacking,backtick,old-raise-syntax,old-ne-operator,long-suffix,dict-view-method,dict-iter-method,metaclass-assignment,next-method-called,raising-string,indexing-exception,raw_input-builtin,long-builtin,file-builtin,execfile-builtin,coerce-builtin,cmp-builtin,buffer-builtin,basestring-builtin,apply-builtin,filter-builtin-not-iterating,using-cmp-argument,useless-suppression,range-builtin-not-iterating,suppressed-message,no-absolute-import,old-division,cmp-method,reload-builtin,zip-builtin-not-iterating,intern-builtin,unichr-builtin,reduce-builtin,standarderror-builtin,unicode-builtin,xrange-builtin,coerce-method,delslice-method,getslice-method,setslice-method,input-builtin,round-builtin,hex-method,nonzero-method,map-builtin-not-iterating,redefined-builtin,no-self-use,missing-docstring,attribute-defined-outside-init
+disable=import-star-module-level,old-octal-literal,oct-method,print-statement,unpacking-in-except,parameter-unpacking,backtick,old-raise-syntax,old-ne-operator,long-suffix,dict-view-method,dict-iter-method,metaclass-assignment,next-method-called,raising-string,indexing-exception,raw_input-builtin,long-builtin,file-builtin,execfile-builtin,coerce-builtin,cmp-builtin,buffer-builtin,basestring-builtin,apply-builtin,filter-builtin-not-iterating,using-cmp-argument,useless-suppression,range-builtin-not-iterating,suppressed-message,no-absolute-import,old-division,cmp-method,reload-builtin,zip-builtin-not-iterating,intern-builtin,unichr-builtin,reduce-builtin,standarderror-builtin,unicode-builtin,xrange-builtin,coerce-method,delslice-method,getslice-method,setslice-method,input-builtin,round-builtin,hex-method,nonzero-method,map-builtin-not-iterating,redefined-builtin,no-self-use,missing-docstring,attribute-defined-outside-init,redefined-outer-name,import-error
 
 [REPORTS]
 
@@ -339,7 +339,7 @@ max-args=15
 ignored-argument-names=_.*
 
 # Maximum number of locals for function / method body
-max-locals=15
+max-locals=30
 
 # Maximum number of return / yield for function / method body
 max-returns=6
@@ -360,7 +360,7 @@ max-attributes=15
 min-public-methods=0
 
 # Maximum number of public methods for a class (see R0904).
-max-public-methods=20
+max-public-methods=50
 
 # Maximum number of boolean expressions in a if statement
 max-bool-expr=5

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/tests/mock/__init__.py
----------------------------------------------------------------------
diff --git a/tests/mock/__init__.py b/tests/mock/__init__.py
new file mode 100644
index 0000000..14541d0
--- /dev/null
+++ b/tests/mock/__init__.py
@@ -0,0 +1,16 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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 . import models, context, operations

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/tests/mock/context.py
----------------------------------------------------------------------
diff --git a/tests/mock/context.py b/tests/mock/context.py
new file mode 100644
index 0000000..71df67c
--- /dev/null
+++ b/tests/mock/context.py
@@ -0,0 +1,36 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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 aria import context, application_model_storage
+
+from ..storage import InMemoryModelDriver
+from . import models
+
+
+def simple():
+    """
+    Create the following graph in storage:
+    dependency_node <------ dependent_node
+    :return:
+    """
+    storage = application_model_storage(InMemoryModelDriver())
+    storage.setup()
+    return context.workflow.WorkflowContext(
+        model_storage=storage,
+        resource_storage=None,
+        deployment_id=models.DEPLOYMENT_ID,
+        workflow_id=models.WORKFLOW_ID,
+        execution_id=models.EXECUTION_ID
+    )

