django 的 LTS

看到「Django 1.11 released」這篇才發現 django 也有設計 LTS 機制... 在「Django’s release process」這邊有介紹:

Certain feature releases will be designated as long-term support (LTS) releases. These releases will get security and data loss fixes applied for a guaranteed period of time, typically three years.

所以是提供三年的維護期...

Amazon Aurora 改善 ALTER TABLE 時增加 column 的速度

Amazon Aurora (MySQL) 提昇了增加 column 操作的速度:「Amazon Aurora Supports Fast DDL Operations」,細節可以在「Amazon Aurora Under the Hood: Fast DDL」這邊看到。

這次加速是限制在 nullable 欄位:

We’re addressing this mess, starting with the most common DDL operation we’ve seen: adding a nullable column at the end of a table.

MySQL 5.6 (Online DDL Overview) 與 5.7 (Online DDL Overview) 都有列出增加 column 需要 rebuild table。

對於一般的 MySQL server 來說,增加 column 這種事情通常都會用 pt-online-schema-change 解決,Amazon Aurora 這個改善算是讓 DBA 可以輕鬆一些...

HashiCorp 的 Packer 出 1.0 版了

HashiCorpPacker 出 1.0 了:「HashiCorp Packer 1.0」。

在 HashiCorp 推出的一串工具裡面算是比較成熟的產品,就算是先前還在 0.12.x 的版本也已經很穩定。

然後 Logo 改了,居然是用 SVG (可以直接開官網看原始碼),只好用截圖的方式:

Amazon EC2 上的 Ubuntu 的效能提昇

UbuntuAWS 合作,對 AWS 上 EC2 的 kernel 最佳化:「Ubuntu on AWS gets serious performance boost with AWS-tuned kernel」。

透過各界面拉出來的 Ubuntu 16.04 都將會是對 kernel 最佳化過的版本了:

As of March 29th, Ubuntu Cloud Images for Amazon have been enabled with the AWS-tuned Ubuntu kernel by default. The AWS-tuned Ubuntu kernel will receive the same level of support and security maintenance as all supported Ubuntu kernels for the duration of the Ubuntu 16.04 LTS.

可以看到大量的改善:

  • Up to 30% faster kernel boot speeds, on a 15% smaller kernel package
  • Full support for Elastic Network Adapter (ENA), including the latest driver version 1.1.2, supporting up to 20 Gbps network speeds for ENA instance types (currently I3, P2, R4, X1, and m4.16xlarge)
  • Improved i3 instance class support with NVMe storage disks under high IO load
  • Increased I/O performance for i3 instances
  • Improved instance initialization with NVMe backed storage disks
  • Disabled CONFIG_NO_HZ_FULL to eliminate deadlocks on some instance types
  • Resolved CPU throttling with AWS t2.micro instances

所以先前打包好的 AMI 都要再重打一次了... @_@

完全分散式的 BitTorrent 搜尋引擎

BitTorrent 已經有足夠的技術與環境 (ecosystem) 做出完全分散式架構的搜尋引擎了,類似於 eDonkey Network (或是說後來變成主流的 eMule) 上的 search 功能,但一直沒看到類似的東西...

magnetico 算是一個嘗試,完全透過 DHT 搜尋取得結果:

不過這套軟體的 license 是攻擊性超強的 AGPLv3,算是實驗性質吧。要真正普及應該要像 eMule 一樣直接做進 client 內...

ScyllaDB 1.7 要支援 Cassandra 的 Counter 了

Counter 是 Cassandra 裡一個特別的資料型態,總算是要 porting 進 ScyllaDB 了:「Scylla 1.7 introduces experimental support for counters」。

由於資料結構的特殊性,在文章裡有提到想像得到的限制:

  • once deleted, counter column value cannot be used again—this is a consequence of the fact that counters can only be incremented or decremented, they cannot be set to any specific value
  • a table cannot contain both counter and regular columns—without this limitation it wouldn’t be possible to provide proper atomicity and isolation guarantees for updates that modify both counters and regular columns in a single row
  • counter columns cannot be members of primary key
  • updates are not idempotent – in case of a write failure the client cannot safely retry the request
    counter columns cannot have time-to-live set

跟 Cassandra 一樣是透過 CRDT 實做的,行為上會是 eventually consistency:

Scylla implements counters using state-based conflict-free replicated data types (CRDT), which allow atomic operations, like increment or decrement, to be performed locally without the need for synchronization between nodes.

在「Scylla Status and Roadmap」這邊可以看到其他會在 1.7 出現的功能。

AWS EU (Stockholm) Region

由老大 Werner Vogels 出來講一些細節...

AWS EU (Stockholm) Region 預定在 2018 年開張營業:「Välkommen till Stockholm – An AWS Region is coming to the Nordics」。

The new AWS EU (Stockholm) Region will have three Availability Zones and will be ready for customers to use in 2018.

這會是歐洲第五個 Region (還有一個法國預定在今年開):

The new AWS EU (Stockholm) Region, coupled with the existing AWS Regions in Dublin, Frankfurt, and London, and a future one in France, will provide customers with quick, low-latency access to websites, mobile applications, games, SaaS applications, big data analysis, Internet of Things (IoT) applications, and more.

微軟的 Time Service 回應錯誤的時間...

看起來會有不少災情 (像是 SQL Server 遇到使用 server side 的時間的 SQL query):「Windows Time Service is sending out wrong times and that’s a big problem」,報導裡引用了 Reddit 上「PSA: time.windows.com NTP server seems to be sending out wrong time」這邊的討論串。

為了避免這種情況,不同單位會用不同方法解決。像是財力充足的 Google 就自己搞了原子鐘,然後還放 Google Public NTP 出來給大家用。可以不倚靠外部裝置確保自家時間的正確性。

另外是有人用 Raspberry Pi 收 GPS 訊號轉成 NTP service (像是「The Raspberry Pi as a Stratum-1 NTP Server」這邊介紹的方式),不過之前有發生過 GPS 送出來的時間差了 13ms 的事情,也不是完全可靠 (不過相較起來應該還是可以接受):「GPS error caused '12 hours of problems' for companies」。另外可能的方案有 GLONASS (俄羅斯的系統)。

也許之後有機會會需要自己架...