Does it possible to submit duplicated request with the proxy_next_upstream on

[任勇全]

Hi all:
I am wondering if I set:
    proxy_next_upstream error timeout;
Fox example , if the requested service is a counter , I issue the request use the interface http://example.com/incr . The request is failed on my first host A, then it is passed to the second host B , is the counter likely be added twice ?

thanks .