perf: defer log processing if not log level

lib/RequestLogger.js

@@ -434,26 +434,28 @@ class RequestLogger {
                 });
             return;
         }
-        const fields = objectCopy({}, this.fields, logFields || {});
-        const endFlag = isEnd || false;
-
+        // removes object references
+        const _logFields = logFields ?
+            JSON.parse(JSON.stringify(logFields)) : {};
         /*
         * using Date.now() as it's faster than new Date(). logstash component
         * uses this field to generate ISO 8601 timestamp
         */
-        if (fields.time === undefined) {
-            fields.time = Date.now();
+        if (_logFields.time === undefined) {
+            _logFields.time = Date.now();
         }
-
-        fields.req_id = serializeUids(this.uids);
+        _logFields.req_id = serializeUids(this.uids);
+        const endFlag = isEnd || false;
         if (endFlag) {
             this.elapsedTime = process.hrtime(this.startTime);
-            fields.elapsed_ms = this.elapsedTime[0] * 1000
+            _logFields.elapsed_ms = this.elapsedTime[0] * 1000
                 + this.elapsedTime[1] / 1000000;
         }
+        // const fields = objectCopy({}, this.fields, _logFields || {});
+
         const logEntry = {
             level,
-            fields,
+            fields: _logFields,
             msg,
         };
         this.entries.push(logEntry);
@@ -484,24 +486,25 @@ class RequestLogger {
      * @returns {undefined}
      */
     doLogIO(logEntry) {
+        const fields = objectCopy({}, this.fields, logEntry.fields);
         switch (logEntry.level) {
         case 'trace':
-            this.sLogger.trace(logEntry.fields, logEntry.msg);
+            this.sLogger.trace(fields, logEntry.msg);
             break;
         case 'debug':
-            this.sLogger.debug(logEntry.fields, logEntry.msg);
+            this.sLogger.debug(fields, logEntry.msg);
             break;
         case 'info':
-            this.sLogger.info(logEntry.fields, logEntry.msg);
+            this.sLogger.info(fields, logEntry.msg);
             break;
         case 'warn':
-            this.sLogger.warn(logEntry.fields, logEntry.msg);
+            this.sLogger.warn(fields, logEntry.msg);
             break;
         case 'error':
-            this.sLogger.error(logEntry.fields, logEntry.msg);
+            this.sLogger.error(fields, logEntry.msg);
             break;
         case 'fatal':
-            this.sLogger.fatal(logEntry.fields, logEntry.msg);
+            this.sLogger.fatal(fields, logEntry.msg);
             break;
         default:
             throw new Error(`Unexpected log level: ${logEntry.level}`);