Although Mafalda SFU is mainly focused on vertical scaling of Mediasoup and the WebRTC stack, the main problem I’ve found companies are facing is about how to easily implement Medisoup horizontal scaling. I’ve been working on a solution for this problem for a while on, and since Mafalda is build on top of Mediasoup, it’s also needed to help it to provide transparent vertical and horizontal scaling, so let’s see how it works.

Mediasoup-Horizontal is a manager that allows to remotely control multiple instances of Mediasoup, providing a simple and easy to use API based on the one from the Javascript Set object. It allows to add and remove Remote Mediasoup Client objects and manage them, although is not directly tied to them so you can provide your own objects following that same API, for example to also control a local Mediasoup instance in addition to the remote ones.

When adding a Remote Mediasoup Client object to the Mediasoup-Horizontal instance, it checks that all the Remote Mediasoup instances are compatible between them, so you don’t have to worry about in what instance your Mediasoup objects are being created. After that, it monitors the creation of new objects, and also does it with the Client current objects in case they are later destroyed.

Mediasoup-Horizontal also provides a Mediasoup compatible API, so by using it you can auto-magically enable your application to scale horizontally without needing to change your current code. The “magic” happens by using objects that provides the same API of Mediasoup Worker and Router classes, but internally proxying the method calls to their internal Connection objects, shared by all the Client instances currently connected to the same server. This is done this way to be transparent to the actual objects references being done at Mediasoup-Horizontal level.

After that, implementation of pipeToRouter() method is fairly trivial. Code is an optimized version of original Mediasoup one, just only with fine-grain errors management and with some performance optimizations to reduce delay of events propagation, so general behaviour is the same, although there’s space for improvements. In fact, I proposed to move it out officially to a separate library so it can be reused by other projects like this one, but the proposal was rejected.

And that’s it, that’s how Mediasoup-Horizontal works. Next steps I’m planning about are to improve performance and resilience, allowing it to better recover from network re-connections, and also works towards implementing a tool for monitoring in real time the status of all the Remote Mediasoup instances.