Async Hooks

An Async Hooks polyfill for Node < 8, written in TypeScript.

The idea is to provide an interface identical to the native Async Hooks implementation in older versions of Node. If you import the library in Node 8+ it will return the native Async Hooks, otherwise it will return the polyfill.

The docs for Async Hooks here.

This implementation is based largely on the work of Andreas Madsen

Install

$ npm install --save @creditkarma/async-hooks

Usage

createHook

Creates a new AsyncHook object with the supplied callbacks

import * as AsyncHooks from '@creditkarma/async-hooks'

AsyncHooks.createHook({
    init(asyncId: number, type: string, triggerAsyncId: number, resource: object): void {
        // A new async resouce was created
    },
    before(asyncId: number): void {
        // The callback for async resource will be called
    },
    after(asyncId: number): void {
        // The callback for async resource was called
    },
    destroy(asyncId: number): void {
        // The async resource will be garbage collected
    }
}).enable()

In the native implementation of Async Hooks the resource received by the init method is the async object that was created. In the polyfill this resource is likely to not useful and is here for completeness. Usually this will be an empty wrapper object.

executionAsyncId

Returns the unique ID of the currently executing async context.

import * as AsyncHooks from '@creditkarma/async-hooks'

const currentAsyncId: number = AsyncHooks.executionAsyncId()

triggerAsyncId

Returns the unique ID of the parent context for the currently executing async context.

import * as AsyncHooks from '@creditkarma/async-hooks'

const parentAsyncId: number = AsyncHooks.triggerAsyncId()