Then remember about Fluentd. I was using it for filling ElasticSearch with logs when Kibana was still written in PHP by a separate developer and was meant as a somewhat specialized frontend for logstash, not a generic one for ElasticSearch. I'm using it still for shipping logs (again to ElasticSearch) and metrics collected by monitoring, and I have even built a proof-of-concept of a stream processing engine for monitoring out of it.

You could go really far with Fluentd using or writing only few plugins.