在java中如何使用etcd的v2 和v3 api获取配置，并且对配置的变化进行监控和监听

etcd 和zookeeper 很像，都可以用来做配置管理。并且etcd可以在目前流行的Kubernetes中使用。

但是etcd 提供了v2版本合v3的版本的两种api。我们现在分别来介绍一下这两个版本api的使用。

一、Etcd V2版本API

1、java工程中使用maven引入 etcd v2的java api操作jar包

<dependency><groupId>io.netty</groupId><artifactId>netty-all</artifactId><version>4.1.21.Final</version>
</dependency>
<dependency><groupId>org.mousio</groupId><artifactId>etcd4j</artifactId><version>2.15.0</version>
</dependency>

2、etcd的链接

import mousio.etcd4j.EtcdClient;
import java.io.InputStream;
import java.net.URI;
import java.util.Properties;public class EtcdUtil {
//etcd客户端链接
private static EtcdClient client = null;
//链接初始化
public static synchronized EtcdClient getClient(){
if (null == client){
client = new EtcdClient (URI.create(properties.getProperty("http://127.0.0.1:2379")));
}
return client;
}
}

3、如何获取etcd的配置并且对配置进行监听

//初始化获取etcd配置并且进行配置监听
private void initEtcdConfig() {
EtcdKeysResponse dataTree ;
try {
final EtcdClient etcdClient = EtcdUtil.getClient();
//获取etcd中名称叫ETCD文件夹下的配置
EtcdKeyGetRequest etcdKeyGetRequest = etcdClient.getDir("ETCD").consistent();
dataTree = etcdKeyGetRequest.send().get();
//获取etcd的版本
System.out.println("ETCD's version:"+etcdClient.getVersion());
getConfig("/ETCD/example.config",dataTree); //加载配置项
//启动一个线程进行监听
startListenerThread(etcdClient);
} catch (Exception e) {
System.out.println("EtcdClient init cause Exception:"+e.getMessage());
e.printStackTrace();
}
}
private String getConfig(String configFile,EtcdKeysResponse dataTree){
if(null != dataTree && dataTree.getNode().getNodes().size()>0){
for(EtcdKeysResponse.EtcdNode node:dataTree.getNode().getNodes()){
if(node.getKey().equals(configFile)){
return node.getValue();
}
}
}
System.out.println("Etcd configFile"+ configFile+"is not exist,Please Check");
return null;
}
public void startListenerThread(EtcdClient etcdClient){
new Thread(()->{
startListener(etcdClient);
}).start();
}
public void startListener(EtcdClient etcdClient){
ResponsePromise promise =null;
try {
promise = etcdClient.getDir(SYSTEM_NAME).recursive().waitForChange().consistent().send();
promise.addListener(promisea -> {
System.out.println("found ETCD's config cause change");
try {
getConfig("/ETCD/example.config", etcdClient.getDir("ETCD").consistent().send().get()); //加载配置项
} catch (Exception e) {
e.printStackTrace();
System.out.println("listen etcd 's config change cause exception:{}"+e.getMessage());
}
startListener(etcdClient);
});
} catch (Exception e) {
startListener(etcdClient);
System.out.println("listen etcd 's config change cause exception:"+e.getMessage());
e.printStackTrace();
}
}

4、使用dcmp管理 etcd的配置项

dcmp 是一个使用go语言开发的etcd配置界面，不足的时，这个只支持v2的API，项目的地址：

GitHub - silenceper/dcmp: 基于etcd的配置管理系统 (etcd v2)

二、Etcd V3版本API

1、在工程引入如下依赖

<dependency><groupId>io.netty</groupId><artifactId>netty-all</artifactId><version>4.1.15.Final</version>
</dependency>
<dependency><groupId>com.coreos</groupId><artifactId>jetcd-core</artifactId><version>0.0.2</version>
</dependency>

