Improve call stack usage in SequentialExecutor.callListeners()

Converts recursive loop to sequential one for synchronous listeners.

lib/sequential_executor.js

@@ -84,29 +84,31 @@ AWS.SequentialExecutor = AWS.util.inherit({
  * @api private
  */
  callListeners: function callListeners(listeners, args, doneCallback) {
- if (listeners.length === 0) {
- doneCallback.call(this);
- return;
+ var self = this;
+ function callNextListener(err) {
+ if (err) {
+ doneCallback.call(self, err);
+ } else {
+ self.callListeners(listeners, args, doneCallback);
+ }
  }
 
- var self = this, listener = listeners.shift();
- if (listener._isAsync) { // asynchronous listener
- var callNextListener = function(err) {
- if (err) {
+ while (listeners.length > 0) {
+ var listener = listeners.shift();
+ if (listener._isAsync) { // asynchronous listener
+ listener.apply(self, args.concat([callNextListener]));
+ return; // stop here, callNextListener will continue
+ } else { // synchronous listener
+ try {
+ listener.apply(self, args);
+ } catch (err) {
  doneCallback.call(self, err);
- } else {
- self.callListeners(listeners, args, doneCallback);
+ return;
  }
- };
- listener.apply(self, args.concat([callNextListener]));
- } else { // synchronous listener
- try {
- listener.apply(self, args);
- self.callListeners(listeners, args, doneCallback);
- } catch (err) {
- doneCallback.call(self, err);
  }
  }
+
+ doneCallback.call(self);
  },
 
  /**