@Override
    public String toString() {
        return MoreObjects.toStringHelper(this)
                          .add("candidates", candidates)
                          .toString();
    }
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