我已经编写了一个非常基本的Sping Boot 2应用程序，它连接到Zookeeper以进行服务发现（通过使用spring-cloud-starter-zookeeper-discovery）。
应用程序使用以下值在/services/example-service注册：

{"name":"example-service","id":"cb14ad15-4d33-4f1c-a420-29980ddf2fa8","address":"bf3fb9191373","port":8080,"sslPort":null,"payload":{"@class":"org.springframework.cloud.zookeeper.discovery.ZookeeperInstance","id":"application-1","name":"example-service","metadata":{}},"registrationTimeUTC":1524120820273,"serviceType":"DYNAMIC","uriSpec":{"parts":[{"value":"scheme","variable":true},{"value":"://","variable":false},{"value":"address","variable":true},{"value":":","variable":false},{"value":"port","variable":true}]}}

地址是一个id，因为我已经用Docker部署了堆栈。
我的Prometheus配置如下所示：

- job_name: 'example-service'
  metrics_path: '/actuator/prometheus'
  serverset_sd_configs:
  - servers:
    - zookeeper:2181
    paths:
    - '/services/example-service'

Prometheus的服务发现页面显示以下发现的标签：

__address__=":0"  __meta_serverset_endpoint_host=""  __meta_serverset_endpoint_port="0" __meta_serverset_path="/services/example-service/cb14ad15-4d33-4f1c-a420-29980ddf2fa8"  __meta_serverset_shard="0"  __meta_serverset_status="" __metrics_path__="/actuator/prometheus"  __scheme__="http"  job="example-service"

知道为什么__address__是:0吗？