Re: [Tarantool-patches] [PATCH 1/6] replication: refactor replicaset_leader()

[Serge Petrenko via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

05.06.2021 02:37, Vladislav Shpilevoy пишет:
> Firstly, rename it to replicaset_find_join_master(). Now, when
> there is Raft with a concept of an actual leader, the function
> name becomes confusing.
>
> Secondly, do not access ballot member in struct applier in such a
> long way - save the ballot pointer on the stack. This is going to
> become useful when in one of the next patches the ballot will be
> used more.
>
> Part of #5613

Hi! Thanks for the patch!
LGTM.

> ---
>   src/box/box.cc         |  5 ++---
>   src/box/replication.cc | 12 +++++++-----
>   src/box/replication.h  |  5 +++--
>   3 files changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/src/box/box.cc b/src/box/box.cc
> index 6dc991dc8..0e615e944 100644
> --- a/src/box/box.cc
> +++ b/src/box/box.cc
> @@ -1369,7 +1369,7 @@ box_set_replication_anon(void)
>   		 * Wait until the master has registered this
>   		 * instance.
>   		 */
> -		struct replica *master = replicaset_leader();
> +		struct replica *master = replicaset_find_join_master();
>   		if (master == NULL || master->applier == NULL ||
>   		    master->applier->state != APPLIER_CONNECTED) {
>   			tnt_raise(ClientError, ER_CANNOT_REGISTER);
> @@ -3114,8 +3114,7 @@ bootstrap(const struct tt_uuid *instance_uuid,
>   	 */
>   	box_sync_replication(true);
>   
> -	/* Use the first replica by URI as a bootstrap leader */
> -	struct replica *master = replicaset_leader();
> +	struct replica *master = replicaset_find_join_master();
>   	assert(master == NULL || master->applier != NULL);
>   
>   	if (master != NULL && !tt_uuid_is_equal(&master->uuid, &INSTANCE_UUID)) {
> diff --git a/src/box/replication.cc b/src/box/replication.cc
> index aefb812b3..a1c6e3c7c 100644
> --- a/src/box/replication.cc
> +++ b/src/box/replication.cc
> @@ -968,6 +968,7 @@ replicaset_round(bool skip_ro)
>   		struct applier *applier = replica->applier;
>   		if (applier == NULL)
>   			continue;
> +		const struct ballot *ballot = &applier->ballot;
>   		/**
>   		 * While bootstrapping a new cluster, read-only
>   		 * replicas shouldn't be considered as a leader.
> @@ -975,17 +976,18 @@ replicaset_round(bool skip_ro)
>   		 * replicas since there is still a possibility
>   		 * that all replicas exist in cluster table.
>   		 */
> -		if (skip_ro && applier->ballot.is_ro)
> +		if (skip_ro && ballot->is_ro)
>   			continue;
>   		if (leader == NULL) {
>   			leader = replica;
>   			continue;
>   		}
> +		const struct ballot *leader_ballot = &leader->applier->ballot;
>   		/*
>   		 * Try to find a replica which has already left
>   		 * orphan mode.
>   		 */
> -		if (applier->ballot.is_loading && ! leader->applier->ballot.is_loading)
> +		if (ballot->is_loading && !leader_ballot->is_loading)
>   			continue;
>   		/*
>   		 * Choose the replica with the most advanced
> @@ -993,8 +995,8 @@ replicaset_round(bool skip_ro)
>   		 * with the same vclock, prefer the one with
>   		 * the lowest uuid.
>   		 */
> -		int cmp = vclock_compare_ignore0(&applier->ballot.vclock,
> -						 &leader->applier->ballot.vclock);
> +		int cmp = vclock_compare_ignore0(&ballot->vclock,
> +						 &leader_ballot->vclock);
>   		if (cmp < 0)
>   			continue;
>   		if (cmp == 0 && tt_uuid_compare(&replica->uuid,
> @@ -1006,7 +1008,7 @@ replicaset_round(bool skip_ro)
>   }
>   
>   struct replica *
> -replicaset_leader(void)
> +replicaset_find_join_master(void)
>   {
>   	bool skip_ro = true;
>   	/**
> diff --git a/src/box/replication.h b/src/box/replication.h
> index 2ad1cbf66..5cc380373 100644
> --- a/src/box/replication.h
> +++ b/src/box/replication.h
> @@ -356,10 +356,11 @@ struct replica *
>   replica_by_id(uint32_t replica_id);
>   
>   /**
> - * Return the replica set leader.
> + * Find a node in the replicaset on which the instance can try to register to
> + * join the replicaset.
>    */
>   struct replica *
> -replicaset_leader(void);
> +replicaset_find_join_master(void);
>   
>   struct replica *
>   replicaset_first(void);

-- 
Serge Petrenko