http-graceful-shutdown

What is http-graceful-shutdown?

The http-graceful-shutdown npm package provides a way to gracefully shut down HTTP servers in Node.js applications. It ensures that the server stops accepting new connections and waits for existing connections to complete before shutting down, which helps in preventing data loss and ensuring a smooth shutdown process.

What are http-graceful-shutdown's main functionalities?

Basic Graceful Shutdown

This code demonstrates a basic setup for a graceful shutdown of an HTTP server. The server will stop accepting new connections and wait for existing connections to complete before shutting down.

const http = require('http');
const gracefulShutdown = require('http-graceful-shutdown');

const server = http.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
});

server.listen(3000, () => {
  console.log('Server running at http://127.0.0.1:3000/');
});

gracefulShutdown(server);

Custom Shutdown Handlers

This code demonstrates how to add custom shutdown handlers. The `onShutdown` option allows you to define tasks that should be completed before the server shuts down, such as cleaning up resources or logging.

const http = require('http');
const gracefulShutdown = require('http-graceful-shutdown');

const server = http.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
});

server.listen(3000, () => {
  console.log('Server running at http://127.0.0.1:3000/');
});

gracefulShutdown(server, {
  onShutdown: () => {
    return new Promise((resolve) => {
      console.log('Custom shutdown tasks');
      setTimeout(resolve, 1000);
    });
  }
});

Timeout for Shutdown

This code demonstrates how to set a timeout for the shutdown process. If the server does not shut down within the specified time, it will forcefully terminate.

const http = require('http');
const gracefulShutdown = require('http-graceful-shutdown');

const server = http.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
});

server.listen(3000, () => {
  console.log('Server running at http://127.0.0.1:3000/');
});

gracefulShutdown(server, {
  timeout: 30000 // 30 seconds
});

Other packages similar to http-graceful-shutdown

stoppable

The stoppable package provides similar functionality for gracefully shutting down HTTP servers. It allows you to stop accepting new connections and wait for existing connections to complete. Compared to http-graceful-shutdown, stoppable is more lightweight and has fewer configuration options.

graceful-server

The graceful-server package offers a way to gracefully shut down HTTP servers with additional features like handling multiple servers and custom shutdown hooks. It provides more flexibility and control compared to http-graceful-shutdown.

terminus

The terminus package is designed for graceful shutdowns and health checks for Node.js HTTP servers. It integrates with Kubernetes and other orchestration tools, providing more advanced features compared to http-graceful-shutdown.

README

http-graceful-shutdown

  _   _   _                                  __      _        _        _      _
 | |_| |_| |_ _ __ ___ __ _ _ _ __ _ __ ___ / _|_  _| |___ __| |_ _  _| |_ __| |_____ __ ___ _
 | ' \  _|  _| '_ \___/ _` | '_/ _` / _/ -_)  _| || | |___(_-< ' \ || |  _/ _` / _ \ V  V / ' \
 |_||_\__|\__| .__/   \__, |_| \__,_\__\___|_|  \_,_|_|   /__/_||_\_,_|\__\__,_\___/\_/\_/|_||_|
             |_|      |___/

Gracefully shuts down node.js http server. More than 10 Mio downloads overall.

Version 3.0 just released. This version is fully backwards compatible to version 2.x but adds much better handling under the hood. More that 10 Mio downloads.

• can be used with express, koa, fastify, native node http, http2 ... see examples
• simple to use
• configurable to your needs
• add your own cleanup function

Features

http-graceful-shutdown manages a secure and save shutdown of your http server application:

• tracks all connections
• stops the server from accepting new connections on shutdown
• graceful communication to all connected clients of server intention to shut down
• immediately destroys all sockets without an attached HTTP request
• properly handles all HTTP and HTTPS connections
• possibility to define cleanup functions (e.g. closing DB connections)
• preShutdown function if you need to have all HTTP sockets available and untouched
• choose between shutting down by function call or triggered by SIGINT, SIGTERM, ...
• choose between final forceful process termination node.js (process.exit) or clearing event loop (options).

Quick Start

Installation

$ npm install http-graceful-shutdown

Basic Usage

const gracefulShutdown = require('http-graceful-shutdown');
...
// app: can be http, https, express, koa, fastity, ...
server = app.listen(...);
...

