List iterators lose an item when loading the next page fails

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Issue 類型
缺陷
描述清晰度
描述清楚
活躍度
活躍
技術堆疊
java
領域
backend

研究方向

從 core/src/main/java/com/backblaze/b2/client/B2ListFilesIterableBase.java 中的 next()(約第 43-58 行)開始,這裡 currentIndex 在 advanceIfNeeded() 可能拋出例外之前就已遞增;同樣的模式也出現在 B2ListPartsIterableBase.java 約第 30-45 行。撰寫一個測試,使用模擬客戶端,在載入第二頁時失敗,然後在捕捉例外後再次呼叫 next(),以確認該元素遺失。當兩個迭代器都能正確回傳或重試該元素且測試通過時,即視為完成。

由索引模型根據 Issue 內容生成。

描述

What happens

In next(), the iterator moves past the current item and then loads the next page if the current page is used up. If that page load fails, B2RuntimeException is thrown from next() and the item that was just taken is not returned. A caller that catches the exception and continues will not see that item, and the next next() call fails with an IllegalStateException instead of retrying the page.

Where

core/src/main/java/com/backblaze/b2/client/B2ListFilesIterableBase.java:43-58 (next() at about :50 increments currentIndex, then calls advanceIfNeeded()); the same pattern is in core/src/main/java/com/backblaze/b2/client/B2ListPartsIterableBase.java:30-45.

Why it matters

Impact: Wrong request or result (a listing silently misses an item for a caller that continues after the error), loud for the failed call. Severity: Medium, because it needs a page load that fails after retries and a caller that catches the error and keeps iterating (unusual), and a caller that stops on the first error is not affected.

How to check

Found by reading the code, not reproduced. Read next(): the value is read and currentIndex incremented before advanceIfNeeded() can throw. A test with a mocked client that fails on the second page load, and a caller that catches the exception and calls next() again, would show the missing item. Advancing lazily in hasNext() or returning the item before advancing would avoid it.

Version

Seen at v6.5.0. Present on the default branch: present.

主要語言
Java
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103
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