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Attempting to Import Module in Child Process (Javascript) and Failing

I'm currently running a heavy computation (i.e. generating a Monte Carlo tree), which is an expensive operation. I only have a few seconds to build as big of a tree as I can, so I am using subprocesses in Node.js in order to build multiple trees, and then aggregate their data together to make a more informed decision.
I understand that subprocesses do not share information/memory, and I need to use modules within these subprocesses that are located in a file, called "Epilog.js" on my machine.
When I run functions that are in epilog.js from the main file, it works just fine. But all of my functions that are in my worker threads return absolutely nothing.
I have tested to make sure that the parameters of the functions I am trying to use in "epilog.js" aren't empty, and they're not. The problem isn't in the parameter.
I have also tested to see what happens if I simply don't import, and instead of just outputting an undefined array, I get an error saying that there is no function called "findroles".
//My main thread.
var fs = require('fs');
eval(fs.readFileSync('epilog.js') + '');
var process = fork('./buildGraph.js');
process.send({library});
//My worker thread.
//buildGraph.js
var fs = require('fs');
eval(fs.readFileSync('epilog.js') + '');
// receive message from master process
process.on('message', async(message) => {
library = message["library"];
console.log(findroles(library));
// findroles(library) is a function that is defined in epilog.js,
//and this outputs an array of "roles" given a parameter,library.
// For some reason this function outputs [], rather than giving me
// all of the roles. If I run this exact line from my main thread,
// it doesn't give any errors and outputs the right array:
// e.g. ['red', 'white'].
});
I expect to get not the empty array, but [red, white], as I do if I were to run the same line in the main thread. Does anyone have an idea as to the inconsistency of the functions? I'm very new to node.js and this isn't a class focused too much on software engineering in JavaScript, so I'd appreciate if someone can dumb down what is going on, as this is all very new to me.

If your script does not find the function called findroles then there is a problem with the importing method. Using the eval function for importing is not the normal way of importing modules. Try something like this:
// buildGraph.js
const epilog = require("./epilog.js");
......
console.log(epilog.findroles(library));
then epilog.js
exports.findroles = function (library) {
// function content
}
You can find more info here:
https://www.w3schools.com/nodejs/nodejs_modules.asp

Base on the document and example here, everything seem correct but I think the problem come from this line:
var process = fork('./buildGraph.js');
you might override the original process.
try to change it to
const n = fork('./buildGraph.js');

Storing value and then sending everything in Javascript

I am working in Node-red built on node js
I was trying to create one node which will store all inputs from different function node and then will send them all to next node.
in Node-RED each msg process once and it is sent and the msg process is asynchronous by property.
Documentation : http://nodered.org/docs/creating-nodes/node-js.html
This is node-RED wiring screenshot:
There are two functions going to a concatenation node
The concatenation node code is:
module.exports = function(RED) {
function LowerCaseNode(config) {
RED.nodes.createNode(this,config);
var node = this;
this.on('input', function(msg) {
var abc = [];
abc.push(msg.payload);
node.send(msg);
});
}
RED.nodes.registerType("lower-case",LowerCaseNode);
}
the output what I am getting in debug tab is:
The output I wanted in debug tab is:

Your concat node has no way of knowing which function node the incoming message came from, there is no information about the source passed with a message.
The best you could do is set a different topic field in each function node and use this to distinguish inputs.
Also this probably doen't need to be a separate node, you should be able to implement it as a function node and make use of the context variable.

NodeJS, SocketIO and Express logic context build

I read a lot about Express / SocketIO and that's crazy how rarely you get some other example than a "Hello" transmitted directly from the app.js. The problem is it doesn't work like that in the real world ... I'm actually desperate on a logic problem which seems far away from what the web give me, that's why I wanted to point this out, I'm sure asking will be the solution ! :)
I'm refactoring my app (because there were many mistakes like using the global scope to put libs, etc.) ; Let's say I've got a huge system based on SocketIO and NodeJS. There's a loader in the app.js which starts the socket system.
When someone join the app it require() another module : it initializes many socket.on() which are loaded dynamically and go to some /*_socket.js files in a folder. Each function in those modules represent a socket listener, then it's way easier to call it from the front-end, might look like this :
// Will call `user_socket.js` and method `try_to_signin(some params)`
Queries.emit_socket('user.try_to_signin', {some params});
The system itself works really well. But there's a catch : the module that will load all those files which understand what the front-end has sent also transmit libraries linked with req/res (sessions, cookies, others...) and must do it, because the called methods are the core of the app and very often need those libraries.
In the previous example we obviously need to check if the user isn't already logged-in.
// The *_socket.js file looks like this :
var $h = require(__ROOT__ + '/api/helpers');
module.exports = function($s, $w) {
var user_process = require(__ROOT__ + '/api/processes/user_process')($s, $w);
return {
my_method_called: function(reference, params, callback) {
// Stuff using $s, $w, etc.
}
}
// And it's called this way :
// $s = services (a big object)
// $w = workers (a big object depending on $s)
// They are linked with the req/res from the page when they are instantiated
controller_instance = require('../sockets/'+ controller_name +'_socket')($s, $w);
// After some processes ...
socket_io.on(socket_listener, function (datas, callback) {
// Will call the correct function, etc.
$w.queries.handle_socket($w, controller_name, method_name, datas);
});
The good news : basically, it works.
The bad news : every time I refresh the page, the listeners double themselves because they are in a loop called on page load.
Below, this should have been one line :
So I should put all the socket.on('connection'...) stuff outside the page loading, which means when the server starts ... Yes, but I also need the req/res datas to be able to load the libraries, which I get only when the page is loaded !
It's a programing logic problem, I know I did something wrong but I don't know where to go now, I got this big system which "basically" works but there's like a paradox on the way I did it and I can't figure out how to resolve this ... It's been a couple of hours I'm stuck.
How can I refacto to let the possibility to get the current libraries depending on req/res within a socket.on() call ? Is there a trick ? Should I think about changing completely the way I did it ?
Also, is there another way to do what I want to do ?
Thank you everyone !
NOTE : If I didn't explain well or if you want more code, just tell me :)
EDIT - SOLUTION : As seen above we can use sockets.once(); instead of sockets.on(), or there's also the sockets.removeAllListeners() solution which is less clean.

