Handle duplicate meters (open-telemetry#2373)

lzchen · web-flow · commit fb1063ce8954 · 2022-01-14T16:40:44.000-08:00
diff --git a/opentelemetry-sdk/src/opentelemetry/sdk/_metrics/__init__.py b/opentelemetry-sdk/src/opentelemetry/sdk/_metrics/__init__.py
@@ -154,13 +154,15 @@ def __init__(
         shutdown_on_exit: bool = True,
     ):
         self._lock = Lock()
+        self._meter_lock = Lock()
         self._atexit_handler = None
 
         self._measurement_consumer = SynchronousMeasurementConsumer()
 
         if shutdown_on_exit:
             self._atexit_handler = register(self.shutdown)
 
+        self._meters = {}
         self._metric_readers = metric_readers
 
         for metric_reader in self._metric_readers:
@@ -221,7 +223,11 @@ def get_meter(
             )
             return _DefaultMeter(name, version=version, schema_url=schema_url)
 
-        return Meter(
-            InstrumentationInfo(name, version, schema_url),
-            self._measurement_consumer,
-        )
+        info = InstrumentationInfo(name, version, schema_url)
+        with self._meter_lock:
+            if not self._meters.get(info):
+                self._meters[info] = Meter(
+                    info,
+                    self._measurement_consumer,
+                )
+            return self._meters[info]
diff --git a/opentelemetry-sdk/tests/metrics/test_metrics.py b/opentelemetry-sdk/tests/metrics/test_metrics.py
@@ -64,6 +64,30 @@ def test_get_meter(self):
         self.assertEqual(meter._instrumentation_info.version, "version")
         self.assertEqual(meter._instrumentation_info.schema_url, "schema_url")
 
+    def test_get_meter_duplicate(self):
+        """
+        Subsequent calls to `MeterProvider.get_meter` with the same arguments
+        should return the same `Meter` instance.
+        """
+        mp = MeterProvider()
+        meter1 = mp.get_meter(
+            "name",
+            version="version",
+            schema_url="schema_url",
+        )
+        meter2 = mp.get_meter(
+            "name",
+            version="version",
+            schema_url="schema_url",
+        )
+        meter3 = mp.get_meter(
+            "name2",
+            version="version",
+            schema_url="schema_url",
+        )
+        self.assertIs(meter1, meter2)
+        self.assertIsNot(meter1, meter3)
+
     def test_shutdown_subsequent_calls(self):
         """
         No subsequent attempts to get a `Meter` are allowed after calling
