拿 Cloudflare Workers 跑 Geolocation API

Hacker News Daily 上看到拿 Cloudflare Workers 跑 Geolocation API:「How to make simple Geolocation service」。

作者想要做一個很簡單的 Geolocation API,一開始的想法是在 AWS Lambda 上用 MaxMind 的資料,但 latency 偏高:

However, I quickly realized that the response time isn't what I've expected - on average the response took somewhere between from 200ms to 500ms. So I started looking for other options.

所以作者就想到是不是有有機會丟到 Cloudflare Workers 上,但發現 license 看起來是個問題,另外因為把 MaxMind 的資料庫丟進去,會超過 worker 的時間限制:

And for this case MaxMind offers GeoLite2 database, however you'll be in charge of hosting this database on your server and making regular updates of the database. You also need to make sure your project is compliant with MaxMind's License.

However, this solution had one really big caveat - MaxMind GeoLite2 database does not work on Cloudflare Workers due to some runtime limitations.

結果作者後來發現 Cloudflare Workers 上本身就會帶 Geoloation 資訊了,不需要另外拉 MaxMind 的資料查:

And after exploring their documentation, I realized that the Request object in function have an access to cf object, which contains some useful information about the visitor, including visitor's country!

另外我翻了一下價錢,主要是算次數的,看起來 Free Plan 就可以 100K/day (執行時間限制是 10ms),而如果是付費方案的話則是 USD$0.5/M (50ms),這樣對一些小專案來說,Free Plan 似乎是夠用了...

Lambda 可以掛 EFS 了

AWS Lambda 可以掛 Amazon EFS 了:「New – A Shared File System for Your Lambda Functions」。

這有點像是一開始 Amazon EC2 只能把資料存到 Amazon S3 上,後來支援 EBS 的感覺:這使得很多程式可以直接用內建的 library 操作檔案系統,而不需要掛 AWS 專用的 library 操作 Amazon S3。

有了一個 filesystem 後馬上就可以想到很多惡搞的方法,像是用 lambda 搞 serverless PHP 之類的,之後應該會看到很有「創意」的玩法...

Lambda 被放進 Savings Plans 了

前幾天才在 Ptt 上回了一些對 Lambda 與 Serverless 的想法,結果剛剛看到 Lambda 被納入 Savings Plans 裡面了:「Savings Plan Update: Save Up to 17% On Your Lambda Workloads」。

最多 17% 的折扣,看起來比其他的低不少,應該是因為 Lambda 比起 EC2 或是 Fargate 更動態的關係:

Today I am happy to be able to tell you that Compute Savings Plans now apply to the compute time consumed by your AWS Lambda functions, with savings of up to 17%.

現有的 Savings Plans 如果沒有用完的部份也會自動套用進去。先放著看看...

AWS Lambda 的 Provisioned Concurrency

AWS Lambda 推出了 Provisioned Concurrency,降低冷啟動所需要的時間以確保效率:「New – Provisioned Concurrency for Lambda Functions」。

看 benchmark 的資料就很清楚,可以避免冷啟動所產生的延遲:

這邊也可以看出來就算是冷啟動,大約也是多個一秒多。如果這個延遲是需要被處理的,就可以考慮用 Provisioned Concurrency 了。


You only pay for the amount of concurrency that you configure and for the period of time that you configure it. Pricing in US East (N. Virginia) is $0.015 per GB-hour for Provisioned Concurrency and $0.035 per GB-hour for Duration. The number of requests is charged at the same rate as normal functions. You can find more information in the Lambda pricing page.

不過如果量再更大,而且考慮成本,應該會考慮改回傳統的架構,用多台 EC2 instance 跑...

AWS 推出了 Live 時全自動上字幕的功能

AWS 推出了在直播時就自動上字幕的功能:「Introducing Live Streaming with Automated Multi-Language Subtitling」,其實就是把現有的服務兜出來:「Live Streaming with Automated Multi-Language Subtitling」。

The solution deploys Live Streaming on AWS which includes AWS Elemental MediaLive, MediaPackage, Amazon CloudFront. The solution also deploys AWS Lambda, Amazon Simple Storage Service, Amazon Transcribe, and Amazon Translate.