Try As Below.
io.sockets.once('connection', function(socket) {
io.sockets.emit('new-data', {
channel: 'stdout',
value: data
});
});
Use once instead of on.
This problem is similar as given in the following link.
https://stackoverflow.com/questions/25601064/multiple-socket-io-connections-on-page-refresh/25601075#25601075

WebdriverJS dump to terminal?

I am finding it very difficult to debug a test using WebDriverJs because I don't know how to see the value of a variable. For example, I am trying to access the window handle of a pop-up. I can test .toNotBe(null), but I would like to know the actual value. Every time I want to use it in the next logical step of driver.switchTo().window(handle) I get the error that NameOrHandle is not defined. That is probably the next question on SO; but for now I just want to know what node thinks "handle" is if not null but still not defined.
Is there a dump() command, or a helper library I can load into my spec with require that will allow me to dump an object's value to the terminal?

You should just be able to console.log() to dump your output to the terminal. For example:
driver.getAllWindowHandles().then(function(windows){
var originalWindow = windows[0];
var popupWindow = windows[1];
if (popupWindow) {
driver.switchTo().window(popupWindow);
driver.getTitle().then(function(popupTitle){
console.log("popupTitle is set to: ", popupTitle);
next();
});
}
});

How to discover and load js files at runtime?

I'm writing a node.js based server that manages a range of devices. The node.js based server tells connected clients about its abilities. The abilities are defined by separate js files that define objects that are using inheritance via util.inherits().
The problem I have is that right now, I have to define a new js for a new ability and then update the main js program to require the new js, change the code to publish that the ability is available, and then utilise the new ability if requested to by the client.
I would like to make the main code more generic whereby it can
detect the new abilities,
automatically include them,
notify the clients, and
utilise the code.
The detection I can do via the various npm modules out there that support tree browsing, I can just nominate a subdirectory for all capabilities and discover what files are there. I presume that I can use require for step 2 (though not 100% certain), however I don't know how to do step 3 and 4 or use the results from step 2 with step 3 and 4.
I would value any feedback on how to solve this problem.
To clarify my problem. Right now my logic is as per the following:
var logicA = requires('./capabilities/a.js');
var logicB = requires('./capabilities/b.js');
var logicC = requires('./capabilities/c.js');
var Comms.CAPABILITY_A = 'a';
var Comms.CAPABILITY_B = 'b';
var Comms.CAPABILITY_C = 'c';
var Comms.MSG_CAPABILITY = 0;
var Comms.MSG_DO_LOGIC = 1;
function onMessageReceived(comms, msgId, body) {
switch (msgId) {
case(MSG_DO_LOGIC):
doLogic(body);
break;
...
}
}
function doLogic(flag) {
switch(flag) {
case(Comms.CAPABILITY_A):
logicA.doLogic();
break;
case(Comms.CAPABILITY_B):
logicB.doLogic();
break;
case(Comms.CAPABILITY_C):
logicC.doLogic();
break;
}
}
At the client side I have hard coded logic that presumes what is available. I can remove this by having the server send an array of the capabilities to the client, and then the client can choose one of the elements of the array and pass it back as the request to execute the logic. This is not my problem.
My problem is understanding how to cause the host program load all the logic dynamically and then evaluate which logic to execute on the dynamically loaded logic.
I should state that when I say dynamic, I mean that the code available is determined at runtime. However the evaluation is only ever performed when the server is first started.

I solved the problem by creating a register.js where all the protocols are kept. Each time I create a new protocol, I add it to the register.
Via the register I can get an array of all registered protocols. I can pass them back to the client, the client can choose a protocol and I can request an instance of the protocol via the register class.
While there is some hardcoding, it's restricted to the register class which is in the same directory as the protocols.
So in the register I have the following functions:
getList()
getText()
validateProtocolId()
getProtocol()
I use getList() to return an array of the protocol id's that are registered. I use getText() to provide a human readable list of supported protocols. I use validateProtocolId() to validate an id returned from the client to confirm that the id represents a registered protocol and then I use getProtocol() to generate an instance of the registered protocol.
In essence the getProtocol() just does a require('./<protocol file>.js') as appropriate.
It's not as elegant as auto discovery, but it allows tighter controls on what is registered without forcing custom file, etc.