simple ZK discover / query client

ZookeeperTest.java

package com.hazelcast.zookeeper;


import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.curator.x.discovery.ServiceDiscovery;
import org.apache.curator.x.discovery.ServiceDiscoveryBuilder;
import org.apache.curator.x.discovery.ServiceInstance;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

/**
 * Created by vikgamov on 4/13/17.
 */
public class ZookeeperTest {
    private String group;
    private CuratorFramework client;
    private ServiceDiscovery<Void> serviceDiscovery;
    private ServiceInstance<Void> serviceInstance;

    private static final String DEFAULT_PATH = "/discovery/hazelcast";
    private static final String DEFAULT_GROUP = "hazelcast";
    private static final int CURATOR_BASE_SLEEP_TIME_MS = 1000;

    // zookeperUrl {ip-address-of-zookeeper}:{port-of-zookeeper}
    public static void main(String[] args) throws IOException {

        final ZookeeperTest zookeeperTest = new ZookeeperTest();
        final String zookeeperUrl = args[0];
        final CuratorFramework client = zookeeperTest.startCuratorClient(zookeeperUrl);

        Runtime.getRuntime().addShutdownHook(new Thread(client::close));
        System.in.read();
    }

    private void discovery(ServiceDiscovery<Void> serviceDiscovery) {
        try {
            Collection<ServiceInstance<Void>> members = serviceDiscovery.queryForInstances(group);
            List<String> nodes = new ArrayList<>(members.size());
            for (ServiceInstance<Void> serviceInstance : members) {
                String host = serviceInstance.getAddress();
                Integer port = serviceInstance.getPort();

                nodes.add(host + ":" + port);
            }
            System.out.println(nodes);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            throw new IllegalStateException("Error while talking to ZooKeeper", e);
        } catch (Exception e) {
            throw new IllegalStateException("Error while talking to ZooKeeper", e);
        }
    }

    private CuratorFramework startCuratorClient(String zookeeperUrl) {
        if (zookeeperUrl == null) {
            throw new IllegalStateException("Zookeeper URL cannot be null.");
        }

        System.out.println("Using " + zookeeperUrl + " as Zookeeper URL");

        client = CuratorFrameworkFactory.newClient(zookeeperUrl, new ExponentialBackoffRetry(CURATOR_BASE_SLEEP_TIME_MS, 3));
        client.start();

        final ServiceDiscovery<Void> discovery = connectToZk(client);
        discovery(discovery);
        return client;
    }

    private ServiceDiscovery<Void> connectToZk(CuratorFramework client) {
        group = DEFAULT_GROUP;
        ServiceDiscovery<Void> serviceDiscovery;
        try {
            String path = DEFAULT_PATH;
            ServiceDiscoveryBuilder<Void> discoveryBuilder = ServiceDiscoveryBuilder.builder(Void.class)
                    .basePath(path)
                    .client(client);

            serviceDiscovery = discoveryBuilder.build();
            serviceDiscovery.start();
        } catch (Exception e) {
            throw new IllegalStateException("Error while talking to ZooKeeper. ", e);
        }
        return serviceDiscovery;
    }

}