Use NewLockInfo to get a pre-populated value

Using NewLockInfo ensure we start with all required fields filled.

backend/local/backend_local.go

@@ -30,10 +30,8 @@ func (b *Local) context(op *backend.Operation) (*terraform.Context, state.State,
 	}
 
 	if op.LockState {
-		lockInfo := &state.LockInfo{
-			Info: op.Type.String(),
-		}
-
+		lockInfo := state.NewLockInfo()
+		lockInfo.Operation = op.Type.String()
 		_, err := clistate.Lock(s, lockInfo, b.CLI, b.Colorize())
 		if err != nil {
 			return nil, nil, errwrap.Wrapf("Error locking state: {{err}}", err)

command/meta_backend.go

@@ -533,10 +533,8 @@ func (m *Meta) backendFromPlan(opts *BackendOpts) (backend.Backend, error) {
 	}
 
 	// Lock the state if we can
-	lockInfo := &state.LockInfo{
-		Operation: "plan",
-		Info:      "backend from plan",
-	}
+	lockInfo := state.NewLockInfo()
+	lockInfo.Operation = "backend from plan"
 
 	lockID, err := clistate.Lock(realMgr, lockInfo, m.Ui, m.Colorize())
 	if err != nil {
@@ -991,9 +989,8 @@ func (m *Meta) backend_C_r_s(
 	}
 
 	// Lock the state if we can
-	lockInfo := &state.LockInfo{
-		Info: "backend from config",
-	}
+	lockInfo := state.NewLockInfo()
+	lockInfo.Operation = "backend from config"
 
 	lockID, err := clistate.Lock(sMgr, lockInfo, m.Ui, m.Colorize())
 	if err != nil {
@@ -1100,9 +1097,9 @@ func (m *Meta) backend_C_r_S_changed(
 	}
 
 	// Lock the state if we can
-	lockInfo := &state.LockInfo{
-		Info: "backend from config",
-	}
+	lockInfo := state.NewLockInfo()
+	lockInfo.Operation = "backend from config"
+
 	lockID, err := clistate.Lock(sMgr, lockInfo, m.Ui, m.Colorize())
 	if err != nil {
 		return nil, fmt.Errorf("Error locking state: %s", err)
@@ -1261,9 +1258,8 @@ func (m *Meta) backend_C_R_S_unchanged(
 	}
 
 	// Lock the state if we can
-	lockInfo := &state.LockInfo{
-		Info: "backend from config",
-	}
+	lockInfo := state.NewLockInfo()
+	lockInfo.Operation = "backend from config"
 
 	lockID, err := clistate.Lock(sMgr, lockInfo, m.Ui, m.Colorize())
 	if err != nil {

command/meta_backend_migrate.go

@@ -24,9 +24,8 @@ import (
 //
 // This will attempt to lock both states for the migration.
 func (m *Meta) backendMigrateState(opts *backendMigrateOpts) error {
-	lockInfoOne := &state.LockInfo{
-		Info: "migration source state",
-	}
+	lockInfoOne := state.NewLockInfo()
+	lockInfoOne.Operation = "migration source state"
 
 	lockIDOne, err := clistate.Lock(opts.One, lockInfoOne, m.Ui, m.Colorize())
 	if err != nil {
@@ -34,9 +33,8 @@ func (m *Meta) backendMigrateState(opts *backendMigrateOpts) error {
 	}
 	defer clistate.Unlock(opts.One, lockIDOne, m.Ui, m.Colorize())
 
-	lockInfoTwo := &state.LockInfo{
-		Info: "migration source state",
-	}
+	lockInfoTwo := state.NewLockInfo()
+	lockInfoTwo.Operation = "migration source state"
 
 	lockIDTwo, err := clistate.Lock(opts.Two, lockInfoTwo, m.Ui, m.Colorize())
 	if err != nil {

command/taint.go

@@ -74,9 +74,8 @@ func (c *TaintCommand) Run(args []string) int {
 	}
 
 	if c.Meta.stateLock {
-		lockInfo := &state.LockInfo{
-			Operation: "taint",
-		}
+		lockInfo := state.NewLockInfo()
+		lockInfo.Operation = "taint"
 		lockID, err := clistate.Lock(st, lockInfo, c.Ui, c.Colorize())
 		if err != nil {
 			c.Ui.Error(fmt.Sprintf("Error locking state: %s", err))

