Trac 開發版 1.5.1 對 Python 3 的說明

Trac 開發版 1.5.1 的 Change Log 裡可以看到說明:

This will be the only release in the 1.5.x release line that supports Python 2.7. Future releases will support Python 3.5+.

先前在 mailing list 上有看到 Python 3 的計畫,不過好像是第一次在 changelog 裡面看到說明了...

VirtualBox 裡面跑 OS/2 的指引

在「OS/2 on Virtualbox guide」這邊看到在 VirtualBox 上裝 OS/2 的指引,引用的文章在「OS/2 on Virtualbox Guide」這邊。

讓人懷古的東西...

另外文章的作者有提到,有試著在實體機器與其他的 VM 環境裝 (這邊提到了 QEMU),不過結果不太行:

Note: On real hardware, or on other VM platforms, I have found OS/2 to be extremely fragile. When I installed it on my real P1 and P3 Dell machines, I had to reboot multiple times during the setup and driver install processes due to hangs, and I had a ton of issues with random errors on boot.

I also tried all this on QEMU 4.2.0 and had very similar problems, and I had developed some very negative opinions about OS/2's reliability before I switched to Virtualbox and found that it was actually quite solid and the installs went very smoothly.

主要還是有趣吧...

Raspberry Pi 4 推出 8GB 版本

Raspberry Pi 宣佈了 8GB 版本:「8GB Raspberry Pi 4 on sale now at $75」。

除了記憶體變成 8GB 以外,也因為記憶體加大而需要更多電力,所以電供元件的部份也跟著改動,然後也提到 COVID-19 造成的延遲:

To supply the slightly higher peak currents required by the new memory package, James has shuffled the power supply components on the board, removing a switch-mode power supply from the right-hand side of the board next to the USB 2.0 sockets and adding a new switcher next to the USB-C power connnector. While this was a necessary change, it ended up costing us a three-month slip, as COVID-19 disrupted the supply of inductors from the Far East.

超過 4GB 的時候一定會檢視 32-bit 與 64-bit 環境的差異,所以就會發現,在預設的 kernel 因為使用 32-bit LPAE (ARM 上的 PAE),所以雖然是有機會可以使用到 8GB,但單一程式會有 3GB 限制:

Our default operating system image uses a 32-bit LPAE kernel and a 32-bit userland. This allows multiple processes to share all 8GB of memory, subject to the restriction that no single process can use more than 3GB.

目前如果想要原生支援 64-bit 環境的話,需要使用其他作業系統:

But power users, who want to be able to map all 8GB into the address space of a single process, need a 64-bit userland. There are plenty of options already out there, including Ubuntu and Gentoo.

不過另外官方也在測自家的 64-bit 版本,已經有 early beta 版本可以測試看看了 (話說 early beta 這個詞,可以解釋成 alpha 的品質...):

Not to be left out, today we’ve released an early beta of our own 64-bit operating system image. This contains the same set of applications and the same desktop environment that you’ll find in our regular 32-bit image, but built against the Debian arm64 port.

不過上面的 ChromiumFirefox 不完整支援硬體解壓影片的部份還是痛,四代的 CPU 在 YouTube 上是可以硬撐 1080p30 解碼,但畫面順暢度就不太行了,客廳還是用老 Mac Mini (2011 的版本) 來撐場...

微軟開源 1983 年版的 GW-BASIC

微軟用 MIT License 放出 1983 年版的 GW-BASIC:「Microsoft Open-Sources GW-BASIC」。

這次放出來程式看起來是 x86 assembly,不過放出來的版本好像也不能算是「原始」的版本,而是從 "master implementation" 轉譯出來的版本:

This source was ‘translated’?

Each of the assembly source files contains a header stating This translation created 10-Feb-83 by Version 4.3

Since the Instruction Set Architecture (ISA) of the early processors used in home and personal computers weren’t spectacularly different from one another, Microsoft was able to generate a substantial amount of the code for a port from the sources of a master implementation. (Alas, sorry, we’re unable to open-source the ISA translator.)

