In 1.2.0, output threads look like this in top, when using this config:
These should be called >ElasticSearch
Its something that needs to be changed indeed. Found the same issue in the code.
Will be submitting a PR for that to fix it.
Thanks for reporting it!
Since the PR isn't linked, I can't check - I have to assume this is fixed?
As mentioned in http://logstash.net/docs/1.4.2/life-of-an-event
output worker is currently a single thread