zk 10之：Curator之三：服务的注册及发现
Service Discovery
我们通常在调用服务的时候，需要知道服务的地址，端口，或者其他一些信息，通常情况下，我们是把他们写到程序里面，但是随着服务越来越多，维护起来也越来越费劲，更重要的是，由于地址都是在程序中配置的，我们根本不知道远程的服务是否可用，当我们增加或者删除服务，我们又需要到配置文件中配置么？ 这时候，Zookeeper帮大忙了，我们可以把我们的服务注册到Zookeeper中，创建一个临时节点（当连接断开之后，节点将被删除），存放我们的服务信息（url，ip，port等信息），把这些临时节点都存放在以serviceName命名的节点下面，这样我们要获取某个服务的地址，只需要到Zookeeper中找到这个path，然后就可以读取到里面存放的服务信息，这时候我们就可以根据这些信息调用我们的服务。这样，通过Zookeeper我们就做到了动态的添加和删除服务，做到了一旦一个服务时效，就会自动从Zookeeper中移除，基本上Curator中的Service Discovery就是做的这点事。
下面我们用两张图片来比较一下，一般情况下的服务调用，和使用 Dynamic Service Registry 的区别
使用zookeeper做服务注册之后：
关于Apache curator的service discovery的一些介绍可以参考官方文档：http://curator.apache.org/curator-x-discovery/index.html
Service Discovery 的使用
一般而言，分为 Service Registry 和 Service Discovery，对应服务端和客户端。也就是由服务提供者，讲自身的信息注册到Zookeeper，然后，客户端通过到Zookeeper中查找服务信息，然后根据信息就行调用（见上图）。说了这么多，上代码了。
首先我们定义个payload，我们这一在里面存储一些服务信息。这个信息会被保存在Zookeeper，这里只是举个例子，你还可以写入更多你想要的信息。
一般情况下，会在我们服务启动的时候就将服务信息注册，比如我们是web项目的话可以写一个Servlet Listener进行注册，这里为了方便，写一个Main方法进行测试，如果我们把我们的信息存储在payload中的话，UriSpec是可以不定义的。
package com.sf.zkclient.discovery; import org.codehaus.jackson.map.annotate.JsonRootName; @JsonRootName("details") public class InstanceDetails { private String id; private String listenAddress; private int listenPort; private String interfaceName; public InstanceDetails(String id, String listenAddress, int listenPort, String interfaceName) { this.id = id; this.listenAddress = listenAddress; this.listenPort = listenPort; this.interfaceName = interfaceName; } public InstanceDetails() { } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getListenAddress() { return listenAddress; } public void setListenAddress(String listenAddress) { this.listenAddress = listenAddress; } public int getListenPort() { return listenPort; } public void setListenPort(int listenPort) { this.listenPort = listenPort; } public String getInterfaceName() { return interfaceName; } public void setInterfaceName(String interfaceName) { this.interfaceName = interfaceName; } @Override public String toString() { return "InstanceDetails{" + "id='" + id + '\'' + ", listenAddress='" + listenAddress + '\'' + ", listenPort=" + listenPort + ", interfaceName='" + interfaceName + '\'' + '}'; } }
package com.sf.zkclient.discovery; 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.io.IOException; public class ServiceRegistry { private ServiceDiscovery<InstanceDetails> serviceDiscovery; private final CuratorFramework client; public ServiceRegistry(CuratorFramework client, String basePath) throws Exception { this.client = client; JsonInstanceSerializer<InstanceDetails> serializer = new JsonInstanceSerializer<InstanceDetails>( InstanceDetails.class); serviceDiscovery = ServiceDiscoveryBuilder.builder(InstanceDetails.class).client(client).serializer(serializer) .basePath(basePath).build(); serviceDiscovery.start(); } public void registerService(ServiceInstance<InstanceDetails> serviceInstance) throws Exception { serviceDiscovery.registerService(serviceInstance); } public void unregisterService(ServiceInstance<InstanceDetails> serviceInstance) throws Exception { serviceDiscovery.unregisterService(serviceInstance); } public void updateService(ServiceInstance<InstanceDetails> serviceInstance) throws Exception { serviceDiscovery.updateService(serviceInstance); } public void close() throws IOException { serviceDiscovery.close(); } }
package com.sf.zkclient.discovery; import com.google.common.collect.Lists; import com.google.common.collect.Maps; import org.apache.curator.framework.CuratorFramework; import org.apache.curator.utils.CloseableUtils; 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.Closeable; import java.util.List; import java.util.Map; public class ServiceDiscoverer { private ServiceDiscovery<InstanceDetails> serviceDiscovery; private Map<String, ServiceProvider<InstanceDetails>> providers = Maps.newHashMap(); private List<Closeable> closeableList = Lists.newArrayList(); private Object lock = new Object(); public ServiceDiscoverer(CuratorFramework client, String basePath) throws Exception { JsonInstanceSerializer<InstanceDetails> serializer = new JsonInstanceSerializer<InstanceDetails>( InstanceDetails.class); serviceDiscovery = ServiceDiscoveryBuilder.builder(InstanceDetails.class).client(client).basePath(basePath) .serializer(serializer).build(); serviceDiscovery.start(); } public ServiceInstance<InstanceDetails> getInstanceByName(String serviceName) throws Exception { ServiceProvider<InstanceDetails> provider = providers.get(serviceName); if (provider == null) { synchronized (lock) { provider = providers.get(serviceName); if (provider == null) { provider = serviceDiscovery.serviceProviderBuilder().serviceName(serviceName) .providerStrategy(new RandomStrategy<InstanceDetails>()).build(); provider.start(); closeableList.add(provider); providers.put(serviceName, provider); } } } return provider.getInstance(); } public synchronized void close() { for (Closeable closeable : closeableList) { CloseableUtils.closeQuietly(closeable); } } }
package com.sf.zkclient.discovery; import org.apache.curator.framework.CuratorFramework; import org.apache.curator.framework.CuratorFrameworkFactory; import org.apache.curator.retry.ExponentialBackoffRetry; import org.apache.curator.x.discovery.ServiceInstance; import org.apache.curator.x.discovery.UriSpec; import java.util.UUID; /** * User: hupeng * Date: 14-9-16 * Time: 下午8:05 */ public class ServerApp { public static void main(String[] args) throws Exception { CuratorFramework client = CuratorFrameworkFactory.newClient("127.0.0.1:2181", new ExponentialBackoffRetry(1000, 3)); client.start(); ServiceRegistry serviceRegistrar = new ServiceRegistry(client,"services"); ServiceInstance<InstanceDetails> instance1 = ServiceInstance.<InstanceDetails>builder() .name("service1") .port(12345) .address("192.168.1.100") //address不写的话，会取本地ip .payload(new InstanceDetails(UUID.randomUUID().toString(),"192.168.1.100",12345,"Test.Service1")) .uriSpec(new UriSpec("{scheme}://{address}:{port}")) .build(); ServiceInstance<InstanceDetails> instance2 = ServiceInstance.<InstanceDetails>builder() .name("service2") .port(12345) .address("192.168.1.100") .payload(new InstanceDetails(UUID.randomUUID().toString(),"192.168.1.100",12345,"Test.Service2")) .uriSpec(new UriSpec("{scheme}://{address}:{port}")) .build(); serviceRegistrar.registerService(instance1); serviceRegistrar.registerService(instance2); Thread.sleep(Integer.MAX_VALUE); } }
package com.sf.zkclient.discovery; import org.apache.curator.framework.CuratorFramework; import org.apache.curator.framework.CuratorFrameworkFactory; import org.apache.curator.retry.ExponentialBackoffRetry; import org.apache.curator.utils.CloseableUtils; import org.apache.curator.x.discovery.ServiceInstance; public class ClientApp { public static void main(String[] args) throws Exception { CuratorFramework client = CuratorFrameworkFactory.newClient("127.0.0.1:2181", new ExponentialBackoffRetry(1000, 3)); client.start(); ServiceDiscoverer serviceDiscoverer = new ServiceDiscoverer(client,"services"); ServiceInstance<InstanceDetails> instance1 = serviceDiscoverer.getInstanceByName("service1"); System.out.println(instance1.buildUriSpec()); System.out.println(instance1.getPayload()); ServiceInstance<InstanceDetails> instance2 = serviceDiscoverer.getInstanceByName("service1"); System.out.println(instance2.buildUriSpec()); System.out.println(instance2.getPayload()); serviceDiscoverer.close(); CloseableUtils.closeQuietly(client); } }
结果：
17/02/25 16:59:06 INFO zookeeper.ClientCnxn: Socket connection established to 127.0.0.1/127.0.0.1:2181, initiating session
17/02/25 16:59:06 WARN zookeeper.ClientCnxnSocket: Connected to an old server; r-o mode will be unavailable
17/02/25 16:59:06 INFO zookeeper.ClientCnxn: Session establishment complete on server 127.0.0.1/127.0.0.1:2181, sessionid = 0x15a739961cd0011, negotiated timeout = 40000
17/02/25 16:59:06 INFO state.ConnectionStateManager: State change: CONNECTED
http://192.168.1.100:12345
InstanceDetails{id='a197a1b9-a6c6-495e-b500-1160e02bd0a6', listenAddress='192.168.1.100', listenPort=12345, interfaceName='Test.Service1'}
http://192.168.1.100:12345
InstanceDetails{id='a197a1b9-a6c6-495e-b500-1160e02bd0a6', listenAddress='192.168.1.100', listenPort=12345, interfaceName='Test.Service1'}
17/02/25 16:59:07 INFO imps.CuratorFrameworkImpl: backgroundOperationsLoop exiting
17/02/25 16:59:07 INFO zookeeper.ZooKeeper: Session: 0x15a739961cd0011 closed
