Method fastJoinMembersOnStartup

kv/memberlist/memberlist_client.go:750–788

fastJoinMembersOnStartup attempts to reach small subset of nodes (computed as RetransmitMult * log10(number of discovered members + 1)).

(ctx context.Context)

// fastJoinMembersOnStartup attempts to reach small subset of nodes (computed as RetransmitMult * log10(number of discovered members + 1)).
func (m *KV) fastJoinMembersOnStartup(ctx context.Context) error {
	startTime := time.Now()

	nodes, err := m.discoverMembersWithRetries(ctx, m.cfg.JoinMembers)
	if err != nil && len(nodes) == 0 {
		return err
	}

	// Shuffle the node addresses to randomize the ones picked for the fast join.
	math_rand.Shuffle(len(nodes), func(i, j int) {
		nodes[i], nodes[j] = nodes[j], nodes[i]
	})

	// This is the same formula as used by memberlist for number of nodes that a single message should be gossiped to.
	toJoin := m.cfg.RetransmitMult * int(math.Ceil(math.Log10(float64(len(nodes)+1))))

	level.Info(m.logger).Log("msg", "memberlist fast-join starting", "nodes_found", len(nodes), "to_join", toJoin)

	totalJoined := 0
	for toJoin > 0 && len(nodes) > 0 && ctx.Err() == nil {
		reached, err := m.memberlist.Join(nodes[0:1]) // Try to join single node only.
		if err != nil {
			level.Info(m.logger).Log("msg", "fast-joining node failed", "node", nodes[0], "err", err)
		}

		totalJoined += reached
		toJoin -= reached

		nodes = nodes[1:]
	}

	if totalJoined < m.cfg.AbortIfFastJoinFailsMinNodes {
		level.Warn(m.logger).Log("msg", "memberlist fast-join failed to reach minimum required seed nodes", "joined_nodes", totalJoined, "required_nodes", m.cfg.AbortIfFastJoinFailsMinNodes, "elapsed_time", time.Since(startTime))
		return fmt.Errorf("fast-join failed to reach minimum required seed nodes: joined %d, required %d", totalJoined, m.cfg.AbortIfFastJoinFailsMinNodes)
	}

	level.Info(m.logger).Log("msg", "memberlist fast-join finished", "joined_nodes", totalJoined, "elapsed_time", time.Since(startTime))
	return nil
}

// The joinMembersOnStartup method resolves the addresses of the given join_members hosts and asks memberlist to join to them.
// This method cannot be called before KV.running state as it may wait for K8S DNS to resolve the service addresses of members