pgpool is a connection server for PostgreSQL. pgpool runs between
PostgreSQL's clients(front ends) and servers(back ends).  A PostgreSQL
client can connect to pgpool as if it were a standard PostgreSQL
server.

pgpool caches the connection to PostgreSQL server to reduce the
overhead to establish the connection to it.  Also, pgpool could use
two PostgreSQL servers for fail over. If the first server goes down,
pgpool will automatically switch to the secondary server.  Moreover,
pgpool supports scheduled switch over.
