nodejs - forked processes get killed if one process calls exit?

Question

I need to fork/spawn processes from my main node application. This processes should run "endless" as they check filesystem for changes in different folders and process new files.

I fork processes in the following way:

var processes = [];
var fork = require('child_process').fork;

var processList = [
    {'servicename':'faxservice1'}, 
    {'servicename':'faxservice2'},
    {'servicename':'faxservice3'}
];

timeOutValue = 10000;

processList.forEach(Service => {

    var cp = fork(['./modules/services/inbound/fax/service.js']);


    cp.on('close', function() {
        console.log('child process has ended');
        process.exit();
    })

    cp.on('message', (m) => {
        console.log(`SVC | ${m}`);
    });

    setTimeout(function() {
        cp.send('stop');
    }, timeOutValue);    

    // Push spawned process to process-array
    processes.push(cp);

    timeOutValue = timeOutValue + 5000;
});

The child processes do the following:

const svcName = 'FAX-INBOUND';

var chokidar = require('chokidar');
var watcher = chokidar.watch('file, dir, or glob', {
    ignored: /[\/\\]\./, persistent: true
  });

var log = console.log.bind(console);

var args = process.argv.slice(2);
console.log(`${svcName} | ${args} | starting`);

process.on('message', (m) => {
    console.log(`${svcName} | ${m} | Service termination command recieved from host`);
    process.exit();
});




watcher
      .on('add', function(path) { log(svcName + " | " + 'File', path, 'has been added'); })
      .on('addDir', function(path) { log(svcName + " | " + 'Directory', path, 'has been added'); })
      .on('change', function(path) { log(svcName + " | " + 'File', path, 'has been changed'); })
      .on('unlink', function(path) { log(svcName + " | " + 'File', path, 'has been removed'); })
      .on('unlinkDir', function(path) { log(svcName + " | " + 'Directory', path, 'has been removed'); })
      .on('error', function(error) { log(svcName + " | " + 'Error happened', error); })
      .on('ready', function() { log(svcName + " | " + 'Initial scan complete. Ready for changes.'); })
      .on('raw', function(event, path, details) { log(svcName + " | " + 'Raw event info:', event, path, details); })

If i run the shown code, i see at the log that three processes where forked:

FAX-INBOUND |  | starting
FAX-INBOUND |  | starting
FAX-INBOUND | Initial scan complete. Ready for changes.
FAX-INBOUND | Initial scan complete. Ready for changes.
FAX-INBOUND |  | starting
FAX-INBOUND | Initial scan complete. Ready for changes.

the setTimeout is only for debugging purposes and should send a message to the three forked processes each by each with a 5 Second delay. After the spawned processes revieve the message, they should exit.

BUT At the console i only see the console output of one forked process:

FAX-INBOUND | stop | Service termination command recieved from host

It seems, that if one forked process calls

process.exit()

all forked processes get killed ?

What am i doing wrong?

Regards

Answer 1

In "cp.on('close', ...)" you exit the parent process as soon as a child died. This in turn will kill all forked processes, since they haven't forked with option.detached=true