capture-exit

What is capture-exit?

The capture-exit npm package is designed to enable graceful shutdown and cleanup of Node.js processes by capturing and managing exit signals. It allows developers to register multiple cleanup functions that will be executed when the process exits, either normally or due to an uncaught exception, or when signals like SIGTERM or SIGINT are received. This is particularly useful for ensuring that resources are properly released and that critical finalization steps are completed before the process exits.

What are capture-exit's main functionalities?

Registering cleanup functions

This feature allows developers to register functions that will be executed when the process exits. The code sample demonstrates how to register a simple cleanup function that logs a message to the console before the process exits.

const captureExit = require('capture-exit');
captureExit.captureExit();

function cleanup() {
  console.log('Cleanup code executed before exit.');
}

captureExit.onExit(cleanup);

Handling multiple cleanup functions

This feature supports the registration of multiple cleanup functions. The code sample shows how to register two separate functions to handle different cleanup tasks, such as closing database connections and clearing cache.

const captureExit = require('capture-exit');
captureExit.captureExit();

function cleanupDatabase() {
  console.log('Database connections closed.');
}

function cleanupCache() {
  console.log('Cache cleared.');
}

captureExit.onExit(cleanupDatabase);
captureExit.onExit(cleanupCache);

Other packages similar to capture-exit

exit-hook

exit-hook is a similar package that provides functionality to execute cleanup code when a Node.js process exits. Compared to capture-exit, exit-hook has a simpler API but does not handle uncaught exceptions by default.

async-exit-hook

async-exit-hook extends the basic functionality of exit-hook by supporting asynchronous cleanup functions. This is useful for handling tasks that require a bit more time to complete, such as asynchronous database shutdowns. It is similar to capture-exit in managing async operations but differs in API and additional configuration options.

README

capture-exit

Allow cooprative async exit handlers, we unfortunately must hijack process.exit.

It allows a handler to ensure exit, without that exit handler impeding other similar handlers

for example, see: sindresorhus/ora#27

Differences between process.on('exit') and captureExit.onExit(...) => https://github.com/ember-cli/capture-exit/issues/12

Installation

yarn add capture-exit
// or
npm install --save capture-exit

Usage

// as early in startup as possible
require('capture-exit').captureExit();

// when you want to schedule some work on exit:
function onExit() {
  return something.processWillExit(); // you can return promises, which will pause exit until fulfilled
}

require('capture-exit').onExit(onExit); // add an exit handler
require('capture-exit').offExit(onExit); // allows one to remove an exit handle if it is not longer required