From 90c0db3d421d88d4a56c0a0d43d18871fbf45c65 Mon Sep 17 00:00:00 2001
From: Xiang Li <xiang.li@coreos.com>
Date: Mon, 8 Sep 2014 21:45:10 -0700
Subject: [PATCH] wal: do not save empty state

---
 raft/node.go      | 12 ++++++++----
 raft/node_test.go |  2 +-
 wal/wal.go        |  4 ++++
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/raft/node.go b/raft/node.go
index 502c1e378..9ebf19bd3 100644
--- a/raft/node.go
+++ b/raft/node.go
@@ -10,7 +10,7 @@ import (
 )
 
 var (
-	EmptyState = pb.State{}
+	emptyState = pb.State{}
 	ErrStopped = errors.New("raft: stopped")
 )
 
@@ -38,8 +38,12 @@ func isStateEqual(a, b pb.State) bool {
 	return a.Term == b.Term && a.Vote == b.Vote && a.LastIndex == b.LastIndex
 }
 
+func IsEmptyState(st pb.State) bool {
+	return isStateEqual(st, emptyState)
+}
+
 func (rd Ready) containsUpdates() bool {
-	return !isStateEqual(EmptyState, rd.State) || len(rd.Entries) > 0 || len(rd.CommittedEntries) > 0 || len(rd.Messages) > 0
+	return !isStateEqual(emptyState, rd.State) || len(rd.Entries) > 0 || len(rd.CommittedEntries) > 0 || len(rd.Messages) > 0
 }
 
 type Node struct {
@@ -106,7 +110,7 @@ func (n *Node) run(r *raft) {
 		}
 
 		if isStateEqual(r.State, prevSt) {
-			rd.State = EmptyState
+			rd.State = emptyState
 		} else {
 			rd.State = r.State
 		}
@@ -128,7 +132,7 @@ func (n *Node) run(r *raft) {
 		case readyc <- rd:
 			r.raftLog.resetNextEnts()
 			r.raftLog.resetUnstable()
-			if !isStateEqual(rd.State, EmptyState) {
+			if !IsEmptyState(rd.State) {
 				prevSt = rd.State
 			}
 			r.msgs = nil
diff --git a/raft/node_test.go b/raft/node_test.go
index 21b800483..10e586e74 100644
--- a/raft/node_test.go
+++ b/raft/node_test.go
@@ -51,7 +51,7 @@ func TestNodeRestart(t *testing.T) {
 	st := raftpb.State{Term: 1, Vote: -1, Commit: 1, LastIndex: 2}
 
 	want := Ready{
-		State: EmptyState,
+		State: emptyState,
 		// commit upto index commit index in st
 		CommittedEntries: entries[:st.Commit],
 	}
diff --git a/wal/wal.go b/wal/wal.go
index 3335fb3d1..bd0a1140a 100644
--- a/wal/wal.go
+++ b/wal/wal.go
@@ -26,6 +26,7 @@ import (
 	"path"
 	"sort"
 
+	"github.com/coreos/etcd/raft"
 	"github.com/coreos/etcd/raft/raftpb"
 	"github.com/coreos/etcd/wal/walpb"
 )
@@ -253,6 +254,9 @@ func (w *WAL) SaveEntry(e *raftpb.Entry) error {
 }
 
 func (w *WAL) SaveState(s *raftpb.State) error {
+	if raft.IsEmptyState(*s) {
+		return nil
+	}
 	log.Printf("path=%s wal.saveState state=\"%+v\"", w.f.Name(), s)
 	b, err := s.Marshal()
 	if err != nil {