feat(logger): add get_correlation_id method (#516)

Author: Michael Brewer

aws_lambda_powertools/logging/logger.py

@@ -387,16 +387,26 @@ def structure_logs(self, append: bool = False, **keys):
             formatter = self.logger_formatter or LambdaPowertoolsFormatter(**log_keys)  # type: ignore
             self.registered_handler.setFormatter(formatter)
 
-    def set_correlation_id(self, value: str):
+    def set_correlation_id(self, value: Optional[str]):
         """Sets the correlation_id in the logging json
 
         Parameters
         ----------
-        value : str
-            Value for the correlation id
+        value : str, optional
+            Value for the correlation id. None will remove the correlation_id
         """
         self.append_keys(correlation_id=value)
 
+    def get_correlation_id(self) -> Optional[str]:
+        """Gets the correlation_id in the logging json
+
+        Returns
+        -------
+        str, optional
+            Value for the correlation id
+        """
+        return self.registered_formatter.log_format.get("correlation_id")
+
     @staticmethod
     def _get_log_level(level: Union[str, int, None]) -> Union[str, int]:
         """Returns preferred log level set by the customer in upper case"""

tests/functional/test_logger.py

@@ -460,6 +460,18 @@ def handler(event, _):
     assert request_id == log["correlation_id"]
 
 
+def test_logger_get_correlation_id(lambda_context, stdout, service_name):
+    # GIVEN a logger with a correlation_id set
+    logger = Logger(service=service_name, stream=stdout)
+    logger.set_correlation_id("foo")
+
+    # WHEN calling get_correlation_id
+    correlation_id = logger.get_correlation_id()
+
+    # THEN it should return the correlation_id
+    assert "foo" == correlation_id
+
+
 def test_logger_set_correlation_id_path(lambda_context, stdout, service_name):
     # GIVEN
     logger = Logger(service=service_name, stream=stdout)