chore: import upstream snapshot with attribution

python/ray/_private/logging_utils.py

@@ -0,0 +1,49 @@
+import sys
+
+from ray._private.utils import open_log
+from ray._raylet import StreamRedirector
+
+
+def redirect_stdout_stderr_if_needed(
+    stdout_filepath: str,
+    stderr_filepath: str,
+    rotation_bytes: int,
+    rotation_backup_count: int,
+):
+    """This function sets up redirection for stdout and stderr if needed, based on the given rotation parameters.
+
+    params:
+    stdout_filepath: the filepath stdout will be redirected to; if empty, stdout will not be redirected.
+    stderr_filepath: the filepath stderr will be redirected to; if empty, stderr will not be redirected.
+    rotation_bytes: number of bytes which triggers file rotation.
+    rotation_backup_count: the max size of rotation files.
+    """
+
+    # Setup redirection for stdout and stderr.
+    if stdout_filepath:
+        StreamRedirector.redirect_stdout(
+            stdout_filepath,
+            rotation_bytes,
+            rotation_backup_count,
+            False,  # tee_to_stdout
+            False,  # tee_to_stderr
+        )
+    if stderr_filepath:
+        StreamRedirector.redirect_stderr(
+            stderr_filepath,
+            rotation_bytes,
+            rotation_backup_count,
+            False,  # tee_to_stdout
+            False,  # tee_to_stderr
+        )
+
+    # Setup python system stdout/stderr.
+    stdout_fileno = sys.stdout.fileno()
+    stderr_fileno = sys.stderr.fileno()
+    # We also manually set sys.stdout and sys.stderr because that seems to
+    # have an effect on the output buffering. Without doing this, stdout
+    # and stderr are heavily buffered resulting in seemingly lost logging
+    # statements. We never want to close the stdout file descriptor, dup2 will
+    # close it when necessary and we don't want python's GC to close it.
+    sys.stdout = open_log(stdout_fileno, unbuffered=True, closefd=False)
+    sys.stderr = open_log(stderr_fileno, unbuffered=True, closefd=False)