前言

程序猿: 今天天氣晴朗，是個適合在家踩地雷的好日子😎

這次中雷的前提是「使用 Cloudflare 做為 MinIO 的網域 Proxy，並開啟 Cache 功能」。

我不知道其它的 S3-like storage 會不會發生，但既然 MinIO SDK 上的 issue 因「Our sdks are validated for highest s3 compatibility so it does not require any fix in the SDK.」而關閉，應該是都會發生吧...

TL;DR 先說結論

在 Cloudflare 上新增 CacheRule，將整個網域 Bypass cache。

遇到問題

我正在寫 Recorder.moe 專案，實作接 MinIO 伺服器作為 Object Storage。其中有一段邏輯使用 StatObject 檢查影片檔案是否存在，而它一直報錯權限不足。

當然，我來回的檢查了 MinIO 上的權限設定，並把 MinIO doc 仔細讀過了一次，確認了我的權限設定並沒有錯。

接著，我使用 mc (minio client) 登入了 root account，並執行了以下的 command:

jim60105 ~ ❯❯❯ mc ls minio/livestream-recorder/videos/
[2023-07-29 21:48:20 CST] 6.1GiB STANDARD _0mKSCIcuiy4.mp4
[2023-07-29 21:48:20 CST] 4.0GiB STANDARD _7_oxT9-XtNs.mp4
[2023-07-29 21:48:20 CST] 1.8GiB STANDARD _I-GNO2YlXOU.mp4
[2023-07-29 21:52:01 CST] 2.0GiB STANDARD _QhYxULIUaoE.mp4
[2023-07-29 21:48:20 CST] 2.4GiB STANDARD _aPI2iLpATvQ.mp4
[2023-07-29 21:48:20 CST] 4.7GiB STANDARD _b0FnpGNF_8Q.mp4
[2023-07-29 21:48:20 CST] 1.6GiB STANDARD _lUeEngcdDb8.mp4
[2023-07-29 21:51:52 CST]  91MiB STANDARD _olHwcQXvCGg.mp4
jim60105 ~ ❯❯❯ mc stat minio/livestream-recorder/videos/_aPI2iLpATvQ.mp4
mc.exe: <ERROR> Unable to stat `minio/livestream-recorder/videos/_aPI2iLpATvQ.mp4`. Insufficient permissions to access this path `https://s3.recorder.moe/livestream-recorder/videos/_aPI2iLpATvQ.mp4`.

蛤，這是 root account 耶

發現問題

我試了好幾種關鍵字，最後用「minio stat no permission」搜到了這個 issue。

最下方的另一個 mentioned issue 講明了問題發生的原因

Same problem here, we were using statObject in our platform, now we started using cloudflare and it stopped working.

The "it is not a bug, it is a feature" is documented in cloudflare:
https://developers.cloudflare.com/cache/best-practices/cache-behavior/#interaction-of-head-requests-with-cache

I think the problem could be in the HEAD and GET endpoints not working in the same way. If our system makes a HEAD call and cloudflare does not have it cached, it converts it to the same GET call, and returns only the headers of the response (which should be the same as if we make a HEAD call). The problem comes when the HEAD and GET endpoints behaviours are not the same.

嗯，看來 MinIO 在 GET 和 HEAD 的處理上不同。然後?

Cloudflare 的 document 寫了這些

Cloudflare converts HEAD requests to GET requests for cacheable requests.

When you make a HEAD request for a cacheable resource and Cloudflare does not have that resource in the edge cache, a cache miss happens. Cloudflare will send a GET request to your origin, cache the full response and return the response headers only. Make sure the origin server is setup to handle GET requests, even if only HEAD requests are expected, so that compatibility with this behavior is ensured.

好喔，就你在搞

解決問題

知道兇手就好解決了，在 Cloudflare 上新增 CacheRule，將整個網域 Bypass cache

結案