sdk: Adding suppress_instrumentation in Metrics (#529)

Suppressing instrumentation in metrics to ensure no infinite loops of emitting telemetry.

Author: hectorhdzg

Diff for: opentelemetry-sdk/src/opentelemetry/sdk/metrics/export/controller.py

@@ -15,6 +15,8 @@
 import atexit
 import threading
 
+from opentelemetry.context import attach, detach, set_value
+
 
 class PushController(threading.Thread):
     """A push based controller, used for exporting.
@@ -50,7 +52,9 @@ def shutdown(self):
     def tick(self):
         # Collect all of the meter's metrics to be exported
         self.meter.collect()
+        token = attach(set_value("suppress_instrumentation", True))
         # Export the given metrics in the batcher
         self.exporter.export(self.meter.batcher.checkpoint_set())
+        detach(token)
         # Perform post-exporting logic based on batcher configuration
         self.meter.batcher.finished_collection()

Diff for: opentelemetry-sdk/tests/metrics/export/test_export.py

@@ -17,6 +17,7 @@
 import unittest
 from unittest import mock
 
+from opentelemetry.context import get_value
 from opentelemetry.sdk import metrics
 from opentelemetry.sdk.metrics.export import (
     ConsoleMetricsExporter,
@@ -511,3 +512,18 @@ def test_push_controller(self):
         controller.shutdown()
         self.assertTrue(controller.finished.isSet())
         exporter.shutdown.assert_any_call()
+
+    def test_push_controller_suppress_instrumentation(self):
+        meter = mock.Mock()
+        exporter = mock.Mock()
+        exporter.export = lambda x: self.assertIsNotNone(
+            get_value("suppress_instrumentation")
+        )
+        with mock.patch(
+            "opentelemetry.context._RUNTIME_CONTEXT"
+        ) as context_patch:
+            controller = PushController(meter, exporter, 30.0)
+            controller.tick()
+            self.assertEqual(context_patch.attach.called, True)
+            self.assertEqual(context_patch.detach.called, True)
+        self.assertEqual(get_value("suppress_instrumentation"), None)