Add Gnocchi datasource

This patch set adds Gnocchi datasource support

Implements: blueprint gnocchi-watcher

Change-Id: I41653149435fd355548071de855586004371c4fc

watcher/datasource/gnocchi.py

@@ -0,0 +1,92 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2017 Servionica
+#
+# Authors: Alexander Chadin <a.chadin@servionica.ru>
+#
+# 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 datetime import datetime
+import time
+
+from oslo_config import cfg
+from oslo_log import log
+
+from watcher.common import clients
+from watcher.common import exception
+
+CONF = cfg.CONF
+LOG = log.getLogger(__name__)
+
+
+class GnocchiHelper(object):
+
+    def __init__(self, osc=None):
+        """:param osc: an OpenStackClients instance"""
+        self.osc = osc if osc else clients.OpenStackClients()
+        self.gnocchi = self.osc.gnocchi()
+
+    def query_retry(self, f, *args, **kwargs):
+        for i in range(CONF.gnocchi_client.query_max_retries):
+            try:
+                return f(*args, **kwargs)
+            except Exception as e:
+                LOG.exception(e)
+                time.sleep(CONF.gnocchi_client.query_timeout)
+        raise
+
+    def statistic_aggregation(self,
+                              resource_id,
+                              metric,
+                              granularity,
+                              start_time=None,
+                              stop_time=None,
+                              aggregation='mean'):
+        """Representing a statistic aggregate by operators
+
+        :param metric: metric name of which we want the statistics
+        :param resource_id: id of resource to list statistics for
+        :param start_time: Start datetime from which metrics will be used
+        :param stop_time: End datetime from which metrics will be used
+        :param granularity: frequency of marking metric point, in seconds
+        :param aggregation: Should be chosen in accrodance with policy
+                            aggregations
+        :return: value of aggregated metric
+        """
+
+        if start_time is not None and not isinstance(start_time, datetime):
+            raise exception.InvalidParameter(parameter='start_time',
+                                             parameter_type=datetime)
+
+        if stop_time is not None and not isinstance(stop_time, datetime):
+            raise exception.InvalidParameter(parameter='stop_time',
+                                             parameter_type=datetime)
+
+        raw_kwargs = dict(
+            metric=metric,
+            start=start_time,
+            stop=stop_time,
+            resource_id=resource_id,
+            granularity=granularity,
+            aggregation=aggregation,
+        )
+
+        kwargs = {k: v for k, v in raw_kwargs.items() if k and v}
+
+        statistics = self.query_retry(
+            f=self.gnocchi.metric.get_measures, **kwargs)
+
+        if statistics:
+            # return value of latest measure
+            # measure has structure [time, granularity, value]
+            return statistics[-1][2]