TTL 是从记录创建时触发，还是像 cron 作业一样以特定时间间隔触发？
Does a TTL get triggered from the time the record is created or at a certain interval like a cron job?
我只是想从记录刷新的确切时间的角度对 TTL 的工作原理有一个基本的了解。假设我在 09:05 UTC 创建了 TTL 为 1800 的 DNS 记录，这是否意味着它将在 09:35 UTC 或 09:30 UTC 刷新？
这种行为对我来说很重要，因为它是后者（记录以 1800 秒的间隔刷新 - 所以每半小时刷新一次），然后我可以为我的 DNS 记录更新计时，以便它们在几分钟的刷新时间，以限制请求指向旧地址的时间。
非常感谢对此的任何帮助。
https://www.varonis.com/blog/dns-ttl/
DNS TTL (time to live) represents the time each step takes for DNS to
cache a record. The TTL is like a stopwatch for how long to keep a DNS
record.
换句话说，TTL 为 1800（30 分钟）的 DNS 记录将“存活”30 分钟......从缓存服务器收到它的时间开始.
来自同一个link:
How Long Will it Take My DNS to Update? To honestly know that everyone
is seeing an updated DNS record, it is essential to calculate how long
it will “actually” take to propagate across DNS. This is accomplished
by using the following formula
TTL X (number of steps) = Fully propagated
For example, if your set TTL is 1800 seconds and there are five steps
(not counting the authoritative server), then your fully propagated
time would be 9000 seconds or no longer than 2 hours and 30 minutes.
我只是想从记录刷新的确切时间的角度对 TTL 的工作原理有一个基本的了解。假设我在 09:05 UTC 创建了 TTL 为 1800 的 DNS 记录，这是否意味着它将在 09:35 UTC 或 09:30 UTC 刷新？
这种行为对我来说很重要，因为它是后者（记录以 1800 秒的间隔刷新 - 所以每半小时刷新一次），然后我可以为我的 DNS 记录更新计时，以便它们在几分钟的刷新时间，以限制请求指向旧地址的时间。
非常感谢对此的任何帮助。
https://www.varonis.com/blog/dns-ttl/
DNS TTL (time to live) represents the time each step takes for DNS to cache a record. The TTL is like a stopwatch for how long to keep a DNS record.
换句话说，TTL 为 1800（30 分钟）的 DNS 记录将“存活”30 分钟......从缓存服务器收到它的时间开始.
来自同一个link:
How Long Will it Take My DNS to Update? To honestly know that everyone is seeing an updated DNS record, it is essential to calculate how long it will “actually” take to propagate across DNS. This is accomplished by using the following formula
TTL X (number of steps) = Fully propagatedFor example, if your set TTL is 1800 seconds and there are five steps (not counting the authoritative server), then your fully propagated time would be 9000 seconds or no longer than 2 hours and 30 minutes.