Run some code when the process exits
The process.on('exit')
event doesn't catch all the ways a process can exit.
This package is useful for cleaning up before exiting.
npm install exit-hook
import exitHook from 'exit-hook';
exitHook(() => {
console.log('Exiting');
});
// You can add multiple hooks, even across files
exitHook(() => {
console.log('Exiting 2');
});
throw new Error('🦄');
//=> 'Exiting'
//=> 'Exiting 2'
Removing an exit hook:
import exitHook from 'exit-hook';
const unsubscribe = exitHook(() => {});
unsubscribe();
Register a function to run during process.exit
.
Returns a function that removes the hook when called.
Type: function(): void
The callback function to execute when the process exits.
Register a function to run during gracefulExit
.
Returns a function that removes the hook when called.
Please see Async Notes for considerations when using the asynchronous API.
import {asyncExitHook} from 'exit-hook';
asyncExitHook(async () => {
console.log('Exiting');
}, 300);
throw new Error('🦄');
//=> 'Exiting'
Removing an asynchronous exit hook:
import {asyncExitHook} from 'exit-hook';
const unsubscribe = asyncExitHook(async () => {
console.log('Exiting');
}, {
minimumWait: 300
});
unsubscribe();
Type: function(): void | Promise<void>
The callback function to execute when the process exits via gracefulExit
, and will be wrapped in Promise.resolve
.
Type: number
The amount of time in milliseconds that the onExit
function is expected to take.
Exit the process and make a best-effort to complete all asynchronous hooks.
If you are using asyncExitHook
, consider using gracefulExit()
instead of process.exit()
to ensure all asynchronous tasks are given an opportunity to run.
import {gracefulExit} from 'exit-hook';
gracefulExit();
Type: number
Default: 0
The exit code to use. Same as the argument to process.exit()
.
tl;dr If you have 100% control over how your process terminates, then you can swap exitHook
and process.exit
for asyncExitHook
and gracefulExit
respectively. Otherwise, keep reading to understand important tradeoffs if you're using asyncExitHook
.
Node.js does not offer an asynchronous shutdown API by default #1 #2, so asyncExitHook
and gracefulExit
will make a "best effort" attempt to shut down the process and run your asynchronous tasks.
If you have asynchronous hooks registered and your Node.js process is terminated in a synchronous manner, a SYNCHRONOUS TERMINATION NOTICE
error will be logged to the console. To avoid this, ensure you're only exiting via gracefulExit
or that an upstream process manager is sending a SIGINT
or SIGTERM
signal to Node.js.
Asynchronous hooks should make a "best effort" to perform their tasks within the minimumWait
time, but also be written to assume they may not complete their tasks before termination.