Route 53 提供 100% SLA,而 Route 53 Resolver 提供 99.99% SLA

AWS 宣佈 Route 53 提供 100% 的 SLA,而 Route 53 Resolver 則提供 99.99% 的 SLA:「Amazon Route 53 Resolver Endpoints announces 99.99% Service Level Agreement and updates its Service Level Agreement for Route 53 hosted zones」。

Route 53 的部份指的是 hosted zone,參考「Amazon Route 53 Service Level Agreement」這邊,可以看到是 2022/08/29 更新的條款。

Route 53 Resolver 的部份可以參考「Amazon Route 53 Resolver Endpoints Service Level Agreement」這邊,也是 2022/08/29 更新的條款。

要注意 99.99% 是指 Multi-AZ Resolver Endpoints SLA;如果是 Single-AZ Resolver Endpoints SLA 看起來是設定在 99.5%。

不確定是不是 AWS 的第一個 100% SLA 條款...

AWS 在同一區不同 AZ 頻寬費用的特別地方

剛好在處理 AWS 同一個 region 下不同 AZ 之間的傳輸費用,跟帳單互相比對,查了以後才發現跟想像中不一樣,這邊以 EC2 為例子,可以參考「Amazon EC2 On-Demand Pricing」這頁裡面的說明。

從 Internet 端進 AWS 的流量是不計費的:

Data Transfer IN To Amazon EC2 From Internet
All data transfer in $0.00 per GB

但從 AZ 進到另外一個 AZ 時,in 與 out 都要收費:

Data transferred "in" to and "out" from Amazon EC2, Amazon RDS, Amazon Redshift, Amazon DynamoDB Accelerator (DAX), and Amazon ElastiCache instances, Elastic Network Interfaces or VPC Peering connections across Availability Zones in the same AWS Region is charged at $0.01/GB in each direction.

所以直接用 US$0.01/GB 的計算是不夠的,得用 US$0.02/GB 來計算。

同樣的,如果是 Public IP 與 Elastic IP 也都是雙向收費,跨 VPC 也是雙向收費,所以都要用 US$0.02/GB 來算:

IPv4: Data transferred “in” to and “out” from public or Elastic IPv4 address is charged at $0.01/GB in each direction.
IPv6: Data transferred “in” to and “out” from an IPv6 address in a different VPC is charged at $0.01/GB in each direction.

AWS 同一區的 VPC Peering 流量不收費了

AWS 在同一個 AZ 裡面的流量是不收費的,但如果是跨帳號的話,還是要當作 inter-AZ 流量 (收 USD$0.01/GB 的費用),現在則是宣佈不用了:「Amazon VPC Announces Pricing Change for VPC Peering」。

要注意的是不同帳號的 a 不一定相同 (像是 us-east-1a 在不同帳號對應到的實際 AZ 不同),得透過 AWS 提供的資料確認底層實際的 AZ 是哪個。

回朔到這個月月初生效:

Starting May 1st 2021, all data transfer over a VPC Peering connection that stays within an Availability Zone (AZ) is now free. All data transfer over a VPC Peering connection that crosses Availability Zones will continue to be charged at the standard in-region data transfer rates. You can use the Availability Zone-ID to uniquely and consistently identify an Availability Zone across different AWS accounts.

AWS 大阪區開放

AWS 大阪區開放給大家使用了,而且有標準的三個 AZ 可以用:「AWS Asia Pacific (Osaka) Region Now Open to All, with Three AZs and More Services」。

大阪區因為之前就已經有機房 (附加在東京區),所以對應的 routing 看起來不算太差,但也沒有特別好... 剛剛測了一下從 HiNet 光世代過去的 latency,分別是 35.5ms (東京的 ap-northeast-1) 與 34.6ms (大阪的 ap-northeast-3)。

另外測了其他的 ISP,有些上日本的點是以東京為主,反而會多繞了一圈,大阪區的 latency 會比較高。

不過如果放遠來說,東京大阪的直線距離大約是 400km,光纖的傳輸速度大約是光速的 2/3,所以單趟大約差了 2ms,如果有機會最佳化的話應該有機會擠出 4ms 出來?

然後是 EC2Pricing 頁面,上面還是寫 Asia Pacific (Osaka-Local),無法確定是新資料還是舊資料,但以往的慣例應該是更新了...

