NodeJS : Spawn STDIN / STDOUT messaging to node process inside a Docker container

gistfile1.txt

// This is the outside in approach, where the parent process is not within Docker, but the child lives in a docker image.

var externalNodeProcess = require('child_process').spawn('docker', [
  'run',
  '-a', 'stdin', '-a', 'stdout', '-a','stderr',
  '-i',
  'image/name:tag',
  'node','index.js'
], {
  stdio: ['pipe', 'pipe', 'pipe']
});
          
// to make it compatible with `fork` syntax

// provide send to stdin
externalNodeProcess.send = function(msg){
  app.process.stdin.write(JSON.stringify(msg)+'\n');
}

// provide on('message') events from stdout - this will also fire on console.log commands, so you need to wrap those if you want to do any other sort of messaging
externalNodeProcess.stdout.on('data', function writeOutDockerLog(data) {
  let msgs = [];
  try {
    data.toString().split('\n').map((m) => { if ( !_.isEmpty(m) ) msgs.push(JSON.parse(m + '\n')); })
  } catch (e) {
    console.error('Docker STDOUT Error:', e, data.toString())
  } finally {
    msgs.forEach((m)=>{
      externalNodeProcess.emit('message', m);
    })
  }
});

// INSIDE the external index.js which is Dockerized
//---------- index.js -------------
// fork provides process.send() . no fork means it's been spawned
if ( !_.isFunction(process.send)){
  console.log('Docker Detected');
  
  process.send = function(obj){
    try {
      var send = JSON.stringify(obj);
    } catch (e) {
      console.error('App Data Error', e, obj);
    } finally {
      process.stdout.write(`${send}\n`);
    }
  }
  
  process.stdin.on('readable', function(){
    const msg = process.stdin.read();
    // multiple msgs might be sent in one event
    let msgs = _.compact(msg.toString().split('\n'));
    let msgObjs = [];
    if ( !_.isNull(msg)){
      try {
        // parse each one independently! - woot working
        msgObjs = msgs.map((m) => { return JSON.parse(m) });
      } catch (e){
        console.error('App Data In Error:', e, msgs)
      } finally {
        // emit one event for each msg found
        if (msgObjs.length > 0) {
          msgObjs.forEach((m) => {
            process.emit('message', m);
          });
        }
      }
    }
  })
}