Fetch transformations configuration from Nailgun settings

Change-Id: Ic03f729c738745ff18c849cb4f3a4b5b8d3fe90c
Closes-Bug: #1618177

3 files changed, 91 insertions, 12 deletions

diff --git a/README.rst b/README.rst
index e8a886c..76e808d 100644
--- a/README.rst
+++ b/README.rst
@@ -6,6 +6,53 @@ cluster upgrading. This extension used by the fuel-octane project.
 
 Instalation
 -----------
-After installing `fuel-nailgun-extension-cluster-upgrade` package run:
-1) `nailgun_syncdb` - migrate database
-2) restart nailgun service
+After installing ``fuel-nailgun-extension-cluster-upgrade`` package run:
+ #. ``nailgun_syncdb`` - migrate database
+ #. restart nailgun service
+
+Transformer configuration
+-------------------------
+
+Every transformation manager has default config that hardcoded, but
+you can overwrite this config with your own transformations
+extensions. This could be done by extending ``nailgun/settings.yaml``
+file.
+
+**Example**
+
+::
+   CLUSTER_UPGRADE:
+     transformations:
+       cluster:
+         7.0: [transform_vips]
+         9.0: [first_transformation, second_transformation]
+
+   ...
+
+In extension you should define a entrypoint is such way:
+
+::
+   nailgun.cluster_upgrade.transformations.cluster.7.0 =
+      transform_vips = my_project.transformations:transform_cluster_vips
+
+on first line we have entripoint name where
+* ``nailgun.cluster_upgrade.transformations`` - namespace where all
+  transformations defined.
+* ``cluster`` - name of object which data transformed
+* ``7.0`` - cluster version where these transformations should happen
+
+on the second line
+* ``transform_vips`` - unique transformation name that you can use in
+  configuration file or in transformation manager
+* ``my_project.transformations`` - module name
+* ``transform_cluster_vips`` - transformer function name
+
+
+Transformation function must take only one argument - data to
+transform. When you call ``manager.apply(from_version, to_version,
+data)`` all transformer functions ordered by a version called one by
+one, and output of one transformer used as input to the other.
+
+In out example calling ``cluster_manager.apply('6.0', '9.1', data)``
+will call three functions ``transform_vips``,
+``first_transformation``, ``second_transformation``.
diff --git a/cluster_upgrade/tests/test_transformations.py b/cluster_upgrade/tests/test_transformations.py
index 880ee2d..f970702 100644
--- a/cluster_upgrade/tests/test_transformations.py
+++ b/cluster_upgrade/tests/test_transformations.py
@@ -21,13 +21,36 @@ from ..transformations import cluster
 
 
 class TestTransformations(nailgun_test_base.BaseUnitTest):
-    def test_get_config(self):
-        config = object()
-
+    def _test_get_config(self, def_config, settings, expected_result):
         class Manager(transformations.Manager):
-            default_config = config
+            default_config = def_config
+
+        with mock.patch("nailgun.settings.settings.config", new=settings):
+            result = Manager.get_config('testname')
+
+        self.assertEqual(expected_result, result)
+
+    @staticmethod
+    def _trans_settings(config):
+        return {'CLUSTER_UPGRADE': {'transformations': {'testname': config}}}
 
-        self.assertIs(config, Manager.get_config('testname'))
+    def test_get_config_default(self):
+        config = {'9.0': []}
+        self._test_get_config(config, {}, config)
+
+    def test_get_config_no_overwrite(self):
+        self._test_get_config(
+            {'9.0': ['a']},
+            self._trans_settings({'8.0': ['b']}),
+            {'8.0': ['b'], '9.0': ['a']},
+        )
+
+    def test_get_config_overwrite(self):
+        self._test_get_config(
+            {'9.0': ['a']},
+            self._trans_settings({'8.0': ['b'], '9.0': ['c']}),
+            {'8.0': ['b'], '9.0': ['c']},
+        )
 
     def setup_extension_manager(self, extensions):
         p = mock.patch("stevedore.ExtensionManager", spec=['__call__'])
@@ -153,8 +176,9 @@ class TestTransformations(nailgun_test_base.BaseUnitTest):
             ),
         ])
 
+    @mock.patch.object(transformations.Manager, 'get_config')
     @mock.patch.object(transformations.Manager, 'load_transformers')
-    def test_apply(self, mock_load):
+    def test_apply(self, mock_load, mock_config):
         mock_trans = mock.Mock()
         mock_load.return_value = [
             (version.StrictVersion('7.0'), [mock_trans.a, mock_trans.b]),
diff --git a/cluster_upgrade/transformations/__init__.py b/cluster_upgrade/transformations/__init__.py
index 7e1d861..b7d33af 100644
--- a/cluster_upgrade/transformations/__init__.py
+++ b/cluster_upgrade/transformations/__init__.py
@@ -15,10 +15,12 @@ import distutils.version
 import logging
 import threading
 
-import six
 
+import six
 import stevedore
 
+from nailgun.settings import settings
+
 LOG = logging.getLogger(__name__)
 
 
@@ -37,8 +39,14 @@ class Manager(object):
 
     @classmethod
     def get_config(cls, name):
-        # TODO(yorik-sar): merge actual config with defaults
-        return cls.default_config
+        res = cls.default_config.copy()
+        try:
+            conf = settings.config['CLUSTER_UPGRADE']['transformations'][name]
+        except KeyError:
+            pass
+        else:
+            res.update(conf)
+        return res
 
     @staticmethod
     def load_transformers(name, config):