From dca5e43ab095923567bab85be4afedbc1f148834 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Iv=C3=A1n=20Ovejero?= <ivov.src@gmail.com>
Date: Fri, 19 Sep 2025 09:59:46 +0200
Subject: [PATCH] refactor(core): Switch native Python task runner to
 `forkserver` (#19718)

---
 .../@n8n/task-runner-python/src/constants.py  |  4 +++
 packages/@n8n/task-runner-python/src/main.py  |  6 ++++
 .../task-runner-python/src/task_executor.py   | 34 ++++++++++++++-----
 .../@n8n/task-runner-python/src/task_state.py |  4 +--
 4 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/packages/@n8n/task-runner-python/src/constants.py b/packages/@n8n/task-runner-python/src/constants.py
index 2464f12b42c..0325461bc7e 100644
--- a/packages/@n8n/task-runner-python/src/constants.py
+++ b/packages/@n8n/task-runner-python/src/constants.py
@@ -144,3 +144,7 @@ ERROR_DANGEROUS_ATTRIBUTE = "Access to attribute '{attr}' is disallowed, because
 ERROR_DYNAMIC_IMPORT = (
     "Dynamic __import__() calls are not allowed for security reasons."
 )
+ERROR_WINDOWS_NOT_SUPPORTED = (
+    "Error: This task runner is not supported on Windows. "
+    "Please use a Unix-like system (Linux or macOS)."
+)
diff --git a/packages/@n8n/task-runner-python/src/main.py b/packages/@n8n/task-runner-python/src/main.py
index 554fa8e637e..c096728aea0 100644
--- a/packages/@n8n/task-runner-python/src/main.py
+++ b/packages/@n8n/task-runner-python/src/main.py
@@ -1,8 +1,10 @@
 import asyncio
 import logging
 import sys
+import platform
 from typing import Optional
 
+from src.constants import ERROR_WINDOWS_NOT_SUPPORTED
 from src.config.health_check_config import HealthCheckConfig
 from src.config.sentry_config import SentryConfig
 from src.config.task_runner_config import TaskRunnerConfig
@@ -63,4 +65,8 @@ async def main():
 
 
 if __name__ == "__main__":
+    if platform.system() == "Windows":
+        print(ERROR_WINDOWS_NOT_SUPPORTED, file=sys.stderr)
+        sys.exit(1)
+
     asyncio.run(main())
diff --git a/packages/@n8n/task-runner-python/src/task_executor.py b/packages/@n8n/task-runner-python/src/task_executor.py
index 8ae6de67bdc..e2f571f8b06 100644
--- a/packages/@n8n/task-runner-python/src/task_executor.py
+++ b/packages/@n8n/task-runner-python/src/task_executor.py
@@ -6,6 +6,7 @@ import json
 import os
 import sys
 import tempfile
+import logging
 
 from src.errors import (
     TaskResultMissingError,
@@ -23,9 +24,11 @@ from src.constants import (
 )
 from typing import Any, Set
 
-from multiprocessing.context import SpawnProcess
+from multiprocessing.context import ForkServerProcess
 
-MULTIPROCESSING_CONTEXT = multiprocessing.get_context("fork")
+logger = logging.getLogger(__name__)
+
+MULTIPROCESSING_CONTEXT = multiprocessing.get_context("forkserver")
 MAX_PRINT_ARGS_ALLOWED = 100
 
 PrintArgs = list[list[Any]]  # Args to all `print()` calls in a Python code task
@@ -70,7 +73,7 @@ class TaskExecutor:
 
     @staticmethod
     def execute_process(
-        process: SpawnProcess,
+        process: ForkServerProcess,
         queue: multiprocessing.Queue,
         task_timeout: int,
         continue_on_fail: bool,
@@ -80,7 +83,12 @@ class TaskExecutor:
         print_args: PrintArgs = []
 
         try:
-            process.start()
+            try:
+                process.start()
+            except (ProcessLookupError, ConnectionError, BrokenPipeError) as e:
+                logger.error(f"Failed to start child process: {e}")
+                raise TaskProcessExitError(-1)
+
             process.join(timeout=task_timeout)
 
             if process.is_alive():
@@ -95,6 +103,10 @@ class TaskExecutor:
                 returned = queue.get_nowait()
             except Empty:
                 raise TaskResultMissingError()
+            except EOFError as e:
+                logger.error(f"Failed to retrieve results from child process: {e}")
+                raise TaskResultMissingError()
+
             finally:
                 queue.close()
                 queue.join_thread()
@@ -122,17 +134,21 @@ class TaskExecutor:
             raise
 
     @staticmethod
-    def stop_process(process: SpawnProcess | None):
+    def stop_process(process: ForkServerProcess | None):
         """Stop a running subprocess, gracefully else force-killing."""
 
         if process is None or not process.is_alive():
             return
 
-        process.terminate()
-        process.join(timeout=1)  # 1s grace period
+        try:
+            process.terminate()
+            process.join(timeout=1)  # 1s grace period
 
-        if process.is_alive():
-            process.kill()
+            if process.is_alive():
+                process.kill()
+        except (ProcessLookupError, ConnectionError, BrokenPipeError):
+            # subprocess is dead or unreachable
+            pass
 
     @staticmethod
     def _all_items(
diff --git a/packages/@n8n/task-runner-python/src/task_state.py b/packages/@n8n/task-runner-python/src/task_state.py
index cdb42865bea..e16833a9f77 100644
--- a/packages/@n8n/task-runner-python/src/task_state.py
+++ b/packages/@n8n/task-runner-python/src/task_state.py
@@ -1,6 +1,6 @@
 from enum import Enum
 from dataclasses import dataclass
-from multiprocessing.context import SpawnProcess
+from multiprocessing.context import ForkServerProcess
 from typing import Optional
 
 
@@ -14,7 +14,7 @@ class TaskStatus(Enum):
 class TaskState:
     task_id: str
     status: TaskStatus
-    process: Optional[SpawnProcess] = None
+    process: Optional[ForkServerProcess] = None
     workflow_name: Optional[str] = None
     workflow_id: Optional[str] = None
     node_name: Optional[str] = None