[PATCH] hot_standby: reflect amount of recovered rows in box.info

[Vladimir Davydov]

On Tue, Oct 23, 2018 at 06:15:40PM +0300, Serge Petrenko wrote:
> To be able to switch to hot_standby instance with minimal downtime, we
> need to know how far is it behind the primary instance, i.e. up to what
> vclock we have recovered. Previously this was impossible because
> box.info.vclock always referenced replicaset.vclock, which isn't updated
> during hot_standby.
> Introduce a pointer to relevant vclock: either recovery vclock (during
> local recovery) or replicaset.vclock (at all other times) and use it in
> box.info.vclock, box.info.lsn and box.info.signature.
> 
> Closes #3002
> ---
> https://github.com/tarantool/tarantool/issues/3002
> https://github.com/tarantool/tarantool/tree/sp/gh-3002-hot-standby-vclock
> 
>  src/box/box.cc                        | 12 +++++++++++-
>  src/box/box.h                         |  7 +++++++
>  src/box/lua/info.c                    |  6 +++---
>  test/replication/hot_standby.result   | 26 ++++++++++++++++++++++++++
>  test/replication/hot_standby.test.lua | 10 ++++++++++
>  5 files changed, 57 insertions(+), 4 deletions(-)
> 
> diff --git a/src/box/box.cc b/src/box/box.cc
> index c32f731b0..448fe3dcc 100644
> --- a/src/box/box.cc
> +++ b/src/box/box.cc
> @@ -138,6 +138,8 @@ static struct fiber_pool tx_fiber_pool;
>   */
>  static struct cbus_endpoint tx_prio_endpoint;
>  
> +struct vclock *last_row_vclock = &replicaset.vclock;
> +

I took a liberty of renaming last_row_vclock to box_vclock.

Pushed to 1.10.