LuciferYang opened a new issue, #7701:
URL: https://github.com/apache/kyuubi/issues/7701
### Describe the bug
`JavaUtils.findLocalInetAddress()` returns `InetAddress.getLocalHost()`
unchanged unless it is loopback. When it is, the method scans network
interfaces for an address that is neither loopback nor link-local and warns
that it is substituting one. That warning reads its host name and loopback
address from the substitute rather than from the address that resolved to
loopback:
```java
LOG.warn(
"{} was resolved to a loopback address: {}, using {}",
addr.getHostName(),
addr.getHostAddress(),
strippedAddress.getHostAddress());
```
`addr` is the interface address just picked. On a host with no PTR record
for it, `addr.getHostName()` returns the numeric form and all three slots print
the same string:
```
10.0.0.5 was resolved to a loopback address: 10.0.0.5, using 10.0.0.5
```
So the line never says which host was resolved or what it resolved to. The
fallback warning in the same method, taken when no interface has a usable
address, reads from the original address, so the two warnings disagree about
their subject.
There is a second cost. `addr` carries no cached host name, so
`addr.getHostName()` goes to the resolver, and the call sits in the argument
list of the `warn` invocation, so it runs whether or not WARN is enabled.
Timings for that one call on a single host at different times: 0.9 ms, 1.8 ms,
6.5 ms, 324 ms, 1027 ms, 3147 ms, each returning the numeric form. The tail is
the problem, not the median. `InetAddress.getLocalHost()` already carries its
name, so reading from it costs nothing.
The branch is only entered on a host whose name resolves to loopback, which
is the Debian and Ubuntu default (`127.0.1.1` in `/etc/hosts`) and common on
developer machines. Hosts with a routable name never see it.
### Affects Version(s)
master (1.13.0-SNAPSHOT), 1.12, 1.11, 1.10. Introduced by the Java rewrite
in #6499; the Scala predecessor used the original address in both slots.
### Are you willing to submit PR?
Yes.
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