connection pool server and replication proxy for PostgreSQL

 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.