Exit

The purpose of the exit library is to allow for the graceful asynchronous shutdown of resources when signals and exceptions are caught.

This cannot be used with process.exit(). Use Exit.exit() instead.

Installation

npm install --save @leverege/exit

Usage

Include the library in your module:

const Exit = require( '@leverege/exit' )

To configure Exit, you can use init() or the individual set methods. By default, Exit will force and exit in 20 seconds if the shutdown hooks don't complete. When the shutdown hooks complete, Exit will wait 100 ms before calling exit to allow for logs to be written. For testing purposes, the exit function can be set. It will default to process.exit() if one is not supplied.

Exit.init( {
  timeout : 20000,
  exitDelay : 100,
  exit : null
})

Install the default handlers, which will cover SIGINT, SIGHUP, SIGBREAK, SIGTERM, beforeExit, uncaughtException and unhandledRejection.

Exit.installDefaultHandlers()

Installing Shutdown hooks

To install a shutdown hook, use the add() method:

const httpServer = app.listen( 1234 )
const expressShutdown = ( err, { eventType, eventCode } ) => {
  return new Promise( ( resolve, reject ) => { 
    app.close( resolve )
  } )
}

Exit.add( expressShutdown )

If you want to remove the shutdown hook:

Exit.remove( expressShutdown )

Custom Event Handling

You do not have to use Exit.installDefaultHandlers(). If you wish to handle different or addition signals and events, you can elect to register for event individually. The installDefaultHandlers() implementation looks like this:

  handle( 'beforeExit', 0 )

  handle( 'SIGHUP', 128 + 1 )
  handle( 'SIGINT', 128 + 2 )
  handle( 'SIGTERM', 128 + 15 )
  handle( 'SIGBREAK', 128 + 21 )

  handleErr( 'uncaughtException', 1 )
  handleErr( 'unhandledRejection', 1 )

Exit Filtering

You can install a filter against an event type that can cancelled the shutdown and exit procedure. Returning true from a filter will cancel the exit. The following will not exit if the err object has a field called dontExit which is true.

Exit.addFilter( 'uncaughtException', ( err ) => err && err.dontExit === true )
← ErrorPromise →