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

* Connection Pooling * Replication * Load Balance * Limiting Exceeding Connections * Parallel Query

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.

This is version 3 of pgpool-II, the second generation of pgpool.