Changes for trainer.py to support the Gradio webui (#3046)

* changes for trainer to support webui

* Update trainer to support webui

* format

* add a seperated shutdown() function to stop training

* typo fix

* get rid of _stop_viewer_server()

* Update trainer.py

* organize import

---------

Co-authored-by: Brent Yi <[email protected]>

nerfstudio/engine/trainer.py

@@ -28,6 +28,7 @@
 from typing import DefaultDict, Dict, List, Literal, Optional, Tuple, Type, cast
 
 import torch
+import viser
 from rich import box, style
 from rich.panel import Panel
 from rich.table import Table
@@ -137,6 +138,9 @@ def __init__(self, config: TrainerConfig, local_rank: int = 0, world_size: int =
 
         self.viewer_state = None
 
+        # used to keep track of the current step
+        self.step = 0
+
     def setup(self, test_mode: Literal["test", "val", "inference"] = "val") -> None:
         """Setup the Trainer by calling other setup functions.
 
@@ -233,8 +237,15 @@ def train(self) -> None:
         with TimeWriter(writer, EventName.TOTAL_TRAIN_TIME):
             num_iterations = self.config.max_num_iterations
             step = 0
+            self.stop_training = False
             for step in range(self._start_step, self._start_step + num_iterations):
+                self.step = step
+                if self.stop_training:
+                    break
                 while self.training_state == "paused":
+                    if self.stop_training:
+                        self._after_train()
+                        return
                     time.sleep(0.01)
                 with self.train_lock:
                     with TimeWriter(writer, EventName.ITER_TRAIN_TIME, step=step) as train_t:
@@ -291,12 +302,26 @@ def train(self) -> None:
 
                 writer.write_out_storage()
 
+        # save checkpoint at the end of training, and write out any remaining events
+        self._after_train()
+
+    def shutdown(self) -> None:
+        """Stop the trainer and stop all associated threads/processes (such as the viewer)."""
+        self.stop_training = True  # tell the training loop to stop
+        if self.viewer_state is not None:
+            # stop the viewer
+            # this condition excludes the case where `viser_server` is either `None` or an
+            # instance of `viewer_legacy`'s `ViserServer` instead of the upstream one.
+            if isinstance(self.viewer_state.viser_server, viser.ViserServer):
+                self.viewer_state.viser_server.stop()
+
+    def _after_train(self) -> None:
+        """Function to run after training is complete"""
+        self.training_state = "completed"  # used to update the webui state
         # save checkpoint at the end of training
-        self.save_checkpoint(step)
-
+        self.save_checkpoint(self.step)
         # write out any remaining events (e.g., total train time)
         writer.write_out_storage()
-
         table = Table(
             title=None,
             show_header=False,
@@ -309,7 +334,7 @@ def train(self) -> None:
 
         # after train end callbacks
         for callback in self.callbacks:
-            callback.run_callback_at_location(step=step, location=TrainingCallbackLocation.AFTER_TRAIN)
+            callback.run_callback_at_location(step=self.step, location=TrainingCallbackLocation.AFTER_TRAIN)
 
         if not self.config.viewer.quit_on_train_completion:
             self._train_complete_viewer()