The ODL infrautils project proposes a new API to expose metrics from ODL SDN applications. This API is currently in the process of being adopted accross the genius and netvirt projects, and could be of interest and used by other ODL projects as well. The infrautils.metrics API currently already has 2 implementations available (and more could be written). The first one uses a built-in Codehale's Dropwizard Metrics library and exposes metrics via JMX and can dump metrics to local files at regular intervals. The second one offers up metrics over HTTP to an external
https://prometheus.io metrics server scraping from ODL, and can do all sorts of interesting things... (Prometheus is one of the projects of the Cloud Native Computing Foundation
https://www.cncf.io.). A 3rd implementation supporting OpenStack Ceilometer from contributors would be interesting.