Re: [tarantool-patches] Re: [PATCH 2/2] replication: fix garbage collection logic

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

On Thu, Apr 11, 2019 at 10:32:55AM +0300, Konstantin Osipov wrote:
> * Vladimir Davydov <vdavydov.dev@gmail.com> [19/04/09 20:09]:
> > Currently, the garbage collector works with vclock signatures and
> > doesn't take into account vclock components. This works as long as
> > the caller (i.e. relay) makes sure that it doesn't advance a consumer
> > associated with a replica unless its acknowledged vclock is greater
> > than or equal to the vclock of a WAL file fed to it. The bug is that
> > it does not - it only compares vclock signatures. As a result, if
> > a replica has some local changes or changes pulled from other members
> > of the cluster, which render its signature greater, the master may
> > remove files that are still needed by the replica, permanently breaking
> > replication and requiring rebootstrap.
> > 
> > I guess the proper fix would be teaching the garbage collector
> > operate on vclock components rather than signatures, but it's rather
> > difficult to implement. This patch is a quick fix, which simply
> > replaces vclock signature comparison in relay with vclock_compare.
> 
> This patch is OK to push.

Pushed to master, 2.1, 1.10.