want: need transfer leadership with client manually

[siddontang]

Hi

I see transfer leader is not exported to client.

// transferLeadership transfers the leader to the given transferee.
// TODO: maybe expose to client?
func (s *EtcdServer) transferLeadership(ctx context.Context, lead, transferee uint64) error {

It is a very useful feature, assume we have three DC 1, 2, 3, 1 and 2 are in same city with very high speed network, 3 is in another remote city with some network delay (20ms). All our clients are deployed in 1 and 2.

In this case, we must ensure the etcd leader is in 1 or 2, not in 3. If we find leader is in 3, we must transfer to 1 or 2 explicitly.

[gyuho]

It will be fairly simple. Should we support this? /cc @heyitsanthony @xiang90

type Cluster interface {
	// MemberList lists the current cluster membership.
	MemberList(ctx context.Context) (*MemberListResponse, error)

	// MemberAdd adds a new member into the cluster.
	MemberAdd(ctx context.Context, peerAddrs []string) (*MemberAddResponse, error)

	// MemberRemove removes an existing member from the cluster.
	MemberRemove(ctx context.Context, id uint64) (*MemberRemoveResponse, error)

	// MemberUpdate updates the peer addresses of the member.
	MemberUpdate(ctx context.Context, id uint64, peerAddrs []string) (*MemberUpdateResponse, error)

	TransferLeadership(ctx context.Context, transferee uint64) error
}

?

[heyitsanthony]

Probably belongs in Maintenance since it's targeted at one endpoint?

[xiang90]

Let us do this in 3.3. This is useful, but not something urgent i feel.