server.js

var http = require('http'),
    sys = require('sys'),
    couchdb = require('./lib/couchdb'),
    port = process.env.PORT || 8001,
    COUCH_PORT = 5984,
    COUCH_SERVER = 'localhost',
    COUCH_USER = null,
    COUCH_PASSWORD = null;

function getCounter(callback) {
  var client = couchdb.createClient(COUCH_PORT, COUCH_SERVER, COUCH_USER, COUCH_PASSWORD),
    db = client.db('node-heroku-counter'), counter = -1;
  db.getDoc('counter', function(err, doc) {
    if(err) {
      sys.puts(sys.inspect(err));
    } else {
      counter = doc.counter;
    }
    callback(counter);
  });
}

function incrementCounter() {
  var client = couchdb.createClient(COUCH_PORT, COUCH_SERVER, COUCH_USER, COUCH_PASSWORD),
    db = client.db('node-heroku-counter');
  db.getDoc('counter', function(err, doc) {
    if(err) {
      sys.puts(sys.inspect(err));
    } else {
      doc.counter += 1;
      db.saveDoc('counter', doc, function(err, ok) {
        if(err) {
          sys.puts(err.error + ', retrying...');
          incrementCounter();
        } else {
          sys.puts('Counter incremented to ' + doc.counter);
        }
      });
    }
  });
}



http.createServer(function (req, res) {
  switch(req.method) {
    case 'GET':
      getCounter(function(counter) {
        res.writeHead(200, {'Content-Type': 'text/plain'});
        res.end('Hello, ' + counter + '!\n');
      });
      break;
    case 'POST':
      incrementCounter();
      res.writeHead(200, {'Content-Length': 0});
      res.end();
      break;
    default:
      res.writeHead(404, {'Content-Type': 'text/html'});
      res.end('Not Found\n');
  }
}).listen(parseInt(port));

A node server that uses couchdb to provide a counter. The incrementCounter function attempts to update the counter in couchdb, and on a version conflict (or any other error for that matter) retries.