v2: use uint64 for token instead of timestamp

go.mod

@@ -4,6 +4,7 @@ go 1.21
 
 require (
 	cloud.google.com/go/spanner v1.64.0
+	github.com/cespare/xxhash/v2 v2.3.0
 	github.com/google/uuid v1.6.0
 	github.com/googleapis/gax-go/v2 v2.12.5
 	google.golang.org/api v0.187.0
@@ -19,7 +20,6 @@ require (
 	cloud.google.com/go/longrunning v0.5.9 // indirect
 	github.com/GoogleCloudPlatform/grpc-gcp-go/grpcgcp v1.5.0 // indirect
 	github.com/census-instrumentation/opencensus-proto v0.4.1 // indirect
-	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/cncf/xds/go v0.0.0-20240423153145-555b57ec207b // indirect
 	github.com/envoyproxy/go-control-plane v0.12.0 // indirect
 	github.com/envoyproxy/protoc-gen-validate v1.0.4 // indirect

spindle.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"cloud.google.com/go/spanner"
+	"github.com/cespare/xxhash/v2"
 	"github.com/google/uuid"
 	gaxv2 "github.com/googleapis/gax-go/v2"
 	"google.golang.org/api/iterator"
@@ -52,7 +53,7 @@ type Lock struct {
 	id       string // unique id for this instance
 	duration int64  // lock duration in ms
 	iter     atomic.Int64
-	token    *time.Time
+	ttoken   *time.Time
 	mtx      *sync.Mutex
 	logger   *log.Logger
 	active   atomic.Int32
@@ -64,7 +65,10 @@ func (l *Lock) Run(ctx context.Context, done ...chan error) error {
 	var leader atomic.Int32 // for heartbeat
 	go func() {
 		min := (time.Millisecond * time.Duration(l.duration)) / 2
-		bo := gaxv2.Backoff{Max: time.Millisecond * time.Duration(l.duration)}
+		bo := gaxv2.Backoff{
+			Max: time.Millisecond * time.Duration(l.duration),
+		}
+
 		for {
 			if ctx.Err() == context.Canceled {
 				return // not foolproof due to delay
@@ -89,14 +93,14 @@ func (l *Lock) Run(ctx context.Context, done ...chan error) error {
 	}()
 
 	locked := func() bool {
-		// See if there is an active leased lock (could be us, could be somebody else).
-		tokenLocked, diff, err := l.checkLock()
+		// See if there is an active leased lock (could be us, could be someone else).
+		token, diff, err := l.checkLock()
 		if err != nil {
 			l.logger.Println(err)
 			return true // err on safer side
 		}
 
-		if l.tokenString() != "" && l.tokenString() == tokenLocked {
+		if l.token() == token {
 			leader.Add(1)
 			if leader.Load() == 1 {
 				l.heartbeat() // only on 1
@@ -166,7 +170,7 @@ func (l *Lock) Run(ctx context.Context, done ...chan error) error {
 
 			if err == nil {
 				l.setToken(&cts)
-				l.logger.Printf("%v got the lock with token [%v]", prefix, l.tokenString())
+				l.logger.Printf("%v got the lock with token [%v]", prefix, l.token())
 				return
 			}
 
@@ -176,13 +180,13 @@ func (l *Lock) Run(ctx context.Context, done ...chan error) error {
 		// For the succeeding lock attempts.
 		if initial.Load() == 0 {
 			prefix := "[next]"
-			token, _, err := l.getCurrentTokenAndId()
+			token, _, err := l.getCurrentToken()
 			if err != nil {
-				l.logger.Printf("%v getCurrentTokenAndId failed: %v", prefix, err)
+				l.logger.Printf("%v getCurrentToken failed: %v", prefix, err)
 				return
 			}
 
