Stage 08 · 目录 fsync 与启动清理

目标

验证父目录持久性，并在启动时清理临时或未引用的崩溃残留。

动手任务

从stage-07开始，强化并测试 atomic_write、durable_mkdir、DiskStorage.load_buckets 与清理路径。 行为必须留在下列源码同构边界中；不要先复制补丁。

交付文件

• tests/test_storage.py

自查

1. 本阶段的可见性或状态迁移由谁负责？

   答案

   只有对所在目录执行 fsync，原子 rename 才成为持久发布。

2. 如果绕过新边界，哪个测试会最先失败？

   答案

   阅读 tests.txt，找出最窄的新节点，并说出它覆盖的公开调用。

通关命令

uv run pytest -q $(cat journey/stages/08-fsync-recovery/tests.txt)

对应真实 S3 的一课

只有对所在目录执行 fsync，原子 rename 才成为持久发布。

教材

第 5 章

在 GitHub 查看阶段差异

完成后可运行 git checkout stage-08 对照你的结果。

先做后看：stage.patch

diff --git a/tests/test_storage.py b/tests/test_storage.py
index 5faad97..afc9a8a 100644
--- a/tests/test_storage.py
+++ b/tests/test_storage.py
@@ -1,7 +1,9 @@
 """Disk tests pin the manifest publication crash boundary."""

 from pathlib import Path
+
 import pytest
+
 from minis3 import InjectedCrash, MiniS3, NoSuchKey, SequenceCounter
 from minis3.bucket import Bucket
 from minis3.storage import atomic, disk
@@ -96,3 +98,57 @@ def test_crash_after_manifest_publish_exposes_complete_new_state(
     visible = reopened.get_object("b", "new")
     assert visible.body == b"value"
     assert visible.etag == '"2063c1608d6e0baf80249c42e2be5804"'
+
+
+def test_atomic_write_fsyncs_each_new_directory_parent(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    calls: list[Path] = []
+    real_fsync_directory = atomic.fsync_directory
+
+    def recording_fsync_directory(path: Path) -> None:
+        calls.append(path)
+        real_fsync_directory(path)
+
+    monkeypatch.setattr(atomic, "fsync_directory", recording_fsync_directory)
+
+    atomic.atomic_write(tmp_path / "one" / "two" / "value", b"payload")
+
+    assert calls == [tmp_path, tmp_path / "one", tmp_path / "one" / "two"]
+
+
+def test_storage_and_bucket_directory_creation_fsync_parent_chains(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    calls: list[Path] = []
+    real_fsync_directory = disk.fsync_directory
+
+    def recording_fsync_directory(path: Path) -> None:
+        calls.append(path)
+        real_fsync_directory(path)
+
+    monkeypatch.setattr(disk, "fsync_directory", recording_fsync_directory)
+    monkeypatch.setattr(atomic, "fsync_directory", recording_fsync_directory)
+    root = tmp_path / "new-root"
+    storage = DiskStorage(root)
+    storage.create_bucket(Bucket("b"))
+
+    bucket_directory = storage._bucket_directory("b")
+    temporary = storage.buckets_root / f".tmp-{bucket_directory.name}"
+    assert tmp_path in calls
+    assert calls.count(root) >= 1
+    assert calls.count(storage.buckets_root) >= 2
+    assert calls.count(temporary) >= 2
+
+
+def test_recovery_removes_spurious_tmp_files(tmp_path: Path) -> None:
+    store = MiniS3(tmp_path)
+    store.create_bucket("b")
+    stray = next((tmp_path / "buckets").iterdir()) / "manifest.json.tmp-stray"
+    stray.write_text("partial")
+
+    MiniS3(tmp_path)
+
+    assert not stray.exists()