Github user NicoK commented on the issue:
https://github.com/apache/flink/pull/5449
Thanks @StephanEwen indeed - I also did not grasp the full intend of the
change.
Looking at the code again, basically
`ConnectionUtils#findConnectingAddress()` tries to connect with a set of
strategies for a given time and if that passes, it will fall back to the
heuristic. We could argue that if we do not find an interface to connect to the
target address in a given time, we may not do too much about it rather than (a)
failing now, (b) retrying forever, or (c) trying some heuristic that may work
or fail later. The latter is implemented and seems sensible - we also print
warnings to the log in that case.
For the unit test, however, I think, the actual check should be reduced to
"does return something and does not block" since according to the code in
`ConnectionUtils` we wouldn't verify the heuristic was successful anyway:
```
// our attempts timed out. use the heuristic fallback
LOG.warn("Could not connect to {}. Selecting a local address
using heuristics.", targetAddress);
InetAddress heuristic =
findAddressUsingStrategy(AddressDetectionState.HEURISTIC, targetAddress, true);
if (heuristic != null) {
return heuristic;
}
else {
LOG.warn("Could not find any IPv4 address that is not
loopback or link-local. Using localhost address.");
return InetAddress.getLocalHost();
}
```
We could maybe cycle through `InetAddress.getAllByName("localhost")` and
verify the returned value is in there - unless I read this wrong - but I don't
know if that check is of any actual value, to be honest.
If we wanted to test for more, the only outside sign of the heuristic
strategy being used is to look at the logs.
---
