Yes you are right, thanks @Salohy! I tried to reproduce it on my side with kafka 2.1.0 and I only see
2019-08-28T09:08:07.285-0600 INFO kafka/log.go:53 Connected to broker at localhost:9092 (unregistered)
2019-08-28T09:08:07.303-0600 INFO kafka/log.go:53 Closed connection to broker localhost:9092
I can't reproduce the EOF log though. Are you still seeing the same issue? By looking at the metricbeat code, seems like this error happens when trying to connect with a kafka broker or when querying metadata from broker. The error log is not clear enough where it happened exactly, so I will definitely create a PR to improve that.
What version of Kafka are you using? On google I see some similar cases for Kafka like https://github.com/Shopify/sarama/issues/1071, maybe this will help?