How do 'cluster' and 'worker_threads' work in Node.js?

Question

• Did I understand correctly: If I use cluster package, does it mean that a new node instance is created for each created worker?

• What is the difference between cluster and worker_threads packages?

Answer 1

Effectively what you are differing is process based vs thread based. Threads share memory (e.g. SharedArrayBuffer) whereas processes don't. Essentially they are the same thing categorically.

cluster

• One process is launched on each CPU and can communicate via IPC.
• Each process has it's own memory with it's own Node (v8) instance. Creating tons of them may create memory issues.
• Great for spawning many HTTP servers that share the same port b/c the master main process will multiplex the requests to the child processes.

worker threads

• One process total
• Creates multiple threads with each thread having one Node instance (one event loop, one JS engine). Most Node API's are available to each thread except a few. So essentially Node is embedding itself and creating a new thread.
• Shares memory with other threads (e.g. SharedArrayBuffer)
• Great for CPU intensive tasks like processing data or accessing the file system. Because NodeJS is single threaded, synchronous tasks can be made more efficient with workers