Tidy up - Watcher Decision Engine package

Some Python class and packages need to be renamed
for a better compliance with the shared terminology
which provides a better understanding of Watcher
objects and components by every contributor.

This patchset is there to change the code structure by adding the folder
"strategies" and "loading".

Partially implements: blueprint glossary-related-refactoring

Change-Id: I56fb24ee6762b3186eccde5983233e17bb227cc1

watcher/decision_engine/strategy/selection/default.py

@@ -0,0 +1,59 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2015 b<>com
+#
+# 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
+
+from watcher.common.exception import WatcherException
+from watcher.decision_engine.strategy.loading.default import \
+    DefaultStrategyLoader
+from watcher.decision_engine.strategy.selection.base import BaseSelector
+
+LOG = log.getLogger(__name__)
+CONF = cfg.CONF
+
+default_goals = {'DUMMY': 'dummy'}
+
+WATCHER_GOALS_OPTS = [
+    cfg.DictOpt(
+        'goals',
+        default=default_goals,
+        help='Goals used for the optimization. '
+             'Maps each goal to an associated strategy (for example: '
+             'BASIC_CONSOLIDATION:basic, MY_GOAL:my_strategy_1)'),
+]
+goals_opt_group = cfg.OptGroup(name='watcher_goals',
+                               title='Goals available for the optimization')
+CONF.register_group(goals_opt_group)
+CONF.register_opts(WATCHER_GOALS_OPTS, goals_opt_group)
+
+
+class StrategySelector(BaseSelector):
+
+    def __init__(self):
+        self.strategy_loader = DefaultStrategyLoader()
+
+    def define_from_goal(self, goal_name):
+        strategy_to_load = None
+        try:
+            strategy_to_load = CONF.watcher_goals.goals[goal_name]
+            return self.strategy_loader.load(strategy_to_load)
+        except KeyError as exc:
+            LOG.exception(exc)
+            raise WatcherException(
+                "Incorrect mapping: could not find "
+                "associated strategy for '%s'" % goal_name
+            )