[Tarantool-patches] [PATCH v2 1/1] memtx: force async snapshot transactions

[Cyrill Gorcunov]

On Sun, Sep 13, 2020 at 09:39:26PM +0200, Vladislav Shpilevoy wrote:
> Snapshot rows contain not real LSNs. Instead their LSNs are
> signatures, ordinal numbers. Rows in the snap have LSNs from 1 to
> the number of rows. This is because LSNs are not stored with every
> tuple in the storages, and there is no way to store real LSNs in
> the snapshot.
> 
> These artificial LSNs broke the synchronous replication limbo.
> After snap recovery is done, limbo vclock was broken - it
> contained numbers not related to reality, and affected by rows
> from local spaces.
> 
> Also the recovery could stuck because ACKs in the limbo stopped
> working after a first row - the vclock was set to the final
> signature right away.
> 
> This patch makes all snapshot recovered rows async. Because they
> are confirmed by definition. So now the limbo is not involved into
> the snapshot recovery.
> 
> Closes #5298
Reviewed-by: Cyrill Gorcunov <gorcunov at gmail.com>