Curator操作zookeeper

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转自：http://blog.csdn.net/top_code/article/details/53559160点击打开链接

服务发现

随着微服务的日趋火爆，系统拆分之后，各个服务模块的Provider和Consumer之间需要能够查找到对方，我们称之为服务发现。

In SOA/distributed systems, services need to find each other. i.e. a web service might need to find a caching service, etc. DNS can be used for this but it is nowhere near flexible enough for services that are constantly changing. A Service Discovery system provides a mechanism for:
Services to register their availability
Locating a single instance of a particular service
Notifying when the instances of a service change

Curator Service Discovery

Curator Service Discovery就是为了解决这个问题而生的，它对此抽象出了ServiceInstance、ServiceProvider、ServiceDiscovery三个接口，通过它我们可以很轻易的实现Service Discovery。

实践

假如我们需要对外提供一个服务（com.bytebeats.service.HelloService），为了保证服务的高可用行 HelloService服务部署在N台机器上，现在Consumer想要请求这个服务，如何保证HelloService可以灵活部署（随意增加/删除机器）？

思路

首先，HelloService Provider在启动时向Zookeeper 注册本机提供的服务名称、端口号和地址；Consumer启动的时候先查询Zookeeper获取到服务Provider列表，然后通过负载均衡算法（随机、RoundRobin、一致性Hash）选择一台机器去调用服务。

代码实现

Maven依赖

<dependency>    <groupId>org.apache.curator</groupId>    <artifactId>curator-x-discovery</artifactId>    <version>2.11.1</version></dependency>1
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ServerApp.java

package com.bytebeats.zookeeper.curator.discovery;import com.bytebeats.zookeeper.curator.CuratorUtils;import com.bytebeats.zookeeper.curator.discovery.domain.ServerPayload;import com.bytebeats.zookeeper.util.JsonUtils;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.x.discovery.ServiceInstance;import org.apache.curator.x.discovery.UriSpec;import java.util.Collection;import java.util.concurrent.TimeUnit;/** * 模拟服务提供者 * * @author Ricky Fung * @create 2016-12-08 19:24 */public class ServerApp {    public static final String BASE_PATH = "services";    public static final String SERVICE_NAME = "com.bytebeats.service.HelloService";    public static void main(String[] args) {        CuratorFramework client = null;        ServiceRegistry serviceRegistry = null;        try{            client = CuratorUtils.getCuratorClient();            client.start();            serviceRegistry = new ServiceRegistry(client, BASE_PATH);            serviceRegistry.start();            //注册两个service 实例            ServiceInstance<ServerPayload> host1 = ServiceInstance.<ServerPayload>builder()                    .id("host1")                    .name(SERVICE_NAME)                    .port(21888)                    .address("10.99.10.1")                    .payload(new ServerPayload("HZ", 5))                    .uriSpec(new UriSpec("{scheme}://{address}:{port}"))                    .build();            serviceRegistry.registerService(host1);            ServiceInstance<ServerPayload> host2 = ServiceInstance.<ServerPayload>builder()                    .id("host2")                    .name(SERVICE_NAME)                    .port(21888)                    .address("10.99.1.100")                    .payload(new ServerPayload("QD", 3))                    .uriSpec(new UriSpec("{scheme}://{address}:{port}"))                    .build();            serviceRegistry.registerService(host2);            System.out.println("register service success...");            TimeUnit.MINUTES.sleep(1);            Collection<ServiceInstance<ServerPayload>> list = serviceRegistry.queryForInstances(SERVICE_NAME);            if(list!=null && list.size()>0){                System.out.println("service:"+SERVICE_NAME+" provider list:"+ JsonUtils.toJson(list));            } else {                System.out.println("service:"+SERVICE_NAME+" provider is empty...");            }        } catch (Exception e) {            e.printStackTrace();        } finally {            if(serviceRegistry!=null){                try {                    serviceRegistry.close();                } catch (Exception e) {                    e.printStackTrace();                }            }            client.close();        }    }}1
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ServiceRegistry.java

package com.bytebeats.zookeeper.curator.discovery;import com.bytebeats.zookeeper.curator.discovery.domain.ServerPayload;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.x.discovery.ServiceDiscovery;import org.apache.curator.x.discovery.ServiceDiscoveryBuilder;import org.apache.curator.x.discovery.ServiceInstance;import org.apache.curator.x.discovery.details.JsonInstanceSerializer;import java.util.Collection;/** * 服务注册 * * @author Ricky Fung * @create 2016-12-08 19:16 */public class ServiceRegistry {    private ServiceDiscovery<ServerPayload> serviceDiscovery;    private final CuratorFramework client;    public ServiceRegistry(CuratorFramework client, String basePath){        this.client = client;        serviceDiscovery = ServiceDiscoveryBuilder.builder(ServerPayload.class)                .client(client)                .serializer(new JsonInstanceSerializer<>(ServerPayload.class))                .basePath(basePath)                .build();    }    public void updateService(ServiceInstance<ServerPayload> instance) throws Exception {        serviceDiscovery.updateService(instance);    }    public void registerService(ServiceInstance<ServerPayload> instance) throws Exception {        serviceDiscovery.registerService(instance);    }    public void unregisterService(ServiceInstance<ServerPayload> instance) throws Exception {        serviceDiscovery.unregisterService(instance);    }    public Collection<ServiceInstance<ServerPayload>> queryForInstances(String name) throws Exception {        return serviceDiscovery.queryForInstances(name);    }    public ServiceInstance<ServerPayload> queryForInstance(String name, String id) throws Exception {        return serviceDiscovery.queryForInstance(name, id);    }    public void start() throws Exception {        serviceDiscovery.start();    }    public void close() throws Exception {        serviceDiscovery.close();    }}1
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Consumer

