119 lines
4.0 KiB
Markdown
119 lines
4.0 KiB
Markdown
# async-exit-hook
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[](https://travis-ci.org/Tapppi/async-exit-hook)
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[](https://coveralls.io/github/Tapppi/async-exit-hook?branch=master)
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> Run some code when the process exits
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The `process.on('exit')` event doesn't catch all the ways a process can exit. This module catches:
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* process SIGINT, SIGTERM and SIGHUP, SIGBREAK signals
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* process beforeExit and exit events
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* PM2 clustering process shutdown message ([PM2 graceful reload](http://pm2.keymetrics.io/docs/usage/cluster-mode/#graceful-reload))
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Useful for cleaning up. You can also include async handlers, and add custom events to hook and exit on.
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Forked and pretty much rewritten from [exit-hook](https://npmjs.com/package/exit-hook).
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## Install
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```
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$ npm install --save async-exit-hook
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```
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## Usage
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### Considerations and warning
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#### On `process.exit()` and asynchronous code
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**If you use asynchronous exit hooks, DO NOT use `process.exit()` to exit.
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The `exit` event DOES NOT support asynchronous code.**
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>['beforeExit' is not emitted for conditions causing explicit termination, such as process.exit()]
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(https://nodejs.org/api/process.html#process_event_beforeexit)
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#### Windows and `process.kill(signal)`
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On windows `process.kill(signal)` immediately kills the process, and does not fire signal events,
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and as such, cannot be used to gracefully exit. See *Clustering and child processes* for a
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workaround when killing child processes. I'm planning to support gracefully exiting
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with async support on windows soon.
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### Clustering and child processes
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If you use custom clustering / child processes, you can gracefully shutdown your child process
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by sending a shutdown message (`childProc.send('shutdown')`).
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### Example
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```js
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const exitHook = require('async-exit-hook');
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exitHook(() => {
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console.log('exiting');
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});
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// you can add multiple hooks, even across files
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exitHook(() => {
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console.log('exiting 2');
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});
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// you can add async hooks by accepting a callback
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exitHook(callback => {
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setTimeout(() => {
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console.log('exiting 3');
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callback();
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}, 1000);
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});
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// You can hook uncaught errors with uncaughtExceptionHandler(), consequently adding
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// async support to uncaught errors (normally uncaught errors result in a synchronous exit).
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exitHook.uncaughtExceptionHandler(err => {
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console.error(err);
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});
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// You can hook unhandled rejections with unhandledRejectionHandler()
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exitHook.unhandledRejectionHandler(err => {
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console.error(err);
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});
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// You can add multiple uncaught error handlers
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// Add the second parameter (callback) to indicate async hooks
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exitHook.uncaughtExceptionHandler((err, callback) => {
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sendErrorToCloudOrWhatever(err) // Returns promise
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.then(() => {
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console.log('Sent err to cloud');
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});
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.catch(sendError => {
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console.error('Error sending to cloud: ', err.stack));
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})
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.then(() => callback);
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});
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});
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// Add exit hooks for a signal or custom message:
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// Custom signal
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// Arguments are `signal, exitCode` (SIGBREAK is already handled, this is an example)
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exitHook.hookEvent('SIGBREAK', 21);
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// process event: `message` with a filter
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// filter gets all arguments passed to *handler*: `process.on(message, *handler*)`
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// Exits on process event `message` with msg `customShutdownMessage` only
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exitHook.hookEvent('message', 0, msg => msg !== 'customShutdownMessage');
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// All async hooks will work with uncaught errors when you have specified an uncaughtExceptionHandler
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throw new Error('awesome');
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//=> // Sync uncaughtExcpetion hooks called and retun
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//=> '[Error: awesome]'
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//=> // Sync hooks called and retun
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//=> 'exiting'
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//=> 'exiting 2'
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//=> // Async uncaughtException hooks return
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//=> 'Sent error to cloud'
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//=> // Sync uncaughtException hooks return
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//=> 'exiting 3'
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```
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## License
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MIT © Tapani Moilanen
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MIT © [Sindre Sorhus](http://sindresorhus.com)
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