[Tarantool-patches] [PATCH v2 04/10] replication: track registered replica count
Sergey Ostanevich
sergos at tarantool.org
Mon Sep 7 18:45:44 MSK 2020
Hi!
Thanks for the patch, just one comment below.
Regards,
Sergos
On 04 сен 00:51, Vladislav Shpilevoy wrote:
> Struct replicaset didn't store a number of registered replicas.
> Only an array, which was necessary to fullscan each time when want
> to find the count.
>
> That is going to be needed in Raft to calculate election quorum.
> The patch makes the count tracked so as it could be found for
> constant time by simply reading an integer.
>
> Needed for #1146
> ---
> src/box/replication.cc | 3 +++
> src/box/replication.h | 7 +++++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/src/box/replication.cc b/src/box/replication.cc
> index ef0e2411d..20f16206a 100644
> --- a/src/box/replication.cc
> +++ b/src/box/replication.cc
> @@ -247,6 +247,7 @@ replica_set_id(struct replica *replica, uint32_t replica_id)
> tt_uuid_str(&replica->uuid));
> }
> replicaset.replica_by_id[replica_id] = replica;
> + ++replicaset.size;
There's another use of the replica_set_id() inside the register_replica()
of alter.cc. Apparently, it's just for re-assign the ID without adding of
a new node. I would propose to move this counter into replicaset_add()
>
> say_info("assigned id %d to replica %s",
> replica->id, tt_uuid_str(&replica->uuid));
> @@ -267,6 +268,8 @@ replica_clear_id(struct replica *replica)
> * replication.
> */
> replicaset.replica_by_id[replica->id] = NULL;
> + assert(replicaset.size > 0);
> + --replicaset.size;
> if (replica->id == instance_id) {
> /* See replica_check_id(). */
> assert(replicaset.is_joining);
> diff --git a/src/box/replication.h b/src/box/replication.h
> index ddc2bddf4..69cc820c9 100644
> --- a/src/box/replication.h
> +++ b/src/box/replication.h
> @@ -217,6 +217,13 @@ struct replicaset {
> bool is_joining;
> /* A number of anonymous replicas following this instance. */
> int anon_count;
> + /**
> + * Number of registered replicas. That includes all of them - connected,
> + * disconnected, connected not directly, just present in _cluster. If an
> + * instance has an ID, has the same replicaset UUID, then it is
> + * accounted here.
> + */
> + int size;
> /** Applier state. */
> struct {
> /**
> --
> 2.21.1 (Apple Git-122.3)
>
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