The Node.js Cluster module and load balancers are both used to handle incoming network requests but serve different purposes and operate at different layers of the application infrastructure.
How the Cluster Module Works
The Cluster module in Node.js allows you to create multiple instances of your server that can run concurrently on different processor cores. It is a built-in module that provides a way to create child processes, which are instances of the main Node.js process. These child processes can share the same server port and handle incoming requests in parallel, which can significantly improve the performance and scalability of an application[2][3][4][5][6][7][8][11].
When you use the Cluster module, a master process is created first. This master process then spawns a number of worker processes (typically one for each CPU core on the server). The master process listens on a port, accepts incoming connections, and distributes them among the worker processes in a round-robin fashion or using other custom distribution strategies[2][3][4][5][6][7][8][11].
The worker processes handle the actual requests. This model allows the application to handle more requests than it could with a single-threaded setup, as Node.js is inherently single-threaded. If a worker process crashes, it can be restarted by the master process without affecting the other workers, thus providing resilience and better resource utilization[2][3][4][5][6][7][8][11].
Difference Between Cluster Module and Load Balancer
Level of Operation:
Cluster Module: Operates at the application level, within the Node.js runtime environment. It manages multiple instances of the Node.js application on the same server[2][3][4][5][6][7][8][11].
Load Balancer: Operates at the network level and can distribute incoming network traffic across multiple servers, not just multiple processes on the same server. Load balancers can be software-based or hardware-based and are not specific to Node.js applications[1][2].
Purpose:
Cluster Module: Primarily used to maximize the utilization of multi-core systems from within a single Node.js application. It helps to handle more requests by parallelizing them across multiple cores of the same server[2][3][4][5][6][7][8][11].
