Pgpool-II

What Pgpool-II is

Pgpool-II is free middleware that sits between PostgreSQL servers and database clients, relaying PostgreSQL protocol messages. It reuses PostgreSQL server connections with matching properties to reduce connection overhead and improve throughput. With replicated databases, it can distribute SELECT queries across servers to spread load. Its high-availability capabilities include automatic failover, quorum, split-brain prevention, and Watchdog for Pgpool-II availability.

The software also provides replication, online recovery, connection limiting, and an in-memory query cache. Authentication methods include trust, clear-text password, MD5, SCRAM-SHA-256, certificates, PAM, and LDAP; GSSAPI is not supported. SSL can protect frontend and backend communications when enabled, but it is off by default and requires OpenSSL support.

Pgpool-II is self-hosted and available in source and binary formats. The project provides RPM packages for Red Hat Enterprise Linux and compatible distributions; Debian and Ubuntu users are directed to packages from the PostgreSQL community. Official documentation is available in English and Japanese, with tutorials covering basic configuration, Watchdog, AWS, and Aurora. Community help is available through mailing lists and GitHub Issues. SRA OSS K.K. offers commercial technical support, consulting, and system integration.

Who it suits

Pgpool-II suits teams running PostgreSQL that need middleware for connection reuse, query distribution, or high availability. It is a fit for organizations prepared to operate self-hosted software and configure the authentication and SSL options they need.

Limits

The listed plan is Pgpool-II at no cost, as open-source self-hosted middleware. SSL is off by default and requires OpenSSL support; GSSAPI is unsupported.

Getting started

1. Visit the Pgpool-II website and consult the official documentation.
2. Choose a source or binary distribution; RPM packages are available for Red Hat Enterprise Linux and compatible distributions.
3. For Debian or Ubuntu, obtain packages from the PostgreSQL community.
4. Configure Pgpool-II between PostgreSQL servers and database clients.
5. Select supported authentication methods and enable SSL if needed, with OpenSSL support.
6. Use the documentation tutorials for basic configuration, Watchdog, AWS, or Aurora.

Verdict

Choose Pgpool-II if you need free PostgreSQL middleware with connection pooling, query distribution, and failover capabilities, and can run it yourself. Look elsewhere if GSSAPI authentication is required; enabling SSL also requires OpenSSL support and configuration.