Pgpool-II is a middleware that works between PostgreSQL servers and a PostgreSQL database client. It is licensed under BSD license. It provides the following features.

Pgpool-II talks PostgreSQL’s backend and frontend protocol, and relays a connection between them. Therefore, a database application (frontend) thinks that Pgpool-II is the actual PostgreSQL server, and the server (backend) sees Pgpool-II as one of its clients. Because Pgpool-II is transparent to both the server and the client, an existing database application can be used with Pgpool-II almost without a change to its sources.

Pgpool-II License

See License.