cnysa

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: A string or RegExp to filter out AsyncResource types.
• options.highlightTypes: A string or RegExp to highlight certain AsyncResource types and their descendants.
• options.ignoreUnhighlighted: Boolean to determine whether unhighlighted types should be ignored.
• options.padding: Number that represents the amount of space between each depicted event.
• options.colors: An array of strings that represent colors to use when highlighting.
• options.format: A string that represents how the output should be formatted. Currently, the available options are 'default' and 'svg' (which uses ansi-to-svg).

Cnysa#enable()

Starts recording async events.

Cnysa#disable()

Stops recording async events.

Cnysa#getAsyncSnapshot()

Returns a formatted async ancestry tree.

Understanding output

For each AsyncResource, a timeline 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') })"