Fix gnocchi collector metadata collection

This fixes metadata collection failures in the gnocchi collector caused
by resources having measures in periods where they are supposed to be deleted.
Metadata is now collected over a three-period window in the gnocchi collector.

Story: 2004895
Task: 29202
Change-Id: I52020cb44fc0adbcbe6228c507fe169f4b13b6e4

cloudkitty/collector/gnocchi.py

@@ -98,6 +98,16 @@ GNOCCHI_EXTRA_SCHEMA = {
 }
 
 
+class AssociatedResourceNotFound(Exception):
+    """Exception raised when no resource can be associated with a metric."""
+
+    def __init__(self, resource_key, resource_id):
+        super(AssociatedResourceNotFound, self).__init__(
+            'Resource with {}={} could not be found'.format(
+                resource_key, resource_id),
+        )
+
+
 class GnocchiCollector(collector.BaseCollector):
 
     collector_name = 'gnocchi'
@@ -227,12 +237,18 @@ class GnocchiCollector(collector.BaseCollector):
 
         # Get gnocchi specific conf
         extra_args = self.conf[metric_name]['extra_args']
-        # Build query
-        query_parameters = self._generate_time_filter(start, end)
-
         resource_type = extra_args['resource_type']
         scope_key = CONF.collect.scope_key
 
+        # Build query
+
+        # FIXME(peschk_l): In order not to miss any resource whose metrics may
+        # contain measures after its destruction, we scan resources over three
+        # collect periods.
+        start -= CONF.collect.period
+        end += CONF.collect.period
+        query_parameters = self._generate_time_filter(start, end)
+
         if project_id:
             kwargs = {scope_key: project_id}
             query_parameters.append(self.gen_filter(**kwargs))
@@ -312,8 +328,12 @@ class GnocchiCollector(collector.BaseCollector):
         # metadata as defined in the conf
         metadata = dict()
         if resources_info is not None:
-            resource = resources_info[
+            resource_key = metconf['extra_args']['resource_key']
-                groupby[metconf['extra_args']['resource_key']]]
+            resource_id = groupby[resource_key]
+            try:
+                resource = resources_info[resource_id]
+            except KeyError:
+                raise AssociatedResourceNotFound(resource_key, resource_id)
             for i in metconf['metadata']:
                 metadata[i] = resource.get(i, '')
         qty = data['measures']['measures']['aggregated'][0][2]
@@ -348,8 +368,19 @@ class GnocchiCollector(collector.BaseCollector):
         for d in data:
             # Only if aggregates have been found
             if d['measures']['measures']['aggregated']:
+                try:
                     metadata, groupby, qty = self._format_data(
                         met, d, resources_info)
+                except AssociatedResourceNotFound as e:
+                    LOG.warning(
+                        '[{}] An error occured during data collection '
+                        'between {} and {}: {}'.format(
+                            project_id,
+                            ck_utils.ts2dt(start),
+                            ck_utils.ts2dt(end),
+                            e),
+                    )
+                    continue
                 data = self.t_cloudkitty.format_item(
                     groupby,
                     metadata,

cloudkitty/tests/collectors/test_gnocchi.py

@@ -17,13 +17,33 @@
 from cloudkitty.collector import gnocchi
 from cloudkitty import tests
 from cloudkitty.tests import samples
+from cloudkitty import transformer
 
 
 class GnocchiCollectorTest(tests.TestCase):
     def setUp(self):
         super(GnocchiCollectorTest, self).setUp()
         self._tenant_id = samples.TENANT
-        self.collector = gnocchi.GnocchiCollector
+        self.conf.set_override('collector', 'gnocchi', 'collect')
+        self.conf.set_override(
+            'gnocchi_auth_type', 'basic', 'collector_gnocchi')
+
+        self.collector = gnocchi.GnocchiCollector(
+            transformer.get_transformers(),
+            period=3600,
+            conf=samples.DEFAULT_METRICS_CONF,
+        )
+
+    def test_format_data_raises_exception(self):
+        metconf = {'extra_args': {'resource_key': 'id'}}
+        data = {'group': {'id': '281b9dc6-5d02-4610-af2d-10d0d6887f48'}}
+        self.assertRaises(
+            gnocchi.AssociatedResourceNotFound,
+            self.collector._format_data,
+            metconf,
+            data,
+            resources_info={},
+        )
 
     # Filter generation
     def test_generate_one_field_filter(self):

releasenotes/notes/fix-gnocchi-metadata-collection-74665e862483a383.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Metadata collection failures in the gnocchi collector caused by resources
+    having measures in periods where they are supposed to be deleted have
+    been fixed. Metadata is now collected over a three-period window in the
+    gnocchi collector.