Add hooks for Image Import plugins

This change adds hooks for pulling in plugins for
Interoperable Image Import taksflow. Boilerplate Noop
plugin is provided as an example and for testing.

Change-Id: If14c7dc4f38360006f9cb350fbba54fa2f33be61

glance/async/flows/api_image_import.py

@@ -23,6 +23,7 @@ from taskflow.patterns import linear_flow as lf
 from taskflow import retry
 from taskflow import task
 
+import glance.async.flows.plugins as import_plugins
 from glance.common import exception
 from glance.common.scripts.image_import import main as image_import
 from glance.common.scripts import utils as script_utils
@@ -35,9 +36,42 @@ LOG = logging.getLogger(__name__)
 CONF = cfg.CONF
 
 
+api_import_opts = [
+    cfg.ListOpt('image_import_plugins',
+                item_type=cfg.types.String(quotes=True),
+                bounds=True,
+                sample_default='[no_op]',
+                default=[],
+                help=_("""
+Image import plugins to be enabled for task processing.
+
+Provide list of strings reflecting to the task Objects
+that should be included to the Image Import flow. The
+task objects needs to be defined in the 'glance/async/
+flows/plugins/*' and may be implemented by OpenStack
+Glance project team, deployer or 3rd party.
+
+By default no plugins are enabled and to take advantage
+of the plugin model the list of plugins must be set
+explicitly in the glance-image-import.conf file.
+
+The allowed values for this option is comma separated
+list of object names in between ``[`` and ``]``.
+
+Possible values:
+    * no_op (only logs debug level message that the
+      plugin has been executed)
+    * Any provided Task object name to be included
+      in to the flow.
+""")),
+]
+
+CONF.register_opts(api_import_opts, group='image_import_opts')
+
 # TODO(jokke): We should refactor the task implementations so that we do not
 # need to duplicate what we have already for example in base_import.py.
 
+
 class _DeleteFromFS(task.Task):
 
     def __init__(self, task_id, task_type):
@@ -336,8 +370,8 @@ def get_flow(**kwargs):
     flow = lf.Flow(task_type, retry=retry.AlwaysRevert())
     flow.add(_VerifyStaging(task_id, task_type, task_repo, uri))
 
-    # TODO(jokke): For the pluggable tasks like image verification or
-    # image conversion we need to implement the plugin logic here.
+    for plugin in import_plugins.get_import_plugins(**kwargs):
+        flow.add(plugin)
 
     import_to_store = _ImportToStore(task_id,
                                      task_type,

glance/async/flows/plugins/__init__.py

@@ -0,0 +1,31 @@
+# Copyright 2017 Red Hat, 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 oslo_config import cfg
+from stevedore import named
+
+
+CONF = cfg.CONF
+
+
+def get_import_plugins(**kwargs):
+    task_list = CONF.image_import_opts.image_import_plugins
+    extensions = named.NamedExtensionManager('glance.image_import.plugins',
+                                             names=task_list,
+                                             name_order=True,
+                                             invoke_on_load=True,
+                                             invoke_kwds=kwargs)
+    for extension in extensions.extensions:
+        yield extension.obj

glance/async/flows/plugins/no_op.py

@@ -0,0 +1,62 @@
+# Copyright 2017 Red Hat, 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 oslo_config import cfg
+from oslo_log import log as logging
+from taskflow.patterns import linear_flow as lf
+from taskflow import task
+
+LOG = logging.getLogger(__name__)
+
+CONF = cfg.CONF
+
+
+class _Noop(task.Task):
+
+    def __init__(self, task_id, task_type, image_repo):
+        self.task_id = task_id
+        self.task_type = task_type
+        self.image_repo = image_repo
+        super(_Noop, self).__init__(
+            name='%s-Noop-%s' % (task_type, task_id))
+
+    def execute(self, **kwargs):
+
+        LOG.debug("No_op import plugin")
+        return
+
+    def revert(self, result=None, **kwargs):
+        # NOTE(flaper87): If result is None, it probably
+        # means this task failed. Otherwise, we would have
+        # a result from its execution.
+        if result is not None:
+            LOG.debug("No_op import plugin failed")
+            return
+
+
+def get_flow(**kwargs):
+    """Return task flow for no-op.
+
+    :param task_id: Task ID.
+    :param task_type: Type of the task.
+    :param image_repo: Image repository used.
+    """
+    task_id = kwargs.get('task_id')
+    task_type = kwargs.get('task_type')
+    image_repo = kwargs.get('image_repo')
+
+    return lf.Flow(task_type).add(
+        _Noop(task_id, task_type, image_repo),
+    )

glance/opts.py

@@ -18,6 +18,7 @@ __all__ = [
     'list_scrubber_opts',
     'list_cache_opts',
     'list_manage_opts',
+    'list_image_import_opts',
 ]
 
 import copy
@@ -27,6 +28,7 @@ from osprofiler import opts as profiler
 
 import glance.api.middleware.context
 import glance.api.versions
+import glance.async.flows.api_image_import
 import glance.async.flows.convert
 import glance.async.taskflow_executor
 import glance.common.config
@@ -107,6 +109,9 @@ _cache_opts = [
 _manage_opts = [
     (None, [])
 ]
+_image_import_opts = [
+    ('image_import_opts', glance.async.flows.api_image_import.api_import_opts)
+]
 
 
 def list_api_opts():
@@ -153,3 +158,8 @@ def list_cache_opts():
 def list_manage_opts():
     """Return a list of oslo_config options available in Glance manage."""
     return [(g, copy.deepcopy(o)) for g, o in _manage_opts]
+
+
+def list_image_import_opts():
+    """Return a list of oslo_config options available for Image Import"""
+    return [(g, copy.deepcopy(o)) for g, o in _image_import_opts]

setup.cfg

@@ -71,6 +71,9 @@ glance.flows.import =
     introspect = glance.async.flows.introspect:get_flow
     ovf_process = glance.async.flows.ovf_process:get_flow
 
+glance.image_import.plugins =
+    no_op = glance.async.flows.plugins.no_op:get_flow
+
 [build_sphinx]
 builder = html man
 all_files = 1