Log errors (#7105)

Re-add change that was inadvertently undone in #6995

langchain/callbacks/tracers/evaluation.py

@@ -1,4 +1,5 @@
 """A tracer that runs evaluators over completed runs."""
+import logging
 from concurrent.futures import Future, ThreadPoolExecutor, wait
 from typing import Any, Optional, Sequence, Set, Union
 from uuid import UUID
@@ -8,6 +9,8 @@ from langchainplus_sdk import LangChainPlusClient, RunEvaluator
 from langchain.callbacks.tracers.base import BaseTracer
 from langchain.callbacks.tracers.schemas import Run
 
+logger = logging.getLogger(__name__)
+
 
 class EvaluatorCallbackHandler(BaseTracer):
     """A tracer that runs a run evaluator whenever a run is persisted.
@@ -47,7 +50,7 @@ class EvaluatorCallbackHandler(BaseTracer):
         max_workers: Optional[int] = None,
         client: Optional[LangChainPlusClient] = None,
         example_id: Optional[Union[UUID, str]] = None,
-        **kwargs: Any
+        **kwargs: Any,
     ) -> None:
         super().__init__(**kwargs)
         self.example_id = (
@@ -60,6 +63,17 @@ class EvaluatorCallbackHandler(BaseTracer):
         )
         self.futures: Set[Future] = set()
 
+    def _evaluate_run(self, run: Run, evaluator: RunEvaluator) -> None:
+        try:
+            self.client.evaluate_run(run, evaluator)
+        except Exception as e:
+            logger.error(
+                f"Error evaluating run {run.id} with "
+                f"{evaluator.__class__.__name__}: {e}",
+                exc_info=True,
+            )
+            raise e
+
     def _persist_run(self, run: Run) -> None:
         """Run the evaluator on the run.
 
@@ -72,9 +86,7 @@ class EvaluatorCallbackHandler(BaseTracer):
         run_ = run.copy()
         run_.reference_example_id = self.example_id
         for evaluator in self.evaluators:
-            self.futures.add(
+            self.futures.add(self.executor.submit(self._evaluate_run, run_, evaluator))
-                self.executor.submit(self.client.evaluate_run, run_, evaluator)
-            )
 
     def wait_for_futures(self) -> None:
         """Wait for all futures to complete."""