feat(logging): Include exception_name (#320)

* feat(logging): Include exception_name

* tests(logging): Add test for exception_name

* docs(logging): Add note on exception_name

Author: Michael Brewer

aws_lambda_powertools/logging/formatter.py

@@ -126,6 +126,24 @@ def _extract_log_exception(self, log_record: logging.LogRecord) -> Optional[str]
 
         return None
 
+    def _extract_log_exception_name(self, log_record: logging.LogRecord) -> Optional[str]:
+        """Extract the exception name, if available
+
+        Parameters
+        ----------
+        log_record : logging.LogRecord
+            Log record to extract exception name from
+
+        Returns
+        -------
+        log_record: Optional[str]
+            Log record with exception name
+        """
+        if log_record.exc_info:
+            return log_record.exc_info[0].__name__
+
+        return None
+
     def _extract_log_keys(self, log_record: logging.LogRecord) -> Dict:
         """Extract and parse custom and reserved log keys
 
@@ -164,6 +182,7 @@ def _extract_log_keys(self, log_record: logging.LogRecord) -> Dict:
     def format(self, record):  # noqa: A003
         formatted_log = self._extract_log_keys(log_record=record)
         formatted_log["message"] = self._extract_log_message(log_record=record)
+        formatted_log["exception_name"] = self._extract_log_exception_name(log_record=record)
         formatted_log["exception"] = self._extract_log_exception(log_record=record)
         formatted_log.update({"xray_trace_id": self._get_latest_trace_id()})  # fetch latest Trace ID, if any
 

docs/core/logger.md

@@ -451,7 +451,7 @@ You can also change the order of the following log record keys via the `log_reco
 
 #### Logging exceptions
 
-When logging exceptions, Logger will add a new key named `exception`, and will serialize the full traceback as a string.
+When logging exceptions, Logger will add new keys named `exception_name` and `exception` with the full traceback as a string.
 
 === "logging_an_exception.py"
 
@@ -475,6 +475,7 @@ When logging exceptions, Logger will add a new key named `exception`, and will s
        "timestamp": "2020-08-28 18:11:38,886",
        "service": "service_undefined",
        "sampling_rate": 0.0,
+       "exception_name":"ValueError",
        "exception": "Traceback (most recent call last):\n  File \"<input>\", line 2, in <module>\nValueError: something went wrong"
     }
     ```

tests/functional/test_logger.py

@@ -422,3 +422,18 @@ def test_logger_log_twice_when_log_filter_isnt_present_and_root_logger_is_setup(
     # since child's log records propagated to root logger should be rejected
     logs = list(stdout.getvalue().strip().split("\n"))
     assert len(logs) == 4
+
+
+def test_logger_exception_extract_exception_name(stdout, service_name):
+    # GIVEN Logger is initialized
+    logger = Logger(service=service_name, stream=stdout)
+
+    # WHEN calling a logger.exception with a ValueError
+    try:
+        raise ValueError("something went wrong")
+    except Exception:
+        logger.exception("Received an exception")
+
+    # THEN we expect a "exception_name" to be "ValueError"
+    log = capture_logging_output(stdout)
+    assert "ValueError" == log["exception_name"]