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A comment on Load balancing and its different types. Parent comment

Re:Load balancing and its different types by samprotas on Tuesday January 26, 2021 @01:32PM (#25919452)
Having executed several "no-downtime" cutovers between systems via DNS updates, I will warn you that a surprising number of clients never re-resolve DNS, so the TTL is effectively "forever" from their point of view.

For the rare case of lift-and-shift-ing for a system upgrade I felt morally okay about eventually pulling the plug on them, but I'd hesitate to design a system that relied on well-behaved DNS clients if I had a reasonable alternative.

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Re:Load balancing and its different types by tyldum on Tuesday January 26, 2021 @05:02PM (#25921581)
Another gotcha would be UDP based services. Since it is packet oriented and not connection oriented, when should it re-resolve? Most will not until the application is restarted.
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Re:Load balancing and its different types by gary_0 on Tuesday January 26, 2021 @02:09PM (#25919887)
When I last updated a domain most clients saw the change within the TTL (1 hour)... except for my cable ISP at home. It took them the better part of a week.
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Re:Load balancing and its different types by xorcist on Tuesday January 26, 2021 @06:03PM (#25922070)
Moving by DNS change isn't usually that bad. The old system (load balancer) can proxy requests to the new system. Most clients will follow DNS but the laggers won't have too much trouble. Assuming the service already works behind a load balancer of course, that is usually not something than can be fork-lifted in.
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