tail.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
mongoose.connect('localhost', 'test');

var schema = new Schema({
    _id: Number
  , name: String
  // etc
});

var A = mongoose.model('A', schema);

mongoose.connection.on('open', function () {
  var lastId = 0
    , done = false;

  function tail () {
    var stream = A.find({ _id: { $gt: lastId }}).tailable().stream();

    stream.on('data', function (doc) {
      lastId = doc._id;
      // do something with doc
      console.log(doc);
    });

    stream.on('close', function (err) {
      if (done) return;
      console.log('restarting from %s', lastId);
      tail();
    });

    stream.on('error', function (err) {
      console.error('stream error:', err);
      done = true;
      disconnect();
    })
  }

  tail();
});

function disconnect (err) {
  if (err) console.error('error', err && err.stack || err);
  console.error('disconnecting');
  mongoose.disconnect();
};