Prevent signals from propagating to child process (NodeJS)

Question

I have NodeJS code like the following:

[myFile.js]

var path  = require("path");
var cp  = require("child_process");
var child = cp.spawn( "python",["HelloWorld.py"], { stdio:'pipe', });

child.stdout.on('data', (data) => {
    console.log(`CHILD stdout: ${data }`);
});

child.stderr.on('data', (data) => {
  console.log(`CHILD stderr: ${data}`);
});

process.on("SIGINT",()=>{
    // close gracefully
    console.log("Received SIGINT");
})
child.on('exit',(code)=>{console.log(`child Process exited with code ${code}`)})

and python script like:

[HelloWorld.py]

print 'Hi there'
import time
time.sleep(5)

I want to manage the shutdown gracefully, but when I start this code at the command line via:

> node myFile.js

and press control-C, I get this printed to the console:

^CReceived SIGINT
CHILD stdout: Hi there

CHILD stderr: Traceback (most recent call last):
  File "HelloWorld.py", line 3, in <module>
    time.sleep(5)
KeyboardInterrupt

child Process exited with code 1

indicating that python (running in the child process) received the '^C' keyboard event. However, I'd prefer exit the child process a bit more gracefully, rather than crashing on a keyboard interrupt.

I tried a variety of combinations for the options.stdio, including [undefined,'pipe','pipe'] (which didn't work), and ['ignore','pipe','pipe'] (which caused the child process to crash), and I tried worker.stdin.end() (which also caused the child process to crash).

Is there a way to not inherit the standard in from the parent NodeJS process?

Answer 1

RTFM: setting options.detached to true is what prevents propagating the kill signals, which (surprise) is how attached child processes are killed when the parent is killed...