retry an async action until it doesn't fail

attempt.js

// attempt to do an async action in a loop, until it doesn't
// return an error or a max number of retries is reached.
function attempt(opts, fun, next) {
  var lastError = null, retry = 0,
    increment = opts.increment || 500,
    nextTimeout = typeof opts.initial !== 'undefined' ? opts.initial : 500,
    maxRetries = typeof opts.retries !== 'undefined' ? opts.retries : 0;

  function nextRetry() {
    if (maxRetries && retry >= maxRetries) {
      return next(lastError);
    }

    retry++;

    setTimeout(function() {
      fun(function(err, res) {
        if (err) {
          lastError = err;
          return nextRetry();
        }
        next(null, res);
      });
    }, nextTimeout);

    nextTimeout += increment;
  }

  nextRetry();
}

usage example:

var retry = 0;
attempt({initial: 0, increment: 100, retries: 8}, function(next) {
  if (++retry < 5) {
    return next(new Error('action failed'));
  }

  var results = {foo: 'bar', num: retry};
  next(null, results);
}, function(err, results) {
  if (err) {
    console.error('error: too many attempts without success');
    console.error('error: '+err.message);
    return;
  }

  console.log('success in retry '+results.num+', foo: '+results.foo);
});