func (r *RoundRobin) NextEndpoint(req request.Request) (endpoint.Endpoint, error) {
r.mutex.Lock()
defer r.mutex.Unlock()
e, err := r.nextEndpoint(req)
if err != nil {
return nil, err
}
lastAttempt := req.GetLastAttempt()
// This is the first try, so just return the selected endpoint
if lastAttempt == nil {
return e, nil
}
// Try to prevent failover to the same endpoint that we've seen before,
// that reduces the probability of the scenario when failover hits same endpoint
// on the next attempt and fails, so users will see a failed request.
var endpoint endpoint.Endpoint
for _ = range r.endpoints {
endpoint, err = r.nextEndpoint(req)
if err != nil {
return nil, err
}
if !hasAttempted(req, endpoint) {
return endpoint, nil
}
}
return endpoint, nil
}