// this enables the graceful shutdown
gracefulShutdown(server);

Explanation

Functionality

                                                                    PARENT Process (e.g. nodemon, shell, kubernetes, ...)
─────────────────────────┬───────────────────────────────────────────────────────────────────────────────────────────────
                         │ Signal (SIGINT, SIGTERM, ...)
                         │
                         │
           (1)       (2) v                                                 NODE SERVER (HTTP, Express, koa, fastity, ...)
    ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇
           │             │ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ │ <─ shutdown procedure
           │             │ shutdown initiated           │ │                                            │
           │             │                              │ │                                            │
           │             │                              │ │    (8) shutdown function    (9) finally fn │
           │             │ ▄▄▄▄▄▄▄▄▄▄▄▄ ▄▄▄             │ │ ▄▄ ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ▄▄▄▄▄▄▄▄▄▄▄▄▄▄ │
           │             └ (3)          (4) close       │ └ (7) destroy                                │
           │               preShutdown  idle sockets    │   remaining sockets                          │
           │                                            │                                              │ (10)
     serve │      serving req. (open connection)        │          (5)                                 └ SERVER terminated
        ▄▄▄│      ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄┤           ^ blocked
        ^  │      ^  last request before                │           │
        │  │      │  receiving shutdown signal          │           │
        │  │      │                                     │           │
        │  │      │                                     │           │
        │  │      │                                     │           │
        │  │      │ Long request                        │           │
Request │  V Resp │                                     V Resp.     │
        │         │                                                 │                                                   CLIENT
────────┴─────────┴─────────────────────────────────────────────────┴─────────────────────────────────────────────────────────

1. usually, your NODE http server (the black bar in the middle) replies to client requests and sends responses
2. if your server receives a termination signal (e.g. SIGINT - Ctrl-C) from its parent, http-graceful-shutdown starts the shutdown procedure
3. first, http-graceful-shutdown will run the "preShutdown" (async) function. Place your own function here (passed to the options object), if you need to have all HTTP sockets available and untouched.
4. then all empty connections are closed and destroyed and
5. http-graceful-shutdown will block any new requests
6. if possible, http-graceful-shutdown communicates to the clients that the server is about to close (connection close header)
7. http-graceful-shutdown now tries to wait till all sockets are finished, then destroys the all remaining sockets
8. now it is time to run the "onShutdown" (async) function (if such a function is passed to the options object)
9. as soon as this onShutdown function has ended, the "finally" (sync) function is executed (if passed to the options)
10. now the event loop is cleared up OR process.exit() is triggered (can be defined in the options) and the server process ends.

Options

option	default	Comments
timeout	30000	timeout till forced shutdown (in milliseconds)
signals	'SIGINT SIGTERM'	define the signals, that should be handled (separated by SPACE)
development	false	if set to true, no graceful shutdown is proceeded to speed up dev-process
preShutdown	-	not time-consuming callback function. Needs to return a promise. Here, all HTTP sockets are still available and untouched
onShutdown	-	not time-consuming callback function. Needs to return a promise.
forceExit	true	force process.exit - otherwise just let event loop clear
finally	-	small, not time-consuming function, that will be handled at the end of the shutdown (not in dev-mode)

Option Explanation

• timeout: You can define the maximum time that the shutdown process may take (timeout option). If after this time, connections are still open or the shutdown process is still running, then the remaining connections will be forcibly closed and the server process is terminated.
• signals Here you can define which signals can trigger the shutdown process (SIGINT, SIGTERM, SIGKILL, SIGHUP, SIGUSR2, ...)
• development If true, the shutdown process is much shorter, because it just terminates the server, ignoring open connections, shutdown function, finally function ...
• preShutdown Place your own (not time-consuming) callback function here, if you need to have all HTTP sockets available and untouched during cleanup. Needs to return a promise. (async). If you add an input parameter to your cleanup function (optional), the SIGNAL type that caused the shutdown is passed to your cleanup function. See example.
• onShutdown place your (not time-consuming) callback function, that will handle your additional cleanup things (e.g. close DB connections). Needs to return a promise. (async). If you add an input parameter to your cleanup function (optional), the SIGNAL type that caused the shutdown is passed to your cleanup function. See example.
• finally here you can place a small (not time-consuming) function, that will be handled at the end of the shutdown e.g. for logging of shutdown. (sync)
• forceExit force process.exit() at the end of the shutdown process, otherwise just let event loop clear

Advanced Options Example

You can pass an options-object to specify your specific options for the graceful shutdown

The following example uses all possible options:

const gracefulShutdown = require('http-graceful-shutdown');
...
// app: can be http, https, express, koa, fastity, ...
server = app.listen(...);
...

