Question

I have the following code:

import java.net.InetAddress;

public class lookup {

  public static void main(String[] args) throws Exception {
    for(String host : args){
      for(InetAddress addr : InetAddress.getAllByName(host)){
      System.out.println(addr.getHostAddress());
    }
  }
}
}

We recently changed the CNAME for a host we’ll call foo.example.com from pointing at bar.example.com to point at baz.example.com. If I run:

java -Djava.net.preferIPv4Stack=true lookup foo.example.com

I get baz.example.com’s ip address, as expected. However if I run:

java lookup foo.example.com

I still get bar.example.com’s ip address.

I’ve confirmed that neither bar.example.com nor baz.example.com have AAAA records. dig and ping both resolve baz.example.com as expected. How do I get java’s ipv6 stack to properly resolve this?

Answer 1

The problem was nscd was running and had cached the records. Why it didn’t respect the TTLs and why ping doesn’t use the cache are still a mystery.