Simplify the pool executor handling

grand_challenge_forge/partials/example-evaluation-method/example-evaluation-method{{cookiecutter._}}/helpers.py

@@ -99,22 +99,9 @@ def _start_pool_worker(fn, predictions, max_workers, results, errors):
 
 
 def _pool_worker(*, fn, predictions, max_workers, results, errors):
-    terminating_child_processes = False
-
+    caught_exception = False
     with ProcessPoolExecutor(max_workers=max_workers) as executor:
         try:
-
-            def handle_error(error, prediction):
-                nonlocal terminating_child_processes
-                if terminating_child_processes:
-                    return
-
-                executor.shutdown(wait=False, cancel_futures=True)
-                errors.append((prediction, error))
-
-                terminating_child_processes = True
-                _terminate_child_processes()
-
             # Submit the processing tasks of the predictions
             futures = [
                 executor.submit(fn, prediction) for prediction in predictions
@@ -129,11 +116,16 @@ def handle_error(error, prediction):
                     result = future.result()
                     results.append(result)
                 except Exception as e:
-                    handle_error(e, prediction=future_to_predictions[future])
+                    errors.append((future_to_predictions[future], e))
+
+                    if not caught_exception:  # Hard stop
+                        caught_exception = True
+
+                        executor.shutdown(wait=False, cancel_futures=True)
+                        _terminate_child_processes()
         finally:
-            if not terminating_child_processes:
-                terminating_child_processes = True
-                _terminate_child_processes()
+            # Be aggresive in cleaning up any left-over processes
+            _terminate_child_processes()
 
 
 def _terminate_child_processes():