2、v3 api操作工具类

public class EtcdUtil {//etcl客户端链接private static Client client = null;//链接初始化public static synchronized Client getEtclClient(){if(null == client){client = Client.builder().endpoints(props.getProperty("http://127.0.0.1:2379")).build();}return client;}/*** 根据指定的配置名称获取对应的value* @param key 配置项* @return* @throws Exception*/public static String getEtcdValueByKey(String key) throws Exception {List<KeyValue> kvs = EtcdUtil.getEtclClient().getKVClient().get(ByteSequence.fromString(key)).get().getKvs();if(kvs.size()>0){String value = kvs.get(0).getValue().toStringUtf8();return value;}else {return null;}}/*** 新增或者修改指定的配置* @param key* @param value* @return*/public static void putEtcdValueByKey(String key,String value) throws Exception{EtcdUtil.getEtclClient().getKVClient().put(ByteSequence.fromString(key),ByteSequence.fromBytes(value.getBytes("utf-8")));}/*** 删除指定的配置* @param key* @return*/public static void deleteEtcdValueByKey(String key){EtcdUtil.getEtclClient().getKVClient().delete(ByteSequence.fromString(key));}
}
//V3 api配置初始化和监听
public void init(){
try {//加载配置getConfig(EtcdUtil.getEtclClient().getKVClient().get(ByteSequence.fromString(ETCD_CONFIG_FILE_NAME)).get().getKvs());
//启动监听线程new Thread(() -> {
//对某一个配置进行监听Watch.Watcher watcher = EtcdUtil.getEtclClient().getWatchClient().watch(ByteSequence.fromString("etcd_key"));try {while(true) {watcher.listen().getEvents().stream().forEach(watchEvent -> {KeyValue kv = watchEvent.getKeyValue();//获取事件变化类型System.out.println(watchEvent.getEventType());//获取发生变化的keySystem.out.println(kv.getKey().toStringUtf8());//获取变化后的valueString afterChangeValue = kv.getValue().toStringUtf8();});}} catch (InterruptedException e) {e.printStackTrace();}}).start();
} catch (Exception e) {e.printStackTrace();}}
private String getConfig(List<KeyValue> kvs){if(kvs.size()>0){String config = kvs.get(0).getValue().toStringUtf8();System.out.println("etcd 's config 's configValue is :"+config);return config;}else {return null;}
}

v3版本的正式版本代码（可以直接使用的工具类，并且加上了日志）：

import com.coreos.jetcd.Client;
import com.coreos.jetcd.Watch;
import com.coreos.jetcd.data.ByteSequence;
import com.coreos.jetcd.data.KeyValue;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.List;
/***  etcd 链接和操作工具，包括启动监听 操作etcd v3 版本协议，此操作不支持v2 版本协议。*  v2版本的协议可以参考 https://www.cnblogs.com/laoqing/p/8967549.html*/
public class EtcdUtil {public static Logger log = LoggerFactory.getLogger(EtcdUtil.class);//etcl客户端链接private static Client client = null;//链接初始化 单例模式public static synchronized Client getEtclClient(){if(null == client){client = Client.builder().endpoints("http://xxx.xxx.xxx.xxx:2379").build();}return client;}/*** 根据指定的配置名称获取对应的value* @param key 配置项* @return* @throws Exception*/public static String getEtcdValueByKey(String key) throws Exception {List<KeyValue> kvs = EtcdUtil.getEtclClient().getKVClient().get(ByteSequence.fromString(key)).get().getKvs();if(kvs.size()>0){String value = kvs.get(0).getValue().toStringUtf8();return value;}else {return null;}}/*** 新增或者修改指定的配置* @param key* @param value* @return*/public static void putEtcdValueByKey(String key,String value) throws Exception{EtcdUtil.getEtclClient().getKVClient().put(ByteSequence.fromString(key),ByteSequence.fromBytes(value.getBytes("utf-8")));}/*** 删除指定的配置* @param key* @return*/public static void deleteEtcdValueByKey(String key){EtcdUtil.getEtclClient().getKVClient().delete(ByteSequence.fromString(key));}/*** etcd的监听，监听指定的key，当key 发生变化后，监听自动感知到变化。* @param key 指定需要监听的key*/public static void initListen(String key){try {//加载配置getConfig(EtcdUtil.getEtclClient().getKVClient().get(ByteSequence.fromString(key)).get().getKvs());new Thread(() -> {Watch.Watcher watcher = EtcdUtil.getEtclClient().getWatchClient().watch(ByteSequence.fromString(key));try {while(true) {watcher.listen().getEvents().stream().forEach(watchEvent -> {KeyValue kv = watchEvent.getKeyValue();log.info("etcd event:{} ,change key is:{},afterChangeValue:{}",watchEvent.getEventType(),kv.getKey().toStringUtf8(),kv.getValue().toStringUtf8());});}} catch (InterruptedException e) {log.info("etcd listen start cause Exception:{}",e);}}).start();} catch (Exception e) {log.info("etcd listen start cause Exception:{}",e);}}private static String getConfig(List<KeyValue> kvs){if(kvs.size()>0){String config = kvs.get(0).getKey().toStringUtf8();String value = kvs.get(0).getValue().toStringUtf8();log.info("etcd 's config 's config key is :{},value is:{}",config,value);return value;}else {return null;}}
}

运行后的效果：