If nameservice caching is disabled, concurrent resolver requests for the same host are currently serialized on a lock [1] which calls the underlying native resolver library. But even without caching, all queued requests for the same host should immediately return the same result given by the underlying native resolver library.

The background for this is that many of our production services completely disable DNS caching because it can only be configured with a granularity in seconds, which is much too high for many use cases. In these cases, hiccups in the local resolver can lead to a high number of queued requests and a high tail latency.

[1] https://github.com/openjdk/jdk/blob/34f241317ecd7473cfb6dcc2e6e5cf3a40299e2c/src/java.base/share/classes/java/net/InetAddress.java#L1043