Docker containers and Node.js clusters

Question

I have an api server running Node.js that was using it\'s cluster module and testing looked to be pretty good. Now our IT department wants to move to using Docker containers whi

Answer 1

I have a system with 4 logical cores with me and I ran following line on my machine as well as on docker installed on same machine.

const numCPUs = require('os').cpus().length;
console.log(numCPUs)

This lines prints 4 on my machine and 2 inside docker container. Which means if we use clustering in docker container only 2 instance would be running. So docker container doesn't see cores same as actual machine does. Also running 5 docker container with clustering mode enabled gives 10 instance of machine which ultimately be manages by kernel of OS with 4 logical cores.

So I think best approach is to use multiple docker container instance in swarm mode with node.js clustering disabled. This should give the best performance.