對照文章裡有提到支援的機器,目前看起來還沒有很齊,像是目前都還沒有 AMDARM 架構的機器,另外也沒有 GPU 類型的機器:

The Asia Pacific (Osaka) Region supports the C5, C5d, D2, I3, I3en, M5, M5d, R5d, and T3 instance types, in On-Demand, Spot, and Reserved Instance form. X1 and X1e instances are available in a single AZ.

就支援的類型隨意挑了幾個 instance type 比較,翻了一下價錢看起來跟東京的一樣。

整體看起來,如果是有考慮到異地的需求是可以考慮,另外如果是新的服務的話也可以考慮看看 (畢竟各 ISP 應該有機會再把 latency 壓出來),但既有的服務應該不需要急著搬...

Eventbrite 的 MySQL 升級計畫

在 2021 年看到 EventbiteMySQL 升級計畫:「MySQL High Availability at Eventbrite」。

看起來是 2019 年年初的時候 MySQL 5.1 出問題,後續決定安排升級,在 2019 年年中把系統升級到 MySQL 5.7 (Percona Server 版本):

Our first major hurdle was to get current with our version of MySQL. In July, 2019 we completed the MySQL 5.1 to MySQL 5.7 (v5.7.19-17-log Percona Server to be precise) upgrade across all MySQL instances.

然後看起來是直接在 EC2 上跑,不過這邊提到的空間問題就不太確定了,是真的把 EBS 的空間上限用完嗎?比較常使用的 gp2gp3 上限都是 16TB,不確定是不是真的用到接近爆掉了:

Not only was support for MySQL 5.1 at End-of-Life (more than 5 years ago) but our MySQL 5.1 instances on EC2/AWS had limited storage and we were scheduled to run out of space at the end of July. Our backs were up against the wall and we had to deliver!

另外在升級到 5.7 的時候,順便把本來是 INT 的 primary key 都換成 BIGINT

As part of the cut-over to MySQL 5.7, we also took the opportunity to bake in a number of improvements. We converted all primary key columns from INT to BIGINT to prevent hitting MAX value.

然後系統因為舊版的 Django 沒辦法配合 MySQL 5.7,得升級到 Django 1.6 (要注意 Django 1 系列的最新版是 1.11,看起來光是升級到 1.6 勉強會動就升不上去了?):

In parallel with the MySQL 5.7 upgrade we also Upgraded Django to 1.6 due a behavioral change in MySQL 5.7 related to how transactions/commits were handled for SELECT statements. This behavior change was resulting in errors with older version of Python/Django running on MySQL 5.7

然後採用了 GitHub 家研發的 gh-ost 當作改變 schema 的工具:

In December 2019, the Eventbrite DBRE successfully implemented a table ALTER via gh-ost on one of our larger MySQL tables.

看起來主要的原因是有遇到 pt-online-schema-change 的限制 (在「GitHub 發展出來的 ALTER TABLE 方式」這邊有提到):

Eventbrite had traditionally used pt-online-schema-change (pt-osc) to ALTER MySQL tables in production. pt-osc uses MySQL triggers to move data from the original to the “duplicate” table which is a very expensive operation and can cause replication lag. Matter of fact, it had directly resulted in several outages in H1 of 2019 due to replication lag or breakage.

另外一個引入的技術是 Orchestrator,看起來是先跟 HAProxy 搭配,不過他們打算要再換到 ProxySQL

Next on the list was implementing improvements to MySQL high availability and automatic failover using Orchestrator. In February of 2020 we implemented a new HAProxy layer in front of all DB clusters and we released Orchestrator to production!

Orchestrator can successfully detect the primary failure and promote a new primary. The goal was to implement Orchestrator with HAProxy first and then eventually move to Orchestrator with ProxySQL.

然後最後題到了 Square 研發的 Shift,把 gh-ost 包裝起來變成有個 web UI 可以操作:

2021 還可以看到這類文章還蠻有趣的...

AWS 南韓區開第四個 AZ

AWS 南韓區開第四個 AZ 了,比想像中的快不少:「Now Open – Fourth Availability Zone in the AWS Asia Pacific (Seoul) Region」。

而且不像東京,新客戶只能看到三個 AZ:「Regions and Availability Zones」。

*New customers can access three Availability Zones in Asia Pacific (Tokyo).

雖然台灣過去的 routing 都還是沒改善...

