Reload module at runtime

Question

I am considering to port a highly demanded(lots of traffic) sockets-based architecture from .NET to Node.JS using Socket.IO.

My current system is developed in .NET and use some scripting languages, loaded at runtime, so I can do hot-fixes if needed by issuing a reload command to the server, without having to restart the different servers/dispatcher processes.

I originally built it this way so, like I said, I could do hot fixes if needed and also keep the system available with transparent fixes.

I am new to Node.JS but this is what I want to accomplish:

Load javascript files on demand at runtime, store them in variables somewhere and call the script functions.

What would be the best solution? How to call a specific function from a javascript file loaded at runtime as a string? Can i load a javascript file, store it in a variable and call functions in a normal way just like a require?

Thanks!

I'm sorry - I'm not sure I understand the question - what are you trying to do? Are you asking how to use `require` with custom scripts of your own? Because [it's just like you think](http://stackoverflow.com/questions/4481058/load-and-execute-external-js-file-in-node-js-with-access-to-local-variables) — yuvi, Oct 29 '14 at 15:21
Are you asking how you can reload imported scripts to your main? — majidarif, Oct 29 '14 at 15:23
Actually, i want to load external javascript file at runtime, be able to modify these files and their functions and reload them without having to kill and restart the Node.JS process. — SlashJ, Oct 29 '14 at 15:25

majidarif · Accepted Answer · 2014-10-29T15:37:35.183

If I understood your question correctly. You can check the vm module out.

Or if you want to be able to reload required files, you must clear the cache and reload the file, something this package can do. Check the code, you'll get the idea.

Modules are cached after the first time they are loaded. This means (among other things) that every call to require('foo') will get exactly the same object returned, if it would resolve to the same file.

Multiple calls to require('foo') may not cause the module code to be executed multiple times. This is an important feature. With it, "partially done" objects can be returned, thus allowing transitive dependencies to be loaded even when they would cause cycles.

More information can be found here.

Delete the cached module:

delete require.cache[require.resolve('./mymodule.js')]

Require it again. (maybe a require inside a function you can call)

update

Someone I know is implementing a similar approach. You can find the code here.

Franck Freiburger · Answer 2 · 2017-03-02T15:32:40.880

You can have a look at my module-invalidate module that allows you to invalidate a required module. The module will then be automatically reloaded on further access.

Example:

module ./myModule.js

module.invalidable = true;
var count = 0;
exports.count = function() {
    return count++;
}

main module ./index.js

require('module-invalidate');

var myModule = require('./myModule.js');

console.log( myModule.count() ); // 0
console.log( myModule.count() ); // 1

mySystem.on('hot-reload-requested', function() {

    module.invalidateByPath('./myModule.js'); // or module.constructor.invalidateByExports(myModule);
    console.log( myModule.count() ); // 0
    console.log( myModule.count() ); // 1
});

Please don't post identical answers to multiple questions. Post one good answer, then vote/flag to close the other questions as duplicates. If the question is not a duplicate, *tailor your answers to the question.* — Baum mit Augen, Mar 02 '17 at 14:51

Reload module at runtime

2 Answers2