Method CancelOperation

core/services/galleryop/service.go:327–386

CancelOperation cancels an in-progress operation by its ID. In distributed mode the UI's cancel click may land on a different replica than the one running the operation. We still publish the cancel event in that case — the peer holding the cancellation func picks it up via the SubjectGalleryCancelW

(id string)

// SubjectGalleryCancelWildcard subscriber and runs it locally. The caller
// gets a non-error reply so the UI shows the cancel as accepted.
func (g *GalleryService) CancelOperation(id string) error {
	g.Lock()

	if status, ok := g.statuses[id]; ok && status.Cancelled {
		g.Unlock()
		return fmt.Errorf("operation %q is already cancelled", id)
	}

	cancelFunc, localExists := g.cancellations[id]
	if localExists {
		delete(g.cancellations, id)
	}

	nc := g.natsClient
	store := g.galleryStore

	if !localExists && nc == nil {
		g.Unlock()
		return fmt.Errorf("operation %q not found or already completed", id)
	}

	if status, ok := g.statuses[id]; ok {
		status.Cancelled = true
		status.Processed = true
		status.Message = "cancelled"
	} else {
		g.statuses[id] = &OpStatus{
			Cancelled:   true,
			Processed:   true,
			Message:     "cancelled",
			Cancellable: false,
		}
	}
	g.Unlock()

	// Persist the terminal status so the cancel survives a restart. Without
	// this the row stays in its active state and re-hydrates straight back into
	// processingBackends on the next replica boot — the UI spins again on an op
	// the admin already cancelled. The peer that broadcasts wins the write; a
	// no-op when standalone (store nil).
	if store != nil {
		if err := store.Cancel(id); err != nil {
			xlog.Warn("Failed to persist gallery operation cancellation", "op_id", id, "error", err)
		}
	}

	// I/O and user-provided callback after Unlock — the cancel-wildcard
	// subscriber loops back into applyCancel on this same replica, which
	// would otherwise deadlock on g.Mutex.
	if cancelFunc != nil {
		cancelFunc()
	}
	if nc != nil {
		if err := nc.Publish(messaging.SubjectGalleryCancel(id), GalleryCancelEvent{JobID: id}); err != nil {
			xlog.Warn("Failed to broadcast gallery cancel", "op_id", id, "error", err)
		}
	}