func shouldProcessGossip()

in swim/member.go [215:274]

• 29 lines of code
• 10 McCabe index (conditional complexity)

func shouldProcessGossip(old *Member, gossip *Member) bool {
	// tombstones will not be accepted if we have no knowledge about the member
	if gossip.Status == Tombstone && old == nil {
		return false
	}

	// accept the gossip if we learn about the member through a gossip
	if old == nil {
		return true
	}

	// gossips with a higher incarnation number will always be accepted since
	// it is a newer version of the member than we know
	if gossip.Incarnation > old.Incarnation {
		return true
	}

	// gossips with a lower incarnation number will never be accepted as we
	// have a newer version of the member already
	if gossip.Incarnation < old.Incarnation {
		return false
	}

	// now we know that the incarnation number of the gossip and the current
	// view of the member are the same 'age'. Lets evaluate member state to see
	// which version to pick

	// if the status of the gossip takes precedence over the status of our
	// current member we will accept the gossip.
	if statePrecedence(gossip.Status) > statePrecedence(old.Status) {
		return true
	}

	if statePrecedence(gossip.Status) < statePrecedence(old.Status) {
		return false
	}

	// keep the checksum values in local variables. The checksums are not cached
	// and require some compute to get them, better to do once than twice.
	gossipLabelsChecksum := gossip.Labels.checksum()
	oldLabelsChecksum := old.Labels.checksum()

	// Gossips with a higher checksum should be processed to let the cluster
	// converge to the labels that cause the highest checksum.
	if gossipLabelsChecksum > oldLabelsChecksum {
		return true
	}

	// If the gossipped labels have a lower checksum we do want to keep the
	// current memberstate in our memberlist, therefore the gossip should not be
	// processed.
	if gossipLabelsChecksum < oldLabelsChecksum {
		return false
	}

	// we prefer the old member over the gossiped member if they have the same
	// internal state. This prevents the gossip to be continuously be gossiped
	// around in the network
	return false
}