Add test case for metric lifetime error handling

qa/python_models/custom_metrics/model.py

@@ -213,6 +213,34 @@ def test_dup_metric_empty_labels(self):
         # underlying metric, and all instances will be updated
         self._dup_metric_helper()
 
+    def test_metric_lifetime_error(self):
+        # Test the error handling when the corresponding 'MetricFamily' is
+        # deleted before the 'Metric' is deleted, and the 'Metric' is still
+        # being used for metric operations
+        metric_family = pb_utils.MetricFamily(
+            name="test_metric_lifetime_error",
+            description="test metric lifetime error",
+            kind=pb_utils.MetricFamily.COUNTER)
+        labels = {"example1": "counter_label1", "example2": "counter_label2"}
+        metric = metric_family.Metric(labels=labels)
+
+        # Intentionally delete the 'MetricFamily' before the 'Metric' being deleted
+        del metric_family
+
+        error_msg = "Invalid metric operation as the corresponding 'MetricFamily' has been deleted."
+
+        with self.assertRaises(pb_utils.TritonModelException) as ex:
+            metric.set(10)
+        self.assertIn(error_msg, str(ex.exception))
+
+        with self.assertRaises(pb_utils.TritonModelException) as ex:
+            metric.increment(10)
+        self.assertIn(error_msg, str(ex.exception))
+
+        with self.assertRaises(pb_utils.TritonModelException) as ex:
+            metric.value()
+        self.assertIn(error_msg, str(ex.exception))
+
 
 class TritonPythonModel: