zookeeper java实例_zookeeper实战之服务注册与发现
zookeeper应用场景
回顾下zk应用场景：
数据发布与订阅
服务注册与发现
分布式锁
分布式队列
master选举
配置中心
命名服务
负载均衡
zookeeper实现服务注册与发现
服务注册与发现
再来看看zk在服务注册与发现中的应用：
代码实现逻辑：
服务注册：
public class ServiceRegister {
private static final String BASE_SERVICES = "/services";
private static final String SERVICE_NAME="/products";
public static void register(String address,int port) {
try {
ZooKeeper zooKeeper = new ZooKeeper("localhost:2181",5000,(watchedEvent)->{});
Stat exists = zooKeeper.exists(BASE_SERVICES + SERVICE_NAME, false);
if(exists==null) {
zooKeeper.create(BASE_SERVICES + SERVICE_NAME,"".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
}
String server_path = address+":"+port;
//创建的临时的有序节点
//临时的话断开连接了可以监听到,有序节点创建代表每一个节点否则相同节点名称无法创建
zooKeeper.create(BASE_SERVICES + SERVICE_NAME+"/child",server_path.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);
System.out.println("产品服务注册成功");
} catch (Exception e) {
e.printStackTrace();
}
}
}
发现服务：
public class InitListener implements ServletContextListener {
private static final String BASE_SERVICES = "/services";
private static final String SERVICE_NAME="/products";
private ZooKeeper zooKeeper;
@Override
public void contextInitialized(ServletContextEvent sce) {
try {
zooKeeper = new ZooKeeper("localhost:2181",5000,(watchedEvent)->{
if(watchedEvent.getType() == Watcher.Event.EventType.NodeChildrenChanged && watchedEvent.getPath().equals(BASE_SERVICES+SERVICE_NAME)) {
updateServiceList();
}
});
updateServiceList();
} catch (Exception e) {
e.printStackTrace();
}
}
private void updateServiceList() {
try{
List children = zooKeeper.getChildren(BASE_SERVICES + SERVICE_NAME, true);
List newServerList = new ArrayList();
for(String subNode:children) {
byte[] data = zooKeeper.getData(BASE_SERVICES + SERVICE_NAME + "/" + subNode, false, null);
String host = new String(data, "utf-8");
System.out.println("host:"+host);
newServerList.add(host);
}
//保存注册服务的ip端口信息，以供远程rpc调用
LoadBalance.SERVICE_LIST = newServerList;
}catch (Exception e) {
e.printStackTrace();
}
}
}
public abstract class LoadBalance {
public volatile static List SERVICE_LIST;
public abstract String choseServiceHost();
}
/**
* 随机负载均衡算法
*/
public class RamdomLoadBalance extends LoadBalance {
@Override
public String choseServiceHost() {
String result = "";
if(!CollectionUtils.isEmpty(SERVICE_LIST)) {
int index = new Random().nextInt(SERVICE_LIST.size());
result = SERVICE_LIST.get(index);
}
return result ;
}
}
再讲讲几个关键点
1.注册服务的时候需要创建临时节点,断开连接的时候也就是服务端挂了后节点删除可监听到
2.注册服务的时候创建的是有序节点,一般来说相同服务都是有几台机器的,创建顺序节点可区分多台机器的服务
3.发现服务的一端监听服务节点的子节点，有子节点被删除了或者有新子节点创建即重新发现服务可用的机器
dubbo中基于zk的服务注册与发现也是这个原理