[forwarder][lambda]: don't fail to parse on managed instances report log (#1041)

* skip logs where keys dont exist

* update comment

* lint

Author: duncanista

aws/logs_monitoring/enhanced_lambda_metrics.py

@@ -289,7 +289,9 @@ def parse_metrics_from_json_report_log(log_message):
     metrics = []
 
     for record_key, metric_name in RUNTIME_METRICS_BY_RECORD_KEY.items():
-        metric_point_value = record_metrics[record_key]
+        metric_point_value = record_metrics.get(record_key)
+        if metric_point_value is None:
+            continue
 
         if metric_name in METRIC_ADJUSTMENT_FACTORS:
             metric_point_value *= METRIC_ADJUSTMENT_FACTORS[metric_name]
@@ -301,9 +303,10 @@ def parse_metrics_from_json_report_log(log_message):
             )
         )
 
-    tags = [
-        f"{MEMORY_ALLOCATED_FIELD_NAME}:{record_metrics[MEMORY_ALLOCATED_RECORD_KEY]}"
-    ]
+    tags = []
+    memory_allocated = record_metrics.get(MEMORY_ALLOCATED_RECORD_KEY)
+    if memory_allocated is not None:
+        tags.append(f"{MEMORY_ALLOCATED_FIELD_NAME}:{memory_allocated}")
 
     init_duration = record_metrics.get(INIT_DURATION_RECORD_KEY)
     if init_duration:
@@ -317,15 +320,19 @@ def parse_metrics_from_json_report_log(log_message):
     else:
         tags.append("cold_start:false")
 
-    metrics.append(
-        DatadogMetricPoint(
-            f"{ENHANCED_METRICS_NAMESPACE_PREFIX}.{ESTIMATED_COST_METRIC_NAME}",
-            calculate_estimated_cost(
-                record_metrics[BILLED_DURATION_RECORD_KEY],
-                record_metrics[MEMORY_ALLOCATED_RECORD_KEY],
-            ),
+    # Billed duration only available for On-Demand Lambda functions,
+    # for Managed Instances, this is no longer available.
+    billed_duration = record_metrics.get(BILLED_DURATION_RECORD_KEY)
+    if billed_duration is not None and memory_allocated is not None:
+        metrics.append(
+            DatadogMetricPoint(
+                f"{ENHANCED_METRICS_NAMESPACE_PREFIX}.{ESTIMATED_COST_METRIC_NAME}",
+                calculate_estimated_cost(
+                    billed_duration,
+                    memory_allocated,
+                ),
+            )
         )
-    )
 
     if record.get("status") == "timeout":
         metrics.append(

aws/logs_monitoring/tests/test_enhanced_lambda_metrics.py

@@ -86,6 +86,31 @@ class TestEnhancedLambdaMetrics(unittest.TestCase):
             },
         }
     )
+    managed_instances_metrics_json_report = json.dumps(
+        {
+            "time": "2026-01-08T18:22:35.343Z",
+            "type": "platform.report",
+            "record": {
+                "requestId": "4f423807-598d-47ae-9652-4f7ee31d4d10",
+                "metrics": {
+                    "durationMs": 2.524,
+                },
+                "spans": [
+                    {
+                        "name": "responseLatency",
+                        "start": "2026-01-08T18:22:35.342Z",
+                        "durationMs": 0.642,
+                    },
+                    {
+                        "name": "responseDuration",
+                        "start": "2026-01-08T18:22:35.343Z",
+                        "durationMs": 0.075,
+                    },
+                ],
+                "status": "success",
+            },
+        }
+    )
 
     def test_parse_lambda_tags_from_arn(self):
         verify_as_json(
@@ -129,6 +154,21 @@ def test_parse_metrics_from_timeout_json_report_log(self):
         parsed_metrics = parse_metrics_from_json_report_log(self.timeout_json_report)
         verify_as_json(parsed_metrics)
 
+    def test_parse_metrics_from_partial_metrics_json_report_log(self):
+        """Test that JSON report logs with partial/incomplete metrics don't raise KeyError"""
+        parsed_metrics = parse_metrics_from_json_report_log(
+            self.managed_instances_metrics_json_report
+        )
+        # Should only return metrics that are present (duration in this case)
+        # Should not raise KeyError for missing billedDurationMs, maxMemoryUsedMB, memorySizeMB
+        assert len(parsed_metrics) == 1  # Only duration metric
+        assert parsed_metrics[0].name == "aws.lambda.enhanced.duration"
+        # Duration should be converted from ms to seconds (2.524 * 0.001 = 0.002524)
+        assert parsed_metrics[0].value == 0.002524
+        # Tags should include cold_start:false but NOT memorysize since it's missing
+        assert "cold_start:false" in parsed_metrics[0].tags
+        assert not any(tag.startswith("memorysize:") for tag in parsed_metrics[0].tags)
+
     def test_create_out_of_memory_enhanced_metric(self):
         go_out_of_memory_error = "fatal error: runtime: out of memory"
         self.assertEqual(