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node.go
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node.go
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package raft
import (
"context"
"encoding/json"
"fmt"
"io/fs"
"log"
"os"
"sync"
"time"
"unsafe"
pb "github.com/misachi/raft/protos/requestvote"
)
const (
Follower = "Follower"
Candidate = "Candidate"
Leader = "Leader"
)
var (
CurrentNode *Node
NodeDetail = fmt.Sprintf("%s/.config/node-detail.json", os.Getenv("HOME"))
EntryLogFile = fmt.Sprintf("%s/.config/entry_logs.json", os.Getenv("HOME"))
)
type Node struct {
mu sync.Mutex
CurrentTerm int64 `json:"current_term,omitempty"` /* Store the term we're in atm */
VotedFor string `json:"voted_for,omitempty"` /* CandidateId that received vote */
State string `json:"state,omitempty"` /* Current state of the node */
Name string `json:"name,omitempty"` /* Node name */
CommitIndex int `json:"commit_index,omitempty"` /* Index of highest log entry known to be committed */
LastApplied int `json:"last_applied,omitempty"` /* Index of highest log entry applied to state machine */
Nodes []string `json:"nodes,omitempty"` /* Nodes in cluster */
LogEntry []Entry `json:"log_entry,omitempty"` /* Command Entries */
}
func NewNode(serverName string, clusterNodes []string) *Node {
srvIndex, err := getArrayElement(clusterNodes, serverName)
if err != nil {
log.Fatal(err)
}
clusterNodes = removeArrayElement(clusterNodes, srvIndex)
node := Node{
State: Follower,
Name: serverName,
Nodes: clusterNodes,
}
entry := []Entry{}
if err := ReadEntryLog(entry); err != nil {
log.Fatalf("Could not read entry log: %v", err)
}
node.LogEntry = entry
return &node
}
func (n *Node) ReadNodeFromFile(buf []byte, flag int) *Node {
n.mu.Lock()
defer n.mu.Unlock()
store := NewDiskStore(NodeDetail)
fileObj, err := store.CreateFile(0644, flag)
if err != nil {
log.Fatal(err)
}
defer fileObj.Close()
total := 0
for {
nRead, err := store.ReadFile(buf, fileObj)
if err != nil {
break
}
total += nRead
}
if total > 0 {
var node Node
if err := json.Unmarshal(buf[:total], &node); err != nil {
log.Fatal(err)
}
return &node
}
return nil
}
func (n *Node) PersistToDisk(perm fs.FileMode, flag int) error {
n.mu.Lock()
defer n.mu.Unlock()
buf, err := json.Marshal(n)
if err != nil {
return fmt.Errorf("unable to serialize to Json: %v", err)
}
store := NewDiskStore(NodeDetail)
fileObj, err := store.CreateFile(perm, flag)
if err != nil {
log.Fatal(err)
}
defer fileObj.Close()
if err := store.WriteFile(buf, fileObj); err != nil {
return fmt.Errorf("failed %v", err)
}
return nil
}
func (n *Node) String() string {
return fmt.Sprintf("Name: %s State: %s Term: %d", n.Name, n.State, n.CurrentTerm)
}
func avgNodeCount(nList []string) int {
return (len(nList) + 1) / 2
}
func (n *Node) TruncNodeFile(size int64) {
n.mu.Lock()
defer n.mu.Unlock()
if err := os.Truncate(NodeDetail, size); err != nil {
log.Fatalf("unable to resize file: %v", err)
}
}
func (n *Node) RefreshFromDisk() *Node {
return NodeFromDisk()
}
func getRequestVoteResponse(ctx context.Context, n *Node, voteResponseChan chan *pb.RequestVoteResponse, nodeName chan string) {
requestVoteMsg := RequestVoteMsg{}
for _, srv_node := range n.Nodes {
select {
case <-ctx.Done():
log.Println(ctx.Err())
return
default:
go func(ctx context.Context, srv string, currentTerm int64, name string) {
select {
case <-ctx.Done():
log.Println(ctx.Err())
return
case voteResponseChan <- requestVoteMsg.Send(srv, currentTerm, n.Name, 0, 0):
nodeName <- srv
}
}(ctx, srv_node, n.CurrentTerm, n.Name)
}
}
}
func (n *Node) SendRequestVote() {
if n.State != Candidate {
log.Printf("%s Only Candidate nodes can send RequestVote\n", n.Name)
return
}
totalVote, nodeCount := 0, avgNodeCount(n.Nodes)
voteResponseChan := make(chan *pb.RequestVoteResponse)
nodeName := make(chan string)
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
n.CurrentTerm++ /* Increment term by 1 */
totalVote++ /* Vote for myself */
go getRequestVoteResponse(ctx, n, voteResponseChan, nodeName)
for vote_response := range voteResponseChan {
granted := vote_response.GetVoteGranted()
new_term := vote_response.GetTerm()
log.Printf("%s voted %v in term %d\n", <-nodeName, granted, new_term)
if new_term >= n.CurrentTerm && !granted {
n.CurrentTerm = new_term
n.State = Follower
cancel() // Cleanup if a leader exists already
break
}
if granted {
totalVote++
}
if totalVote >= nodeCount {
log.Printf("%s won Election", n.Name)
n.State = Leader
appendLog := NewAppendLog(n)
appendLog.SendHeartBeat()
cancel() // Cleanup if we have majority votes
break
}
}
n.TruncNodeFile(int64(unsafe.Sizeof(n)))
if err := n.PersistToDisk(0644, os.O_CREATE|os.O_WRONLY); err != nil {
log.Fatal(err)
}
}
func (n *Node) VoteForClient(client_name string, term int64, lastLogIdx int64, lastLogTerm int64) (int64, bool) {
if term > n.CurrentTerm {
n.State = Follower
n.CurrentTerm = term
n.VotedFor = client_name
return term, true
}
return n.CurrentTerm, false
}