Send CTRL-C to a Windows console application
Long running stateful processes like servers often hold a lot of
system resources that they need to operate. These are things like
communication ports, file descriptors, database connections, etc... At some point,
when it is time for that process to shut it needs to release all those
resources back to the operating system and exit. This process of
freeing up all the things that were being used is called "graceful
shutdown" and is really important to get right in systems that start
and stop processes repeatedly. On Unix systems, the method for
achieving a graceful shutdown of a process is to send it a signal
(usually either SIGINT or SIGTERM).
The process can then register a handler for this signal which releases any resources that it is holding and exits.
The alternative to a graceful shutdown is a "forced termination". This is what happens when a process is unable to respond to a interrupt or termination signal. In this case, the process is ended immediately without the opprotunity to release any of the resources it holds.
On Unix systems, when you invoke process.kill() on a ChildProcess
object, it sends the SIGTERM signal. That way, if the process has a
SIGTERM handler it has an opportunity to perform a graceful
shutdown.
Windows on the other hand, does not have a method to send signals to a
process, so when you invoke the same process.kill() function on
that platform, what you end up with is a forceful termination
without any cleanup. However, Windows does have a method for
applications to shutdown gracefully, namely hitting CTRL-C on the
console to which the process is attached. And that's what this is all
about. In fact, whenever you hit CTRL-C on a windows console that is
running a node application, node will translate that CTRL-C into
a SIGINT and dispatch any SIGINT handlers that it has
registered. Since most well-behaved long-running Nodejs processes
respond to SIGINT, this allows them to shutdown too.
This module exports a single ctrlc function which accepts a process
id, and sends a CTRL-C event to that console.
Note: This is a no-op on non-windows platforms
import { ctrlc } from 'ctrlc-windows';
export function gracefulShutdown(process) {
if (process.platform === 'win32') {
ctrlc(process.pid);
} else {
process.kill();
}
}
