The CLD2 is a re-implementation of CLD of Project Hail. See https://github.com/jgarzik/hail/tree/master/cld https://hail.wiki.kernel.org/index.php/CLD
Hail's CLD used Berkeley DB in order to elect the master. It worked, but wasn't fun enough.
Systems you should examine before using CLD2 (or CLD for that matter):
- Zookeeper
- etcd
- Consul
- maybe Redis