Make monitor required arg of EarlyStopping callback

CHANGELOG.md

@@ -28,7 +28,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Raise exception in `init_dist_connection()` when torch distibuted is not available ([#10418](https://github.com/PyTorchLightning/pytorch-lightning/issues/10418))
 
 
--
+- The `monitor` argument in the `EarlyStopping` callback is no longer optional ([#10328](https://github.com/PyTorchLightning/pytorch-lightning/pull/10328))
 
 
 -

docs/source/common/lightning_cli.rst

@@ -625,7 +625,7 @@ This can be implemented as follows:
     class MyLightningCLI(LightningCLI):
         def add_arguments_to_parser(self, parser):
             parser.add_lightning_class_args(EarlyStopping, "my_early_stopping")
-            parser.set_defaults({"my_early_stopping.patience": 5})
+            parser.set_defaults({"my_early_stopping.monitor": "val_loss", "my_early_stopping.patience": 5})
 
 
     cli = MyLightningCLI(MyModel)

pytorch_lightning/callbacks/early_stopping.py

@@ -26,7 +26,7 @@
 
 import pytorch_lightning as pl
 from pytorch_lightning.callbacks.base import Callback
-from pytorch_lightning.utilities import rank_zero_deprecation, rank_zero_warn
+from pytorch_lightning.utilities import rank_zero_warn
 from pytorch_lightning.utilities.exceptions import MisconfigurationException
 
 log = logging.getLogger(__name__)
@@ -89,7 +89,7 @@ class EarlyStopping(Callback):
 
     def __init__(
         self,
-        monitor: Optional[str] = None,
+        monitor: str,
         min_delta: float = 0.0,
         patience: int = 3,
         verbose: bool = False,
@@ -101,6 +101,7 @@ def __init__(
         check_on_train_epoch_end: Optional[bool] = None,
     ):
         super().__init__()
+        self.monitor = monitor
         self.min_delta = min_delta
         self.patience = patience
         self.verbose = verbose
@@ -120,13 +121,6 @@ def __init__(
         torch_inf = torch.tensor(np.Inf)
         self.best_score = torch_inf if self.monitor_op == torch.lt else -torch_inf
 
-        if monitor is None:
-            rank_zero_deprecation(
-                "The `EarlyStopping(monitor)` argument will be required starting in v1.6."
-                " For backward compatibility, setting this to `early_stop_on`."
-            )
-        self.monitor = monitor or "early_stop_on"
-
     @property
     def state_key(self) -> str:
         return self._generate_state_key(monitor=self.monitor, mode=self.mode)

tests/callbacks/test_early_stopping.py

@@ -183,7 +183,7 @@ def training_epoch_end(self, outputs):
 
 
 def test_pickling(tmpdir):
-    early_stopping = EarlyStopping()
+    early_stopping = EarlyStopping("foo")
 
     early_stopping_pickled = pickle.dumps(early_stopping)
     early_stopping_loaded = pickle.loads(early_stopping_pickled)
@@ -350,7 +350,7 @@ def validation_epoch_end(self, outputs):
 
 def test_early_stopping_mode_options():
     with pytest.raises(MisconfigurationException, match="`mode` can be .* got unknown_option"):
-        EarlyStopping(mode="unknown_option")
+        EarlyStopping("foo", mode="unknown_option")
 
 
 class EarlyStoppingModel(BoringModel):

tests/deprecated_api/test_remove_1-6.py

@@ -17,7 +17,6 @@
 import pytest
 
 from pytorch_lightning import Trainer
-from pytorch_lightning.callbacks.early_stopping import EarlyStopping
 from pytorch_lightning.plugins.training_type import DDPPlugin
 from pytorch_lightning.utilities.distributed import rank_zero_deprecation, rank_zero_warn
 from pytorch_lightning.utilities.model_helpers import is_overridden
@@ -73,14 +72,6 @@ def test_v1_6_0_is_overridden_model():
         assert not is_overridden("foo", model=model)
 
