A basic visitor counter for Node.js, storing counters in Redis

node-redis-visitor-counter.js

// embed an img element in an HTML page, point it at this.

var sys = require("sys"), http = require("http"), crypto = require("crypto");

var db = require("redis-client").createClient();

http.createServer(function(request, response) {
  var date = new Date;
  var day = date.getUTCFullYear() + "-" + (date.getUTCMonth() + 1) + "-" + date.getUTCDate();

  var urlhash = crypto.createHash("md5").update(request.headers.referer).digest("hex");
  
  var keys = [
    "hits-by-url:" + urlhash, 
    "hits-by-day:" + day, 
    "hits-by-url-by-day:" + urlhash + ":" + day
  ];
  
  for (i in keys)
    db.incr(keys[i]);
  
  response.writeHead(200, { "Content-Type": "image/gif" });
  response.write("BINARY GIF DATA HERE", "binary");        
  response.end();
}).listen(8181);

sys.puts("Server running at http://0.0.0.0:8181/");

Missing check for actual req.headers.referer, not all user-agents set it.