@Nullable
    @Override
    public T pick() {
        if (candidates.isEmpty()) {
            return null;
        }

        final int currentSequence = sequence.getAndIncrement();
        return candidates.get(Math.abs(currentSequence % candidates.size()));
    }
A round robin {@link LoadBalancer}.

<p>For example, with node a, b and c, then select result is abc abc ...
core/src/main/java/com/linecorp/armeria/common/loadbalancer/RoundRobinLoadBalancer.java