 
-def test_v1_6_0_early_stopping_monitor(tmpdir):
-    with pytest.deprecated_call(
-        match=r"The `EarlyStopping\(monitor\)` argument will be required starting in v1.6."
-        " For backward compatibility, setting this to `early_stop_on`."
-    ):
-        EarlyStopping()
-
-
 def test_v1_6_0_extras_with_gradients(tmpdir):
     class TestModel(BoringModel):
         def training_step(self, *args):

tests/trainer/connectors/test_callback_connector.py

@@ -33,7 +33,7 @@ def test_checkpoint_callbacks_are_last(tmpdir):
     checkpoint1 = ModelCheckpoint(tmpdir)
     checkpoint2 = ModelCheckpoint(tmpdir)
     model_summary = ModelSummary()
-    early_stopping = EarlyStopping()
+    early_stopping = EarlyStopping("foo")
     lr_monitor = LearningRateMonitor()
     progress_bar = TQDMProgressBar()
 
@@ -154,7 +154,7 @@ def _attach_callbacks(trainer_callbacks, model_callbacks):
         cb_connector._attach_model_callbacks()
         return trainer
 
-    early_stopping = EarlyStopping()
+    early_stopping = EarlyStopping("foo")
     progress_bar = TQDMProgressBar()
     lr_monitor = LearningRateMonitor()
     grad_accumulation = GradientAccumulationScheduler({1: 1})
@@ -169,14 +169,14 @@ def _attach_callbacks(trainer_callbacks, model_callbacks):
 
     # same callback type twice, different instance
     trainer = _attach_callbacks(
-        trainer_callbacks=[progress_bar, EarlyStopping()],
+        trainer_callbacks=[progress_bar, EarlyStopping("foo")],
         model_callbacks=[early_stopping],
     )
     assert trainer.callbacks == [progress_bar, trainer.accumulation_scheduler, early_stopping]
 
     # multiple callbacks of the same type in trainer
     trainer = _attach_callbacks(
-        trainer_callbacks=[LearningRateMonitor(), EarlyStopping(), LearningRateMonitor(), EarlyStopping()],
+        trainer_callbacks=[LearningRateMonitor(), EarlyStopping("foo"), LearningRateMonitor(), EarlyStopping("foo")],
         model_callbacks=[early_stopping, lr_monitor],
     )
     assert trainer.callbacks == [trainer.accumulation_scheduler, early_stopping, lr_monitor]
@@ -186,9 +186,9 @@ def _attach_callbacks(trainer_callbacks, model_callbacks):
         trainer_callbacks=[
             LearningRateMonitor(),
             progress_bar,
-            EarlyStopping(),
+            EarlyStopping("foo"),
             LearningRateMonitor(),
-            EarlyStopping(),
+            EarlyStopping("foo"),
         ],
         model_callbacks=[early_stopping, lr_monitor, grad_accumulation, early_stopping],
     )
@@ -198,8 +198,10 @@ def _attach_callbacks(trainer_callbacks, model_callbacks):
 def test_attach_model_callbacks_override_info(caplog):
     """Test that the logs contain the info about overriding callbacks returned by configure_callbacks."""
     model = LightningModule()
-    model.configure_callbacks = lambda: [LearningRateMonitor(), EarlyStopping()]
-    trainer = Trainer(enable_checkpointing=False, callbacks=[EarlyStopping(), LearningRateMonitor(), TQDMProgressBar()])
+    model.configure_callbacks = lambda: [LearningRateMonitor(), EarlyStopping("foo")]
+    trainer = Trainer(
+        enable_checkpointing=False, callbacks=[EarlyStopping("foo"), LearningRateMonitor(), TQDMProgressBar()]
+    )
     trainer.model = model
     cb_connector = CallbackConnector(trainer)
     with caplog.at_level(logging.INFO):

tests/trainer/flags/test_fast_dev_run.py

@@ -65,7 +65,7 @@ def test_step(self, batch, batch_idx):
 
     checkpoint_callback = ModelCheckpoint()
     checkpoint_callback.save_checkpoint = Mock()
-    early_stopping_callback = EarlyStopping()
+    early_stopping_callback = EarlyStopping(monitor="foo")
     early_stopping_callback._evaluate_stopping_criteria = Mock()
     trainer_config = dict(
         default_root_dir=tmpdir,