DynamoDB Autoscaling 的各種眉眉角角...

AdRollDynamoDB Autoscaling 的踩雷記錄,裡面有些資訊如果不是跳下去玩應該不會注意到 (魔鬼藏在細節裡的感覺):「Managing DynamoDB Autoscaling with Lambda and Cloudwatch」。

第一個提到的問題是 autoscaling 的觀察對象:

Ideally, the table should scale based on the number of requests that we are making , not the number of requests that are successful.

另外一個是 autoscaling 遇到完全不用的情況下不會 scale down,看起來是某種保護機制。但這使得平常只有拿來讀取的表格在跑完 batch job 後得自己處理 write scale down 問題:

Additionally, at the time of implementing this algorithm, the DynamoDB capacity could not be brought down automatically if the consumption was exactly zero, which can happen if you write to your table in batch instead of realtime, for example.

This meant that, when enabling autoscaling, tables that were read in realtime, but written to in batch, still needed manual intervention to bring the write capacity down after our jobs were done writing.

另外一個問題是 scale down 是有次數限制的:

Another interesting point that might bite users is that capacity decreases are an expensive operation for AWS, so they’re limited.

The number of decreases cited in the documentation can be achieved under very special conditions, since you need to have 4 decreases in the first hour of the day plus one for each of the remaining hours, for a total of 4 (first hour) + 23 (1 hourly) = 27.

後面就是自己研究什麼 algorithm 可以調整的更細,然後用 lambda 重寫... 最後省下 30% 的成本:

Here is where we detected our costs for our batch tables dropping to around 30% of the initial cost.

AdRoll 的規模應該是不小,所以為了省 30% 可以花不少力氣在上面...

AWS Lambda 可以直接掛進 ALB 了...

AWS 這次對 Lambda 還發表了不少功能,除了前面提到透過 Layout 支援其他語言以外 (e.g. Ruby),這邊要再提到另外一個重要的功能。

這次是 ALB 可以直接呼叫 lambda function 了:「Lambda functions as targets for Application Load Balancers」。

以前還得靠 API Gateway 整半天 (因為版本設定),現在直接用 ALB 接就可以了?而且 ALB 這邊有規劃對應的 quota:

There is no change to the hourly price of ALB. The load balancer capacity units (LCUs) of ALB now include 0.4 GB per hour of data processing to AWS Lambda targets.

這樣就更接近 serverless 了...

AWS Lambda 支援 Ruby 2.5 以及其他語言

AWS 宣佈 Lambda 支援 Ruby 2.5:「AWS Lambda Supports Ruby」。

另外宣佈可以透過 Layer 的方式讓任何程式語言在上面跑 (前面提到的 Ruby 看起來就是用這個方式支援的):「New for AWS Lambda – Use Any Programming Language and Share Common Components」。

The Runtime API is the future of how we’ll support new languages in Lambda. For example, this is how we built support for the Ruby language.

Amazon API Gateway 推出分級收費 (降價)

Amazon API Gateway 推出分級收費:「Amazon API Gateway Announces Tiered Pricing」。

原先的費用不變,大多數的地區是超過 333M reqs/month 的部分降價了... (不過雪梨跟南非是超過 1B reqs/month,而且北卡超過 333M 的部分也只降個零頭,實際比較深的折扣還是在 1B),333M reqs/month 這個量換算下來需要 11.1M reqs/day,平均值要 128 reqs/sec,看起來是設計給整個站都搬上去的折扣方案 (不然就是本身量就超大)。

AWS Lambda 也提供 SLA 了

在「AWS Lambda announces service level agreement」這邊看到 AWS Lambda 提供 99.95% 的 SLA :

We have published a service level agreement (SLA) for AWS Lambda. We will use commercially reasonable efforts to make Lambda available with a Monthly Uptime Percentage for each AWS region, during any monthly billing cycle, of at least 99.95% (the “Service Commitment”).

不過這種東西都是宣示意味比較重 (至少表示 AWS 認為產品穩定度夠上 SLA),倒不是希望會用到...