Multi Processes & Threads

multiple processes listening on the same port

testing machine: dual core processor cpu

nginx master process and worker process listening on the same port, using the kernel load balance SO_REUSEPORT to distribute socket request（each socket need have the same process UID）

pm2 / node:cluster mode, master process handles socket request, then distribute to worker process by round-roubin, worker process has not port listening.
pm2 underlying use node:cluster, and cluster underlying use child_process.fork, while bare forking requires you to handle the connections on your own.
fork mode only support nodejs subprocess.

node threads using in cpu-intensive javascript operations

worker threads could using multiple cpu cores at the same time，each thread has it’s own standalone V8 and EventLoop，no GIL

V8 allows you to spawn isolated V8 runtimes. V8 Isolate is isolated instances with their Javascript heaps and micro-task queues.These segregated V8 engines operate worker threads, with each worker having its V8 engine and event queue.

browser main js thread

can be blocked by alert('something')

coroutine

Unlike processes or threads, coroutine is cooperative multitasking, not preemptive multitasking. It’s implemented based on single thread, and switch context by user rather than system.