lightning-pool

About

High performance resource pool written with TypeScript.

• The fastest Resource Pool implementation for JavaScript ever! Check out benchmark results
• Advanced configuration options, suits for enterprise level applications
• Configuration can be changed while pool running
• Promise based factory supported
• Supports validation and resource reset
• Fully tested. (%100 coverage)

Installation

• npm install lightning-pool --save

Example

import {Pool} from 'lightning-pool';
import dbDriver from 'some-db-driver';

/**
 * Step 1 - Create a factory object
 */
const factory = {
    create: async function(opts) {
        const client = await DbDriver.createClient();
        return client;
    },
    destroy: async function(client) {  
       await client.close();       
    },
    reset: async function(client){   
       await client.rollback();       
    },
    validate: async function(client) {
       await client.query('select 1');       
    }    
};

/**
 * Step 2 - Create a the pool object
 */
const pool = new Pool(factory, {  
    max: 10,    // maximum size of the pool
    min: 2,     // minimum size of the pool
    minIdle: 2  // minimum idle resources
});

/**
 * Step 3 - Use pool in your code to acquire/release resources
 */
// acquire connection - Promise is resolved
const client = await pool.acquire();
// once a resource becomes available
// Use resource
await client.query("select * from foo");
// return object back to pool
await pool.release(client);

/**
 * Step 4 - Shutdown pool (optional)
 * Call close(force) when you need to shutdown the pool
 */

// Wait for active resource for 5 sec than force shutdown
await pool.close(5000);

Documentation

Creating a Pool instance

lightning-pool module exports createPool() method and Pool class. Both can be used to instantiate a Pool.

import {createPool} from 'lightning-pool';
const pool = createPool(factory, options);

import {Pool} from 'lightning-pool';
const pool = new Pool(factory, options);

factory

Can be any object/instance with the following properties:

• create : The function that the Pool will call when it needs a new resource. It should return a Promise<resouce>.
• destroy : The function that the Pool will call when it wants to destroy a resource. It should accept first argument as resource, where resource is whatever factory.create made. It should return a Promise<>.
• reset (optional) : The function that the Pool will call before any resource back to the Pool. It should accept first argument as resource, where resource is whatever factory.create made. It should return a Promise<>. Pool will destroy and remove the resource from the Pool on any error.
• validate (optional) : The function that the Pool will call when any resource needs to be validated. It should accept first argument as resource, where resource is whatever factory.create made. It should return a Promise<>. Pool will destroy and remove the resource from the Pool on any error.

options

• acquireMaxRetries: Maximum number that Pool will try to create a resource before returning the error. (Default 0)
• acquireRetryWait: Time in millis that Pool will wait after each tries. (Default 2000)
• acquireTimeoutMillis: Time in millis an acquire call will wait for a resource before timing out. (Default 0 - no limit)
• fifo: If true resources will be allocated first-in-first-out order. resources will be allocated last-in-first-out order. (Default true)
• idleTimeoutMillis: The minimum amount of time in millis that an resource may sit idle in the Pool. (Default 30000)
• houseKeepInterval: Time period in millis that Pool will make a cleanup. (Default 1000)
• min: Minimum number of resources that Pool will keep. (Default 0)
• minIdle: Minimum number of resources that Pool will keep in idle state. (Default 0)
• max: Maximum number of resources that Pool will create. (Default 10)
• maxQueue: Maximum number of request that Pool will accept. (Default 1000)
• resetOnReturn: If true Pool will call reset() function of factory before moving it idle state. (Default true)
• validation: If true Pool will call validation() function of factory when it needs it. If false, validation() never been called. (Default true)

Methods

Pool.prototype.acquire()

Acquires a resource from the Pool or create a new one.

Usage

pool.acquire()

• Returns: A Promise

var promise = pool.acquire();
promise.then(resource => {
  // Do what ever you want with resource
}).catch(err =>{
  // Handle Error  
});

Pool.prototype.isAcquired()

Returns if a resource has been acquired from the Pool and not yet released or destroyed.

Usage

pool.isAcquired(resource)

• resource: A previously acquired resource
• Returns: True if the resource is acquired, else False

if (pool.isAcquired(resource)) {
  // Do any thing
}

Pool.prototype.includes()

Returns if the Pool contains a resource

Usage

pool.includes(resource)

• resource: A resource object
• Returns: True if the resource is in the Pool, else False

if (pool.includes(resource)) {
  // Do any thing
}

Pool.prototype.release()

Releases an allocated resource and let it back to pool.

