Re: [Tarantool-patches] [PATCH 3/6] iproto: Add negotiation phase

[lvasiliev <lvasiliev@tarantool.org>]

On 25.03.2020 13:56, Eugene Leonovich wrote:
> 
>     A much simpler way to do it is to have a server switch to enable
>     new features.
>     It is less flexible, of course, because you can't have old and new
>     clients, but do you really want to have old and new clients?
> 
> 
> I do agree with Kostya, I think it's a good compromise. In my humble 
> opinion, the extended error feature in its current state is not worth 
> the complexity and overhead it adds. Instead, why not introduce a 
> Tarantool setting to choose whether you want to deal with a legacy or 
> extended error response type (and it's very unlikely that someone will 
> need to have 2 types at the same time). By default this setting will be 
> set to use the legacy mode, then after N minor 2.x releases, it can be 
> changed to use the new error type, the setting itself will be marked as 
> deprecated and removed in the next major release. From a connector's 
> point of view, it will also be easy to check if there are any additional 
> fields in the response body, which would mean that the connector has 
> received a "new" error.
> 
> -- 
> Thank you and best regards,
> Eugene Leonovich
Hi! Thanks for the feedback.
It sounds like a soft break of the backward compatibility.
"From a connector's point of view, it will also be easy to check if 
there are any additional fields in the response body, which would mean 
that the connector has received a "new" error." - No, the format of a 
message has been changed.
About negotiation phase - it's optional and I think it can be used for 
flexible session setup in the future (not only for errors).
If you use a default settings of the session negotiation phase is absent 
and don't add additional overhad.