Introduction

pgpool-II is basically a middleware solution that works as an interface between a PostgreSQL server and a PostgreSQL client application. pgpool-II talks about the PostgreSQL's backend and frontend protocol and relays a connection between the two. pgpool-II caches incoming connections to PostgreSQL servers and reuses them whenever a new connection with the same properties comes in. This way it reduces connection overhead and improves overall throughput.

pgpool-II in fact offers a lot more features than connection pooling. pgpool-II offers the load balancing and replication modes along with the parallel query feature. However, since this chapter is dedicated to connection pooling, we are going to focus only on the connection pooling feature.

Pgbouncer is also a lightweight connection pooler for PostgreSQL. Applications connect to the Pgbouncer port just like the way it would connect to a Postgresql database on the database port. By using pgbouncer we can lower the connection overload...