CODEWITHSUNDEEP
javascriptnode.js
SlashJ
SlashJ

Reputation: 807

Reload module at runtime

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:

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!

Upvotes: 8

Views: 9934

Answers (2)

Franck Freiburger
Franck Freiburger

Reputation: 28448

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
});

Upvotes: 3

majidarif
majidarif

Reputation: 19985

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.

  1. Delete the cached module:

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

  2. 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.

Upvotes: 18

Related Questions