Usage

pool.release(resource)

• resource: A previously acquired resource
• Returns: undefined

pool.release(resource);

Pool.prototype.destroy()

Releases, destroys and removes any resource from Pool.

Usage

pool.destroy(resource)

• resource: A previously acquired resource
• Returns: undefined

pool.destroy(resource);

Pool.prototype.start()

Starts the Pool and begins creating of resources, starts house keeping and any other internal logic.

Note: This method is not need to be called. Pool instance will automatically be started when acquire() method is called

Usage

pool.start()

• Returns: undefined

pool.start();

Pool.prototype.close()

Shuts down the Pool and destroys all resources.

Usage

close(callback: Callback): void; close(terminateWait: number, callback?: Callback): Promise<void>; close(force: boolean, callback?: Callback): void;

• force: If true, Pool will immediately destroy resources instead of waiting to be released
• terminateWait: If specified, Pool will wait for active resources to release
• callback: If specified, callback will be called after close. If not specified a promise returns.

var promise = pool.close();
promise.then(() => {
  console.log('Pool has been shut down') 
}).catch(err => {
  console.error(err);  
});

Properties

• acquired (Number): Returns number of acquired resources.
• available (Number): Returns number of idle resources.
• creating (Number): Returns number of resources currently been created.
• pending (Number): Returns number of acquire request waits in the Pool queue.
• size (Number): Returns number of total resources.
• state (PoolState): Returns current state of the Pool.
• options (PoolOptions): Returns object instance that holds configuration properties
  • acquireMaxRetries (Get/Set): Maximum number that Pool will try to create a resource before returning the error. (Default 0)
  • acquireRetryWait (Get/Set): Time in millis that Pool will wait after each tries. (Default 2000)
  • acquireTimeoutMillis (Get/Set): Time in millis an acquire call will wait for a resource before timing out. (Default 0 - no limit)
  • fifo (Get/Set): If true resources will be allocated first-in-first-out order. resources will be allocated last-in-first-out order. (Default true)
  • idleTimeoutMillis (Get/Set): The minimum amount of time in millis that an resource may sit idle in the Pool. (Default 30000)
  • houseKeepInterval (Get/Set): Time period in millis that Pool will make a cleanup. (Default 1000)
  • min (Get/Set): Minimum number of resources that Pool will keep. (Default 0)
  • minIdle (Get/Set): Minimum number of resources that Pool will keep in idle state. (Default 0)
  • max (Get/Set): Maximum number of resources that Pool will create. (Default 10)
  • maxQueue (Get/Set): Maximum number of request that Pool will acceps. (Default 1000)
  • resetOnReturn (Get/Set): If true Pool will call reset() function of factory before moving it idle state. (Default true)
  • validation (Get/Set): If true Pool will call validation() function of factory when it needs it. If false, validation() never been called. (Default true)

Events

Pool derives from EventEmitter and produce the following events:

• acquire: Emitted when a resource acquired.

pool.on('acquire', function(resource){
  //....
})

• create: Emitted when a new resource is added to the Pool.

pool.on('create', function(resource){
  //....
})

• create-error: Emitted when a factory.create informs any error.

pool.on('create-error', function(error){
  //Log stuff maybe
})

• destroy: Emitted when a resource is destroyed and removed from the Pool.
• destroy-error: Emitted when a factory.destroy informs any error.

pool.on('destroy-error', function(error, resource){
  //Log stuff maybe
})

• return: Emitted when an acquired resource returns to the Pool.

pool.on('start', function(resource){
  //...
})

• start: Emitted when the Pool started.

pool.on('start', function(){
  //...
})

• closing: Emitted when before closing the Pool.

pool.on('closing', function(){
  //...
})

• close: Emitted when after closing the Pool.

pool.on('close', function(){
  //...
})

• validate-error: Emitted when a factory.validate informs any error.

pool.on('validate-error', function(error, resource){
  //Log stuff maybe
})

PoolState enum

Pool.PoolState (Number):

• IDLE: 0, // Pool has not been started

• STARTED: 1, // Pool has been started

• CLOSING: 2, // Pool shutdown in progress

• CLOSED: 3 // Pool has been shut down

Node Compatibility

• node >= 16.0;

License

MIT