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

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Mon, Aug 19, 2019 at 11:57:21PM +0300, Konstantin Osipov wrote:
> * Vladimir Davydov <vdavydov.dev@gmail.com> [19/08/19 19:57]:
> > Historically, we join a new replica off the last checkpoint. As a
> > result, we must always keep the last memtx snapshot and all vinyl data
> > files corresponding to it. Actually, there's no need to use the last
> > checkpoint for joining a replica. Instead we can use the current read
> > view as both memtx and vinyl support it. This should speed up the
> > process of joining a new replica, because we don't need to replay all
> > xlogs written after the last checkpoint, only those that are accumulated
> > while we are relaying the current read view. This should also allow us
> > to avoid creating a snapshot file on bootstrap, because the only reason
> > why we need it is allowing joining replicas. Besides, this is a step
> > towards decoupling the vinyl metadata log from checkpointing in
> > particular and from xlogs in general.
> > 
> 
> How does this work given relay_* functions are running in a relay thread? 

Those functions don't run in a relay thread. Just like in case of index
build, we open and use iterators in the tx thread.