EBS io1 推出可以同時掛到多台的選項

EBS 的 io1 推出了可以同時掛到 16 台 EC2 instance 的選項:「New – Multi-Attach for Provisioned IOPS (io1) Amazon EBS Volumes」。

先看支援的區域,傳統主力區域 (us-east-1 與 eu-west-1) 都支援了,而亞洲區這邊反倒是南韓先支援了:

Multi-Attach for Provisioned IOPS (io1) volumes on Amazon Elastic Block Store (EBS) is available today at no extra charge to customers in the US East (N. Virginia & Ohio), US West (Oregon), EU (Ireland), and Asia Pacific (Seoul) regions.

其中常用的目的是 HA:

Multi-Attach capability makes it easier to achieve higher availability for applications that provide write ordering to maintain storage consistency.

Heartbeat 類的應用應該可以用上這個東西,不過本來就可以透過 command line API 做到 detach & attach,用這個只是少了一個動作...

第二個想到的是,在實體機房的環境下,有些 filesystem (在「Shared-disk file systems」裡面可以翻到一些) 可以同時掛同一個 block storage (通常是透過 SAN),現在在 AWS 上面也可以這樣搞了。

不過 io1 記得不便宜啊...

AWS 大阪區要轉成正式區域

看到 AWS 公佈了大阪區要轉成正式區域的消息:「In the Works – AWS Osaka Local Region Expansion to Full Region」。

大阪區本來是東京區的 local region,主要是提供給東京區的用戶備份以及備援,現在如果變成 full region 的話可以觀察看看 routing,如果從日本西側進骨幹的話,有機會快個 4ms (直線約 400km)?

另外一個是價位不知道會跟東京差多少,畢竟東京週邊的各種物價與地價都算貴的,當然也有可能就全部照日本區的價錢算...

目前喊出來的目標是 2021 年年初會有 3 AZ,也就是標準 region 的架構:

Today, we are excited to announce that, due to high customer demand for additional services in Osaka, the Osaka Local Region will be expanded into a full AWS Region with three Availability Zones by early 2021.

Amazon RDS 推出了 Connection Pool 的產品

Amazon RDS 推出了 Connection Pool 的產品,叫做 Amazon RDS Proxy:「Introducing Amazon RDS Proxy (Preview)」。

目前支援 MySQL (包括了傳統的與 Aurora 版本的):

Amazon RDS Proxy supports Amazon RDS for MySQL and Amazon Aurora with MySQL compatibility, with support for additional RDS database engines coming soon.

定價策略看起來是依照後端資料庫的 vCPU 計算:

Pricing is simple and predictable: you pay per vCPU of the database instance for which the proxy is enabled.

翻了一下價錢頁是 USD$0.015/vCPU (用 us-east-1 的資料),而如果是 t2 系列的機器,最低是以 2 vCPUs 計算,不是照使用比例算:

RDS Proxy pricing correlates to the number of vCPUs of the database instance for which it is enabled, with a minimum charge for 2 vCPUs.

這樣一個 vCPU 一個月大約要 USD$21.6,算起來頗貴的... 如果 SLA 允許的話,用基本的方式 failover 也許就 ok 了...

如果 SLA 真的要追求到這麼高的話,可以在這些區域測試:

Amazon RDS Proxy is available in preview for RDS MySQL and Aurora MySQL in US East (N. Virginia), US East (Ohio), US West (Oregon), EU West (Ireland), and Asia Pacific (Tokyo) regions. Support for RDS PostgreSQL and Aurora PostgreSQL is coming soon.

Canonical 推出的 Dqlite (High-Availability SQLite)

第一眼看到的時候直接有種不知道 Canonical 在幹什麼的感覺,翻完說明後大概知道可以用的地方,但還是覺得範圍有點小:「Dqlite - High-Availability SQLite」。

一種使用情境是,在 embedded system 上面同步資料的一種方案... 吧?例如網路連線的頻寬或是品質受限,無法順利傳到 Internet 端的伺服器上,所以希望在本地端就可以解決一些事情,但又不方便在本地端直接弄個 PostgreSQL 出來?

Dqlite is a fast, embedded, persistent SQL database with Raft consensus that is perfect for fault-tolerant IoT and Edge devices.

另外一個是用到了 C 實做的 Raft 協定:

Dqlite (“distributed SQLite”) extends SQLite across a cluster of machines, with automatic failover and high-availability to keep your application running. It uses C-Raft, an optimised Raft implementation in C, to gain high-performance transactional consensus and fault tolerance while preserving SQlite’s outstanding efficiency and tiny footprint.

讓 IoT 裝置參與 Raft 嗎... 好像只能說有趣... XD