#147: Feature request: Add ECS compatibility

src/pythonjsonlogger/jsonlogger.py

@@ -24,20 +24,23 @@
     'processName', 'relativeCreated', 'stack_info', 'thread', 'threadName')
 
 
-def merge_record_extra(record: logging.LogRecord, target: Dict, reserved: Union[Dict, List]) -> Dict:
+
+def merge_record_extra(record: logging.LogRecord, target: Dict, reserved: Union[Dict, List], rename_fields: Dict[str,str]) -> Dict:
     """
     Merges extra attributes from LogRecord object into target dictionary
 
     :param record: logging.LogRecord
     :param target: dict to update
     :param reserved: dict or list with reserved keys to skip
+    :param rename_fields: an optional dict, used to rename field names in the output.
+            Rename levelname to log.level: {'levelname': 'log.level'}
     """
     for key, value in record.__dict__.items():
         # this allows to have numeric keys
         if (key not in reserved
             and not (hasattr(key, "startswith")
                      and key.startswith('_'))):
-            target[key] = value
+            target[rename_fields.get(key,key)] = value
     return target
 
 
@@ -172,7 +175,7 @@ def add_fields(self, log_record: Dict[str, Any], record: logging.LogRecord, mess
 
         log_record.update(self.static_fields)
         log_record.update(message_dict)
-        merge_record_extra(record, log_record, reserved=self._skip_fields)
+        merge_record_extra(record, log_record, reserved=self._skip_fields, rename_fields=self.rename_fields)
 
         if self.timestamp:
             key = self.timestamp if type(self.timestamp) == str else 'timestamp'

tests/tests.py

@@ -276,6 +276,28 @@ def encode_complex(z):
         msg = self.buffer.getvalue()
         self.assertEqual(msg, "{\"message\": \" message\", \"special\": [3.0, 8.0]}\n")
 
+    def test_rename_reserved_attrs(self):
+        log_format = lambda x: ['%({0:s})s'.format(i) for i in x]
+        reserved_attrs_map = {
+            'exc_info': 'error.type',
+            'exc_text': 'error.message',
+            'funcName': 'log.origin.function',
+            'levelname': 'log.level',
+            'module': 'log.origin.file.name',
+            'processName': 'process.name',
+            'threadName': 'process.thread.name',
+            'msg': 'log.message'
+        }
+
+        custom_format = ' '.join(log_format(reserved_attrs_map.keys()))
+        reserved_attrs = [_ for _ in jsonlogger.RESERVED_ATTRS if _ not in list(reserved_attrs_map.keys())]
+        formatter = jsonlogger.JsonFormatter(custom_format, reserved_attrs=reserved_attrs, rename_fields=reserved_attrs_map)
+        self.log_handler.setFormatter(formatter)
+        self.log.info("message")
+
+        msg = self.buffer.getvalue()
+        self.assertEqual(msg, '{"error.type": null, "error.message": null, "log.origin.function": "test_rename_reserved_attrs", "log.level": "INFO", "log.origin.file.name": "tests", "process.name": "MainProcess", "process.thread.name": "MainThread", "log.message": "message"}\n')
+
 
 if __name__ == '__main__':
     if len(sys.argv[1:]) > 0: