Yes, etcd can be used for a few different use-cases on CoreOS clusters. You can do service discovery by "announcing" each container to the cluster. With an etcd watch, any process on the cluster could be listening for changes to your service discovery keyspace, and take any action you specify (Reconfigure proxies, etc.)

Etcd also provides distributed locking for the cluster through a module. If you need to prevent an action from happening more than once, you can take a lock on a specific key to prevent others from processing that item.

Related to locking is the leader election module which offers an easy way to choose a new leader for a distributed service. Module docs are here: https://github.com/coreos/etcd/blob/master/Documentation/mod...

etcd[1] is a distributed key-value store with some interesting properties for making things like locking mechanisms. It's like zookeeper[2] except it uses the raft consensus algorithm[3][pdf] and is written in Go.

[1]: https://github.com/coreos/etcd

[2]: http://zookeeper.apache.org/

[3]: https://ramcloud.stanford.edu/wiki/download/attachments/1137...