热评：Load balancing via DNS is entirely dependent on the behavior of caching DNS resolvers. Clients are beholden to how answers are sorted and it’s rarely fair. Even with a zero second TTL, the TTL of answers is often ignored. The situation is even worse with a TTL, as the answers are rarely re-resolved after the expiration. The JVM, for example, is notorious for defaulting to ignoring TTL entirely ruining round-robin load abounding via DNS. That’s not to say that it can’t be defective but its limitations should be well understood.
通过 DNS 实现负载平衡完全取决于缓存 DNS 解析器的行为。客户端受制于答案的排序方式，而这种排序方式很少是公平的。即使是零秒 TTL，答案的 TTL 也经常被忽略。如果使用 TTL，情况会更糟，因为答案很少会在过期后重新解析。例如，JVM 因默认完全忽略 TTL 而破坏了 DNS 的循环负载而臭名昭著。这并不是说它不可能有缺陷，但我们应该充分了解它的局限性。

Hyperknot

Understanding Round Robin DNS

In which I try to understand how browsers and Cloudflare choose which server to use

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