Squash Odysseus development history

core/atomic_io.py

@@ -15,29 +15,53 @@ from __future__ import annotations
 
 import json
 import os
+import uuid
 from typing import Any, Optional
 
 
 def atomic_write_json(path: str, data: Any, *, indent: Optional[int] = None) -> None:
     """Atomically persist `data` as JSON at `path`.
 
-    The temp file uses the live PID as a suffix so two processes saving the
-    same file (e.g. unit tests) don't collide on the rename target.
+    The temp file uses a random suffix so two concurrent writers saving the
+    same file don't collide on the rename target. A PID suffix does not do
+    this: the PID is constant for the life of a process, so two writers on
+    the same path within one process (or one single-process container, where
+    the PID never changes at all) still race for the same temp file.
     """
     os.makedirs(os.path.dirname(path) or ".", exist_ok=True)
-    tmp = f"{path}.tmp.{os.getpid()}"
-    with open(tmp, "w") as f:
-        json.dump(data, f, indent=indent)
-        f.flush()
-        os.fsync(f.fileno())
-    os.replace(tmp, path)
+    tmp = f"{path}.tmp.{uuid.uuid4().hex}"
+
+    try:
+        with open(tmp, "w", encoding="utf-8") as f:
+            json.dump(data, f, indent=indent)
+            f.flush()
+            os.fsync(f.fileno())
+        os.replace(tmp, path)
+    finally:
+        # Directly unlink to avoid a check-then-act race condition.
+        # Swallows FileNotFoundError (on success path) and other cleanup OSErrors.
+        try:
+            os.unlink(tmp)
+        except OSError:
+            pass
 
 
 def atomic_write_text(path: str, text: str) -> None:
+    if not isinstance(text, str):
+        raise TypeError("atomic_write_text expects a string")
     os.makedirs(os.path.dirname(path) or ".", exist_ok=True)
-    tmp = f"{path}.tmp.{os.getpid()}"
-    with open(tmp, "w") as f:
-        f.write(text)
-        f.flush()
-        os.fsync(f.fileno())
-    os.replace(tmp, path)
+    tmp = f"{path}.tmp.{uuid.uuid4().hex}"
+
+    try:
+        with open(tmp, "w", encoding="utf-8") as f:
+            f.write(text)
+            f.flush()
+            os.fsync(f.fileno())
+        os.replace(tmp, path)
+    finally:
+        # Directly unlink to avoid a check-then-act race condition.
+        # Swallows FileNotFoundError (on success path) and other cleanup OSErrors.
+        try:
+            os.unlink(tmp)
+        except OSError:
+            pass