Repository: Project-MONAI/MONAI

Issue:
Add  support to track `engine.state.XXX` in handlers
**Is your feature request related to a problem? Please describe.**
Referring to the latest ignite built-in handlers, I think we can add support to track specified state in `StatsHandler`, etc.
https://github.com/pytorch/ignite/blob/master/ignite/contrib/handlers/base_logger.py#L55




Discussion:

Patch:
diff --git a/monai/handlers/mlflow_handler.py b/monai/handlers/mlflow_handler.py
--- a/monai/handlers/mlflow_handler.py
+++ b/monai/handlers/mlflow_handler.py
@@ -9,7 +9,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import TYPE_CHECKING, Any, Callable, Optional
+from typing import TYPE_CHECKING, Any, Callable, Optional, Sequence
 
 import torch
 
@@ -59,6 +59,8 @@ class MLFlowHandler:
         global_epoch_transform: a callable that is used to customize global epoch number.
             For example, in evaluation, the evaluator engine might want to track synced epoch number
             with the trainer engine.
+        state_attributes: expected attributes from `engine.state`, if provided, will extract them
+            when epoch completed.
         tag_name: when iteration output is a scalar, `tag_name` is used to track, defaults to `'Loss'`.
 
     For more details of MLFlow usage, please refer to: https://mlflow.org/docs/latest/index.html.
@@ -72,6 +74,7 @@ def __init__(
         iteration_logger: Optional[Callable[[Engine], Any]] = None,
         output_transform: Callable = lambda x: x[0],
         global_epoch_transform: Callable = lambda x: x,
+        state_attributes: Optional[Sequence[str]] = None,
         tag_name: str = DEFAULT_TAG,
     ) -> None:
         if tracking_uri is not None:
@@ -81,6 +84,7 @@ def __init__(
         self.iteration_logger = iteration_logger
         self.output_transform = output_transform
         self.global_epoch_transform = global_epoch_transform
+        self.state_attributes = state_attributes
         self.tag_name = tag_name
 
     def attach(self, engine: Engine) -> None:
@@ -144,7 +148,8 @@ def iteration_completed(self, engine: Engine) -> None:
     def _default_epoch_log(self, engine: Engine) -> None:
         """
         Execute epoch level log operation.
-        Default to track the values from Ignite `engine.state.metrics` dict.
+        Default to track the values from Ignite `engine.state.metrics` dict and
+        track the values of specified attributes of `engine.state`.
 
         Args:
             engine: Ignite Engine, it can be a trainer, validator or evaluator.
@@ -157,6 +162,10 @@ def _default_epoch_log(self, engine: Engine) -> None:
         current_epoch = self.global_epoch_transform(engine.state.epoch)
         mlflow.log_metrics(log_dict, step=current_epoch)
 
+        if self.state_attributes is not None:
+            attrs = {attr: getattr(engine.state, attr, None) for attr in self.state_attributes}
+            mlflow.log_metrics(attrs, step=current_epoch)
+
     def _default_iteration_log(self, engine: Engine) -> None:
         """
         Execute iteration log operation based on Ignite `engine.state.output` data.
diff --git a/monai/handlers/stats_handler.py b/monai/handlers/stats_handler.py
--- a/monai/handlers/stats_handler.py
+++ b/monai/handlers/stats_handler.py
@@ -11,7 +11,7 @@
 
 import logging
 import warnings
-from typing import TYPE_CHECKING, Any, Callable, Optional
+from typing import TYPE_CHECKING, Any, Callable, Optional, Sequence
 
 import torch
 
@@ -47,6 +47,7 @@ def __init__(
         iteration_print_logger: Optional[Callable[[Engine], Any]] = None,
         output_transform: Callable = lambda x: x[0],
         global_epoch_transform: Callable = lambda x: x,
+        state_attributes: Optional[Sequence[str]] = None,
         name: Optional[str] = None,
         tag_name: str = DEFAULT_TAG,
         key_var_format: str = DEFAULT_KEY_VAL_FORMAT,
@@ -68,6 +69,8 @@ def __init__(
             global_epoch_transform: a callable that is used to customize global epoch number.
                 For example, in evaluation, the evaluator engine might want to print synced epoch number
                 with the trainer engine.
+            state_attributes: expected attributes from `engine.state`, if provided, will extract them
+                when epoch completed.
             name: identifier of logging.logger to use, defaulting to ``engine.logger``.
             tag_name: when iteration output is a scalar, tag_name is used to print
                 tag_name: scalar_value to logger. Defaults to ``'Loss'``.
@@ -80,6 +83,7 @@ def __init__(
         self.iteration_print_logger = iteration_print_logger
         self.output_transform = output_transform
         self.global_epoch_transform = global_epoch_transform
+        self.state_attributes = state_attributes
         self.logger = logging.getLogger(name)
         self._name = name
 
