elasticsearch/logstash — pull request #1416 by wiibaa (2014-06-03 05:47:37+00:00)
Title: Raise configuration error in fingerprint#register when key is missing

Issue a LogStash::ConfigurationError from register method of fingerprint filter when key parameter is required for selected method instead of a simple error log.
Contribute to [LOGSTASH-2240](https://logstash.jira.com/browse/LOGSTASH-2240),
the needed enhancement of the doc remains open