If you wanted to generalize this, you could allow the user to specify a length and offset into the log as part of the request (which would fix [SPARK-608](https://spark-project.atlassian.net/browse/SPARK-608)).  This would support the `tail` use case and also enable fancy things like long-polling-based Javascript log viewers.  To more easily support `tail`, you could have the start offset work like a Python array index so you could pass -1024 to start reading from the last 1024 bytes of the log.