Re: [tarantool-patches] Re: [PATCH v2] replication: fix assertion with duplicated connect to same master

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

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On Sat, Sep 22, 2018 at 10:04:57AM +0300, Olga Arkhangelskaia wrote:
> *
> 
> Hi! Thanks for the review. I will fix most of the comments and observations.
> 
> However, I guess I need to know that we are on the same page.
> 
> When we do box.cfg{replication={44441, 44441}}
> 
> we have two replicas, each one has its onw applier, etc. In
> replicaset_update()we are able to
> 
> identify  that the replicas are same. At this point we raise exceptions.
> Problem occurs when we try to delete the second one. For proper deletion we
> need to stop applier, clear it and than delete replica. As I understand we
> need to:
> 
> applier_stop(replica->applier);
> 
> replica_clear_applier(replica);replica_delete(replica);

If you change the call sequence to

  replica_clear_applier(replica);
  replica_delete(replica);
  applier_stop(replica->applier);

you won't be facing this problem.

> 
> The reason I added replica_on_applier_off(replica) is because when an
> applier enters stopped state, it state marks as APPLIER_OFF. Trigger on
> change states reacts on this change with
> 
> replica_on_applier_state_f. That leads us to on_applier_sync. Instead we
> should react on APPLIER_DISCONNECTED. And the only way we react on this
> state  - is to try to load applier again.
> 
> So replica_on_applier_off is used in case when we want to stop applier
> forever, before replica deletion. I think we do need this function. May be
> in some other form that I did.