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snapshot.go
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snapshot.go
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package raft
import (
"encoding/json"
"fmt"
"hash/crc32"
"io"
"io/ioutil"
"os"
"github.com/gogo/protobuf/proto"
"github.com/goraft/raft/protobuf"
)
// Snapshot represents an in-memory representation of the current state of the system.
type Snapshot struct {
LastIndex uint64 `json:"lastIndex"`
LastTerm uint64 `json:"lastTerm"`
// Cluster configuration.
Peers []*Peer `json:"peers"`
State []byte `json:"state"`
Path string `json:"path"`
}
// The request sent to a server to start from the snapshot.
type SnapshotRecoveryRequest struct {
LeaderName string
LastIndex uint64
LastTerm uint64
Peers []*Peer
State []byte
}
// The response returned from a server appending entries to the log.
type SnapshotRecoveryResponse struct {
Term uint64
Success bool
CommitIndex uint64
}
// The request sent to a server to start from the snapshot.
type SnapshotRequest struct {
LeaderName string
LastIndex uint64
LastTerm uint64
}
// The response returned if the follower entered snapshot state
type SnapshotResponse struct {
Success bool `json:"success"`
}
// save writes the snapshot to file.
func (ss *Snapshot) save() error {
// Open the file for writing.
file, err := os.OpenFile(ss.Path, os.O_CREATE|os.O_WRONLY, 0600)
if err != nil {
return err
}
defer file.Close()
// Serialize to JSON.
b, err := json.Marshal(ss)
if err != nil {
return err
}
// Generate checksum and write it to disk.
checksum := crc32.ChecksumIEEE(b)
if _, err = fmt.Fprintf(file, "%08x\n", checksum); err != nil {
return err
}
// Write the snapshot to disk.
if _, err = file.Write(b); err != nil {
return err
}
// Ensure that the snapshot has been flushed to disk before continuing.
if err := file.Sync(); err != nil {
return err
}
return nil
}
// remove deletes the snapshot file.
func (ss *Snapshot) remove() error {
if err := os.Remove(ss.Path); err != nil {
return err
}
return nil
}
// Creates a new Snapshot request.
func newSnapshotRecoveryRequest(leaderName string, snapshot *Snapshot) *SnapshotRecoveryRequest {
return &SnapshotRecoveryRequest{
LeaderName: leaderName,
LastIndex: snapshot.LastIndex,
LastTerm: snapshot.LastTerm,
Peers: snapshot.Peers,
State: snapshot.State,
}
}
// Encodes the SnapshotRecoveryRequest to a buffer. Returns the number of bytes
// written and any error that may have occurred.
func (req *SnapshotRecoveryRequest) Encode(w io.Writer) (int, error) {
protoPeers := make([]*protobuf.SnapshotRecoveryRequest_Peer, len(req.Peers))
for i, peer := range req.Peers {
protoPeers[i] = &protobuf.SnapshotRecoveryRequest_Peer{
Name: proto.String(peer.Name),
ConnectionString: proto.String(peer.ConnectionString),
}
}
pb := &protobuf.SnapshotRecoveryRequest{
LeaderName: proto.String(req.LeaderName),
LastIndex: proto.Uint64(req.LastIndex),
LastTerm: proto.Uint64(req.LastTerm),
Peers: protoPeers,
State: req.State,
}
p, err := proto.Marshal(pb)
if err != nil {
return -1, err
}
return w.Write(p)
}
// Decodes the SnapshotRecoveryRequest from a buffer. Returns the number of bytes read and
// any error that occurs.
func (req *SnapshotRecoveryRequest) Decode(r io.Reader) (int, error) {
data, err := ioutil.ReadAll(r)
if err != nil {
return 0, err
}
totalBytes := len(data)
pb := &protobuf.SnapshotRecoveryRequest{}
if err = proto.Unmarshal(data, pb); err != nil {
return -1, err
}
req.LeaderName = pb.GetLeaderName()
req.LastIndex = pb.GetLastIndex()
req.LastTerm = pb.GetLastTerm()
req.State = pb.GetState()
req.Peers = make([]*Peer, len(pb.Peers))
for i, peer := range pb.Peers {
req.Peers[i] = &Peer{
Name: peer.GetName(),
ConnectionString: peer.GetConnectionString(),
}
}
return totalBytes, nil
}
// Creates a new Snapshot response.
func newSnapshotRecoveryResponse(term uint64, success bool, commitIndex uint64) *SnapshotRecoveryResponse {
return &SnapshotRecoveryResponse{
Term: term,
Success: success,
CommitIndex: commitIndex,
}
}
// Encode writes the response to a writer.
