testing: add in-memory metrics exporter (#653)

Adding InMemoryMetricsExporter to help with unit-tests, as part of the change i'm also adding meter_provider and memory_metrics_exporter to TestBase

Co-authored-by: Mauricio Vásquez <mauricio@kinvolk.io>

Author: alrex

opentelemetry-sdk/src/opentelemetry/sdk/metrics/export/in_memory_metrics_exporter.py

@@ -0,0 +1,58 @@
+# Copyright The OpenTelemetry 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 threading
+from typing import Sequence
+
+from . import MetricRecord, MetricsExporter, MetricsExportResult
+
+
+class InMemoryMetricsExporter(MetricsExporter):
+    """Implementation of `MetricsExporter` that stores metrics in memory.
+
+    This class can be used for testing purposes. It stores exported metrics
+    in a list in memory that can be retrieved using the
+    :func:`.get_exported_metrics` method.
+    """
+
+    def __init__(self):
+        self._exported_metrics = []
+        self._stopped = False
+        self._lock = threading.Lock()
+
+    def clear(self):
+        """Clear list of collected metrics."""
+        with self._lock:
+            self._exported_metrics.clear()
+
+    def export(
+        self, metric_records: Sequence[MetricRecord]
+    ) -> MetricsExportResult:
+        if self._stopped:
+            return MetricsExportResult.FAILURE
+        with self._lock:
+            self._exported_metrics.extend(metric_records)
+        return MetricsExportResult.SUCCESS
+
+    def get_exported_metrics(self):
+        """Get list of collected metrics."""
+        with self._lock:
+            return tuple(self._exported_metrics)
+
+    def shutdown(self) -> None:
+        """Shuts down the exporter.
+
+        Called when the SDK is shut down.
+        """
+        self._stopped = True

tests/util/src/opentelemetry/test/test_base.py

@@ -16,7 +16,12 @@
 import unittest
 from contextlib import contextmanager
 
+from opentelemetry import metrics as metrics_api
 from opentelemetry import trace as trace_api
+from opentelemetry.sdk.metrics import MeterProvider
+from opentelemetry.sdk.metrics.export.in_memory_metrics_exporter import (
+    InMemoryMetricsExporter,
+)
 from opentelemetry.sdk.trace import TracerProvider, export
 from opentelemetry.sdk.trace.export.in_memory_span_exporter import (
     InMemorySpanExporter,
@@ -26,14 +31,19 @@
 class TestBase(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.original_provider = trace_api.get_tracer_provider()
+        cls.original_tracer_provider = trace_api.get_tracer_provider()
         result = cls.create_tracer_provider()
         cls.tracer_provider, cls.memory_exporter = result
         trace_api.set_tracer_provider(cls.tracer_provider)
+        cls.original_meter_provider = metrics_api.get_meter_provider()
+        result = cls.create_meter_provider()
+        cls.meter_provider, cls.memory_metrics_exporter = result
+        metrics_api.set_meter_provider(cls.meter_provider)
 
     @classmethod
     def tearDownClass(cls):
-        trace_api.set_tracer_provider(cls.original_provider)
+        trace_api.set_tracer_provider(cls.original_tracer_provider)
+        metrics_api.set_meter_provider(cls.original_meter_provider)
 
     def setUp(self):
         self.memory_exporter.clear()
@@ -53,7 +63,7 @@ def create_tracer_provider(**kwargs):
 
         Returns:
             A list with the tracer provider in the first element and the
-            memory exporter in the second.
+            in-memory span exporter in the second.
         """
         tracer_provider = TracerProvider(**kwargs)
         memory_exporter = InMemorySpanExporter()
@@ -62,6 +72,20 @@ def create_tracer_provider(**kwargs):
 
         return tracer_provider, memory_exporter
 
+    @staticmethod
+    def create_meter_provider(**kwargs):
+        """Helper to create a configured meter provider
+
+        Creates a `MeterProvider` and an `InMemoryMetricsExporter`.
+
+        Returns:
+            A list with the meter provider in the first element and the
+            in-memory metrics exporter in the second
+        """
+        meter_provider = MeterProvider(**kwargs)
+        memory_exporter = InMemoryMetricsExporter()
+        return meter_provider, memory_exporter
+
     @staticmethod
     @contextmanager
     def disable_logging(highest_level=logging.CRITICAL):