From f0f2220abb592d46a50b4f3d1010bf9a1e4739d2 Mon Sep 17 00:00:00 2001
From: James Bardin <j.bardin@gmail.com>
Date: Thu, 25 May 2017 11:01:25 -0400
Subject: [PATCH] add mutexes to remote.State

---
 state/remote/state.go      | 21 +++++++++++++++++++++
 state/remote/state_test.go | 22 ++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/state/remote/state.go b/state/remote/state.go
index c87416705..dccbab18a 100644
--- a/state/remote/state.go
+++ b/state/remote/state.go
@@ -2,6 +2,7 @@ package remote
 
 import (
 	"bytes"
+	"sync"
 
 	"github.com/hashicorp/terraform/state"
 	"github.com/hashicorp/terraform/terraform"
@@ -12,6 +13,8 @@ import (
 // local caching so every persist will go to the remote storage and local
 // writes will go to memory.
 type State struct {
+	mu sync.Mutex
+
 	Client Client
 
 	state, readState *terraform.State
@@ -19,17 +22,26 @@ type State struct {
 
 // StateReader impl.
 func (s *State) State() *terraform.State {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	return s.state.DeepCopy()
 }
 
 // StateWriter impl.
 func (s *State) WriteState(state *terraform.State) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	s.state = state
 	return nil
 }
 
 // StateRefresher impl.
 func (s *State) RefreshState() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	payload, err := s.Client.Get()
 	if err != nil {
 		return err
@@ -52,6 +64,9 @@ func (s *State) RefreshState() error {
 
 // StatePersister impl.
 func (s *State) PersistState() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	s.state.IncrementSerialMaybe(s.readState)
 
 	var buf bytes.Buffer
@@ -64,6 +79,9 @@ func (s *State) PersistState() error {
 
 // Lock calls the Client's Lock method if it's implemented.
 func (s *State) Lock(info *state.LockInfo) (string, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	if c, ok := s.Client.(ClientLocker); ok {
 		return c.Lock(info)
 	}
@@ -72,6 +90,9 @@ func (s *State) Lock(info *state.LockInfo) (string, error) {
 
 // Unlock calls the Client's Unlock method if it's implemented.
 func (s *State) Unlock(id string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	if c, ok := s.Client.(ClientLocker); ok {
 		return c.Unlock(id)
 	}
diff --git a/state/remote/state_test.go b/state/remote/state_test.go
index 90a60e9c4..26a031b7e 100644
--- a/state/remote/state_test.go
+++ b/state/remote/state_test.go
@@ -1,6 +1,7 @@
 package remote
 
 import (
+	"sync"
 	"testing"
 
 	"github.com/hashicorp/terraform/state"
@@ -13,3 +14,24 @@ func TestState_impl(t *testing.T) {
 	var _ state.StateRefresher = new(State)
 	var _ state.Locker = new(State)
 }
+
+func TestStateRace(t *testing.T) {
+	s := &State{
+		Client: nilClient{},
+	}
+
+	current := state.TestStateInitial()
+
+	var wg sync.WaitGroup
+
+	for i := 0; i < 100; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			s.WriteState(current)
+			s.PersistState()
+			s.RefreshState()
+		}()
+	}
+	wg.Wait()
+}