fix checkpointing to remote file paths (#2925)

pytorch_lightning/callbacks/model_checkpoint.py

@@ -16,7 +16,7 @@
 from pytorch_lightning import _logger as log
 from pytorch_lightning.callbacks.base import Callback
 from pytorch_lightning.utilities import rank_zero_warn, rank_zero_only
-from pytorch_lightning.utilities.cloud_io import gfile, makedirs
+from pytorch_lightning.utilities.cloud_io import gfile, makedirs, is_remote_path
 
 
 class ModelCheckpoint(Callback):
@@ -122,10 +122,10 @@ def __init__(self, filepath: Optional[str] = None, monitor: str = 'val_loss', ve
             if gfile.isdir(filepath):
                 self.dirpath, self.filename = filepath, '{epoch}'
             else:
-                filepath = os.path.realpath(filepath)
+                if not is_remote_path(filepath):  # dont normalize remote paths
+                    filepath = os.path.realpath(filepath)
                 self.dirpath, self.filename = os.path.split(filepath)
-            if not gfile.exists(self.dirpath):
-                makedirs(self.dirpath)
+            makedirs(self.dirpath)  # calls with exist_ok
         self.save_last = save_last
         self.save_top_k = save_top_k
         self.save_weights_only = save_weights_only
@@ -174,7 +174,12 @@ def _del_model(self, filepath):
                 # dependencies exist then this will work fine.
                 gfile.remove(filepath)
             except AttributeError:
-                os.remove(filepath)
+                if is_remote_path(filepath):
+                    log.warning("Unable to remove stale checkpoints due to running gfile in compatibility mode."
+                                " Please install tensorflow to run gfile in full mode"
+                                " if writing checkpoints to remote locations")
+                else:
+                    os.remove(filepath)
 
     def _save_model(self, filepath, trainer, pl_module):
 

pytorch_lightning/trainer/distrib_data_parallel.py

@@ -127,6 +127,7 @@ def train_fx(trial_hparams, cluster_manager, _):
 
 """
 
+import io
 import os
 import re
 from abc import ABC, abstractmethod
@@ -146,6 +147,7 @@ def train_fx(trial_hparams, cluster_manager, _):
 from pytorch_lightning.utilities.distributed import rank_zero_warn, rank_zero_info
 from pytorch_lightning.core.datamodule import LightningDataModule
 from pytorch_lightning.core.lightning import LightningModule
+from pytorch_lightning.utilities.cloud_io import cloud_open
 
 
 try:
@@ -435,10 +437,13 @@ def transfer_distrib_spawn_state_on_fit_end(self, model, mp_queue, results):
                 # Can't use the new zipfile serialization for 1.6.0 because there's a bug in
                 # torch.hub.load_state_dict_from_url() that prevents it from loading the new files.
                 # More details can be found here: https://github.com/pytorch/pytorch/issues/42239
+                bytesbuffer = io.BytesIO()
                 if LooseVersion(torch.__version__).version[:3] == [1, 6, 0]:
-                    torch.save(model.state_dict(), last_path, _use_new_zipfile_serialization=False)
+                    torch.save(model.state_dict(), bytesbuffer, _use_new_zipfile_serialization=False)
                 else:
-                    torch.save(model.state_dict(), last_path)
+                    torch.save(model.state_dict(), bytesbuffer)
+                with cloud_open(last_path, 'wb') as f:
+                    f.write(bytesbuffer.getvalue())
             mp_queue.put(last_path)
 
     def save_spawn_weights(self, model):

pytorch_lightning/trainer/trainer.py

@@ -53,6 +53,7 @@
 from pytorch_lightning.utilities import parsing, rank_zero_info, rank_zero_only, rank_zero_warn, AMPType
 from pytorch_lightning.utilities.debugging import InternalDebugger
 from pytorch_lightning.utilities.exceptions import MisconfigurationException
+from pytorch_lightning.utilities.cloud_io import is_remote_path
 
 # warnings to ignore in trainer
 warnings.filterwarnings(
@@ -880,7 +881,7 @@ def default_root_dir(self) -> str:
         The default location to save artifacts of loggers, checkpoints etc.
         It is used as a fallback if logger or checkpoint callback do not define specific save paths.
         """
-        if "://" in str(self._default_root_dir):
+        if is_remote_path(self._default_root_dir):
             # it is a remote uri, use as is
             return self._default_root_dir
         return os.path.normpath(self._default_root_dir)
@@ -891,7 +892,7 @@ def weights_save_path(self) -> str:
         The default root location to save weights (checkpoints), e.g., when the
         :class:`~pytorch_lightning.callbacks.model_checkpoint.ModelCheckpoint` does not define a file path.
         """
-        if "://" in str(self._weights_save_path):
+        if is_remote_path(self._weights_save_path):
             # it is a remote uri, use as is
             return self._weights_save_path
         return os.path.normpath(self._weights_save_path)

pytorch_lightning/trainer/training_io.py

@@ -83,6 +83,7 @@
 
 """
 
+import io
 import os
 import re
 import signal
@@ -104,7 +105,7 @@
 )
 from pytorch_lightning.utilities import rank_zero_warn, AMPType
 from pytorch_lightning.utilities.cloud_io import load as pl_load
-from pytorch_lightning.utilities.cloud_io import gfile, makedirs
+from pytorch_lightning.utilities.cloud_io import cloud_open, gfile, makedirs
 
 try:
     import torch_xla
@@ -269,15 +270,16 @@ def _atomic_save(self, checkpoint, filepath: str):
             filepath: The path to which the checkpoint will be saved.
                 This points to the file that the checkpoint will be stored in.
         """
-        tmp_path = str(filepath) + ".part"
+        bytesbuffer = io.BytesIO()
         # Can't use the new zipfile serialization for 1.6.0 because there's a bug in
         # torch.hub.load_state_dict_from_url() that prevents it from loading the new files.
         # More details can be found here: https://github.com/pytorch/pytorch/issues/42239
         if LooseVersion(torch.__version__).version[:3] == [1, 6, 0]:
-            torch.save(checkpoint, tmp_path, _use_new_zipfile_serialization=False)
+            torch.save(checkpoint, bytesbuffer, _use_new_zipfile_serialization=False)
         else:
-            torch.save(checkpoint, tmp_path)
-        os.replace(tmp_path, filepath)
+            torch.save(checkpoint, bytesbuffer)
+        with cloud_open(filepath, 'wb') as f:
+            f.write(bytesbuffer.getvalue())
 
     def save_checkpoint(self, filepath, weights_only: bool = False):
         checkpoint = self.dump_checkpoint(weights_only)

pytorch_lightning/utilities/cloud_io.py

@@ -28,6 +28,14 @@ def load(path_or_url: str, map_location=None):
     return torch.hub.load_state_dict_from_url(path_or_url, map_location=map_location)
 
 
+def is_remote_path(path: pathlike):
+    """Determine if a path is a local path or a remote path like s3://bucket/path
+
+    This should catch paths like s3:// hdfs:// and gcs://
+    """
+    return "://" in str(path)
+
+
 def modern_gfile():
     """Check the version number of tensorboard.
 
@@ -61,6 +69,7 @@ def cloud_open(path: pathlike, mode: str, newline: str = None):
 
 def makedirs(path: pathlike):
     if hasattr(gfile, "makedirs") and modern_gfile():
-        return gfile.makedirs(str(path))
+        if not gfile.exists(str(path)):
+            return gfile.makedirs(str(path))
     # otherwise minimal dependencies are installed and only local files will work
     return os.makedirs(path, exist_ok=True)