Pool - Backendjs Documentation

Pool

new Pool(options)

Description:

Create a resource pool, create and close callbacks must be given which perform allocation and deallocation of the resources like db connections.

Source:

lib/pool.js, line 9

Parameters:

Name Type Description

options

object

defines the following properties

Properties

Name	Type	Attributes	Description
`create`	function	<optional>	method to be called to return a new resource item, takes 1 argument, a callback as `function(err, item)`
`destroy`	function	<optional>	method to be called to destroy a resource item
`reset`	function	<optional>	method to be called just before releasing an item back to the resource pool, this is a chance to reset the item to the initial state
`validate`	function	<optional>	method to verify active resource item, return false if it needs to be destroyed
`init`	function	<optional>	method to cal on pool.init, it may be called multiple times
`shutdown`	function	<optional>	method to call on pool shutdown to clear other resources
`min`	int	<optional>	min number of active resource items
`max`	int	<optional>	max number of active resource items
`max_queue`	int	<optional>	how big the waiting queue can be, above this all requests will be rejected immediately
`timeout`	int	<optional>	number of milliseconds to wait for the next available resource item, cannot be 0
`idle`	int	<optional>	number of milliseconds before starting to destroy all active resources above the minimum, 0 to disable. If no create implementation callback is given then all operations are basically noop still calling the callbacks.

Example

var pool = new lib.Pool({
    min: 1,
    max: 5,
    create: function(cb) {
        someDb.connect((err) => { cb(err, this) }
    },
    destroy: function(client) {
        client.close() }
    })
});

pool.use((err, client) => {
    ...
    pool.release(client);
});

const { err, client } = await pool.ause();
if (!err) {
    ...
    pool.release(client);
}