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What is pgpool-II?

pgpool-II is a middleware that works between PostgreSQL servers and a PostgreSQL database client. It is licensed under BSD license. It provides the following features.

Connection Pooling

pgpool-II saves connections to the PostgreSQL servers, and reuse them whenever a new connection with the same properties (i.e. username, database, protocol version) comes in. It reduces connection overhead, and improves system's overall throughput.

Replication

pgpool-II can manage multiple PostgreSQL servers. Using the replication function enables creating a realtime backup on 2 or more physical disks, so that the service can continue without stopping servers in case of a disk failure.

Load Balance

If a database is replicated, executing a SELECT query on any server will return the same result. pgpool-II takes an advantage of the replication feature to reduce the load on each PostgreSQL server by distributing SELECT queries among multiple servers, improving system's overall throughput. At best, performance improves proportionally to the number of PostgreSQL servers. Load balance works best in a situation where there are a lot of users executing many queries at the same time.

Limiting Exceeding Connections

There is a limit on the maximum number of concurrent connections with PostgreSQL, and connections are rejected after this many connections. Setting the maximum number of connections, however, increases resource consumption and affect system performance. pgpool-II also has a limit on the maximum number of connections, but extra connections will be queued instead of returning an error immediately.

Parallel Query

Using the parallel query function, data can be divided among the multiple servers, so that a query can be executed on all the servers concurrently to reduce the overall execution time. Parallel query works the best when searching large-scale data.

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.

pgpool-II License

Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the name of the author not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. The author makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty.

What's new (Stable)

Missing regression test suite in pgpool-II 3.3.0.tar.gz (2013/07/31)

New regression test suite was not accidentally included in the pgpool-II 3.3.0.tar.gz tar ball. You can get it from git repository or download from here.

pgpool-II 3.3 and pgpoolAdmin 3.3 officially released (2013/07/30)

Pgpool-II 3.3 is now officially released.

You can download them here.

V3.3's new features are:

Enhancements for watchdog
- New monitoring method of watchdog lifecheck using heartbeat signal
- Interlocking of failover/failback script
- Secure watchdog communication
- PCP command for retrieving the watchdog status
- etc.
Othres
- Import PostgreSQL 9.2 raw parser
- New pgpool_setup tool
- Support for using CREATE EXTENSION to install pgpool specific extensions
- regression test suit
- etc.

pgpool-II 3.2.5, 3.1.8, 3.0.12 officially released (2013/07/10)

Theese are the latest stable versions of each major branches.

You can download them here.

Learn more about pgpool-II 3.2.5:

Learn more about pgpool-II 3.1.8:

Learn more about pgpool-II 3.0.12:

What's new (Development)