refactoring castellan configuration

This change adds a module for listing configuration options and setting
their defaults. It also changes the key manager base class to
incorporate a configuration during creation. By default, the key manager
will continue to use the global CONF object from the oslo.config
package.

For the most part, this change will be backwards compatible. The one
exception is the creation of sample configuration files. Previously,
importing castellan was sufficient to add these options to the global
configuration object. Now, these options will need to be applied by
using the castellan.options.list_opts function, or adding them through
other means, to create sample configuration files. Similar applies for
setting configuration before instantiating a key manager.

changes
* adding castellan.options with list_opts and set_defaults functions
* changing KeyManager abc to include a configuration option to __init__
* changing barbican and not_implemented key managers to accept
  configuration parameters
* adding tests for set_defaults function
* fixing barbican tests to accomodate new configuration parameter
* adding documentation about configuration usage
* adding castellan configs to oslo entry point in setup.cfg
* adding a genconfig target to tox for producing a sample castellan
  configuration file
* adding the sample configuration file to the git ignore
* renaming barbican option api_version to barbican_api_version

Change-Id: I86d6d7d49a893beaae6f311060ec593e0482d889
Implements: blueprint improved-configuration-options

.gitignore

@@ -51,3 +51,7 @@ ChangeLog
 *~
 .*.swp
 .*sw?
+
+# generated configuration files
+etc/castellan/castellan.conf.sample
+etc/castellan/castellan-functional.conf.sample

castellan/key_manager/__init__.py

@@ -16,7 +16,6 @@
 from oslo_config import cfg
 from oslo_utils import importutils
 
-
 key_manager_opts = [
     cfg.StrOpt('api_class',
                default='castellan.key_manager.barbican_key_manager'
@@ -24,10 +23,10 @@ key_manager_opts = [
                help='The full class name of the key manager API class'),
 ]
 
-CONF = cfg.CONF
-CONF.register_opts(key_manager_opts, group='key_manager')
 
+def API(configuration=None):
+    conf = configuration or cfg.CONF
+    conf.register_opts(key_manager_opts, group='key_manager')
 
-def API():
-    cls = importutils.import_class(CONF.key_manager.api_class)
-    return cls()
+    cls = importutils.import_class(conf.key_manager.api_class)
+    return cls(configuration=conf)

castellan/key_manager/barbican_key_manager.py

@@ -35,27 +35,25 @@ barbican_opts = [
     cfg.StrOpt('barbican_endpoint',
                default='http://localhost:9311/',
                help='Use this endpoint to connect to Barbican'),
-    cfg.StrOpt('api_version',
+    cfg.StrOpt('barbican_api_version',
                default='v1',
                help='Version of the Barbican API'),
 ]
 
-CONF = cfg.CONF
 BARBICAN_OPT_GROUP = 'barbican'
 
-CONF.register_opts(barbican_opts, group=BARBICAN_OPT_GROUP)
-
-session.Session.register_conf_options(CONF, BARBICAN_OPT_GROUP)
-
 LOG = logging.getLogger(__name__)
 
 
 class BarbicanKeyManager(key_manager.KeyManager):
     """Key Manager Interface that wraps the Barbican client API."""
 
-    def __init__(self):
+    def __init__(self, configuration):
         self._barbican_client = None
         self._base_url = None
+        self.conf = configuration
+        self.conf.register_opts(barbican_opts, group=BARBICAN_OPT_GROUP)
+        session.Session.register_conf_options(self.conf, BARBICAN_OPT_GROUP)
 
     def _get_barbican_client(self, context):
         """Creates a client to connect to the Barbican service.
@@ -92,9 +90,9 @@ class BarbicanKeyManager(key_manager.KeyManager):
 
     def _get_keystone_session(self, context):
         sess = session.Session.load_from_conf_options(
-            CONF, BARBICAN_OPT_GROUP)
+            self.conf, BARBICAN_OPT_GROUP)
 
-        self._barbican_endpoint = CONF.barbican.barbican_endpoint
+        self._barbican_endpoint = self.conf.barbican.barbican_endpoint
 
         auth = token_endpoint.Token(self._barbican_endpoint,
                                     context.auth_token)
@@ -102,8 +100,8 @@ class BarbicanKeyManager(key_manager.KeyManager):
         return sess
 
     def _create_base_url(self):
-        base_url = urllib.parse.urljoin(self._barbican_endpoint,
-                                        CONF.barbican.api_version)
+        base_url = urllib.parse.urljoin(
+            self._barbican_endpoint, self.conf.barbican.barbican_api_version)
         return base_url
 
     def create_key(self, context, algorithm, length, expiration=None):

castellan/key_manager/key_manager.py

@@ -30,6 +30,15 @@ class KeyManager(object):
     Key Manager is responsible for creating, reading, and deleting keys.
     """
 
