Don't throw exception when missing metrics

When querying data from datasource, it's possible to miss some data.
In this case if we throw an exception, Audit will failed because of
the exception. We should remove the exception and give the decision
to the strategy.

Change-Id: I1b0e6b78b3bba4df9ba16e093b3910aab1de922e
Closes-Bug: #1847434

watcher/decision_engine/datasources/base.py

@@ -19,8 +19,6 @@ import time
 from oslo_config import cfg
 from oslo_log import log
 
-from watcher.common import exception
-
 CONF = cfg.CONF
 LOG = log.getLogger(__name__)
 
@@ -79,7 +77,6 @@ class DataSourceBase(object):
                 LOG.warning("Retry {0} of {1} while retrieving metrics retry "
                             "in {2} seconds".format(i+1, num_retries, timeout))
                 time.sleep(timeout)
-        raise exception.DataSourceNotAvailable(datasource=self.NAME)
 
     @abc.abstractmethod
     def query_retry_reset(self, exception_instance):

watcher/decision_engine/datasources/ceilometer.py

@@ -136,19 +136,18 @@ class CeilometerHelper(base.DataSourceBase):
 
     def list_metrics(self):
         """List the user's meters."""
-        try:
         meters = self.query_retry(f=self.ceilometer.meters.list)
-        except Exception:
+        if not meters:
             return set()
         else:
             return meters
 
     def check_availability(self):
-        try:
+        status = self.query_retry(self.ceilometer.resources.list)
-            self.query_retry(self.ceilometer.resources.list)
+        if status:
-        except Exception:
-            return 'not available'
             return 'available'
+        else:
+            return 'not available'
 
     def query_sample(self, meter_name, query, limit=1):
         return self.query_retry(f=self.ceilometer.samples.list,

watcher/decision_engine/datasources/gnocchi.py

@@ -52,17 +52,16 @@ class GnocchiHelper(base.DataSourceBase):
         self.gnocchi = self.osc.gnocchi()
 
     def check_availability(self):
-        try:
+        status = self.query_retry(self.gnocchi.status.get)
-            self.query_retry(self.gnocchi.status.get)
+        if status:
-        except Exception:
-            return 'not available'
             return 'available'
+        else:
+            return 'not available'
 
     def list_metrics(self):
         """List the user's meters."""
-        try:
         response = self.query_retry(f=self.gnocchi.metric.list)
-        except Exception:
+        if not response:
             return set()
         else:
             return set([metric['name'] for metric in response])
@@ -91,8 +90,9 @@ class GnocchiHelper(base.DataSourceBase):
                 f=self.gnocchi.resource.search, **kwargs)
 
             if not resources:
-                raise exception.ResourceNotFound(name='gnocchi',
+                LOG.warning("The {0} resource {1} could not be "
-                                                 id=resource_id)
+                            "found".format(self.NAME, resource_id))
+                return
 
             resource_id = resources[0]['id']
 
@@ -110,6 +110,7 @@ class GnocchiHelper(base.DataSourceBase):
         statistics = self.query_retry(
             f=self.gnocchi.metric.get_measures, **kwargs)
 
+        return_value = None
         if statistics:
             # return value of latest measure
             # measure has structure [time, granularity, value]

watcher/decision_engine/datasources/grafana.py

@@ -179,6 +179,9 @@ class GrafanaHelper(base.DataSourceBase):
         kwargs = {k: v for k, v in raw_kwargs.items() if k and v}
 
         resp = self.query_retry(self._request, **kwargs)
+        if not resp:
+            LOG.warning("Datasource {0} is not available.".format(self.NAME))
+            return
 
         result = translator.extract_result(resp.content)
 

watcher/decision_engine/datasources/monasca.py

@@ -73,11 +73,11 @@ class MonascaHelper(base.DataSourceBase):
             self.monasca = self.osc.monasca()
 
     def check_availability(self):
-        try:
+        result = self.query_retry(self.monasca.metrics.list)
-            self.query_retry(self.monasca.metrics.list)
+        if result:
-        except Exception:
-            return 'not available'
             return 'available'
+        else:
+            return 'not available'
 
     def list_metrics(self):
         # TODO(alexchadin): this method should be implemented in accordance to

watcher/tests/decision_engine/datasources/test_base.py

@@ -19,7 +19,6 @@
 import mock
 from oslo_config import cfg
 
-from watcher.common import exception
 from watcher.decision_engine.datasources import base as datasource
 from watcher.tests import base
 
@@ -61,9 +60,8 @@ class TestBaseDatasourceHelper(base.BaseTestCase):
         helper = datasource.DataSourceBase()
         helper.query_retry_reset = mock.Mock()
 
-        # Maximum number of retries exceeded query_retry should raise error
+        # Maximum number of retries exceeded query_retry should return None
-        self.assertRaises(exception.DataSourceNotAvailable,
+        self.assertIsNone(helper.query_retry(f=method))
-                          helper.query_retry, f=method)
         # query_retry_reset should be called twice
         helper.query_retry_reset.assert_has_calls(
             [mock.call(exc), mock.call(exc)])

watcher/tests/decision_engine/datasources/test_grafana_helper.py

@@ -132,11 +132,7 @@ class TestGrafana(base.BaseTestCase):
 
         t_grafana = grafana.GrafanaHelper(osc=mock.Mock())
 
-        self.assertRaises(
+        self.assertIsNone(t_grafana.get_host_cpu_usage(self.m_compute_node))
-            exception.DataSourceNotAvailable,
-            t_grafana.get_host_cpu_usage,
-            self.m_compute_node
-        )
 
     def test_no_metric_raise_error(self):
         """Test raising error when specified meter does not exist"""