[Tarantool-patches] [RFC] gc/xlog: delay xlog cleanup until relays are subscribed

[Konstantin Osipov]

* Cyrill Gorcunov <gorcunov at gmail.com> [21/03/18 00:54]:
> On Thu, Mar 18, 2021 at 12:23:50AM +0300, Konstantin Osipov wrote:
> > * Cyrill Gorcunov via Tarantool-patches <tarantool-patches at dev.tarantool.org> [21/03/17 22:01]:
> >
> > > In case if replica managed to be far behind the master node
> > > (so there are a number of xlog files present after the last
> > > master's snapshot) then once master node get restarted it
> > > may clean up the xlogs needed by the replica to subscribe
> > > in a fast way and instead the replica will have to rejoin
> > > reading a number of data back.
> > 
> > Should be in 1.10 as well.
> 
> Sure, but first I need to be sure if current rfc is acceptable
> in general and I didn't miss something. I suspect we might
> need to extend this code and better to not make some design
> mistakes which gonna be hard to resolve later. I've a test
> case for this simply didn't posted it yet.

This is a case where a configuration setting would be suitable. I
don't think it's necessary to keep these logs forever by default,
4-6 hours should be a good default for many setups. Some will set
the default to, say, 5 minutes, essentially to keep the old
behaviour, and some can set it to infinity, to get the current
behaviour of the patch.

All tarantool setting follow the convention to start from
subsystem name, so it got to be wal_{something}, e.g.
wal_keep_logs

-- 
Konstantin Osipov, Moscow, Russia