From d94ea1678082307cb5bb6a36f6cd8eb0c117614a Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Wed, 2 Mar 2022 04:48:31 -0500
Subject: [PATCH] update

---
 src/raft/config.go | 30 ++++++++++++++++++++----------
 src/raft/raft.go   |  4 ++--
 2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/src/raft/config.go b/src/raft/config.go
index f3f4b90..cc956b8 100644
--- a/src/raft/config.go
+++ b/src/raft/config.go
@@ -170,7 +170,7 @@ func (cfg *config) applier(i int, applyCh chan ApplyMsg) {
 				err_msg = fmt.Sprintf("server %v apply out of order %v", i, m.CommandIndex)
 			}
 			if err_msg != "" {
-				log.Fatalf("apply error: %v\n", err_msg)
+				log.Fatalf("apply error: %v", err_msg)
 				cfg.applyErr[i] = err_msg
 				// keep reading after error so that Raft doesn't block
 				// holding locks...
@@ -181,13 +181,17 @@ func (cfg *config) applier(i int, applyCh chan ApplyMsg) {
 
 // returns "" or error string
 func (cfg *config) ingestSnap(i int, snapshot []byte, index int) string {
+	if snapshot == nil {
+		log.Fatalf("nil snapshot")
+		return "nil snapshot"
+	}
 	r := bytes.NewBuffer(snapshot)
 	d := labgob.NewDecoder(r)
 	var lastIncludedIndex int
 	var xlog []interface{}
 	if d.Decode(&lastIncludedIndex) != nil ||
 		d.Decode(&xlog) != nil {
-		log.Fatalf("snapshot decode error\n")
+		log.Fatalf("snapshot decode error")
 		return "snapshot Decode() error"
 	}
 	if index != -1 && index != lastIncludedIndex {
@@ -206,15 +210,21 @@ const SnapShotInterval = 10
 
 // periodically snapshot raft state
 func (cfg *config) applierSnap(i int, applyCh chan ApplyMsg) {
+	cfg.mu.Lock()
+	rf := cfg.rafts[i]
+	cfg.mu.Unlock()
+	if rf == nil {
+		return // ???
+	}
+
 	for m := range applyCh {
 		err_msg := ""
 		if m.SnapshotValid {
-			cfg.mu.Lock()
-			if cfg.rafts[i].CondInstallSnapshot(m.SnapshotTerm,
-				m.SnapshotIndex, m.Snapshot) {
+			if rf.CondInstallSnapshot(m.SnapshotTerm, m.SnapshotIndex, m.Snapshot) {
+				cfg.mu.Lock()
 				err_msg = cfg.ingestSnap(i, m.Snapshot, m.SnapshotIndex)
+				cfg.mu.Unlock()
 			}
-			cfg.mu.Unlock()
 		} else if m.CommandValid {
 			if m.CommandIndex != cfg.lastApplied[i]+1 {
 				err_msg = fmt.Sprintf("server %v apply out of order, expected index %v, got %v", i, cfg.lastApplied[i]+1, m.CommandIndex)
@@ -243,13 +253,13 @@ func (cfg *config) applierSnap(i int, applyCh chan ApplyMsg) {
 					xlog = append(xlog, cfg.logs[i][j])
 				}
 				e.Encode(xlog)
-				cfg.rafts[i].Snapshot(m.CommandIndex, w.Bytes())
+				rf.Snapshot(m.CommandIndex, w.Bytes())
 			}
 		} else {
 			// Ignore other types of ApplyMsg.
 		}
 		if err_msg != "" {
-			log.Fatalf("apply error: %v\n", err_msg)
+			log.Fatalf("apply error: %v", err_msg)
 			cfg.applyErr[i] = err_msg
 			// keep reading after error so that Raft doesn't block
 			// holding locks...
@@ -497,7 +507,7 @@ func (cfg *config) nCommitted(index int) (int, interface{}) {
 
 		if ok {
 			if count > 0 && cmd != cmd1 {
-				cfg.t.Fatalf("committed values do not match: index %v, %v, %v\n",
+				cfg.t.Fatalf("committed values do not match: index %v, %v, %v",
 					index, cmd, cmd1)
 			}
 			count += 1
@@ -532,7 +542,7 @@ func (cfg *config) wait(index int, n int, startTerm int) interface{} {
 	}
 	nd, cmd := cfg.nCommitted(index)
 	if nd < n {
-		cfg.t.Fatalf("only %d decided for index %d; wanted %d\n",
+		cfg.t.Fatalf("only %d decided for index %d; wanted %d",
 			nd, index, n)
 	}
 	return cmd
diff --git a/src/raft/raft.go b/src/raft/raft.go
index 29ea521..afe91ea 100644
--- a/src/raft/raft.go
+++ b/src/raft/raft.go
@@ -18,11 +18,11 @@ package raft
 //
 
 import (
-//	"bytes"
+	//	"bytes"
 	"sync"
 	"sync/atomic"
 
-//	"6.824/labgob"
+	//	"6.824/labgob"
 	"6.824/labrpc"
 )