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

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  • 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?

clusterize core v8 node.js process
1 Answers

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
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