node-exit-hook

Node.js cancellable exit-hooks

Installation

npm install exit-hook2 --save

Usage

var exitHook = require('exit-hook2')

exitHook(function (canCancel, signal, code) {
    var allowShutdown = canCancel && false;
    
    return allowShutdown;
});

• context An optional context for the 'callback' function. If undefined, the callback will have it's own context.
• callback A function to execute when the application is exiting.
  • canCancel When true the exit can be cancelled by returning false.
  • signal Originating signal (if any).
  • code Exit code.

A full list of exit codes can be found here (new window).

Returning false terminates the shutdown sequence and stops the callback loop. If the shutdown cannot be cancelled ('canCancel' = false) the callback loop will not stop running.

If 'canCancel' is set to false then only synchronous code can execute. Any asynchronous operations WILL NOT RUN.

Graceful shutdown with asynchronous operations

exitHook(function (canCancel, signal, code) {
    if (canCancel) {
        exitHook.removeListener(this);
        
        server.close(function () {
            process.exit(code);
        });
        
        return false;
    }
});

exitHook.list

Returns an array with all the events currently listened to.

var list = exitHook.list(); // ['SIGINT', 'SIGTERM', 'SIGHUP', ...]

exitHook.bind

Binds a new event to treat as a shutdown signal.

exitHook.bind('CUSTOM1', true).list(); // ['SIGINT', 'SIGTERM', 'SIGHUP', 'CUSTOM1', ...]

• signal Shutdown signal to listen for.
• canCancel Boolean passed to the handlers signaling whether the shutdown can be cancelled.

exitHook.unbind

Unbinds a previously bound shutdown signal.

exitHook.unbind('CUSTOM1').list(); // ['SIGINT', 'SIGTERM', 'SIGHUP', ...]
exitHook.unbind('SIGTERM').list(); // ['SIGINT', 'SIGHUP', ...]

• signal Shutdown signal to stop listening for. Pass "everything" to clear the module of all shutdown signals.

exitHook.removeListener

Removes a previously added shutdown listener.

exitHook(function () {
    performCleanup();
    
    // Make sure the cleanup script isn't executed multiple times
    exitHook.removeListener(this);
});

Custom events

// Let 'CUSTOM1' act as a cancellable shutdown signal
exitHook.bind('CUSTOM1', true);

exitHook(function (canCancel, signal, code) {
    canCancel; // true
    signal; // CUSTOM1
    code; // 128
    
    // Don't let the process terminate
    return false;
});

process.emit('CUSTOM1', 128);

License

MIT