APMSVLS-65 first draft of extractor helper function and inclusion in extract_dd_trace_context

Author: rithikanarayan

datadog_lambda/tracing.py

@@ -536,6 +536,25 @@ def extract_context_from_step_functions(event, lambda_context):
         logger.debug("The Step Functions trace extractor returned with error %s", e)
         return extract_context_from_lambda_context(lambda_context)
 
+def extract_context_from_appsync_event(event, lambda_context):
+    """
+    Extract Datadog trace context from an AppSync event. Intended to replace
+    need for customers to provide custom extractor function in their code. 
+    """
+    nested_json = event.get("request", {}).get("headers", {})
+    trace_id = nested_json.get("x-datadog-trace-id")
+    parent_id = nested_json.get("x-datadog-parent-id")
+    sampling_priority = nested_json.get("x-datadog-sampling-priority")
+    context = Context(
+            trace_id=int(trace_id),
+            span_id=int(parent_id),
+            sampling_priority=int(sampling_priority),
+        )
+
+    if not _is_context_complete(context):
+        return extract_context_from_lambda_context(lambda_context)
+
+    return context
 
 def extract_context_custom_extractor(extractor, event, lambda_context):
     """
@@ -641,6 +660,8 @@ def extract_dd_trace_context(
         context = extract_context_from_kinesis_event(event, lambda_context)
     elif event_source.equals(EventTypes.STEPFUNCTIONS):
         context = extract_context_from_step_functions(event, lambda_context)
+    elif event_source.equals(EventTypes.APPSYNC):
+        context = extract_context_from_appsync_event(event, lambda_context)
     else:
         context = extract_context_from_lambda_context(lambda_context)