feat: support durable task cancellation without foreign keys

sdk/go/worker_connection.go

@@ -47,16 +47,17 @@ type workerFrame struct {
 // 本类型不自动重连、不自动续租、不运行处理器。关闭连接不等于取消业务效果。
 // 最多 32 个在途控制请求、8 个未读派发；超时关闭连接以便按原消息身份核对。
 type WorkerConnection struct {
-	conn         *websocket.Conn
-	ctx          context.Context
-	cancel       context.CancelFunc
-	welcome      WorkerWelcome
-	registration WorkerRegistration
-	assignments  chan WorkerAssignment
-	done         chan struct{}
-	mu           sync.Mutex
-	err          error
-	pending      map[string]chan workerFrame
+	conn          *websocket.Conn
+	ctx           context.Context
+	cancel        context.CancelFunc
+	welcome       WorkerWelcome
+	registration  WorkerRegistration
+	assignments   chan WorkerAssignment
+	cancellations chan WorkerCancellation
+	done          chan struct{}
+	mu            sync.Mutex
+	err           error
+	pending       map[string]chan workerFrame
 }
 
 // DialWorker 使用 Authorization 和固定子协议连接；ctx 只控制握手。
@@ -116,7 +117,7 @@ func (c *Client) DialWorker(ctx context.Context, registration WorkerRegistration
 		return nil, ErrWorkerProtocol
 	}
 	lifetime, cancel := context.WithCancel(context.Background())
-	w := &WorkerConnection{conn: conn, ctx: lifetime, cancel: cancel, welcome: welcome, registration: r, assignments: make(chan WorkerAssignment, 8), done: make(chan struct{}), pending: make(map[string]chan workerFrame)}
+	w := &WorkerConnection{conn: conn, ctx: lifetime, cancel: cancel, welcome: welcome, registration: r, assignments: make(chan WorkerAssignment, 8), cancellations: make(chan WorkerCancellation, 32), done: make(chan struct{}), pending: make(map[string]chan workerFrame)}
 	ok = true
 	go w.readLoop()
 	return w, nil
@@ -175,6 +176,20 @@ func (w *WorkerConnection) readLoop() {
 			}
 			continue
 		}
+		if f.Type == "task.cancel" {
+			var c WorkerCancellation
+			if !w.registration.CancellationNotifications || f.ReplyTo != "" || json.Unmarshal(f.Body, &c) != nil || !validID(c.TaskID) || !validID(c.AttemptID) || c.Epoch == 0 || c.RequestedAt.IsZero() {
+				w.fail(ErrWorkerProtocol)
+				return
+			}
+			select {
+			case w.cancellations <- c:
+			default:
+				w.fail(ErrWorkerBackpressure)
+				return
+			}
+			continue
+		}
 		if f.Type != "ack" && f.Type != "error" {
 			w.fail(ErrWorkerProtocol)
 			return
@@ -222,6 +237,28 @@ func (w *WorkerConnection) NextAssignment(ctx context.Context) (WorkerAssignment
 	}
 }
 
+// NextCancellation 等待特定尝试的停止提示；需注册 CancellationNotifications 并持续读取。
+// 提示允许迟到或重复；只取消匹配 TaskID/AttemptID/Epoch 的处理器，结果仍通过 Finish 确认。
+func (w *WorkerConnection) NextCancellation(ctx context.Context) (WorkerCancellation, error) {
+	if !w.registration.CancellationNotifications {
+		return WorkerCancellation{}, errors.New("cancellation notifications not enabled")
+	}
+	if err := ctx.Err(); err != nil {
+		return WorkerCancellation{}, err
+	}
+	select {
+	case <-ctx.Done():
+		return WorkerCancellation{}, ctx.Err()
+	case <-w.ctx.Done():
+		return WorkerCancellation{}, w.Err()
+	case c := <-w.cancellations:
+		if err := w.Err(); err != nil {
+			return WorkerCancellation{}, err
+		}
+		return c, nil
+	}
+}
+
 func (w *WorkerConnection) call(ctx context.Context, kind, id string, in, out any) (time.Time, error) {
 	started := time.Now()
 	if !validID(id) {
@@ -335,7 +372,7 @@ func (w *WorkerConnection) Finish(ctx context.Context, id string, in WorkerFinis
 	if in.Retryable && in.Outcome != WorkerFailed {
 		return out, errors.New("retryable is only valid for known failure")
 	}
-	if (in.Outcome != WorkerSucceeded && in.Outcome != WorkerFailed && in.Outcome != WorkerUnknown) || len(in.Result) > 256<<10 || bytes.Equal(bytes.TrimSpace(in.Result), []byte("null")) || validateWorkerJSON(in.Result) != nil {
+	if (in.Outcome != WorkerSucceeded && in.Outcome != WorkerFailed && in.Outcome != WorkerUnknown && in.Outcome != WorkerCancelled) || len(in.Result) > 256<<10 || bytes.Equal(bytes.TrimSpace(in.Result), []byte("null")) || validateWorkerJSON(in.Result) != nil {
 		return out, errors.New("invalid Worker result outcome or JSON")
 	}
 	if in.Outcome == WorkerSucceeded && in.ErrorCode != "" || in.Outcome != WorkerSucceeded && !workerName(in.ErrorCode, 64) {