support recursion detection (#4111)

Author: AllanZhengYP

.changes/next-release/feature-util-e4a2f425.json

@@ -0,0 +1,5 @@
+{
+  "type": "feature",
+  "category": "util",
+  "description": "set the X-Amzn-Trace-Id header if lambda function name and trace id environmental variables are set"
+}

lib/event_listeners.js

@@ -211,6 +211,24 @@ AWS.EventListeners = {
       req.httpRequest.headers['Host'] = req.httpRequest.endpoint.host;
     });
 
+    add('SET_TRACE_ID', 'afterBuild', function SET_TRACE_ID(req) {
+      var traceIdHeaderName = 'X-Amzn-Trace-Id';
+      if (AWS.util.isNode() && !Object.hasOwnProperty.call(req.httpRequest.headers, traceIdHeaderName)) {
+        var ENV_LAMBDA_FUNCTION_NAME = 'AWS_LAMBDA_FUNCTION_NAME';
+        var ENV_TRACE_ID = '_X_AMZN_TRACE_ID';
+        var functionName = process.env[ENV_LAMBDA_FUNCTION_NAME];
+        var traceId = process.env[ENV_TRACE_ID];
+        if (
+          typeof functionName === 'string' &&
+          functionName.length > 0 &&
+          typeof traceId === 'string' &&
+          traceId.length > 0
+        ) {
+          req.httpRequest.headers[traceIdHeaderName] = traceId;
+        }
+      }
+    });
+
     add('RESTART', 'restart', function RESTART() {
       var err = this.response.error;
       if (!err || !err.retryable) return;