command/testdata/statelocker.go

@@ -23,7 +23,11 @@ func main() {
 		Path: os.Args[1],
 	}
 
-	lockID, err := s.Lock(&state.LockInfo{Operation: "test", Info: "state locker"})
+	info := state.NewLockInfo()
+	info.Operation = "test"
+	info.Info = "state locker"
+
+	lockID, err := s.Lock(info)
 	if err != nil {
 		io.WriteString(os.Stderr, err.Error())
 		return

command/untaint.go

@@ -62,9 +62,8 @@ func (c *UntaintCommand) Run(args []string) int {
 	}
 
 	if c.Meta.stateLock {
-		lockInfo := &state.LockInfo{
-			Operation: "untaint",
-		}
+		lockInfo := state.NewLockInfo()
+		lockInfo.Operation = "untaint"
 		lockID, err := clistate.Lock(st, lockInfo, c.Ui, c.Colorize())
 		if err != nil {
 			c.Ui.Error(fmt.Sprintf("Error locking state: %s", err))

state/local_test.go

@@ -20,9 +20,8 @@ func TestLocalStateLocks(t *testing.T) {
 	defer os.Remove(s.Path)
 
 	// lock first
-	info := &LockInfo{
-		Operation: "test",
-	}
+	info := NewLockInfo()
+	info.Operation = "test"
 	lockID, err := s.Lock(info)
 	if err != nil {
 		t.Fatal(err)

state/remote/s3.go

@@ -8,7 +8,6 @@ import (
 	"log"
 	"os"
 	"strconv"
-	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"
@@ -210,15 +209,16 @@ func (c *S3Client) Lock(info *state.LockInfo) (string, error) {
 	}
 
 	stateName := fmt.Sprintf("%s/%s", c.bucketName, c.keyName)
+	info.Path = stateName
 
+	if info.ID == "" {
 		lockID, err := uuid.GenerateUUID()
 		if err != nil {
 			return "", err
 		}
 
 		info.ID = lockID
-	info.Path = stateName
-	info.Created = time.Now().UTC()
+	}
 
 	putParams := &dynamodb.PutItemInput{
 		Item: map[string]*dynamodb.AttributeValue{
@@ -228,7 +228,7 @@ func (c *S3Client) Lock(info *state.LockInfo) (string, error) {
 		TableName:           aws.String(c.lockTable),
 		ConditionExpression: aws.String("attribute_not_exists(LockID)"),
 	}
-	_, err = c.dynClient.PutItem(putParams)
+	_, err := c.dynClient.PutItem(putParams)
 
 	if err != nil {
 		getParams := &dynamodb.GetItemInput{
@@ -241,7 +241,7 @@ func (c *S3Client) Lock(info *state.LockInfo) (string, error) {
 
 		resp, err := c.dynClient.GetItem(getParams)
 		if err != nil {
-			return "", fmt.Errorf("s3 state file %q locked, failed to retrieve info: %s", stateName, err)
+			return info.ID, fmt.Errorf("s3 state file %q locked, failed to retrieve info: %s", stateName, err)
 		}
 
 		var infoData string
@@ -252,12 +252,12 @@ func (c *S3Client) Lock(info *state.LockInfo) (string, error) {
 		lockInfo := &state.LockInfo{}
 		err = json.Unmarshal([]byte(infoData), lockInfo)
 		if err != nil {
-			return "", fmt.Errorf("s3 state file %q locked, failed get lock info: %s", stateName, err)
+			return info.ID, fmt.Errorf("s3 state file %q locked, failed get lock info: %s", stateName, err)
 		}
 
-		return "", lockInfo.Err()
+		return info.ID, lockInfo.Err()
 	}
-	return "", nil
+	return info.ID, nil
 }
 
 func (c *S3Client) Unlock(string) error {

state/remote/testing.go

@@ -57,14 +57,13 @@ func TestRemoteLocks(t *testing.T, a, b Client) {
 		t.Fatal("client B not a state.Locker")
 	}
 
