Github user zentol commented on the issue:
https://github.com/apache/flink/pull/4586
I configured 3 ports `9001-9003`. Each reporter logged `2017-10-25
13:10:14,848 INFO org.apache.flink.metrics.prometheus.PrometheusReporter
- Started PrometheusReporter HTTP server on port 9001.`, which should only be
possible if they can successfully create the HttpServer.---
