tiny improvement (#19341)

src/lightning/data/streaming/downloader.py

@@ -12,6 +12,7 @@
 # limitations under the License.
 import os
 import shutil
+import subprocess
 from abc import ABC
 from typing import Any, Dict, List
 from urllib import parse
@@ -40,29 +41,45 @@ def download_file(self, remote_chunkpath: str, local_chunkpath: str) -> None:
 class S3Downloader(Downloader):
     def __init__(self, remote_dir: str, cache_dir: str, chunks: List[Dict[str, Any]]):
         super().__init__(remote_dir, cache_dir, chunks)
-        self._client = S3Client()
+        self._s5cmd_available = os.system("s5cmd > /dev/null 2>&1") == 0
+
+        if not self._s5cmd_available:
+            self._client = S3Client()
 
     def download_file(self, remote_filepath: str, local_filepath: str) -> None:
         obj = parse.urlparse(remote_filepath)
 
         if obj.scheme != "s3":
             raise ValueError(f"Expected obj.scheme to be `s3`, instead, got {obj.scheme} for remote={remote_filepath}")
 
-        from boto3.s3.transfer import TransferConfig
-
-        extra_args: Dict[str, Any] = {}
+        if os.path.exists(local_filepath):
+            return
 
         try:
-            with FileLock(local_filepath + ".lock", timeout=1):
-                if not os.path.exists(local_filepath):
-                    # Issue: https://github.com/boto/boto3/issues/3113
-                    self._client.client.download_file(
-                        obj.netloc,
-                        obj.path.lstrip("/"),
-                        local_filepath,
-                        ExtraArgs=extra_args,
-                        Config=TransferConfig(use_threads=False),
+            with FileLock(local_filepath + ".lock", timeout=0):
+                if self._s5cmd_available:
+                    proc = subprocess.Popen(
+                        f"s5cmd --numworkers 64 cp {remote_filepath} {local_filepath}",
+                        shell=True,
+                        stdout=subprocess.PIPE,
                     )
+                    proc.wait()
+                else:
+                    from boto3.s3.transfer import TransferConfig
+
+                    extra_args: Dict[str, Any] = {}
+
+                    # try:
+                    #     with FileLock(local_filepath + ".lock", timeout=1):
+                    if not os.path.exists(local_filepath):
+                        # Issue: https://github.com/boto/boto3/issues/3113
+                        self._client.client.download_file(
+                            obj.netloc,
+                            obj.path.lstrip("/"),
+                            local_filepath,
+                            ExtraArgs=extra_args,
+                            Config=TransferConfig(use_threads=False),
+                        )
         except Timeout:
             # another process is responsible to download that file, continue
             pass

tests/tests_data/streaming/test_downloader.py

@@ -0,0 +1,13 @@
+import os
+from unittest.mock import MagicMock
+
+from lightning.data.streaming.downloader import S3Downloader, subprocess
+
+
+def test_s3_downloader_fast(tmpdir, monkeypatch):
+    monkeypatch.setattr(os, "system", MagicMock(return_value=0))
+    popen_mock = MagicMock()
+    monkeypatch.setattr(subprocess, "Popen", MagicMock(return_value=popen_mock))
+    downloader = S3Downloader(tmpdir, tmpdir, [])
+    downloader.download_file("s3://random_bucket/a.txt", os.path.join(tmpdir, "a.txt"))
+    popen_mock.wait.assert_called()