Zookeeper::RoundRobinBalancer

RoundRobinBalancer.java

public class RoundRobinBalancer implements Balancer {

    private CuratorFramework zkClient;

    public RoundRobinBalancer(CuratorFramework zkClient){
        this.zkClient = zkClient;
    }

    @Override
    public String select() throws Exception {
        List<String> workers = zkClient.getChildren().forPath("/workers");
        if(workers == null){
            return null;
        }
        int size = workers.size();
        if(size == 0){
            return null;
        }

        int round = -1;
        SharedCount sc = new SharedCount(zkClient, "/round", -1);
        boolean success = false;
        try {
            sc.start();
            while(!success){
                round = sc.getCount();
                round++;
                if(round >= Integer.MAX_VALUE){
                    round = -1;
                }
                success = sc.trySetCount(round);
            }
        }finally{
            CloseableUtils.closeQuietly(sc);
        }

        int index = round % size;
        return workers.get(index);
    }

}