[Tarantool-patches] [RFC 4/4] qsync: allow to specify replication_synchro_quorum as a formula
sergepetrenko at tarantool.org
Fri Nov 20 15:41:12 MSK 2020
20.11.2020 15:01, Cyrill Gorcunov пишет:
> On Fri, Nov 20, 2020 at 01:50:50PM +0300, Serge Petrenko wrote:
>>> @@ -4216,6 +4217,7 @@ unregister_replica(struct trigger *trigger, void * /* event */)
>>> struct replica *replica = replica_by_uuid(&old_uuid);
>>> assert(replica != NULL);
>>> + replication_on_cluster_update();
>>> return 0;
>> We usually perform all the work related to replica register/unregister
>> directly in replica_set_id
>> and replica_clear_id.
>> Besides, these are the places where replicaset.registered_count is updated,
>> so it'd be nice to call replication_on_cluster_update from there.
>>> --- a/src/box/box.cc
>>> +++ b/src/box/box.cc
>>> @@ -634,14 +634,6 @@ box_check_replication_synchro_quorum(void)
>>> int value = replication_synchro_quorum;
>>> quorum = eval_replication_synchro_quorum(value);
>>> Pass replicaset.registered_count instead of replication_synchro_quorum here.
> Wait, this is bootstrap, replicaset.registered_count is 0 at this moment, no?
Hm, I didn't think of this.
Yes, this is either bootstrap or reconfiguration.
Well, if we have a max(1, value) guard nothing bad should happen even if we
pass 0 on bootstrap. The formula will be reevaluated each time
a replica is registered anyway. Even when the node registers itself.
Anyway, passing replication_synchro_quorum as parameter to evaluate quorum
is even more random.
>>> + * Evaluate the new synchro quorum number when replica
>>> + * get registered/unregistered and the quorum depends on
>>> + * their amount via formula in config.
>>> + */
>>> + if (!replication_synchro_quorum_eval)
>>> + return;
>>> + /*
>>> + * Account only registered replicas when evaluating
>>> + * quorum number from a fromula present in config.
>>> + */
>>> + int value = replicaset.registered_count - replicaset.anon_count;
>> registered_count stands for 'normal' replica count, so no need to subtract
>> anon_count from it.
> Yeah, thanks!
>>> + say_info("replication: evaluated quorum is %d", quorum);
>> quorum -> replication_synchro_quorum
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