Add HandlerAwaitableSignal class to be used for signaling when creati…

…ng step and item directories asynchronously during checkpointing.

PiperOrigin-RevId: 716129191

checkpoint/orbax/checkpoint/_src/futures/synchronization.py

@@ -0,0 +1,57 @@
+# Copyright 2024 The Orbax Authors.
+#
+# 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.
+
+"""Synchronization utilities for futures."""
+
+import enum
+import itertools
+from orbax.checkpoint._src.multihost import multihost
+
+
+class HandlerAwaitableSignal(enum.Enum):
+  """Defines signals that may be awaited by a `CheckpointHandler`.
+
+  Signals may be passed from `CheckpointManager` or `Checkpointer` layers to
+  `CheckpointHandler or below.`
+
+  Attributes:
+    STEP_DIRECOTRY_CREATION: When recieved, indicates that the step directory
+      has been created. The handler should not attemp to write files before the
+      directory is created.
+    ITEM_DIRECTORY_CREATION: When recieved, indicates that the item directory
+      has been created. The handler should not attemp to write files before the
+      directory is created.
+  """
+
+  STEP_DIRECTORY_CREATION = 'step_directory_creation'
+  ITEM_DIRECTORY_CREATION = 'item_directory_creation'
+
+
+class HandlerAwaitableSignalBarrierKeyGenerator:
+  """A unique barrier key generator for a `HandlerAwaitableSignal`."""
+
+  _barrier_key_counter = itertools.count()
+  _barrier_key_counter_value = None
+
+  @classmethod
+  def step_barrier_key_counter(cls) -> int:
+    cls._barrier_key_counter_value = next(cls._barrier_key_counter)
+    return cls._barrier_key_counter_value
+
+  @classmethod
+  def get_unique_barrier_key(cls, signal: HandlerAwaitableSignal) -> str:
+    """Returns a unique barrier key for the signal."""
+    return multihost.unique_barrier_key(
+        signal.value, suffix=str(cls._barrier_key_counter_value)
+    )

checkpoint/orbax/checkpoint/_src/futures/synchronization_test.py

@@ -0,0 +1,41 @@
+# Copyright 2024 The Orbax Authors.
+#
+# 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.
+
+from absl.testing import absltest
+from absl.testing import parameterized
+from orbax.checkpoint._src.futures import synchronization
+from orbax.checkpoint._src.multihost import multihost
+
+
+class HandlerAwaitableSignalBarrierKeyGeneratorTest(parameterized.TestCase):
+
+  @parameterized.parameters("0", "1", "2")
+  def test_get_unique_barrier_key(self, suffix):
+    step_directory_creation_signal = (
+        synchronization.HandlerAwaitableSignal.STEP_DIRECTORY_CREATION
+    )
+    expected_barrier_key = multihost.unique_barrier_key(
+        step_directory_creation_signal.value, suffix=suffix
+    )
+
+    synchronization.HandlerAwaitableSignalBarrierKeyGenerator.step_barrier_key_counter()
+    barrier_key = synchronization.HandlerAwaitableSignalBarrierKeyGenerator.get_unique_barrier_key(
+        step_directory_creation_signal
+    )
+
+    self.assertEqual(barrier_key, expected_barrier_key)
+
+
+if __name__ == "__main__":
+  absltest.main()