disabling parallel download for windows

Author: yuanjieding-db

databricks/sdk/mixins/files.py

@@ -836,6 +836,13 @@ def download_to(
         if not overwrite and os.path.exists(destination):
             raise FileExistsError(destination)
         if use_parallel:
+            # Parallel download is not supported for Windows due to the limit of only one open file handle
+            # for writing. If parallel download is requested on Windows, fall back to sequential download with
+            # a warning.
+            if platform.system() == "Windows":
+                _LOG.warning("Parallel download is not supported on Windows. Falling back to sequential download.")
+                self._sequential_download_to_file(destination, remote_path=file_path)
+                return DownloadFileResult()
             if parallelism is None:
                 parallelism = self._config.files_ext_parallel_download_default_parallelism
             if parallelism < 1 or parallelism > 64:

tests/test_files.py

@@ -4,13 +4,14 @@
 import json
 import logging
 import os
+import platform
 import random
 import re
 import time
 from dataclasses import dataclass
 from datetime import datetime, timedelta, timezone
 from enum import Enum
-from tempfile import NamedTemporaryFile, mkstemp
+from tempfile import NamedTemporaryFile
 from threading import Lock
 from typing import Any, Callable, List, Optional, Type, Union
 from urllib.parse import parse_qs, urlparse
@@ -199,6 +200,8 @@ def to_string(test_case: "FilesApiDownloadTestCase") -> str:
         return test_case.name
 
     def run(self, config: Config, monkeypatch) -> None:
+        if self.use_parallel and platform.system() == "Windows":
+            pytest.skip("Skipping parallel download tests on Windows")
         config = config.copy()
         config.enable_experimental_files_api_client = self.enable_new_client
         config.files_ext_client_download_max_total_recovers = self.max_recovers_total
@@ -935,6 +938,9 @@ def processor() -> list:
             raise RuntimeError("Unexpected request " + str(request))
 
     def run_one_case(self, config: Config, monkeypatch, download_mode: DownloadMode, use_parallel: bool) -> None:
+        if use_parallel and platform.system() == "Windows":
+            logger.debug("Parallel download is not supported on Windows. Falling back to sequential download.")
+            return
         config = config.copy()
         config.enable_experimental_files_api_client = True
         config.enable_presigned_download_api = True
@@ -1149,7 +1155,8 @@ def save_part(self, part_number: int, part_content: bytes, etag: str) -> None:
         # part might already have been uploaded
         with self.global_lock:
             if part_number not in self.uploaded_parts:
-                fd, part_file = mkstemp()
+                with NamedTemporaryFile(mode="wb", delete=False) as f:
+                    part_file = f.name
                 self.uploaded_parts[part_number] = [part_file, etag, Lock()]
             existing_part = self.uploaded_parts[part_number]
         with existing_part[2]:  # lock per part
@@ -1275,9 +1282,9 @@ def clear_state(self) -> None:
     def get_upload_file(self, content: bytes, source_type: "UploadSourceType") -> Union[str, io.BytesIO]:
         """Returns a file or stream to upload based on the source type."""
         if source_type == UploadSourceType.FILE:
-            fd, file_path = mkstemp()
-            with open(fd, "wb") as f:
+            with NamedTemporaryFile(mode="wb", delete=False) as f:
                 f.write(content)
+                file_path = f.name
             self.created_temp_files.append(file_path)
             return file_path
         elif source_type == UploadSourceType.STREAM:
@@ -2211,8 +2218,8 @@ def save_part(self, start_offset: int, end_offset_incl: int, part_content: bytes
         if unconfirmed_delta > 0:
             part_content = part_content[:-unconfirmed_delta]
 
-        fd, part_file = mkstemp()
-        with open(fd, "wb") as f:
+        with NamedTemporaryFile(mode="wb", delete=False) as f:
+            part_file = f.name
             f.write(part_content)
 
         self.uploaded_parts.append(part_file)