主要還是 PR,然後帶一些考古價值...

PHP 8 將會移除 XML-RPC,改放到 PECL 內

Twitter 上看到「PHP RFC: Unbundle ext/xmlrpc」這則消息,PHP 官方打算把 XML-RPC (也就是 git repository 裡面的 ext/xmlrpc) 拆出去,移到 PECL

Unbundle ext/xmlrpc (i.e. move it to PECL) without any explicit deprecation.

主要的考慮是在於目前的 library 已經年久失修:

ext/xmlrpc relies on on libxmlrpc-epi, which is abandoned. Even worse, we are bundling a modified 0.51, while the latest version is 0.54.1. This is exacerbated by the fact that the system library is usually built against libexpat, but the bundled library is likely to be built against libxml2 using our compatibility layer.

另外應該也是因為 XML-RPC 用的人不多吧,投票是沒什麼玄念的 50:0,而且在 Packagist 上面也可以翻到一些用 PHP 實做的替代品,拿 xmlrpc 這個關鍵字搜了一下可以看到一些...

用 C 與 Makefile 開發的 Android 專案

上個禮拜在 Hacker News Daily 上看到「cnlohr/rawdrawandroid」這個專案:

Build android apps without any java, entirely in C and Make

看起來包括了 cross-compile 的支援,只要在 Makefile 裡面設定對應的平台就可以了:

You may want to support multiple platforms natively. Add the following to your Makefile: TARGETS:=makecapk/lib/arm64-v8a/lib$(APPNAME).so makecapk/lib/armeabi-v7a/lib$(APPNAME).so makecapk/lib/x86/lib$(APPNAME).so makecapk/lib/x86_64/lib$(APPNAME).so

當然專案的成熟度一定跟很多人用的 Android Studio 這些環境有差,但可以看出作者還是投入了不少精神在上面擴充各種可能性,可以看到這幾天還是一直有在修改文件與程式碼...

另外這個專案也試著讓使用者可以在 Windows 下使用 (透過 WSL 的實做)。

MongoDB 的欺騙性廣告

Jepsen 最近丟出了一篇新的測試報告在測新版的 MongoDB 4.2.6,而且語氣看起來比以前兇很多,翻了一下前因後果,看起來起因是出自 Twitter 上的這則推,提到了 MongoDB 拿 Jepsen 宣傳的頁面:

然後 Jepsen 的官方帳號這邊也回應,覺得不可置信:

過兩個禮拜後 Jepsen 就丟出由老大 Kyle Kingsbury 發表的「Jepsen: MongoDB 4.2.6」,這篇測試 MongoDB 4.2.6 最新版的測試報告了。

在這篇報告裡面提到了很多不道德的行為,首先是在之前的測試發現有很多會掉資料的問題,但在 MongoDB 官方的宣傳文件「MongoDB and Jepsen」裡面則是完全沒提到,而且還宣稱有業界最強的資料一致性與正確性 (與 Jepsen 報告所提供的資料不符),所以 Jepsen 建議把這些問題列到這個頁面上,以避免使用者受到「誤解」:

Curiously, MongoDB omitted any mention of these findings in their MongoDB and Jepsen page. Instead, that page discusses only passing results, makes no mention of read or write concern, buries the actual report in a footnote, and goes on to claim:

MongoDB offers among the strongest data consistency, correctness, and safety guarantees of any database available today.

We encourage MongoDB to report Jepsen findings in context: while MongoDB did appear to offer per-document linearizability and causal consistency with the strongest settings, it also failed to offer those properties in most configurations. We think users might want to be aware that their database could lose data by default, but MongoDB’s summary of our work omits any mention of this behavior.

