ZooKeeper for Java/Spring Config?

Question

Are there any well documented use cases of Apache ZooKeeper being used to distribute configuration of Java applications, and in particular Spring services?

Like many use

Answer 1

After finding a suggestion to use a FactoryBean to populate a regular PropertyPlaceholderConfigurer I've built this:

package fms;

import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.config.AbstractFactoryBean;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.util.Properties;

public class ZkPropertiesFactoryBean extends AbstractFactoryBean implements Watcher {
    private Logger LOGGER = LoggerFactory.getLogger(ZkPropertiesFactoryBean.class);
    private String zkConnect;
    private String path;
    private int timeout = 1000;

    @Override protected Properties createInstance() throws Exception {
        long start = System.currentTimeMillis();
        Properties p = new Properties();
        p.load(new ByteArrayInputStream(loadFromZk()));
        double duration = (System.currentTimeMillis() - start)/1000d;
        LOGGER.info(String.format("Loaded %d properties from %s:%s in %2.3f sec", p.size(), zkConnect, path, duration));
        return p;
    }

    @Override public Class getObjectType() {
        return Properties.class;
    }

    private byte[] loadFromZk() throws IOException, KeeperException, InterruptedException {Stat stat = new Stat();
        ZooKeeper zk = new ZooKeeper(zkConnect, timeout, this);
        return zk.getData(path, false, stat);
    }

    @Override public void process(WatchedEvent event) {}

    public void setPath(String path) {this.path = path;}

    public void setZkConnect(String zkConnect) {this.zkConnect = zkConnect;}
}

In the spring-config.xml you create the beans as follows: