add statemachine interface

server.go

@@ -62,7 +62,7 @@ type Server struct {
 	heartbeatTimeout     time.Duration
 	currentSnapshot      *Snapshot
 	lastSnapshot         *Snapshot
-	machineState		 int 	//TODO CHANGE THIS TO INTERFACE: recovery and store
+	stateMachine         StateMachine
 }
 
 //------------------------------------------------------------------------------
@@ -812,7 +812,13 @@ func (s *Server) takeSnapshot() error {
 
 	path := s.SnapshotPath(lastIndex, lastTerm)
 
-	s.currentSnapshot = &Snapshot{lastIndex, lastTerm, s.machineState , path}
+	state, err := s.stateMachine.Save()	
+
+	if err !=nil {
+		return err
+	}
+
+	s.currentSnapshot = &Snapshot{lastIndex, lastTerm, state, path}
 
 	s.saveSnapshot()
 
@@ -857,13 +863,13 @@ func (s *Server) SnapshotRecovery(req *SnapshotRequest) (*SnapshotResponse, erro
 	defer s.mutex.Unlock()
 
 	//recovery machine state
-	s.machineState = req.MachineState
+	s.stateMachine.Recovery(req.State)
 
 	//update term and index
 	s.currentTerm = req.LastTerm
 	s.log.UpdateCommitIndex(req.LastIndex)
 	snapshotPath := s.SnapshotPath(req.LastIndex, req.LastTerm)
-	s.currentSnapshot = &Snapshot{req.LastIndex, req.LastTerm, req.MachineState, snapshotPath}
+	s.currentSnapshot = &Snapshot{req.LastIndex, req.LastTerm, req.State, snapshotPath}
 	s.saveSnapshot() 
 	s.log.Compact(req.LastIndex, req.LastTerm)
 
@@ -913,15 +919,21 @@ func (s *Server) LoadSnapshot() error {
 		&lastIndex, &lastTerm)
 
 	if err != nil {
-		panic(err)
+		return err
 	}
 
 	if n != 4 {
-		panic(n)
+		return errors.New("Bad snapshot file")
 	}
 
-	s.lastSnapshot = &Snapshot{lastIndex, lastTerm, 1, snapshotPath}
-	s.machineState = machineState
+	state, err := s.stateMachine.Save()
+	if err != nil {
+		return err
+	}
+
+	s.lastSnapshot = &Snapshot{lastIndex, lastTerm, state, snapshotPath}
+	err = s.stateMachine.Recovery(state)
+
 	s.log.SetStartTerm(lastTerm)
 	s.log.SetStartIndex(lastIndex)
 	s.log.UpdateCommitIndex(lastIndex)

snapshot.go

@@ -20,7 +20,7 @@ type Snapshot struct {
 	lastIndex uint64
 	lastTerm uint64
 	// cluster configuration. 
-	machineState int
+	state []byte
 	path string
 }
 
@@ -46,9 +46,13 @@ func (ss *Snapshot) Save() error {
 	defer file.Close()
 
 
-	// Write log entry with checksum.
-	if _, err = fmt.Fprintf(file, "%08x\n%s\n%v\n%v\n", checksum, b.String(), 
-		ss.lastIndex, ss.lastTerm); err != nil {
+	// Write snapshot with checksum.
+	if _, err = fmt.Fprintf(file, "%08x\n%v\n%v\n", checksum, ss.lastIndex, 
+		ss.lastTerm); err != nil {
+		return err
+	}
+
+	if 	_, err = file.Write(ss.state); err != nil {
 		return err
 	}
 

snapshot_request.go

@@ -5,7 +5,7 @@ type SnapshotRequest struct {
 	LeaderName   string      `json:"leaderName"`
 	LastIndex    uint64 	 `json:"lastTerm"`
 	LastTerm	 uint64		 `json:"lastIndex"`
-	MachineState int 		 `json:"machineState"`
+	State        []byte      `json:"state"`
 }
 
 // The response returned from a server appending entries to the log.
@@ -27,7 +27,7 @@ func NewSnapshotRequest(leaderName string, snapshot *Snapshot) *SnapshotRequest
 		LeaderName:   leaderName,
 		LastIndex:    snapshot.lastIndex,
 		LastTerm:	  snapshot.lastTerm,
-		MachineState: snapshot.machineState,
+		State:        snapshot.state,
 	}
 }
 

statemachine.go

@@ -0,0 +1,15 @@
+package raft
+
+//------------------------------------------------------------------------------
+//
+// Typedefs
+//
+//------------------------------------------------------------------------------
+
+// StateMachine is the interface for allowing the host application to save and 
+// recovery the state machine
+type StateMachine interface {
+	Save() ([]byte, error)
+	Recovery([]byte) error
+
+}