basho/lager — pull request #102 by Vagabond (2012-12-11 22:26:13+00:00)
Title: Support backend modules defining their own gen_event handler ID

To address a backend properly (for loglevel changes, tracing, etc) you need to have a 'handler ID' when installing the gen_event backend. The file backend was hardcoded to always use {?MODULE, FileName}, but a similar problem arises if you want to have (for example) multiple syslog backends, each writing to a different facility or whatever.

Thus, we add this optional callback to the backend module to allow the module to generate a unique handler ID from its config.