[Tarantool-patches] [PATCH v2 04/10] replication: track registered replica count

[Serge Petrenko]

04.09.2020 01:51, Vladislav Shpilevoy пишет:
> 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
Thanks for the patch!

LGTM with one comment.

> ---
>   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;
>   
>   	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;

We already have `anon_count`. Maybe call this field `registered_count` 
for consistency?
Besides `size` is too general of a term.

>   	/** Applier state. */
>   	struct {
>   		/**

-- 
Serge Petrenko