Any-DB connection pool

npm install any-db-pool
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any-db-pool - database agnostic connection pool

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var anyDB = require('any-db')

var pool = anyDB.createPool('postgres://user:pass@localhost/dbname', {
  min: 5, max: 15,
  reset: function (conn, done) {
    conn.query('ROLLBACK', done)

// Proxies to mysql's connection.query
var q = pool.query('SELECT 1', function (err, res) { })

Note: As shown above, ConnectionPool instances are usually created with anyDB.createPool. The any-db package will be installed alongside any adapters (e.g. any-db-postgres), so most users should depend on their adapter and not on any-db or any-db-pool.


This package contains a database connection pool that can be used with any driver, but it requires an any-db compliant adapter. If you are writing a library that needs to support multiple database backends (e.g. SQLite3 or Postgres or MySQL) then it's strongly recommended that you add any-db toyour peerDependencies and rely on createPool instead of depending on this package directly.


module.exports := (Adapter, adapterConfig: Object, PoolConfig) => ConnectionPool

ConnectionPool := EventEmitter & {
  adapter: String,
  query:   (String, Array?, Continuation<ResultSet>?) => Query,
  acquire: (Continuation<Connection>) => void,
  release: (Connection) => void,
  close:   (Continuation<void>?) => void,

PoolConfig := {
  min: Number?,
  max: Number?,
  onConnect: (Connection, ready: Continuation<Connection>) => void
  reset: (Connection, done: Continuation<void>) => void


A PoolConfig is generally a plain object with any of the following properties (they are all optional):

  • min (default 0) The minimum number of connections to keep open in the pool.
  • max (default 10) The maximum number of connections to keep open in the pool. When this limit is reached further requests for connections will queue waiting for an existing connection to be released back into the pool.
  • onConnect Called immediately after a connection is first established. Use this to do one-time setup of new connections. The supplied Connection will not be added to the pool until you pass it to the done continuation.
  • reset Called each time a connection is returned to the pool. Use this to restore a connection to it's original state (e.g. rollback transactions, set the database session vars). If reset fails to call the done continuation the connection will be lost in limbo.


(String, Array?, Continuation<ResultSet>?) => Query

Implements Queryable.query by automatically acquiring a connection and releasing it when the query completes.


(Continuation<Connection>) => void

Remove a connection from the pool. If you use this method you must return the connection back to the pool using ConnectionPool.release


(Connection) => void

Return a connection to the pool. This should only be called with connections you've manually acquired. You must not continue to use the connection after releasing it.


(Continuation<void>?) => void

Stop giving out new connections, and close all existing database connections as they are returned to the pool.


The string name of the adapter used for this connection pool, e.g. 'sqlite3'.

ConnectionPool events

  • 'acquire' - emitted whenever pool.acquire is called
  • 'release' - emitted whenever pool.release is called
  • 'query', query - emitted immediately after .query is called on a connection via pool.query. The argument is a Query object.
  • 'close' - emitted when the connection pool has closed all of it connections after a call to close().

Why wouldn't I just use generic-pool?

generic-pool is awesome, but it's very generic. This is a Good Thing for a library with "generic" in the name, but not so good for the very common but slightly more specialized case of pooling stateful SQL database connections. This library uses generic-pool and simply augments it with some added niceties:

  • Hooks for initializing and/or resetting connection state when connections are added or returned to the pool.
  • A query method that allows queries to be performed without the user needing a reference to a connection object (and potentially leaking that reference).

Stop telling me not to use this directly

Ok, if you really want to use this package without using the any-db frontend you should provide a compliant Adapter implementation:

var ConnectionPool = require('any-db-pool')
var adapter = require('my-custom-adapter')
var connectionParams = { user: 'scott', password: 'tiger' }
var poolParams = {
  min: 5, max: 15,
  reset: function (conn, done) {
    conn.query('ROLLBACK', done)
var pool = new ConnectionPool(adapter, connectionParams, poolParams)

However, it would be awesome if you just published your adapter as a package named any-db-$name so that everybody could use it :+1:



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