Possible to safely increment BigInteger in a thread safe way, perhaps with AtomicReference, w/o locking?

Question

A lot of our code is legacy but we are moving to a "Big Data" back-end and I'm trying to evangelize the newer API calls, encourage the use of the latest Spring libraries etc. One of our problems is application layer ID generation. For reasons I don't understand, a higher authority wants sequential BigInteger's. I would have made them random with re-generate and re-try on failed insertions but I done got vetoed.

Grumbling aside, I'm in a position where I need to increment and get a BigInteger across threads and do it in a safe and performant manner. I've never used AtomicReference before but it looks pretty close to perfect for this application. Right now we have a synchronized code block which hurts our performance pretty badly.

Is this the right way to go? Syntax examples?

I should mention that the way this module works, it hits the database using a Stored Procedure to grab a range of values to use. Tens of thousands at a time so that it only happens maybe once in 20 minutes. This keeps the various servers from stepping on each-other but it also adds the wrinkle of having to set the BigInteger to an arbitrarily subsequent value. Of course, that needs to be thread safe also.

P.S. I still think my random generation idea is better than handling all this threading stuff. A BigInteger is a ridiculously large number and the odds of ever generating the same one twice have to be close to nil.

Answer 1

It is possible using AtomicReference here's a quick draft :

public final class AtomicBigInteger {

    private final AtomicReference<BigInteger> valueHolder = new AtomicReference<>();

    public AtomicBigInteger(BigInteger bigInteger) {
        valueHolder.set(bigInteger);
    }

    public BigInteger incrementAndGet() {
        for (; ; ) {
            BigInteger current = valueHolder.get();
            BigInteger next = current.add(BigInteger.ONE);
            if (valueHolder.compareAndSet(current, next)) {
                return next;
            }
        }
    }
}

It is basically a copy of the AtomicLong code for incrementAndGet()