chore(utils): move encoding utils and process to their respective modules (#2029)

Signed-off-by: Steven Palma <imstevenpmwork@ieee.org>

src/lerobot/rl/actor.py

@@ -63,6 +63,7 @@ from lerobot.configs.train import TrainRLServerPipelineConfig
 from lerobot.policies.factory import make_policy
 from lerobot.policies.sac.modeling_sac import SACPolicy
 from lerobot.processor import TransitionKey
+from lerobot.rl.process import ProcessSignalHandler
 from lerobot.robots import so100_follower  # noqa: F401
 from lerobot.teleoperators import gamepad, so101_leader  # noqa: F401
 from lerobot.teleoperators.utils import TeleopEvents
@@ -75,7 +76,6 @@ from lerobot.transport.utils import (
     send_bytes_in_chunks,
     transitions_to_bytes,
 )
-from lerobot.utils.process import ProcessSignalHandler
 from lerobot.utils.queue import get_last_item_from_queue
 from lerobot.utils.random_utils import set_seed
 from lerobot.utils.robot_utils import busy_wait

src/lerobot/rl/learner.py

@@ -67,6 +67,7 @@ from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.policies.factory import make_policy
 from lerobot.policies.sac.modeling_sac import SACPolicy
 from lerobot.rl.buffer import ReplayBuffer, concatenate_batch_transitions
+from lerobot.rl.process import ProcessSignalHandler
 from lerobot.robots import so100_follower  # noqa: F401
 from lerobot.teleoperators import gamepad, so101_leader  # noqa: F401
 from lerobot.teleoperators.utils import TeleopEvents
@@ -83,7 +84,6 @@ from lerobot.utils.constants import (
     PRETRAINED_MODEL_DIR,
     TRAINING_STATE_DIR,
 )
-from lerobot.utils.process import ProcessSignalHandler
 from lerobot.utils.random_utils import set_seed
 from lerobot.utils.train_utils import (
     get_step_checkpoint_dir,

src/lerobot/rl/process.py

@@ -0,0 +1,83 @@
+#!/usr/bin/env python
+
+# Copyright 2025 The HuggingFace Inc. team.
+# All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+import os
+import signal
+import sys
+
+
+class ProcessSignalHandler:
+    """Utility class to attach graceful shutdown signal handlers.
+
+    The class exposes a shutdown_event attribute that is set when a shutdown
+    signal is received. A counter tracks how many shutdown signals have been
+    caught. On the second signal the process exits with status 1.
+    """
+
+    _SUPPORTED_SIGNALS = ("SIGINT", "SIGTERM", "SIGHUP", "SIGQUIT")
+
+    def __init__(self, use_threads: bool, display_pid: bool = False):
+        # TODO: Check if we can use Event from threading since Event from
+        # multiprocessing is the a clone of threading.Event.
+        # https://docs.python.org/3/library/multiprocessing.html#multiprocessing.Event
+        if use_threads:
+            from threading import Event
+        else:
+            from multiprocessing import Event
+
+        self.shutdown_event = Event()
+        self._counter: int = 0
+        self._display_pid = display_pid
+
+        self._register_handlers()
+
+    @property
+    def counter(self) -> int:  # pragma: no cover – simple accessor
+        """Number of shutdown signals that have been intercepted."""
+        return self._counter
+
+    def _register_handlers(self):
+        """Attach the internal _signal_handler to a subset of POSIX signals."""
+
+        def _signal_handler(signum, frame):
+            pid_str = ""
+            if self._display_pid:
+                pid_str = f"[PID: {os.getpid()}]"
+            logging.info(f"{pid_str} Shutdown signal {signum} received. Cleaning up…")
+            self.shutdown_event.set()
+            self._counter += 1
+
+            # On a second Ctrl-C (or any supported signal) force the exit to
+            # mimic the previous behaviour while giving the caller one chance to
+            # shutdown gracefully.
+            # TODO: Investigate if we need it later
+            if self._counter > 1:
+                logging.info("Force shutdown")
+                sys.exit(1)
+
+        for sig_name in self._SUPPORTED_SIGNALS:
+            sig = getattr(signal, sig_name, None)
+            if sig is None:
+                # The signal is not available on this platform (Windows for
+                # instance does not provide SIGHUP, SIGQUIT…). Skip it.
+                continue
+            try:
+                signal.signal(sig, _signal_handler)
+            except (ValueError, OSError):  # pragma: no cover – unlikely but safe
+                # Signal not supported or we are in a non-main thread.
+                continue