To elaborate: twemproxy supports auto_eject_hosts, but the host is removed from the ring until a timeout and it's portion of the keyspace is re-allocated to other machines during this time. There are numerous problems with this, but the biggest problem is that it causes inconsistent views of the ring if one or more client hosts is unable to reach some of the machines in the ring for transient periods of time, which is a pretty normal kind of thing if you've got clients and ring nodes distributed over multiple loosely coupled failure domains. mcrouter is much more capable in terms of handling node failure.
