make-promises-safe   

A node.js module to make the use of promises safe.
It implements the deprecation [DEP0018][unhandled] of Node.js in versions 6+.
Using Promises without this module might cause file descriptor and memory
leaks.

**It is important that this module is only used in top-level program code, not
in reusable modules!**

The Problem

Node.js crashes if there is an uncaught exception, while it does not
crash if there is an 'unhandledRejection', i.e. a Promise without a
.catch() handler.

**If you are using promises, you should attach a .catch() handler
synchronously**.

As an example, the following server will leak a file descriptor because
of a missing .catch()  handler:

``js
const http = require('http')
const server = http.createServer(handle)

server.listen(3000)

function handle (req, res) {
doStuff()
.then((body) => {
res.end(body)
})
}

function doStuff () {
if (Math.random() < 0.5) {
return Promise.reject(new Error('kaboom'))
}

return Promise.resolve('hello world')
}
`

The Solution

make-promises-safe installs an process.on('unhandledRejection')
handler that prints the stacktrace and exits the process with an exit
code of 1, just like any uncaught exception.

Install

`
npm install make-promises-safe --save
`

Usage

`js
'use strict'

require('make-promises-safe') // installs an 'unhandledRejection' handler
const http = require('http')
const server = http.createServer(handle)

server.listen(3000)

function handle (req, res) {
doStuff()
.then((body) => {
res.end(body)
})
}

function doStuff () {
if (Math.random() < 0.5) {
return Promise.reject(new Error('kaboom'))
}

return Promise.resolve('hello world')
}
`

$3

You can add this behavior to any Node.js application by using it as a
preloader:

`
node -r make-promises-safe server.js
`

$3

You can also create a core dump when an unhandled rejection occurs:


`
require('make-promises-safe').abort = true
`

$3

You can add a custom logger to log errors in your own format. To do this override the logError property with a function that takes a single Error parameter. This defaults to console.error.

`
const makePromisesSafe = require('make-promises-safe');
makePromisesSafe.logError = function(err) {
// log the err object
}
``

License

MIT

[unhandled]: https://nodejs.org/dist/latest-v8.x/docs/api/deprecations.html#deprecations_dep0018_unhandled_promise_rejections