1. Apache ActiveMQ. http://activemq.apache.org/. Apache ActiveMQ. http://activemq.apache.org/.
2. Apache Curator. http://curator.apache.org/. Apache Curator. http://curator.apache.org/.
3. CoreOS etcd. https://github.com/coreos/etcd/. CoreOS etcd. https://github.com/coreos/etcd/.
4. JZab. https://github.com/zk1931/jzab/. JZab. https://github.com/zk1931/jzab/.
5. LogCabin. https://github.com/logcabin/. LogCabin. https://github.com/logcabin/.