fix(api):LLM node losing Flask context during parallel iterations (#26098)

api/core/workflow/nodes/iteration/iteration_node.py

@@ -1,9 +1,11 @@
+import contextvars
 import logging
 from collections.abc import Generator, Mapping, Sequence
 from concurrent.futures import Future, ThreadPoolExecutor, as_completed
 from datetime import UTC, datetime
 from typing import TYPE_CHECKING, Any, NewType, cast
 
+from flask import Flask, current_app
 from typing_extensions import TypeIs
 
 from core.variables import IntegerVariable, NoneSegment
@@ -35,6 +37,7 @@ from core.workflow.nodes.base.entities import BaseNodeData, RetryConfig
 from core.workflow.nodes.base.node import Node
 from core.workflow.nodes.iteration.entities import ErrorHandleMode, IterationNodeData
 from libs.datetime_utils import naive_utc_now
+from libs.flask_utils import preserve_flask_contexts
 
 from .exc import (
     InvalidIteratorValueError,
@@ -239,6 +242,8 @@ class IterationNode(Node):
                     self._execute_single_iteration_parallel,
                     index=index,
                     item=item,
+                    flask_app=current_app._get_current_object(),  # type: ignore
+                    context_vars=contextvars.copy_context(),
                 )
                 future_to_index[future] = index
 
@@ -281,8 +286,11 @@ class IterationNode(Node):
         self,
         index: int,
         item: object,
+        flask_app: Flask,
+        context_vars: contextvars.Context,
     ) -> tuple[datetime, list[GraphNodeEventBase], object | None, int]:
         """Execute a single iteration in parallel mode and return results."""
+        with preserve_flask_contexts(flask_app=flask_app, context_vars=context_vars):
             iter_start_at = datetime.now(UTC).replace(tzinfo=None)
             events: list[GraphNodeEventBase] = []
             outputs_temp: list[object] = []