+    @abc.abstractmethod
+    def __init__(self, configuration):
+        """Instantiate a KeyManager object.
+
+        Creates a KeyManager object with implementation specific details
+        obtained from the supplied configuration.
+        """
+        pass
+
     @abc.abstractmethod
     def create_key(self, context, algorithm, length, expiration=None):
         """Creates a symmetric key.

castellan/key_manager/not_implemented_key_manager.py

@@ -25,6 +25,9 @@ class NotImplementedKeyManager(key_manager.KeyManager):
 
     """
 
+    def __init__(self, configuration=None):
+        super(NotImplementedKeyManager, self).__init__(configuration)
+
     def create_key(self, context, algorithm='AES', length=256,
                    expiration=None, **kwargs):
         raise NotImplementedError()

castellan/options.py

@@ -0,0 +1,70 @@
+# Copyright (c) 2015 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 castellan import key_manager as km
+try:
+    from castellan.key_manager import barbican_key_manager as bkm
+except ImportError:
+    bkm = None
+
+
+def set_defaults(conf, api_class=None, barbican_endpoint=None,
+                 barbican_api_version=None):
+    '''Set defaults for configuration values.
+
+    Overrides the default options values.
+
+    :param conf: Config instance in which to set default options.
+
+    :param api_class: The full class name of the key manager API class.
+
+    :param barbican_endpoint: Use this endpoint to connect to Barbican.
+
+    :param barbican_api_version: Version of the Barbican API.
+    '''
+    conf.register_opts(km.key_manager_opts, group='key_manager')
+    if bkm:
+        conf.register_opts(bkm.barbican_opts, group=bkm.BARBICAN_OPT_GROUP)
+
+    if api_class is not None:
+        conf.set_default('api_class', api_class, group='key_manager')
+    if bkm is not None and barbican_endpoint is not None:
+        conf.set_default('barbican_endpoint', barbican_endpoint,
+                         group=bkm.BARBICAN_OPT_GROUP)
+    if bkm is not None and barbican_api_version is not None:
+        conf.set_default('barbican_api_version', barbican_api_version,
+                         group=bkm.BARBICAN_OPT_GROUP)
+
+
+def list_opts():
+    '''Returns a list of oslo.config options available in the library.
+
+    The returned list includes all oslo.config options which may be registered
+    at runtime by the library.
+
+    Each element of the list is a tuple. The first element is the name of the
+    group under which the list of elements in the second element will be
+    registered. A group name of None corresponds to the [DEFAULT] group in
+    config files.
+
+    The purpose of this is to allow tools like the Oslo sample config file
+    generator to discover the options exposed to users by this library.
+
+    :returns: a list of (group_name, opts) tuples
+    '''
+    opts = [('key_manager', km.key_manager_opts)]
+    if bkm is not None:
+        opts.append((bkm.BARBICAN_OPT_GROUP, bkm.barbican_opts))
+    return opts

castellan/tests/unit/key_manager/test_barbican_key_manager.py

@@ -18,6 +18,7 @@ Test cases for the barbican key manager.
 """
 
 import mock
+from oslo_config import cfg
 
 from castellan.common import exception
 from castellan.common.objects import symmetric_key as key_manager_key
@@ -28,7 +29,7 @@ from castellan.tests.unit.key_manager import test_key_manager
 class BarbicanKeyManagerTestCase(test_key_manager.KeyManagerTestCase):
 
     def _create_key_manager(self):
-        return barbican_key_manager.BarbicanKeyManager()
+        return barbican_key_manager.BarbicanKeyManager(cfg.CONF)
 
     def setUp(self):
         super(BarbicanKeyManagerTestCase, self).setUp()

castellan/tests/unit/test_options.py

@@ -0,0 +1,40 @@
+# Copyright (c) 2015 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 castellan.key_manager import barbican_key_manager as bkm
+from castellan import options
+from castellan.tests import base
+
+
+class TestOptions(base.TestCase):
+
+    def test_set_defaults(self):
+        conf = cfg.ConfigOpts()
+
+        api_class = 'test.api.class'
+        options.set_defaults(conf, api_class=api_class)
+        self.assertEqual(api_class, conf.key_manager.api_class)
+
+        barbican_endpoint = 'http://test-server.org:9311/'
+        options.set_defaults(conf, barbican_endpoint=barbican_endpoint)
+        self.assertEqual(barbican_endpoint,
+                         conf.get(bkm.BARBICAN_OPT_GROUP).barbican_endpoint)
+
+        barbican_api_version = 'vSomething'
+        options.set_defaults(conf, barbican_api_version=barbican_api_version)
+        self.assertEqual(barbican_api_version,
+                         conf.get(bkm.BARBICAN_OPT_GROUP).barbican_api_version)