@@ -150,22 +154,22 @@ def exception_raised(self, engine: Engine, e: Exception) -> None:
     def _default_epoch_print(self, engine: Engine) -> None:
         """
         Execute epoch level log operation.
-        Default to print the values from Ignite `engine.state.metrics` dict.
+        Default to print the values from Ignite `engine.state.metrics` dict and
+        print the values of specified attributes of `engine.state`.
 
         Args:
             engine: Ignite Engine, it can be a trainer, validator or evaluator.
 
         """
-        prints_dict = engine.state.metrics
-        if not prints_dict:
-            return
         current_epoch = self.global_epoch_transform(engine.state.epoch)
 
-        out_str = f"Epoch[{current_epoch}] Metrics -- "
-        for name in sorted(prints_dict):
-            value = prints_dict[name]
-            out_str += self.key_var_format.format(name, value)
-        self.logger.info(out_str)
+        prints_dict = engine.state.metrics
+        if prints_dict is not None and len(prints_dict) > 0:
+            out_str = f"Epoch[{current_epoch}] Metrics -- "
+            for name in sorted(prints_dict):
+                value = prints_dict[name]
+                out_str += self.key_var_format.format(name, value)
+            self.logger.info(out_str)
 
         if (
             hasattr(engine.state, "key_metric_name")
@@ -175,7 +179,13 @@ def _default_epoch_print(self, engine: Engine) -> None:
             out_str = f"Key metric: {engine.state.key_metric_name} "  # type: ignore
             out_str += f"best value: {engine.state.best_metric} "  # type: ignore
             out_str += f"at epoch: {engine.state.best_metric_epoch}"  # type: ignore
-        self.logger.info(out_str)
+            self.logger.info(out_str)
+
+        if self.state_attributes is not None and len(self.state_attributes) > 0:
+            out_str = "State values: "
+            for attr in self.state_attributes:
+                out_str += f"{attr}: {getattr(engine.state, attr, None)} "
+            self.logger.info(out_str)
 
     def _default_iteration_print(self, engine: Engine) -> None:
         """
diff --git a/monai/handlers/tensorboard_handlers.py b/monai/handlers/tensorboard_handlers.py
--- a/monai/handlers/tensorboard_handlers.py
+++ b/monai/handlers/tensorboard_handlers.py
@@ -10,7 +10,7 @@
 # limitations under the License.
 
 import warnings
-from typing import TYPE_CHECKING, Any, Callable, Optional
+from typing import TYPE_CHECKING, Any, Callable, Optional, Sequence
 
 import numpy as np
 import torch
@@ -85,6 +85,7 @@ def __init__(
         iteration_interval: int = 1,
         output_transform: Callable = lambda x: x[0],
         global_epoch_transform: Callable = lambda x: x,
+        state_attributes: Optional[Sequence[str]] = None,
         tag_name: str = DEFAULT_TAG,
     ) -> None:
         """
@@ -107,6 +108,8 @@ def __init__(
             global_epoch_transform: a callable that is used to customize global epoch number.
                 For example, in evaluation, the evaluator engine might want to use trainer engines epoch number
                 when plotting epoch vs metric curves.
+            state_attributes: expected attributes from `engine.state`, if provided, will extract them
+                when epoch completed.
             tag_name: when iteration output is a scalar, tag_name is used to plot, defaults to ``'Loss'``.
         """
         super().__init__(summary_writer=summary_writer, log_dir=log_dir)
@@ -116,6 +119,7 @@ def __init__(
         self.iteration_interval = iteration_interval
         self.output_transform = output_transform
         self.global_epoch_transform = global_epoch_transform
+        self.state_attributes = state_attributes
         self.tag_name = tag_name
 
     def attach(self, engine: Engine) -> None:
@@ -164,7 +168,8 @@ def iteration_completed(self, engine: Engine) -> None:
     def _default_epoch_writer(self, engine: Engine, writer: SummaryWriter) -> None:
         """
         Execute epoch level event write operation.
-        Default to write the values from Ignite `engine.state.metrics` dict.
+        Default to write the values from Ignite `engine.state.metrics` dict and
+        write the values of specified attributes of `engine.state`.
 
