遍历map之前先重置

loop.md

Connection.prototype._cleanupCalls = function (err) {
  var count = 0;
  var calls = this.calls;
  this.calls = {}; // should reset calls before traverse it.
  for (var id in calls) {
    var call = calls[id];
    call.setException(err);
    count++;
  }
  // this.calls = {};
  debug('conn#%d: clenaup %d calls, send "%s:%s" response.', this.id, count, err.name, err.message);
};

setException会触发一个callback，然后callback里面的一些代码，又会触发_cleanupCalls，然后就杯具发生了。