presto-main/src/main/java/io/prestosql/server/remotetask/RequestErrorTracker.java/RequestErrorTracker/startRequest
class RequestErrorTracker:    public void startRequest()
    {
        // before scheduling a new request clear the error timer
        // we consider a request to be "new" if there are no current failures
        if (backoff.getFailureCount() == 0) {
            requestSucceeded();
        }
        backoff.startRequest();
    }