add mutexes to Local, Backup, and InmemState

state/backup.go

@@ -1,12 +1,17 @@
 package state
 
-import "github.com/hashicorp/terraform/terraform"
+import (
+	"sync"
+
+	"github.com/hashicorp/terraform/terraform"
+)
 
 // BackupState wraps a State that backs up the state on the first time that
 // a WriteState or PersistState is called.
 //
 // If Path exists, it will be overwritten.
 type BackupState struct {
+	mu   sync.Mutex
 	Real State
 	Path string
 
@@ -22,6 +27,9 @@ func (s *BackupState) RefreshState() error {
 }
 
 func (s *BackupState) WriteState(state *terraform.State) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	if !s.done {
 		if err := s.backup(); err != nil {
 			return err
@@ -32,6 +40,9 @@ func (s *BackupState) WriteState(state *terraform.State) error {
 }
 
 func (s *BackupState) PersistState() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	if !s.done {
 		if err := s.backup(); err != nil {
 			return err

state/backup_test.go

@@ -3,6 +3,7 @@ package state
 import (
 	"io/ioutil"
 	"os"
+	"sync"
 	"testing"
 )
 
@@ -31,3 +32,34 @@ func TestBackupState(t *testing.T) {
 		t.Fatalf("bad: %d", fi.Size())
 	}
 }
+
+func TestBackupStateRace(t *testing.T) {
+	f, err := ioutil.TempFile("", "tf")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	f.Close()
+	defer os.Remove(f.Name())
+
+	ls := testLocalState(t)
+	defer os.Remove(ls.Path)
+	bs := &BackupState{
+		Real: ls,
+		Path: f.Name(),
+	}
+
+	current := TestStateInitial()
+
+	var wg sync.WaitGroup
+	for i := 0; i < 100; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			bs.WriteState(current)
+			bs.PersistState()
+			bs.RefreshState()
+		}()
+	}
+
+	wg.Wait()
+}

state/inmem.go

@@ -10,18 +10,28 @@ import (
 
 // InmemState is an in-memory state storage.
 type InmemState struct {
+	mu    sync.Mutex
 	state *terraform.State
 }
 
 func (s *InmemState) State() *terraform.State {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	return s.state.DeepCopy()
 }
 
 func (s *InmemState) RefreshState() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	return nil
 }
 
 func (s *InmemState) WriteState(state *terraform.State) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	state.IncrementSerialMaybe(s.state)
 	s.state = state
 	return nil

state/local.go

@@ -8,6 +8,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"sync"
 	"time"
 
 	multierror "github.com/hashicorp/go-multierror"
@@ -16,6 +17,8 @@ import (
 
 // LocalState manages a state storage that is local to the filesystem.
 type LocalState struct {
+	mu sync.Mutex
+
 	// Path is the path to read the state from. PathOut is the path to
 	// write the state to. If PathOut is not specified, Path will be used.
 	// If PathOut already exists, it will be overwritten.
@@ -42,6 +45,9 @@ type LocalState struct {
 
 // SetState will force a specific state in-memory for this local state.
 func (s *LocalState) SetState(state *terraform.State) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	s.state = state
 	s.readState = state
 }
@@ -58,6 +64,9 @@ func (s *LocalState) State() *terraform.State {
 //
 // StateWriter impl.
 func (s *LocalState) WriteState(state *terraform.State) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	if s.stateFileOut == nil {
 		if err := s.createStateFiles(); err != nil {
 			return nil
@@ -99,6 +108,9 @@ func (s *LocalState) PersistState() error {
 
 // StateRefresher impl.
 func (s *LocalState) RefreshState() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	var reader io.Reader
 	if !s.written {
 		// we haven't written a state file yet, so load from Path
@@ -141,6 +153,9 @@ func (s *LocalState) RefreshState() error {
 
 // Lock implements a local filesystem state.Locker.
 func (s *LocalState) Lock(info *LockInfo) (string, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	if s.stateFileOut == nil {
 		if err := s.createStateFiles(); err != nil {
 			return "", err
@@ -170,6 +185,9 @@ func (s *LocalState) Lock(info *LockInfo) (string, error) {
 }
 
 func (s *LocalState) Unlock(id string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	if s.lockID == "" {
 		return fmt.Errorf("LocalState not locked")
 	}

state/local_test.go

@@ -4,6 +4,7 @@ import (
 	"io/ioutil"
 	"os"
 	"os/exec"
+	"sync"
 	"testing"
 
 	"github.com/hashicorp/terraform/terraform"
@@ -15,6 +16,22 @@ func TestLocalState(t *testing.T) {
 	TestState(t, ls)
 }
 
+func TestLocalStateRace(t *testing.T) {
+	ls := testLocalState(t)
+	defer os.Remove(ls.Path)
+
+	current := TestStateInitial()
+
+	var wg sync.WaitGroup
+	for i := 0; i < 100; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			ls.WriteState(current)
+		}()
+	}
+}
+
 func TestLocalStateLocks(t *testing.T) {
 	s := testLocalState(t)
 	defer os.Remove(s.Path)