Add a watcher to constantly check for stop signal from the UI. This will force a stop within 2 seconds instead of having to wait on a long hung process.

extensions_built_in/sd_trainer/UITrainer.py

@@ -5,7 +5,9 @@ import asyncio
 import concurrent.futures
 from extensions_built_in.sd_trainer.SDTrainer import SDTrainer
 from typing import Literal, Optional
-
+import threading
+import time
+import signal
 
 AITK_Status = Literal["running", "stopped", "error", "completed"]
 
@@ -30,6 +32,49 @@ class UITrainer(SDTrainer):
         self._async_tasks = []
         # Initialize the status
         self._run_async_operation(self._update_status("running", "Starting"))
+        self._stop_watcher_started = False
+        self.start_stop_watcher(interval_sec=2.0)
+    
+    def start_stop_watcher(self, interval_sec: float = 5.0):
+        """
+        Start a daemon thread that periodically checks should_stop()
+        and terminates the process immediately when triggered.
+        """
+        if getattr(self, "_stop_watcher_started", False):
+            return
+        self._stop_watcher_started = True
+        t = threading.Thread(
+            target=self._stop_watcher_thread, args=(interval_sec,), daemon=True
+        )
+        t.start()
+
+    def _stop_watcher_thread(self, interval_sec: float):
+        while True:
+            try:
+                if self.should_stop():
+                    # Mark and update status (non-blocking; uses existing infra)
+                    self.is_stopping = True
+                    self._run_async_operation(
+                        self._update_status("stopped", "Job stopped (remote)")
+                    )
+                    # Best-effort flush pending async ops
+                    try:
+                        asyncio.run(self.wait_for_all_async())
+                    except RuntimeError:
+                        pass
+                    # Try to stop DB thread pool quickly
+                    try:
+                        self.thread_pool.shutdown(wait=False, cancel_futures=True)
+                    except TypeError:
+                        self.thread_pool.shutdown(wait=False)
+                    print("")
+                    print("****************************************************")
+                    print("    Stop signal received; terminating process.      ")
+                    print("****************************************************")
+                    os.kill(os.getpid(), signal.SIGINT)
+                time.sleep(interval_sec)
+            except Exception:
+                time.sleep(interval_sec)
 
     def _run_async_operation(self, coro):
         """Helper method to run an async coroutine and track the task."""