// your personal cleanup function
// - must return a promise
// - the input parameter is optional (only needed if you want to
//   access the signal type inside this function)
// - this function here in this example takes one second to complete
function shutdownFunction(signal) {
  return new Promise((resolve) => {
    console.log('... called signal: ' + signal);
    console.log('... in cleanup')
    setTimeout(function() {
      console.log('... cleanup finished');
      resolve();
    }, 1000)
  });
}

// finally function
// -- sync function
// -- should be very short (not time consuming)
function finalFunction() {
  console.log('Server gracefulls shutted down.....')
}

// this enables the graceful shutdown with advanced options
gracefulShutdown(server,
  {
    signals: 'SIGINT SIGTERM',
    timeout: 10000,                   // timeout: 10 secs
    development: false,               // not in dev mode
    forceExit: true,                  // triggers process.exit() at the end of shutdown process
    preShutdown: preShutdownFunction, // needed operation before httpConnections are shutted down
    onShutdown: shutdownFunction,     // shutdown function (async) - e.g. for cleanup DB, ...
    finally: finalFunction            // finally function (sync) - e.g. for logging
  }
);

Trigger shutdown manually

You can now trigger gracefulShutdown programatically (e.g. for tests) like so:

let shutdown
beforeAll(() => {
  shutdown = gracefulShutdown(...)
})

afterAll(async () => {
  await shutdown()
})

Do not force process.exit()

With the forceExit option, you can define how your node server process ends: when setting forceExit to false, you just let the event loop clear and then the proccess ends automatically:

const gracefulShutdown = require('http-graceful-shutdown');
...
// app: can be http, https, express, koa, fastity, ...
server = app.listen(...);
...

// enable graceful shutdown with options:
// this option lets the event loop clear to end your node server
// no explicit process.exit() will be triggered.

gracefulShutdown(server, {
  forceExit: false
});

If you want an explicit process.exit() at the end, set forceExit to true (which is the default).

Debug

If you want to get debug notes (debug is a dependency of this module), just set the DEBUG environment variable to enable debugging:

export DEBUG=http-graceful-shutdown

OR on Windows:

set DEBUG=http-graceful-shutdown

Examples

You can find examples how to use http-graceful-shutdown with Express, Koa, http, http2, fastify in the examples directory. To run the examples, be sure to install debug and express, koa or fastify.

npm install debug express koa fastify

Version history

Version	Date	Comment
3.1.12	2023-02-11	fix forceExit default value
3.1.11	2022-11-18	updated examples
3.1.10	2022-11-17	forceExit handling adapted
3.1.9	2022-10-24	updated docs, code cleanup
3.1.8	2022-07-27	updated docs, fixed typos
3.1.7	2022-03-18	updated dependencies, updated docs
3.1.6	2022-02-27	updated dependencies
3.1.5	2021-11-08	updated docs
3.1.4	2021-08-27	updated docs
3.1.3	2021-08-03	fixed handle events once (thanks to Igor Basov)
3.1.2	2021-06-15	fixed cleanupHttp() no timeout
3.1.1	2021-05-13	updated docs
3.1.0	2021-05-08	refactoring, added preShutdown
3.0.2	2021-04-08	updated docs
3.0.1	2021-02-26	code cleanup
3.0.0	2021-02-25	version 3.0 release
2.4.0	2021-02-15	added forceExit option (defaults to true)
2.3.2	2019-06-14	typescript typings fix
2.3.1	2019-05-31	updated docs, added typescript typings
2.3.0	2019-05-30	added manual shutdown (for tests) see docs below
2.2.3	2019-02-01	updated docs, debug
2.2.2	2018-12-28	updated docs, keywords
2.2.1	2018-11-20	updated docs
2.2.0	2018-11-19	added (optional) signal type to shutdown function - see example
2.1.3	2018-11-06	updated docs
2.1.2	2018-11-03	updated dependencies (version bump), updated docs
2.1.1	2018-02-28	extended isFunction to support e.g. AsyncFunctions
2.1.0	2018-02-11	bug fixing onShutdown method was called before server.close
2.0.6	2017-11-06	updated docs, code cleanup
2.0.5	2017-11-06	updated dependencies, modifications gitignore, added docs
2.0.4	2017-09-21	updated dependencies, modifications gitignore
2.0.3	2017-06-18	updated dependencies
2.0.2	2017-05-27	fixed return value 0
2.0.1	2017-04-24	modified documentation
2.0.0	2017-04-24	added 'onShutdown' option, renamed 'callback' option to 'finally'
1.0.6	2016-02-03	adding more explicit debug information and documentation
1.0.5	2016-02-01	better handling of closing connections
1.0.4	2015-10-01	small fixes
1.0.3	2015-09-15	updated docs
1.0.1	2015-09-14	updated docs, reformated code
1.0.0	2015-09-14	initial release

Comments

If you have ideas, comments or questions, please do not hesitate to contact me.

Sincerely,

Sebastian Hildebrandt, +innovations

Credits

Written by Sebastian Hildebrandt sebhildebrandt

Contributors

• Deepak Bhattarai bring2dip
• Shen shenfe
• Jeff Hansen jeffijoe
• Igor Basov IgorBasov

License

The MIT License (MIT)

Copyright © 2015-2023 Sebastian Hildebrandt, +innovations.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.