chore: import upstream snapshot with attribution

python/ray/train/v2/_internal/callbacks/user_callback.py

@@ -0,0 +1,54 @@
+from typing import Any, Dict, List
+
+from ray.train.v2._internal.execution.callback import (
+    ReportCallback,
+    WorkerGroupCallback,
+)
+from ray.train.v2._internal.execution.context import TrainRunContext
+from ray.train.v2._internal.execution.training_report import _TrainingReport
+from ray.train.v2._internal.execution.worker_group import WorkerGroupPollStatus
+from ray.train.v2.api.callback import UserCallback
+
+
+class UserCallbackHandler(WorkerGroupCallback, ReportCallback):
+    """Responsible for calling methods of subscribers implementing
+    the `UserCallback` interface.
+    """
+
+    def __init__(
+        self, user_callbacks: List[UserCallback], train_run_context: TrainRunContext
+    ):
+        self._user_callbacks = user_callbacks
+        self._train_run_context = train_run_context
+
+    # --------------------------
+    # ReportCallback
+    # --------------------------
+
+    def after_report(
+        self,
+        training_report: _TrainingReport,
+        metrics: List[Dict[str, Any]],
+    ):
+        for user_callback in self._user_callbacks:
+            user_callback.after_report(
+                run_context=self._train_run_context,
+                metrics=metrics,
+                checkpoint=training_report.checkpoint,
+            )
+
+    # --------------------------
+    # WorkerGroupCallback
+    # --------------------------
+
+    def after_worker_group_poll_status(
+        self, worker_group_status: WorkerGroupPollStatus
+    ):
+        if not worker_group_status.errors:
+            return
+
+        for user_callback in self._user_callbacks:
+            user_callback.after_exception(
+                run_context=self._train_run_context,
+                worker_exceptions=worker_group_status.errors,
+            )