NSOperationQueue problem with 1 maxConcurrentOperations

I am confused and need your support. I am implementing synchron http requests in separate thread and therefore I want to use NSOperationQueue .

But there is a one problem connected with following:

When current request failed,I am going to do another recovery request,this means I should add new prior item to my queue and after that r开发者_运维知识库epeat that request which failed .

Thanks for help