cnysa

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

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.typeFilter: String or RegExp to use as a filter for AsyncResource types.

Cnysa#enable()

Starts emitting output.

Cnysa#disable()

Stops emitting output.

Understanding output

For each init, before, promiseResolve, and destroy event, a line will be printed.

Each of those lines start with a symbol:

• + Init
• * Before
• - Destroy
• : Promise Fulfillment

The number that follows is the current time in seconds, mod 1000. This number might be useful in distinguishing "clusters" of async events.

A string after represents the async resource type.

The async resource's execution ID follows. For init events, if the trigger ID is different than the current execution ID, it is displayed as well.

before-after pairs are visualized as indents.

Examples

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

(sleep 2 && curl localhost:8080) & node --require cnysa/register -e "http.createServer((req, res) => res.send('hi')).listen(8080)"

https://gist.github.com/kjin/a499bfcb7c5e12a80f8c6ad66a30b740