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/tests/mock/models.py
----------------------------------------------------------------------
diff --git a/tests/mock/models.py b/tests/mock/models.py
new file mode 100644
index 0000000..633adbb
--- /dev/null
+++ b/tests/mock/models.py
@@ -0,0 +1,132 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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 datetime import datetime
+
+from aria.storage import models
+
+from . import operations
+
+DEPLOYMENT_ID = 'test_deployment_id'
+BLUEPRINT_ID = 'test_blueprint_id'
+WORKFLOW_ID = 'test_workflow_id'
+EXECUTION_ID = 'test_execution_id'
+
+
+def get_dependency_node():
+    return models.Node(
+        id='dependency_node',
+        host_id='dependency_node',
+        blueprint_id=BLUEPRINT_ID,
+        type='test_node_type',
+        type_hierarchy=[],
+        number_of_instances=1,
+        planned_number_of_instances=1,
+        deploy_number_of_instances=1,
+        properties={},
+        operations=dict((key, {}) for key in operations.NODE_OPERATIONS),
+        relationships=[],
+        min_number_of_instances=1,
+        max_number_of_instances=1,
+    )
+
+
+def get_dependency_node_instance(dependency_node=None):
+    return models.NodeInstance(
+        id='dependency_node_instance',
+        host_id='dependency_node_instance',
+        deployment_id=DEPLOYMENT_ID,
+        runtime_properties={},
+        version=None,
+        relationship_instances=[],
+        node=dependency_node or get_dependency_node()
+    )
+
+
+def get_relationship(target=None):
+    return models.Relationship(
+        target_id=target.id or get_dependency_node().id,
+        source_interfaces={},
+        source_operations=dict((key, {}) for key in operations.RELATIONSHIP_OPERATIONS),
+        target_interfaces={},
+        target_operations=dict((key, {}) for key in operations.RELATIONSHIP_OPERATIONS),
+        type='rel_type',
+        type_hierarchy=[],
+        properties={},
+    )
+
+
+def get_relationship_instance(target_instance=None, relationship=None):
+    return models.RelationshipInstance(
+        target_id=target_instance.id or get_dependency_node_instance().id,
+        target_name='test_target_name',
+        type='some_type',
+        relationship=relationship or get_relationship(target_instance.node
+                                                      if target_instance else None)
+    )
+
+
+def get_dependent_node(relationship=None):
+    return models.Node(
+        id='dependent_node',
+        host_id='dependent_node',
+        blueprint_id=BLUEPRINT_ID,
+        type='test_node_type',
+        type_hierarchy=[],
+        number_of_instances=1,
+        planned_number_of_instances=1,
+        deploy_number_of_instances=1,
+        properties={},
+        operations=dict((key, {}) for key in operations.NODE_OPERATIONS),
+        relationships=[relationship or get_relationship()],
+        min_number_of_instances=1,
+        max_number_of_instances=1,
+    )
+
+
+def get_dependent_node_instance(relationship_instance, dependent_node=None):
+    return models.NodeInstance(
+        id='dependent_node_instance',
+        host_id='dependent_node_instance',
+        deployment_id=DEPLOYMENT_ID,
+        runtime_properties={},
+        version=None,
+        relationship_instances=[relationship_instance or get_relationship_instance()],
+        node=dependent_node or get_dependency_node()
+    )
+
+
+def get_execution():
+    return models.Execution(
+        id=EXECUTION_ID,
+        status=models.Execution.STARTED,
+        deployment_id=DEPLOYMENT_ID,
+        workflow_id=WORKFLOW_ID,
+        blueprint_id=BLUEPRINT_ID,
+        started_at=datetime.now(),
+        parameters=None
+    )
+
+
+def get_deployment():
+    now = datetime.now()
+    return models.Deployment(
+        id=DEPLOYMENT_ID,
+        description=None,
+        created_at=now,
+        updated_at=now,
+        blueprint_id=BLUEPRINT_ID,
+        workflows={}
+    )

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/tests/mock/operations.py
----------------------------------------------------------------------
diff --git a/tests/mock/operations.py b/tests/mock/operations.py
new file mode 100644
index 0000000..407061f
--- /dev/null
+++ b/tests/mock/operations.py
@@ -0,0 +1,33 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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.
+
+NODE_OPERATIONS_INSTALL = [
+    'aria.interfaces.lifecycle.create',
+    'aria.interfaces.lifecycle.configure',
+    'aria.interfaces.lifecycle.start',
+    ]
+NODE_OPERATIONS_UNINSTALL = [
+    'aria.interfaces.lifecycle.stop',
+    'aria.interfaces.lifecycle.delete',
+]
+NODE_OPERATIONS = NODE_OPERATIONS_INSTALL + NODE_OPERATIONS_UNINSTALL
+
+RELATIONSHIP_OPERATIONS_INSTALL = [
+    'aria.interfaces.relationship_lifecycle.preconfigure',
+    'aria.interfaces.relationship_lifecycle.postconfigure',
+    'aria.interfaces.relationship_lifecycle.establish',
+    ]
+RELATIONSHIP_OPERATIONS_UNINSTALL = ['aria.interfaces.relationship_lifecycle.unlink']
+RELATIONSHIP_OPERATIONS = RELATIONSHIP_OPERATIONS_INSTALL + RELATIONSHIP_OPERATIONS_UNINSTALL

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/tests/test_logger.py
----------------------------------------------------------------------
diff --git a/tests/test_logger.py b/tests/test_logger.py
index 7891dd6..37731bb 100644
--- a/tests/test_logger.py
+++ b/tests/test_logger.py
@@ -80,7 +80,7 @@ def test_create_file_log_handler():
         assert handler.baseFilename == temp_file.name
         assert handler.maxBytes == 5 * 1000 * 1024
         assert handler.backupCount == 10
-        assert handler.delay is True
+        assert handler.stream is None
         assert handler.level == logging.DEBUG
         assert handler.formatter == _default_file_formatter
 

http://git-wip-us.apache.org/repos/asf/incubator-ariatosca/blob/9002019e/tests/workflows/__init__.py
----------------------------------------------------------------------
diff --git a/tests/workflows/__init__.py b/tests/workflows/__init__.py
index ae1e83e..fe04b2f 100644
--- a/tests/workflows/__init__.py
+++ b/tests/workflows/__init__.py
@@ -12,3 +12,5 @@
 # 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 . import api, builtin, core