另外當然就是重測 MongoDB 4.2.6 版,沒時間看內容的人可以先瞄一下標題,裡面就已經點出不少東西了:

3 Results
3.1 Sometimes, Programs That Use Transactions… Are Worse
3.2 How ACID is Snapshot Isolation, Anyway
3.3 Indeterminate Errors
3.4 Duplicate Effects
3.5 Read Skew
3.6 Cyclic Information Flow
3.7 Read Your (Future) Writes

不過在最後面的 Discussion 比較清楚。

首先是批評 snapshot isolation 不是 ACID:

MongoDB 4.2.6 claims to offer “full ACID transactions” via snapshot isolation. However, the use of these transactions is complicated by weak defaults, confusing APIs, and undocumented error codes. Snapshot isolation is questionably compatible with the marketing phrase “full ACID”. Even at the highest levels of read and write concern, MongoDB’s transaction mechanism exhibited various anomalies which violate snapshot isolation.

Snapshot isolation is a reasonably strong consistency model, but claiming that snapshot isolation is “full ACID” is questionable.

而且即使把所有的資料安全性相關的設定都調到最高,也根本就做不到宣稱的 snapshot isolation:

Finally, even with the strongest levels of read and write concern for both single-document and transactional operations, we observed cases of G-single (read skew), G1c (cyclic information flow), duplicated writes, and a sort of retrocausal internal consistency anomaly: within a single transaction, reads could observe that transaction’s own writes from the future. MongoDB appears to allow transactions to both observe and not observe prior transactions, and to observe one another’s writes. A single write could be applied multiple times, suggesting an error in MongoDB’s automatic retry mechanism. All of these behaviors are incompatible with MongoDB’s claims of snapshot isolation.

過程中也發現就算設定了 snapshot 層級,MongoDB 在讀取時也不會遵守 snapshot isolation:

MongoDB’s default read and write concern for single-document operations remains local, which can observe uncommitted data, and w: 1, which can lose committed writes. Even when users select safer settings in their clients at the database or collection level, transactions ignore these settings and default again to local and w: 1. The snapshot read concern does not actually guarantee snapshot isolation, and must always be used in conjunction with write concern majority. This holds even for transactions which perform no writes.

然後所有的官方文件都沒有教 snapshot isolation 要怎麼設定,你必須在第三方的文件上才有機會找到:

Nor can users rely on examples to demonstrate snapshot isolated behavior. MongoDB’s transaction documentation and tutorial blog posts show only write-only transactions, using read concern local rather than snapshot. Other examples from MongoDB don’t specify a read concern or run entirely with defaults. Learn MongoDB The Hard Way uses read concern snapshot but write concern local, despite performing writes. Tutorials from DZone, Several Nines, Percona, The Code Barbarian, and Spring.io all claim that transactions are either ACID or offer snapshot isolation, but none set either read or write concern. There are some examples of MongoDB transactions which are snapshot isolated—for instance, from BMC, +N Consulting, and Maciej Zgadzaj, but most uses of MongoDB transactions we found ran—either intentionally or inadvertently—with settings that would (in general) allow write loss and aborted reads.

基本上就是一個老大被惹怒了,丟出來炸,而且看他的語氣還有很多東西沒測,打算要再炸一篇?

WireGuard 的 OpenBSD porting

在「WireGuard patchset for OpenBSD」這邊看到有人試著把 WireGuard 放入 OpenBSD 的消息。

整包 patchset 包括了 kernel 與 userland 的實做,可以在 mailing list 上「WireGuard patchset for OpenBSD」這邊可以看到,整串討論可以在「'WireGuard patchset for OpenBSD' thread - MARC」這邊看到,目前看起來還在 code review 的階段,有看到討論提到應該用 OpenBSD 內已經實做的 Chacha20-Poly1305,所以可能還會需要一些時間...

看起來慢慢的在滲進每個作業系統中,蠻有希望在幾年後成為業界標準...

模擬 Windows XP 風格的 CSS

Hacker News 首頁上翻到的,先前提到的「模擬 Windows 98 風格的 CSS」是對 Windows 98 風格設計出的 CSS,接下來就有人也生出經典的 Windows XP 版本出來:「XP.css」。

XP.css started as a fork of 98.css (a fun project started by Jordan Scales) and is now trying to boilerplate the GUI to be able to theme it easily.