p-concurrency

Decorate an async function with limited concurrency, which can be used as the decorator in the future.

Install

$ npm install p-concurrency --save

Usage

const {concurrency} = require('p-concurrency')

// used as a decorator
@concurrency(1)
async function get (n) {
  return await remoteGetSomething(n)
}

// or
get = concurrency(1)(get)

// only one promise is run at once
Promise.all([
  get(),
  get(),
  get()
]).then(result => {
  console.log(result)
})

It can also be used with classes

class Foo {
  @concurrency(1)
  async bar (n) {
    return await remoteGetSomething(n)
  }
}

const foo = new Foo

// only one promise is run at once
Promise.all([
  foo.bar(),
  foo.bar(),
  foo.bar()
]).then(result => {
  console.log(result)
})

Use as no decorators with classes

class Foo {
  constructor () {
    this.bar = concurrency(1)(this.bar)
  }

  async bar (n) {
    return await remoteGetSomething(n)
  }
}

Or (recommended)

class Foo {
  async bar (n) {
    return await remoteGetSomething(n)
  }
}

const {prototype} = Foo
prototype.bar = concurrency(1)(prototype.bar)

concurrency(max)

Which is equivalent to:

concurrency({
  concurrency: max
})

concurrency(options)

• options
  • concurrency number max concurrency
  • promise Function (handler: Function)
  • when? Function (): bool
  • global? boolean = false use global concurrency limiter. If true, all instances of a class will share a same concurrency queue
  • key string | Symbol the key to save the queue

License

MIT