// Returns the number of bytes written and any error that occurs.
func (req *SnapshotRecoveryResponse) Encode(w io.Writer) (int, error) {
pb := &protobuf.SnapshotRecoveryResponse{
Term: proto.Uint64(req.Term),
Success: proto.Bool(req.Success),
CommitIndex: proto.Uint64(req.CommitIndex),
}
p, err := proto.Marshal(pb)
if err != nil {
return -1, err
}
return w.Write(p)
}
// Decodes the SnapshotRecoveryResponse from a buffer.
func (req *SnapshotRecoveryResponse) Decode(r io.Reader) (int, error) {
data, err := ioutil.ReadAll(r)
if err != nil {
return 0, err
}
totalBytes := len(data)
pb := &protobuf.SnapshotRecoveryResponse{}
if err := proto.Unmarshal(data, pb); err != nil {
return -1, err
}
req.Term = pb.GetTerm()
req.Success = pb.GetSuccess()
req.CommitIndex = pb.GetCommitIndex()
return totalBytes, nil
}
// Creates a new Snapshot request.
func newSnapshotRequest(leaderName string, snapshot *Snapshot) *SnapshotRequest {
return &SnapshotRequest{
LeaderName: leaderName,
LastIndex: snapshot.LastIndex,
LastTerm: snapshot.LastTerm,
}
}
// Encodes the SnapshotRequest to a buffer. Returns the number of bytes
// written and any error that may have occurred.
func (req *SnapshotRequest) Encode(w io.Writer) (int, error) {
pb := &protobuf.SnapshotRequest{
LeaderName: proto.String(req.LeaderName),
LastIndex: proto.Uint64(req.LastIndex),
LastTerm: proto.Uint64(req.LastTerm),
}
p, err := proto.Marshal(pb)
if err != nil {
return -1, err
}
return w.Write(p)
}
// Decodes the SnapshotRequest from a buffer. Returns the number of bytes read and
// any error that occurs.
func (req *SnapshotRequest) Decode(r io.Reader) (int, error) {
data, err := ioutil.ReadAll(r)
if err != nil {
return 0, err
}
totalBytes := len(data)
pb := &protobuf.SnapshotRequest{}
if err := proto.Unmarshal(data, pb); err != nil {
return -1, err
}
req.LeaderName = pb.GetLeaderName()
req.LastIndex = pb.GetLastIndex()
req.LastTerm = pb.GetLastTerm()
return totalBytes, nil
}
// Creates a new Snapshot response.
func newSnapshotResponse(success bool) *SnapshotResponse {
return &SnapshotResponse{
Success: success,
}
}
// Encodes the SnapshotResponse to a buffer. Returns the number of bytes
// written and any error that may have occurred.
func (resp *SnapshotResponse) Encode(w io.Writer) (int, error) {
pb := &protobuf.SnapshotResponse{
Success: proto.Bool(resp.Success),
}
p, err := proto.Marshal(pb)
if err != nil {
return -1, err
}
return w.Write(p)
}
// Decodes the SnapshotResponse from a buffer. Returns the number of bytes read and
// any error that occurs.
func (resp *SnapshotResponse) Decode(r io.Reader) (int, error) {
data, err := ioutil.ReadAll(r)
if err != nil {
return 0, err
}
totalBytes := len(data)
pb := &protobuf.SnapshotResponse{}
if err := proto.Unmarshal(data, pb); err != nil {
return -1, err
}
resp.Success = pb.GetSuccess()
return totalBytes, nil
}