Please indicate in http://logback.qos.ch/manual/filters.html what is expected to happen if a custom ch.qos.logback.core.filter.Filter throws an exception. By the looks of it, the exception suppresses logging silently. No error message is ever printed out or logged.

Users should be cautioned to catch all runtime exceptions; otherwise, they risk silent log failures.

We should also consider whether the current default behavior makes sense (versus, say logging an error if a filter throws an exception unexpectedly).