Add automatic node promotion / demotion.

server/demote_command.go

@@ -0,0 +1,49 @@
+package server
+
+import (
+	"github.com/coreos/etcd/log"
+	"github.com/coreos/etcd/third_party/github.com/coreos/raft"
+)
+
+func init() {
+	raft.RegisterCommand(&DemoteCommand{})
+}
+
+// DemoteCommand represents a command to change a peer to a proxy.
+type DemoteCommand struct {
+	Name string `json:"name"`
+}
+
+// CommandName returns the name of the command.
+func (c *DemoteCommand) CommandName() string {
+	return "etcd:demote"
+}
+
+// Apply executes the command.
+func (c *DemoteCommand) Apply(context raft.Context) (interface{}, error) {
+	ps, _ := context.Server().Context().(*PeerServer)
+
+	// Save URLs.
+	clientURL, _ := ps.registry.ClientURL(c.Name)
+	peerURL, _ := ps.registry.PeerURL(c.Name)
+
+	// Perform a removal.
+	(&RemoveCommand{Name: c.Name}).Apply(context)
+
+	// Register node as a proxy.
+	ps.registry.RegisterProxy(c.Name, peerURL, clientURL)
+
+	// Update mode if this change applies to this server.
+	if c.Name == ps.Config.Name {
+		log.Infof("Set mode after demotion: %s", c.Name)
+		ps.SetMode(ProxyMode)
+	}
+
+	return nil, nil
+}
+
+// NodeName returns the name of the affected node.
+func (c *DemoteCommand) NodeName() string {
+	return c.Name
+}
+

server/peer_server.go

@@ -26,7 +26,7 @@ import (
 )
 
 const ThresholdMonitorTimeout = 5 * time.Second
-const ActiveMonitorTimeout = 5 * time.Second
+const ActiveMonitorTimeout = 1 * time.Second
 
 type PeerServerConfig struct {
 	Name           string
@@ -644,7 +644,7 @@ func (s *PeerServer) monitorActive(closeChan chan bool) {
 		if peerCount > activeSize {
 			peer := peers[rand.Intn(len(peers))]
 			fmt.Println("active.demote»", peer)
-			if _, err := s.raftServer.Do(&RemoveCommand{Name: peer}); err != nil {
+			if _, err := s.raftServer.Do(&DemoteCommand{Name: peer}); err != nil {
 				log.Infof("%s: warning: demotion error: %v", s.Config.Name, err)
 			}
 			continue