Add command to rollback release to CLI and API

This adds a command to the CLI and API to rollback a release name to a
specified version.

Change-Id: Ie1434da42ccc75c658b7bde7164b3f4c909be7c4

armada/api/controller/rollback.py

@@ -0,0 +1,64 @@
+# Copyright 2018 The Armada Authors.
+#
+# 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.
+
+import json
+
+import falcon
+from oslo_config import cfg
+
+from armada import api
+from armada.common import policy
+from armada.handlers.tiller import Tiller
+
+CONF = cfg.CONF
+
+
+class Rollback(api.BaseResource):
+    """Controller for performing a rollback of a release
+    """
+
+    @policy.enforce('armada:rollback_release')
+    def on_post(self, req, resp, release):
+        try:
+            dry_run = req.get_param_as_bool('dry_run')
+
+            tiller = Tiller(
+                tiller_host=req.get_param('tiller_host'),
+                tiller_port=req.get_param_as_int(
+                    'tiller_port') or CONF.tiller_port,
+                tiller_namespace=req.get_param(
+                    'tiller_namespace', default=CONF.tiller_namespace),
+                dry_run=dry_run)
+
+            tiller.rollback_release(
+                release,
+                req.get_param_as_int('version') or 0,
+                wait=req.get_param_as_bool('wait'),
+                timeout=req.get_param_as_int('timeout') or 0)
+
+            resp.body = json.dumps(
+                {
+                    'message': ('(dry run) ' if dry_run else '') +
+                    'Rollback of {} complete.'.format(release),
+                }
+            )
+
+            resp.content_type = 'application/json'
+            resp.status = falcon.HTTP_200
+        except Exception as e:
+            self.logger.exception('Caught unexpected exception')
+            err_message = 'Failed to rollback release: {}'.format(e)
+            self.error(req.context, err_message)
+            self.return_error(
+                resp, falcon.HTTP_500, message=err_message)