[server-dev] [RFC] Interactive transactions in IProto

[Vladimir Davydov]

On Wed, Nov 14, 2018 at 05:09:48PM +0300, Vladislav Shpilevoy wrote:
> More questions to think about:
> 
> 1. How to balance streams processing? How to choose from which stream
> of many ones TX thread should pick up a request? I think, round-robin
> is fair enough, but maybe I am wrong.

I'd rather leave all the balancing to the fiber scheduler. IProto would
simply queue responses to the appropriate stream to be processed by the
fiber that is currently executing a request that belongs to the same
stream, or if there's none, start a new fiber.

> 
> 2. How about storing and balancing request queues in iproto thread?
> I think we should not waste TX thread time on this pure technical
> things. The only problem I see, it requires storing struct txn * in
> iproto thread inside struct stream (or any other struct <name>).

We could probably queue all requests that belong to the same stream
internally in IProto before sending them to TX in one batch, if that's
what you mean.

Come to think of it, there's another question. How is this feature going
to play with net_msg_max limit? Suppose there's a hundred messages
queued to the same stream. Do we need to account them all to
net_msg_max? Or rather account distinct streams only?