> In 9.4, Logical Decoding supplies a new API for reading, filtering and manipulating the PostgreSQL replication stream. This interface is the foundation for new replication tools, such as Bi-Directional Replication, which supports the creation of multi-master PostgreSQL clusters. Other improvements in the replication system, such as replication slots and time-delayed replicas, improve management and utility of replica servers.
See also, ye manual: http://www.postgresql.org/docs/9.4/interactive/high-availabi...