Does a blocking operation on a single request block all other requests from beginning?

Question

Does a blocking operation on a single request block all other requests from beginning?

I just started going through the node.js beginners guide

http://www.nodebeginner.org

And wanted to know if there were any examples or ways I can experience first hand if a blocking operation on a single request would block other requests from starting. Essentially I want to open up two different browsers and trigger a blocking operation from one browser, then access another browser and observe that I am being blocked until the first request finishes.

Also for this code snippet

var http = require("http");
function onRequest(request, response) {
  response.write("Hello World");
  response.end();
}
http.createServer(onRequest).listen(8888);

Shouldn't the onRequest function accept arguments if it is going to called?

http.createServer(onRequest(request, response)).listen(8888);

node.js

Answer 1

For the question in the title, yes. You can try it by, say, having something like this:

function onRequest(req, res) {
    if(req.url === '/block') {
        while(true) {}
    }else{
        res.end("Still accepting requests…");
    }
}

Then go to http://localhost:8888/block in one browser and http://localhost:8888/ in the other. The latter request will not yield a response. (Neither will the first one, for that matter.)

For your other question, no; you're not calling onRequest and passing the return value to createServer, but rather passing the function itself to createServer.

In JavaScript, functions are first-class, which is to say they're an object like any other: you can pass them as arguments, put them in variables or in other objects, etc. If you're used to C you can think of it like a function pointer except possibly with an implicit context argument pulled along with it to carry references to the variables of its enclosing lexical scopes.