From e24edec81fd50962bc1915abdabe5618b65b68e0 Mon Sep 17 00:00:00 2001
From: David Norton <dgnorton@gmail.com>
Date: Thu, 30 Oct 2014 12:06:30 -0400
Subject: [PATCH] Fix #943: don't try to take 2 snapshots at a time

---
 _vendor/raft/server.go        |  2 ++
 _vendor/raft/snapshot_test.go | 13 +++++++++++++
 coordinator/raft_server.go    |  2 ++
 3 files changed, 17 insertions(+)

diff --git a/_vendor/raft/server.go b/_vendor/raft/server.go
index 922a0466963..b012af1a5f5 100644
--- a/_vendor/raft/server.go
+++ b/_vendor/raft/server.go
@@ -1203,6 +1203,7 @@ func (s *server) TakeSnapshot() error {
 
 	state, err := s.stateMachine.Save()
 	if err != nil {
+		s.pendingSnapshot = nil
 		return err
 	}
 
@@ -1237,6 +1238,7 @@ func (s *server) saveSnapshot() error {
 
 	// Write snapshot to disk.
 	if err := s.pendingSnapshot.save(); err != nil {
+		s.pendingSnapshot = nil
 		return err
 	}
 
diff --git a/_vendor/raft/snapshot_test.go b/_vendor/raft/snapshot_test.go
index ac840e9559d..3cbde39b9bd 100644
--- a/_vendor/raft/snapshot_test.go
+++ b/_vendor/raft/snapshot_test.go
@@ -1,6 +1,7 @@
 package raft
 
 import (
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -121,6 +122,18 @@ func TestSnapshotRequest(t *testing.T) {
 	})
 }
 
+func TestTakeSnapshotWhenStateMachineSaveFails(t *testing.T) {
+	runServerWithMockStateMachine(Leader, func(s Server, m *mock.Mock) {
+		m.On("Save").Return([]byte("foo"), errors.New("test error message"))
+
+		s.Do(&testCommand1{})
+		err := s.TakeSnapshot()
+		assert.Equal(t, err.Error(), "test error message")
+		assert.Nil(t, s.(*server).pendingSnapshot)
+		s.Stop()
+	})
+}
+
 func runServerWithMockStateMachine(state string, fn func(s Server, m *mock.Mock)) {
 	var m mockStateMachine
 	s := newTestServer("1", &testTransporter{})
diff --git a/coordinator/raft_server.go b/coordinator/raft_server.go
index ee3ed19c9d3..0ffd1ac66d8 100644
--- a/coordinator/raft_server.go
+++ b/coordinator/raft_server.go
@@ -331,6 +331,8 @@ const (
 )
 
 func (s *RaftServer) ForceLogCompaction() error {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
 	err := s.raftServer.TakeSnapshot()
 	if err != nil {
 		log.Error("Cannot take snapshot: %s", err)