package com.bytebeats.zookeeper.curator.discovery;import com.bytebeats.zookeeper.curator.CuratorUtils;import com.bytebeats.zookeeper.curator.discovery.domain.ServerPayload;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.x.discovery.ServiceInstance;import java.io.IOException;import java.util.concurrent.TimeUnit;/** * 模拟服务消费者 * * @author Ricky Fung * @create 2016-12-08 20:13 */public class ClientApp {    public static void main(String[] args) {        CuratorFramework client = null;        ServiceDiscover serviceDiscover = null;        try{            client = CuratorUtils.getCuratorClient();            client.start();            serviceDiscover = new ServiceDiscover(client, ServerApp.BASE_PATH);   //服务发现            serviceDiscover.start();            for(int i=0;i<10;i++){                ServiceInstance<ServerPayload> instance = serviceDiscover.getServiceProvider(ServerApp.SERVICE_NAME);                System.out.println("service:"+ServerApp.SERVICE_NAME+" instance id:"+instance.getId()+                        ", name:"+instance.getName()+ ", address:"+instance.getAddress()+", port:"+instance.getPort());                TimeUnit.SECONDS.sleep(3);            }        } catch (Exception e) {            e.printStackTrace();        } finally {            if(serviceDiscover!=null){                try {                    serviceDiscover.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            client.close();        }    }}1
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ServiceDiscover.java

package com.bytebeats.zookeeper.curator.discovery;import com.bytebeats.zookeeper.curator.discovery.domain.ServerPayload;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.x.discovery.ServiceDiscovery;import org.apache.curator.x.discovery.ServiceDiscoveryBuilder;import org.apache.curator.x.discovery.ServiceInstance;import org.apache.curator.x.discovery.ServiceProvider;import org.apache.curator.x.discovery.details.JsonInstanceSerializer;import org.apache.curator.x.discovery.strategies.RandomStrategy;import java.io.IOException;import java.util.Map;import java.util.concurrent.ConcurrentHashMap;/** * 服务发现 * * @author Ricky Fung * @create 2016-12-08 20:04 */public class ServiceDiscover {    private ServiceDiscovery<ServerPayload> serviceDiscovery;    private final ConcurrentHashMap<String, ServiceProvider<ServerPayload>> serviceProviderMap = new ConcurrentHashMap<>();    public ServiceDiscover(CuratorFramework client , String basePath){        serviceDiscovery = ServiceDiscoveryBuilder.builder(ServerPayload.class)                .client(client)                .basePath(basePath)                .serializer(new JsonInstanceSerializer<>(ServerPayload.class))                .build();    }    /**     * Note: When using Curator 2.x (Zookeeper 3.4.x) it's essential that service provider objects are cached by your application and reused.     * Since the internal NamespaceWatcher objects added by the service provider cannot be removed in Zookeeper 3.4.x,     * creating a fresh service provider for each call to the same service will eventually exhaust the memory of the JVM.     */    public ServiceInstance<ServerPayload> getServiceProvider(String serviceName) throws Exception {        ServiceProvider<ServerPayload> provider = serviceProviderMap.get(serviceName);        if (provider == null) {            provider = serviceDiscovery.serviceProviderBuilder().                    serviceName(serviceName).                    providerStrategy(new RandomStrategy<ServerPayload>())                    .build();            ServiceProvider<ServerPayload> oldProvider = serviceProviderMap.putIfAbsent(serviceName, provider);            if (oldProvider != null) {                provider = oldProvider;            }else {                provider.start();            }        }        return provider.getInstance();    }    public void start() throws Exception {        serviceDiscovery.start();    }    public void close() throws IOException {        for (Map.Entry<String, ServiceProvider<ServerPayload>> me : serviceProviderMap.entrySet()){            try{                me.getValue().close();            }catch (Exception e){                e.printStackTrace();            }        }        serviceDiscovery.close();    }}1
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点此下载完整demo：https://github.com/TiFG/zookeeper-samples

参考

Service Discovery：http://curator.apache.org/curator-x-discovery/index.html

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