cnysa (unpronouncible) is a module that allows you to see information about what the async_hooks module is doing under the covers.

Note: This module currently uses the colors module.

Pre-Require Hook

Pre-require cynsa/register in your application:

node --require cynsa/register app.js

If cnysa.json exists in the current working directory, it will be used as the configuration passed to the Cnysa constructor as described below.

API

const { Cnysa } = require('cnysa');

new Cnysa(options)

All options are optional.

• options.width: Maximum number of characters to print on a single line before wrapping. Defaults to the current terminal width.
• options.ignoreTypes: String or RegExp to filter out AsyncResource types.
• options.highlightTypes: String or RegExp to highlight certain AsyncResource types and their descendants.

Cnysa#enable()

Starts recording async events and registers a process exit hook.

Cnysa#disable()

Stops recording async events and unregisters the process exit hook.

Understanding output

For each AsyncResource, a time line will be printed, with a number of colored symbols:

• Green * represents the async resource creation.
• Red * represents its destruction.
• Blue {...} represent running in an async scope.
• Gray - indicates the lifetime of the resource creation, and is bookended by * symbols.

Examples

node --require cnysa/register -e "fs.readFile('package.json', (err, contents) => { console.log('done reading') })"