-			if token == "" {
+			if token == 0 {
 				l.logger.Printf("%v read token failed: empty", prefix)
 				return
 			}
@@ -230,7 +234,7 @@ func (l *Lock) Run(ctx context.Context, done ...chan error) error {
 				}
 
 				l.setToken(&nts) // doesn't mean we're leader
-				l.logger.Printf("%v got the lock: token=%v", prefix, l.tokenString())
+				l.logger.Printf("%v got the lock: token=%v", prefix, l.token())
 			}
 		}
 	}
@@ -267,17 +271,17 @@ func (l *Lock) Run(ctx context.Context, done ...chan error) error {
 }
 
 // HasLock returns true if this instance got the lock, together with the lock token.
-func (l *Lock) HasLock() (bool, string) {
+func (l *Lock) HasLock() (bool, uint64) {
 	if l.active.Load() == 0 {
-		return false, ""
+		return false, 0
 	}
 
-	token, _, err := l.getCurrentTokenAndId()
+	token, _, err := l.getCurrentToken()
 	if err != nil {
 		return false, token
 	}
 
-	if token != "" && token == l.tokenString() {
+	if token == l.token() {
 		return true, token
 	}
 
@@ -290,7 +294,7 @@ func (l *Lock) Leader() (string, error) {
 		return "", ErrNotRunning
 	}
 
-	_, w, err := l.getCurrentTokenAndId()
+	_, w, err := l.getCurrentToken()
 	return w, err
 }
 
@@ -303,29 +307,30 @@ func (l *Lock) Iterations() int64 { return l.iter.Load() }
 // Client returns the Spanner client.
 func (l *Lock) Client() *spanner.Client { return l.db }
 
-func (l *Lock) tokenString() string {
+func (l *Lock) token() uint64 {
 	l.mtx.Lock()
 	defer l.mtx.Unlock()
-	if l.token == nil {
-		return ""
+	if l.ttoken == nil {
+		return 0
 	}
 
-	return (*l.token).UTC().Format(time.RFC3339Nano)
+	v := (*l.ttoken).UTC().Format(time.RFC3339Nano)
+	return xxhash.Sum64String(v)
 }
 
 func (l *Lock) setToken(v *time.Time) {
 	l.mtx.Lock()
 	defer l.mtx.Unlock()
-	l.token = v
+	l.ttoken = v
 }
 
 type diffT struct {
 	Diff  spanner.NullInt64
 	Token spanner.NullTime
 }
 
-func (l *Lock) checkLock() (string, int64, error) {
-	var tokenLocked string
+func (l *Lock) checkLock() (uint64, int64, error) {
+	var token string
 	var diff int64
 
 	err := func() error {
@@ -361,21 +366,21 @@ func (l *Lock) checkLock() (string, int64, error) {
 			}
 
 			diff = v.Diff.Int64
-			tokenLocked = v.Token.Time.UTC().Format(time.RFC3339Nano)
+			token = v.Token.Time.UTC().Format(time.RFC3339Nano)
 		}
 
 		return retErr
 	}()
 
-	return tokenLocked, diff, err
+	return xxhash.Sum64String(token), diff, err
 }
 
 type tokenT struct {
 	Token  spanner.NullTime
 	Writer spanner.NullString
 }
 
-func (l *Lock) getCurrentTokenAndId() (string, string, error) {
+func (l *Lock) getCurrentToken() (uint64, string, error) {
 	var q strings.Builder
 	fmt.Fprintf(&q, "select token, writer from %s ", l.table)
 	fmt.Fprintf(&q, "where name = @name")
@@ -394,13 +399,13 @@ func (l *Lock) getCurrentTokenAndId() (string, string, error) {
 		}
 
 		if err != nil {
-			return token, writer, err
+			return 0, writer, err
 		}
 
 		var v tokenT
 		err = row.ToStruct(&v)
 		if err != nil {
-			return token, writer, err
+			return 0, writer, err
 		}
 
 		token = v.Token.Time.UTC().Format(time.RFC3339Nano)
@@ -409,7 +414,7 @@ func (l *Lock) getCurrentTokenAndId() (string, string, error) {
 		}
 	}
 
-	return token, writer, nil
+	return xxhash.Sum64String(token), writer, nil
 }
 
 func (l *Lock) heartbeat() {