(fix) GCS bucket logger - apply truncate_standard_logging_payload_content to standard_logging_payload and ensure GCS flushes queue on fails (#7519)

* fix async_send_batch for gcs

* fix truncate GCS logger

* test_truncate_standard_logging_payload

litellm/integrations/custom_logger.py

@@ -293,3 +293,60 @@ class CustomLogger:  # https://docs.litellm.ai/docs/observability/custom_callbac
         except Exception:
             print_verbose(f"Custom Logger Error - {traceback.format_exc()}")
             pass
+
+    # Useful helpers for custom logger classes
+
+    def truncate_standard_logging_payload_content(
+        self,
+        standard_logging_object: StandardLoggingPayload,
+    ):
+        """
+        Truncate error strings and message content in logging payload
+
+        Some loggers like DataDog/ GCS Bucket have a limit on the size of the payload. (1MB)
+
+        This function truncates the error string and the message content if they exceed a certain length.
+        """
+        MAX_STR_LENGTH = 10_000
+
+        # Truncate fields that might exceed max length
+        fields_to_truncate = ["error_str", "messages", "response"]
+        for field in fields_to_truncate:
+            self._truncate_field(
+                standard_logging_object=standard_logging_object,
+                field_name=field,
+                max_length=MAX_STR_LENGTH,
+            )
+
+    def _truncate_field(
+        self,
+        standard_logging_object: StandardLoggingPayload,
+        field_name: str,
+        max_length: int,
+    ) -> None:
+        """
+        Helper function to truncate a field in the logging payload
+
+        This converts the field to a string and then truncates it if it exceeds the max length.
+
+        Why convert to string ?
+        1. User was sending a poorly formatted list for `messages` field, we could not predict where they would send content
+            - Converting to string and then truncating the logged content catches this
+        2. We want to avoid modifying the original `messages`, `response`, and `error_str` in the logging payload since these are in kwargs and could be returned to the user
+        """
+        field_value = standard_logging_object.get(field_name)  # type: ignore
+        if field_value:
+            str_value = str(field_value)
+            if len(str_value) > max_length:
+                standard_logging_object[field_name] = self._truncate_text(  # type: ignore
+                    text=str_value, max_length=max_length
+                )
+
+    def _truncate_text(self, text: str, max_length: int) -> str:
+        """Truncate text if it exceeds max_length"""
+        return (
+            text[:max_length]
+            + "...truncated by litellm, this logger does not support large content"
+            if len(text) > max_length
+            else text
+        )