CPU utilization of Node.js on Amazon EC2

Question

Seeing as how node is single threaded, If I have node server running on an amazon EC2 instance with 4 EC2 Compute units will it run any faster / handle more load than if I have

Answer 1

To fully utilize compute resources of N cores, you need at least N threads ready to do useful work. This has nothing to do with EC2; it's just the way computers work. I assume from your question that you are choosing between the m1.medium and m1.large instance types, which have 1 and 2 dedicated cores, respectively (the m1.small is half of a shared core, and the m1.xlarge is the full dedicated 4-core box). Thus, you need at least 2 processes doing useful work in order to utilize the larger box (unless you just want access to more memory / io).

Each Node.js process is single threaded by design. This lets it provide a clean programming paradigm free of locking semantics. This is very much by design.

For a Node.js app to utilize multiple cores, it must spawn multiple processes. These processes would then use some form of messaging (pipes, sockets, etc) to communicate -- versus "shared memory" where code can directly mutate memory locations visible to multiple processes, something that would require locking semantics.

In practice, this is dirt simple easy to set up. Back in Node.JS v0.6.X the "cluster" module was integrated into the standard distribution, making it easy to set up multiple node workers that can listen on a single port. Note that this "cluster" module is NOT the same as the learnboost "cluster" module which has a different API and owns the "cluster" name in the NPMjs registry.

http://nodejs.org/docs/latest/api/cluster.html

if (cluster.isMaster) {
  // Fork workers.
  for (var i = 0; i < numCPUs; i++) {
    cluster.fork();
  }
} else {
  http.Server(function(req, res) { ... }).listen(8000);
}