When a Node.js process can exit() directly without triggering other signal events (uncaughtException, SIGINT, SIGTERM...)

Question

I work on an application with a REDIS data store. To maintain the data integrity I would like to cleanup the store on process shutdown.

I created a function handler and bind it (with process.on()) to signal events: uncaughtException, SIGINT, SIGTERM, SIGQUIT and it works well (CTRL+C, process killing, exception, ...).

But I've read that in certain conditions the process can exit directly without triggering the other signal events.

The problem in this particular case is that process.on('exit') handler can only process synchronous tasks.

I made different test to try to kill the process in different ways. And (except with SIGTERM on Windows) I wasn't able to identify the case where process.on('exit') is triggered directly without SIGINT, SIGTERM or other event firing.

So my question is (on Linux system), under what conditions the process can exit directly without firing on of this event: http://nodejs.org/api/all.html#all_signal_events ?

Answer 1

As of now, reading the documentation and doing some research, it seems there is only four way a node.js app exit:

• process.exit(), which is handled by process.on('exit')
• Receiving a *nix signal, which can be handled by process.on('signal_name')`
• Having a exception going back to the event loop, handled by process.on('UncaughtException')
• The computer being plugged out, destroyed, the node.js binary blowing up, or a SIGKILL/kill -9, and there is no handling to that.

It usually happen someone don t understand the error message from a uncaughtException, and mistakenly believe it is "something else" that killed node.js.