[tarantool-patches] Re: [PATCH v2 7/7] relay: join new replicas off read view

[Konstantin Osipov]

* Vladimir Davydov <vdavydov.dev at gmail.com> [19/08/20 17:08]:
> On Tue, Aug 20, 2019 at 04:50:07PM +0300, Konstantin Osipov wrote:
> > * Vladimir Davydov <vdavydov.dev at gmail.com> [19/08/20 15:10]:
> > > Well, yeah, kinda. OTOH they do relay data to a replica that's why I
> > > named them relay_something :-/ Also, those functions live in relay.cc,
> > > which is consistent with the relay_ prefix.
> > 
> > engine_send? I'll think about it.
> 
> But the code is engine-agnostic now - it just opens read-view iterators
> and sends whatever they return to a replica :-/

OK. Let's move it out of relay then. It's OK to put it in a
special file or move to engine.cc. It's OK that it's
engine-agnostic- engine.cc can have code common to all engines.

relay prefix is also confusing since in replication "relaying" is
used to refer to re-sending some existing files or logs.

The only issue about this patch is that since, unlike a snapshot
iterator, the code runs in tx thread, it may require some
throttling. If the network is fast enough it the send loop may run
at very high speeds. It could even hog 100% of CPU time and nearly
never yield CPU to other transactions.

I see two options here: move it to a separate thread (memtx
iterators allow it, so it would be preferred), or throttle.

-- 
Konstantin Osipov, Moscow, Russia