Jetcd 介绍
Jetcd 是 etcd 的简单 Java 客户端开发包。etcd 是 CoreOS
中的高可用 Key/Value 存储和
示例代码：
EtcdClient client = new EtcdClient(URI.create("http://127.0.0.1:4001/"));
String key = "/watch";
EtcdResult result = this.client.set(key, "hello");
Assert.assertEquals("hello", result.value);
result = this.client.get(key);
Assert.assertEquals("hello", result.value);
ListenableFuture<EtcdResult> watchFuture = this.client.watch(key, result.index + 1);
Assert.assertFalse(watchFuture.isDone());
result = this.client.set(key, "world");
Assert.assertEquals("world", result.value);
EtcdResult watchResult = watchFuture.get(100, TimeUnit.MILLISECONDS);
Assert.assertNotNull(result);
Assert.assertEquals("world", result.value);