Monthly Archives: February 2021

Java – Wait for Multiple Processes

In Java, the function Process.onExit() creates a CompletableFuture as exit handler and this is the enabling feature in Java to wait for any termination of a set of processes. 

public Process anyProcTermination(List<Process> procs)  {
    CompletableFuture<Process>[] exitHandlers =
            procs.stream()
                    .map(p -> p.onExit())
                    .toArray(CompletableFuture[]::new);
    CompletableFuture<Object> exitHandle = CompletableFuture.anyOf(exitHandlers);
    return  (Process) exitHandle.join();
}

IPv6 resolving hostnames faster

The title of this post might be misleading. IPv6 is not faster than IPv4, but nowadays applications assume IPv6 being the default, having an implication onto the time to establish a connection to a remote host.

Before an application is able to connect to a specific host, first its hostname has got to be resolved via DNS to get to know the corresponding remote IP address.

By default the resolver tries to resolve the corresponding IPv6 address first. If this does not succeed within specific timeout, the resolver is falling back to IPv4.

Thus, if you want to speed up the connection times of your applications, make sure both, your local network and also your internet provider, are supporting IPv6.

If your internet provider does not support native IPv6, it might be better to disable IPv6 in your local network as well, to prevent your local applications from using IPv6 at all.

Do not contract an internet provider for your home area network without IPv6 support!

From the other side of the table, in case you are providing an internet service, your customers might try to connect to your IPv6 service endpoint first, just falling back to IPv4 later. So, your IPv6 endpoint will provide a better usability for your customers.