doc/source/usage.rst

@@ -5,3 +5,102 @@ Usage
 To use castellan in a project::
 
     import castellan
+
+
+Configuring castellan
+~~~~~~~~~~~~~~~~~~~~~
+
+Castellan contains several options which control the key management
+service usage and the configuration of that service. It also contains
+functions to help configure the defaults and produce listings for use
+with the ``oslo-config-generator`` application.
+
+In general, castellan configuration is handled by passing an
+``oslo_config.cfg.ConfigOpts`` object into the
+``castellan.key_manager.API`` call when creating your key manager. By
+default, when no ``ConfigOpts`` object is provided, the key manager will
+use the global ``oslo_config.cfg.CONF`` object.
+
+**Example. Using the global CONF object for configuration.**
+
+.. code:: python
+
+    from castellan import key_manager
+
+    manager = key_manager.API()
+
+**Example. Using a predetermined configuration object.**
+
+.. code:: python
+
+    from oslo_config import cfg
+    from castellan import key_manager
+
+    conf = cfg.ConfigOpts()
+    manager = key_manager.API(configuration=conf)
+
+Controlling default options
+---------------------------
+
+To change the default behavior of castellan, and the key management service
+it uses, the ``castellan.options`` module provides the ``set_defaults``
+function. This function can be used at run-time to change the behavior of
+the library or the key management service provider.
+
+**Example. Changing the barbican endpoint.**
+
+.. code:: python
+
+    from oslo_config import cfg
+    from castellan import options
+    from castellan import key_manager
+
+    conf = cfg.ConfigOpts()
+    options.set_defaults(conf, barbican_endpoint='http://192.168.0.1:9311/')
+    manager = key_manager.API(conf)
+
+**Example. Changing the key manager provider while using the global
+configuration.**
+
+.. code:: python
+
+    from oslo_config import cfg
+    from castellan import options
+    from castellan import key_manager
+
+    options.set_defaults(cfg.CONF, api_class='some.other.KeyManager')
+    manager = key_manager.API()
+
+Generating sample configuration files
+-------------------------------------
+
+Castellan includes a tox configuration for creating a sample configuration
+file. This file will contain only the values that will be used by
+castellan. To produce this file, run the following command from the
+root of the castellan project directory:
+
+.. code:: console
+
+    $ tox -e genconfig
+
+Adding castellan to configuration files
+---------------------------------------
+
+One common task for OpenStack projects is to create project configuration
+files. Castellan provides a ``list_opts`` function in the
+``castellan.options`` module to aid in generating these files when using
+the ``oslo-config-generator``. This function can be specified in the
+:file:`setup.cfg` file of your project to inform oslo of the
+configuration options. *Note, this will use the default values supplied
+by the castellan package.*
+
+**Example. Adding castellan to the oslo.config entry point.**
+
+.. code:: ini
+
+    [entry_points]
+    oslo.config.opts =
+        castellan.config = castellan.options:list_opts
+
+For more information on the oslo configuration generator, please see
+http://docs.openstack.org/developer/oslo.config/generator.html

etc/castellan/sample-config-generator.conf

@@ -0,0 +1,4 @@
+[DEFAULT]
+output_file = etc/castellan/castellan.conf.sample
+wrap_width = 79
+namespace = castellan.config

setup.cfg

@@ -26,6 +26,7 @@ packages =
 [entry_points]
 oslo.config.opts =
     castellan.tests.functional.config = castellan.tests.functional.config:list_opts
+    castellan.config = castellan.options:list_opts
 
 [build_sphinx]
 source-dir = doc/source

tox.ini

@@ -38,7 +38,7 @@ commands = python setup.py testr --slowest --testr-args='{posargs}'
 [testenv:genconfig]
 commands =
     oslo-config-generator --config-file=etc/castellan/functional-config-generator.conf
-#TODO(kfarr): add config generator for main Castellan options
+    oslo-config-generator --config-file=etc/castellan/sample-config-generator.conf
 
 [flake8]
 # H803 skipped on purpose per list discussion.