AWS 環境裡面提供 NTP Service 了 (Amazon Time Sync Service)

以前在 AWS 環境裡都要自己架設兩台可以連外的 NTP server,然後將內部機器指到這兩台上,現在可以用現成的了:「Keeping Time With Amazon Time Sync Service」。

服務放在 169.254.169.123

You can access the service via the link local 169.254.169.123 IP address. This means you don’t need to configure external internet access and the service can be securely accessed from within your private subnets.

然後也有提到 leap second 的解法,用的解法是 leap smearing:

Leap seconds are known to cause application errors and this can be a concern for many savvy developers and systems administrators. The 169.254.169.123 clock smooths out leap seconds some period of time (commonly called leap smearing) which makes it easy for your applications to deal with leap seconds.

先前 AWS 也有 leap time,但不包括 Amazon EC2 這些系統 (EC2 裡的時間是獨立的),不過還是可以看一下 AWS 處理 leap time 的方式,因為這次 NTP Service 就會拿去用了。

最近一次 leap time 是 2016 年底的「Look Before You Leap – December 31, 2016 Leap Second on AWS」,處理的方式跟 2015 年時的方法還是一樣:「Look Before You Leap – The Coming Leap Second and AWS (Updated)」。

類似於下圖左上角這張的變化:

然後全區開放,都可以用了:

This service is provided at no additional charge and is immediately available in all public AWS regions to all instances running in a VPC.

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