How to check for concurrency in Node.js

1. Create a server.

~> vim web-server.js

  var http = require('http');

  var s = createServer(function(req,res) {

  res.writeHead("hello\n");

  setTimeout(function() {

  res.end("world");

  }, 2000);

  });

  s.listen(8000);

2. Run the server
 ~> node web-server.js

3. On another terminal make a request using curl:
~> curl http://localhost:8000/
hello
world

4. The hello and world have a gap of 2 seconds.

5. Run apache bench
ab -n 100 -c 100 http://localhost:8000/


All test happen in 2.0xx seconds.