1 files changed, 155 insertions, 0 deletions
diff --git a/weed/election/cluster.go b/weed/election/cluster.go
new file mode 100644
index 000000000..7c7c1089b
--- /dev/null
+++ b/weed/election/cluster.go
@@ -0,0 +1,155 @@
+package election
+
+import (
+	"github.com/chrislusf/seaweedfs/weed/pb"
+	"math"
+	"sync"
+	"time"
+)
+
+type ClusterNode struct {
+	Address   pb.ServerAddress
+	Version   string
+	counter   int
+	createdTs time.Time
+}
+
+type Leaders struct {
+	leaders [3]pb.ServerAddress
+}
+
+type Cluster struct {
+	nodes     map[pb.ServerAddress]*ClusterNode
+	nodesLock sync.RWMutex
+	leaders   *Leaders
+}
+
+func NewCluster() *Cluster {
+	return &Cluster{
+		nodes:   make(map[pb.ServerAddress]*ClusterNode),
+		leaders: &Leaders{},
+	}
+}
+
+func (cluster *Cluster) AddClusterNode(nodeType string, address pb.ServerAddress, version string) {
+	switch nodeType {
+	case "filer":
+		cluster.nodesLock.Lock()
+		defer cluster.nodesLock.Unlock()
+		if existingNode, found := cluster.nodes[address]; found {
+			existingNode.counter++
+			return
+		}
+		cluster.nodes[address] = &ClusterNode{
+			Address:   address,
+			Version:   version,
+			counter:   1,
+			createdTs: time.Now(),
+		}
+		cluster.ensureLeader(true, address)
+	case "master":
+	}
+}
+
+func (cluster *Cluster) RemoveClusterNode(nodeType string, address pb.ServerAddress) {
+	switch nodeType {
+	case "filer":
+		cluster.nodesLock.Lock()
+		defer cluster.nodesLock.Unlock()
+		if existingNode, found := cluster.nodes[address]; !found {
+			return
+		} else {
+			existingNode.counter--
+			if existingNode.counter <= 0 {
+				delete(cluster.nodes, address)
+				cluster.ensureLeader(false, address)
+			}
+		}
+	case "master":
+	}
+}
+
+func (cluster *Cluster) ListClusterNode(nodeType string) (nodes []*ClusterNode) {
+	switch nodeType {
+	case "filer":
+		cluster.nodesLock.RLock()
+		defer cluster.nodesLock.RUnlock()
+		for _, node := range cluster.nodes {
+			nodes = append(nodes, node)
+		}
+	case "master":
+	}
+	return
+}
+
+func (cluster *Cluster) ensureLeader(isAdd bool, address pb.ServerAddress) {
+	if isAdd {
+		if cluster.leaders.addLeaderIfVacant(address) {
+			// has added the address as one leader
+		}
+	} else {
+		if cluster.leaders.removeLeaderIfExists(address) {
+			// pick the freshest one, since it is less likely to go away
+			var shortestDuration int64 = math.MaxInt64
+			now := time.Now()
+			var candidateAddress pb.ServerAddress
+			for _, node := range cluster.nodes {
+				if cluster.leaders.isOneLeader(node.Address) {
+					continue
+				}
+				duration := now.Sub(node.createdTs).Nanoseconds()
+				if duration < shortestDuration {
+					shortestDuration = duration
+					candidateAddress = node.Address
+				}
+			}
+			if candidateAddress != "" {
+				cluster.leaders.addLeaderIfVacant(candidateAddress)
+			}
+			// removed the leader, and maybe added a new leader
+		}
+	}
+}
+
+func (leaders *Leaders) addLeaderIfVacant(address pb.ServerAddress) (hasChanged bool) {
+	if leaders.isOneLeader(address) {
+		return
+	}
+	for i := 0; i < len(leaders.leaders); i++ {
+		if leaders.leaders[i] == "" {
+			leaders.leaders[i] = address
+			hasChanged = true
+			return
+		}
+	}
+	return
+}
+func (leaders *Leaders) removeLeaderIfExists(address pb.ServerAddress) (hasChanged bool) {
+	if !leaders.isOneLeader(address) {
+		return
+	}
+	for i := 0; i < len(leaders.leaders); i++ {
+		if leaders.leaders[i] == address {
+			leaders.leaders[i] = ""
+			hasChanged = true
+			return
+		}
+	}
+	return
+}
+func (leaders *Leaders) isOneLeader(address pb.ServerAddress) bool {
+	for i := 0; i < len(leaders.leaders); i++ {
+		if leaders.leaders[i] == address {
+			return true
+		}
+	}
+	return false
+}
+func (leaders *Leaders) GetLeaders() (addresses []pb.ServerAddress) {
+	for i := 0; i < len(leaders.leaders); i++ {
+		if leaders.leaders[i] != "" {
+			addresses = append(addresses, leaders.leaders[i])
+		}
+	}
+	return
+}