lightning-pool

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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

``ts
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
});

pool.start();

/**
* 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

$3

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

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

`ts
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.
- 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)

$3

#### Pool.prototype.acquire()

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

##### Usage

pool.acquire(): Promise

pool.acquire(factoryCreateOptions: any): Promise

pool.acquire(callback:Callback): Promise

pool.acquire(factoryCreateOptions?: any, callback:Callback): Promise

- Returns: A Promise


`js
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

`js
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

`js
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

`js
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

`js
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


`js
pool.start();
`

#### Pool.prototype.close()

Shuts down the Pool and destroys all resources.

##### Usage

close(callback: Callback): void;
close(terminateWait: number, callback?: Callback): Promise;
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.


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

$3


- 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)

$3

Pool derives from EventEmitter and produce the following events:

- acquire: Emitted when a resource acquired.

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

- create: Emitted when a new resource is added to the Pool.
`js
pool.on('create', function(resource){
//....
})
`

- create-error: Emitted when a factory.create informs any error.
`js
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.
`js
pool.on('destroy-error', function(error, resource){
//Log stuff maybe
})
`

- return: Emitted when an acquired resource returns to the Pool.
`js
pool.on('start', function(resource){
//...
})
`


- start: Emitted when the Pool started.
`js
pool.on('start', function(){
//...
})
`

- closing: Emitted when before closing the Pool.
`js
pool.on('closing', function(){
//...
})
`


- close: Emitted when after closing the Pool.
`js
pool.on('close', function(){
//...
})
`

- validate-error: Emitted when a factory.validate informs any error.
`js
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`;

$3

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