Shutdown-Hook 

Shutdown-Hook is an injectable shutdown hook (well dah..) module for Node.js applications.

Installation

npm install shutdown-hook

Usage

$3

``
const ShutdownHook = require('shutdown-hook')
let shutdownHook = new ShutdownHook(options)
`

#### Constructor Options:

| Property | Description | Default Value |
| :------: | :---------- | :-----------: |
| timeout | Sets a timeout in ms for the shutdown operation to complete. If the shutdown operations exceed the timeout, the process will exit with code 1| 10000ms |
| lifo | Reverses the execution order of the shutdown functions| false |

$3

shutdownHook.add(_ => doSomething(), options)

Shutdown functions are executed in the order they were added unless:

1. options.order was specified.
2. lifo: true was specified when instantiating the hook.

Shutdown function can return nothing, a value, a Promise, or throw an error.
A rejected promise or error will stop the shutdown sequence (subsequent functions will not be run) and exit the process with code 1.

You can also name shutdown functions:

shutdownHook.add('database', _ => doSomething(), {name: "foo"})

This might be useful when listening to events (see below). If no name was given, the library auto-generates a name for consistency.

#### Options:

| Property | Description | Default Value |
| :------: | :---------- | :-----------: |
| name | the name of the shutdown function. will be used when emitting events ||
| order | the order of the function is the shutdown sequence. functions are ordered in ascending order before execution | 0|




$3

shutdownHook.register()

Registers the shutdown hook to trigger the shutdown sequence when receiving SIGTERM, SIGINT or "shutdown" messages sent through the process event emitter.

$3

`
shutdownHook.on('ShutdownStarted', (e) => log.info('it has began'))
shutdownHook.on('ComponentShutdown', (e) => log.info('shutting down one component'))
shutdownHook.on('ShutdownEnded', (e) => log.info('it has ended'))
`

#### Events structure:

| Event | Property | Type | Description | Optional |
| :---: | :------: | :--: | :---------- | :------: |
| ComponentShutdown | name | String | Name of the shutdown functions that's being executed| No|
|| order | Number | the order of the shutdown function in the sequence | No |
|| index | Number | the index of the shutdown function in the sequence | No |
| ShutdownEnded | code | Number | The exit code the library used when calling process.exit()`| No |
|| error | Error | The error the library caught in case the sequence failed to run | Yes|