node-mongodb-native double confirmation (untested! :)

double-confirm.js

Db.prototype.checkoutRawConnection = function() {
  var conn = this.serverConfig.checkoutWriter();
  return conn.pool[conn.poolIndex++ % conn.pool.length];
};

Db.prototype.lastErrorOnConnection(connection, options, callback) {
  if ('function' === typeof options) callback = options, options = {};

  var command = DbCommand.createGetLastErrorCommand(options, this);

  this.executeCommand(command, {writer: connection}, function(err, error) {
    callback(err, error && error.documents);
  });
};

// to perform a double-callbacked insert, check out a connection
var conn = db.checkoutRawConnection();

// perform the insert, but mandate it uses our connection
// little dirty, piggybacks on safetyoptions, works for update too
db.insert(docs, {safe:{writer: conn}}, function(err, objects) {
  if(!err) {
    // here we can call back to calling code because we succeeded
    // mongo accepted the docs and other connections will see them
  }
});

// now we place an additional callback for the insert
// that gets triggered later than the one above
db.lastErrorOnConnection(conn, {fsync: true, w:2}, function(err, errdocs) {
  // here we can notify externals because
  // we're certain now everything is safely persisted
  // and at least on 2 machines.
});