-	infoA := &state.LockInfo{
-		Operation: "test",
-		Who:       "client A",
-	}
-	infoB := &state.LockInfo{
-		Operation: "test",
-		Who:       "client B",
-	}
+	infoA := state.NewLockInfo()
+	infoA.Operation = "test"
+	infoA.Who = "clientA"
+
+	infoB := state.NewLockInfo()
+	infoB.Operation = "test"
+	infoB.Who = "clientB"
 
 	if _, err := lockerA.Lock(infoA); err != nil {
 		t.Fatal("unable to get initial lock:", err)

state/state.go

@@ -3,12 +3,22 @@ package state
 import (
 	"encoding/json"
 	"fmt"
+	"math/rand"
+	"os"
+	"os/user"
 	"strings"
 	"time"
 
+	uuid "github.com/hashicorp/go-uuid"
 	"github.com/hashicorp/terraform/terraform"
 )
 
+var rngSource *rand.Rand
+
+func init() {
+	rngSource = rand.New(rand.NewSource(time.Now().UnixNano()))
+}
+
 // State is the collection of all state interfaces.
 type State interface {
 	StateReader
@@ -59,15 +69,56 @@ type Locker interface {
 	Unlock(id string) error
 }
 
-// LockInfo stores metadata for locks taken.
+// Generate a LockInfo structure, populating the required fields.
+func NewLockInfo() *LockInfo {
+	// this doesn't need to be cryptographically secure, just unique.
+	// Using math/rand alleviates the need to check handle the read error.
+	// Use a uuid format to match other IDs used throughout Terraform.
+	buf := make([]byte, 16)
+	rngSource.Read(buf)
+
+	id, err := uuid.FormatUUID(buf)
+	if err != nil {
+		// this of course shouldn't happen
+		panic(err)
+	}
+
+	// don't error out on user and hostname, as we don't require them
+	username, _ := user.Current()
+	host, _ := os.Hostname()
+
+	info := &LockInfo{
+		ID:      id,
+		Who:     fmt.Sprintf("%s@%s", username, host),
+		Version: terraform.Version,
+		Created: time.Now().UTC(),
+	}
+	return info
+}
+
+// LockInfo stores lock metadata.
+//
+// Only Operation and Info are required to be set by the caller of Lock.
 type LockInfo struct {
-	ID        string    // unique ID
-	Path      string    // Path to the state file
-	Created   time.Time // The time the lock was taken
-	Version   string    // Terraform version
-	Operation string    // Terraform operation
-	Who       string    // user@hostname when available
-	Info      string    // Extra info field
+	// Unique ID for the lock. NewLockInfo provides a random ID, but this may
+	// be overridden by the lock implementation. The final value if ID will be
+	// returned by the call to Lock.
+	ID string
+
+	// Terraform operation, provided by the caller.
+	Operation string
+	// Extra information to store with the lock, provided by the caller.
+	Info string
+
+	// user@hostname when available
+	Who string
+	// Terraform version
+	Version string
+	// Time that the lock was taken.
+	Created time.Time
+
+	// Path to the state file when applicable. Set by the Lock implementation.
+	Path string
 }
 
 // Err returns the lock info formatted in an error

state/state_test.go

@@ -21,3 +21,24 @@ func TestMain(m *testing.M) {
 	}
 	os.Exit(m.Run())
 }
+
+func TestNewLockInfo(t *testing.T) {
+	info1 := NewLockInfo()
+	info2 := NewLockInfo()
+
+	if info1.ID == "" {
+		t.Fatal("LockInfo missing ID")
+	}
+
+	if info1.Version == "" {
+		t.Fatal("LockInfo missing version")
+	}
+
+	if info1.Created.IsZero() {
+		t.Fatal("LockInfo missing Created")
+	}
+
+	if info1.ID == info2.ID {
+		t.Fatal("multiple LockInfo with identical IDs")
+	}
+}

state/testdata/lockstate.go

@@ -19,7 +19,11 @@ func main() {
 		Path: os.Args[1],
 	}
 
-	_, err := s.Lock(&state.LockInfo{Operation: "test", Info: "state locker"})
+	info := state.NewLockInfo()
+	info.Operation = "test"
+	info.Info = "state locker"
+
+	_, err := s.Lock(info)
 	if err != nil {
 		io.WriteString(os.Stderr, "lock failed")