feat: truncate extracted message preview for root traces

Signed-off-by: Patrick Chin <[email protected]>

Author: thepatrickchin

packages/nvidia_nat_weave/src/nat/plugins/weave/weave_exporter.py

@@ -23,6 +23,7 @@
 from nat.observability.exporter.base_exporter import IsolatedAttribute
 from nat.observability.exporter.span_exporter import SpanExporter
 from nat.utils.log_utils import LogFilter
+from nat.utils.string_utils import truncate_string
 from nat.utils.type_utils import override
 from weave.trace.context import weave_client_context
 from weave.trace.context.call_context import get_current_call
@@ -198,7 +199,7 @@ def _extract_output_message(self, output_data: Any, outputs: dict[str, Any]) ->
         # Handle direct "choices" attribute (non-streaming: output.choices[0].message.content)
         choices = getattr(output_data, 'choices', None)
         if choices:
-            outputs["output_message"] = choices[0].message.content
+            outputs["output_message"] = truncate_string(choices[0].message.content)
             return
 
         # Handle list-based output (streaming or websocket) – content may be in the following formats:
@@ -214,13 +215,13 @@ def _extract_output_message(self, output_data: Any, outputs: dict[str, Any]) ->
             delta = getattr(choices[0], 'delta', None)
 
             if message:
-                outputs["output_message"] = getattr(message, 'content', None)
+                outputs["output_message"] = truncate_string(getattr(message, 'content', None))
             elif delta:
-                outputs["output_preview"] = getattr(delta, 'content', None)
+                outputs["output_preview"] = truncate_string(getattr(delta, 'content', None))
         else:
             value = getattr(output_data[0], 'value', None)
             if value:
-                outputs["output_preview"] = value
+                outputs["output_preview"] = truncate_string(str(value))
 
     def _finish_weave_call(self, step: IntermediateStep) -> None:
         """

src/nat/utils/string_utils.py

@@ -36,3 +36,19 @@ def convert_to_str(value: Any) -> str:
         return str(value)
     else:
         raise ValueError(f"Unsupported type for conversion to string: {type(value)}")
+
+
+def truncate_string(text: str | None, max_length: int = 100) -> str | None:
+    """
+    Truncate a string to a maximum length, adding ellipsis if truncated.
+
+    Args:
+        text: The text to truncate (can be None)
+        max_length: Maximum allowed length (default: 100)
+
+    Returns:
+        The truncated text with ellipsis if needed, or None if input was None
+    """
+    if not text or len(text) <= max_length:
+        return text
+    return text[:max_length - 3] + "..."