exframe Worker Pool

A library for managing a maximum number of concurrent work items locally and scheduling what comes next by priority

installation

npm install exframe-worker-pool

usage

const { WorkerPool } = require('exframe-worker-pool');

const pool = new WorkerPool();
const result = await pool.work(async () => {
  return 10;
});
console.log(result); // 10

pool.eventEmitter.on('empty', () => {
  return 'pool is empty'; //fires when count === 0
})

class WorkerPool

Manages the set of concurrent work and schedules what comes next by priority

`constructor(options?) => WorkerPool`

type options

field	type	description
`max`	integer default = 10	the maximum number of concurrent workers that may be executing
`overflow`	integer default = 5	the buffer over the maximum concurrent workers reserved for executing with the forced flag -- queued work cannot execute until after the workingCount reduces to less than max

`async take<T>(options?) => Promise<Worker>`

Takes a worker resource from the pool, once the calling code is done, it will need to call release on the worker

type options

field	type	description
`priority`	integer default = 1	the priority assigned to the work -- priority is sorted descending, so something with a higher priority will execute first
`force`	boolean default = false	flag to indicate that the work can execute within the overflow buffer if max concurrency has been reached

type Worker

`release() => void`

Releases the worker resource back to the worker pool

`async work<T>(callback: () => Promise<T>, options?) => Promise<T>`

Executes the given callback immediately or once the pool has freed enough worker resources to allow the given callback to execute

type options

field	type	description
`priority`	integer default = 1	the priority assigned to the work -- priority is sorted descending, so something with a higher priority will execute first
`force`	boolean default = false	flag to indicate that the work can execute within the overflow buffer if max concurrency has been reached

`eventEmitter: EventEmitter`

Event emitter that exposes the following events

event	parameters	description
empty	null	Fires whenever a worker is released and the count is reduced to 0

`workingCount: number`

The number of worker that are currently executing

`queuedCount: number`

The number of work items waiting to execute

`max: number`

The maxmium number of concurrent workers

`overflow: number`

The buffer of work items over the max that can be forced into the pool

`fillRatio: number`

The ratio of the current working count over the sum of max and overflow

`queuedRatio: number`

The ratio of the queued count over the sum of max and overflow