Skip and log warning when lambda_metric called with invalid name or…

… value (#553)

datadog_lambda/metric.py

@@ -55,6 +55,22 @@ def lambda_metric(metric_name, value, timestamp=None, tags=None, force_async=Fal
     Note that if the extension is present, it will override the DD_FLUSH_TO_LOG value
     and always use the layer to send metrics to the extension
     """
+    if not metric_name or not isinstance(metric_name, str):
+        logger.warning(
+            "Ignoring metric submission. Invalid metric name: %s", metric_name
+        )
+        return
+
+    try:
+        float(value)
+    except (ValueError, TypeError):
+        logger.warning(
+            "Ignoring metric submission for metric '%s' because the value is not numeric: %r",
+            metric_name,
+            value,
+        )
+        return
+
     flush_to_logs = os.environ.get("DD_FLUSH_TO_LOG", "").lower() == "true"
     tags = [] if tags is None else list(tags)
     tags.append(dd_lambda_layer_tag)

tests/test_metric.py

@@ -92,6 +92,32 @@ def test_lambda_metric_flush_to_log(self):
 
         del os.environ["DD_FLUSH_TO_LOG"]
 
+    @patch("datadog_lambda.metric.logger.warning")
+    def test_lambda_metric_invalid_metric_name_none(self, mock_logger_warning):
+        lambda_metric(None, 1)
+        self.mock_metric_lambda_stats.distribution.assert_not_called()
+        mock_logger_warning.assert_called_once_with(
+            "Ignoring metric submission. Invalid metric name: %s", None
+        )
+
+    @patch("datadog_lambda.metric.logger.warning")
+    def test_lambda_metric_invalid_metric_name_not_string(self, mock_logger_warning):
+        lambda_metric(123, 1)
+        self.mock_metric_lambda_stats.distribution.assert_not_called()
+        mock_logger_warning.assert_called_once_with(
+            "Ignoring metric submission. Invalid metric name: %s", 123
+        )
+
+    @patch("datadog_lambda.metric.logger.warning")
+    def test_lambda_metric_non_numeric_value(self, mock_logger_warning):
+        lambda_metric("test.non_numeric", "oops")
+        self.mock_metric_lambda_stats.distribution.assert_not_called()
+        mock_logger_warning.assert_called_once_with(
+            "Ignoring metric submission for metric '%s' because the value is not numeric: %r",
+            "test.non_numeric",
+            "oops",
+        )
+
 
 class TestFlushThreadStats(unittest.TestCase):
     def setUp(self):