fix(langchain): spans dictionary memory leak (#3216)

Co-authored-by: Claude <[email protected]>

Author: nirga

packages/opentelemetry-instrumentation-langchain/opentelemetry/instrumentation/langchain/callback_handler.py

@@ -178,14 +178,17 @@ def _get_span(self, run_id: UUID) -> Span:
 
     def _end_span(self, span: Span, run_id: UUID) -> None:
         for child_id in self.spans[run_id].children:
-            child_span = self.spans[child_id].span
-            if child_span.end_time is None:  # avoid warning on ended spans
-                child_span.end()
+            if child_id in self.spans:
+                child_span = self.spans[child_id].span
+                if child_span.end_time is None:  # avoid warning on ended spans
+                    child_span.end()
         span.end()
         token = self.spans[run_id].token
         if token:
             context_api.detach(token)
 
+        del self.spans[run_id]
+
     def _create_span(
         self,
         run_id: UUID,
@@ -541,9 +544,8 @@ def on_llm_end(
             self._emit_llm_end_events(response)
         else:
             set_chat_response(span, response)
-        self._end_span(span, run_id)
 
-        # Record duration
+        # Record duration before ending span
         duration = time.time() - self.spans[run_id].start_time
         vendor = span.attributes.get(SpanAttributes.LLM_SYSTEM, "Langchain")
         self.duration_histogram.record(
@@ -554,6 +556,8 @@ def on_llm_end(
             },
         )
 
+        self._end_span(span, run_id)
+
     @dont_throw
     def on_tool_start(
         self,