         Args:
             engine: Ignite Engine, it can be a trainer, validator or evaluator.
@@ -175,6 +180,10 @@ def _default_epoch_writer(self, engine: Engine, writer: SummaryWriter) -> None:
         summary_dict = engine.state.metrics
         for name, value in summary_dict.items():
             writer.add_scalar(name, value, current_epoch)
+
+        if self.state_attributes is not None:
+            for attr in self.state_attributes:
+                writer.add_scalar(attr, getattr(engine.state, attr, None), current_epoch)
         writer.flush()
 
     def _default_iteration_writer(self, engine: Engine, writer: SummaryWriter) -> None:


Test patch:
diff --git a/tests/test_handler_mlflow.py b/tests/test_handler_mlflow.py
--- a/tests/test_handler_mlflow.py
+++ b/tests/test_handler_mlflow.py
@@ -35,10 +35,11 @@ def _train_func(engine, batch):
             def _update_metric(engine):
                 current_metric = engine.state.metrics.get("acc", 0.1)
                 engine.state.metrics["acc"] = current_metric + 0.1
+                engine.state.test = current_metric
 
             # set up testing handler
             test_path = os.path.join(tempdir, "mlflow_test")
-            handler = MLFlowHandler(tracking_uri=Path(test_path).as_uri())
+            handler = MLFlowHandler(tracking_uri=Path(test_path).as_uri(), state_attributes=["test"])
             handler.attach(engine)
             engine.run(range(3), max_epochs=2)
             handler.close()
diff --git a/tests/test_handler_stats.py b/tests/test_handler_stats.py
--- a/tests/test_handler_stats.py
+++ b/tests/test_handler_stats.py
@@ -163,6 +163,47 @@ def _train_func(engine, batch):
         with self.assertRaises(RuntimeError):
             engine.run(range(3), max_epochs=2)
 
+    def test_attributes_print(self):
+        log_stream = StringIO()
+        log_handler = logging.StreamHandler(log_stream)
+        log_handler.setLevel(logging.INFO)
+        key_to_handler = "test_logging"
+
+        # set up engine
+        def _train_func(engine, batch):
+            return [torch.tensor(0.0)]
+
+        engine = Engine(_train_func)
+
+        # set up dummy metric
+        @engine.on(Events.EPOCH_COMPLETED)
+        def _update_metric(engine):
+            if not hasattr(engine.state, "test1"):
+                engine.state.test1 = 0.1
+                engine.state.test2 = 0.2
+            else:
+                engine.state.test1 += 0.1
+                engine.state.test2 += 0.2
+
+        # set up testing handler
+        stats_handler = StatsHandler(
+            name=key_to_handler,
+            state_attributes=["test1", "test2", "test3"],
+            logger_handler=log_handler,
+        )
+        stats_handler.attach(engine)
+
+        engine.run(range(3), max_epochs=2)
+
+        # check logging output
+        output_str = log_stream.getvalue()
+        log_handler.close()
+        grep = re.compile(f".*{key_to_handler}.*")
+        has_key_word = re.compile(".*State values.*")
+        for idx, line in enumerate(output_str.split("\n")):
+            if grep.match(line) and idx in [5, 10]:
+                self.assertTrue(has_key_word.match(line))
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/tests/test_handler_tb_stats.py b/tests/test_handler_tb_stats.py
--- a/tests/test_handler_tb_stats.py
+++ b/tests/test_handler_tb_stats.py
@@ -57,11 +57,15 @@ def _train_func(engine, batch):
             def _update_metric(engine):
                 current_metric = engine.state.metrics.get("acc", 0.1)
                 engine.state.metrics["acc"] = current_metric + 0.1
+                engine.state.test = current_metric
 
             # set up testing handler
             writer = SummaryWriter(log_dir=tempdir)
             stats_handler = TensorBoardStatsHandler(
-                writer, output_transform=lambda x: {"loss": x[0] * 2.0}, global_epoch_transform=lambda x: x * 3.0
+                summary_writer=writer,
+                output_transform=lambda x: {"loss": x[0] * 2.0},
+                global_epoch_transform=lambda x: x * 3.0,
+                state_attributes=["test"],
             )
             stats_handler.attach(engine)
             engine.run(range(3), max_epochs=2)