googleapis/mcp-toolbox · error

failed to list data scans: %w

Error message

failed to list data scans: %w

What it means

This error wraps an unknown (non-gRPC-status) failure returned while iterating Dataplex DataScan results in SearchDataQualityScans. The library first checks whether the error carries a gRPC status; if it does not (e.g. a client-side, context, or transport-level error), it falls back to %w wrapping so the underlying cause is preserved. It means the scan listing operation could not complete for a reason the Dataplex API did not report as a structured status.

Source

Thrown at internal/sources/dataplex/dataplex.go:416

		Parent:   fmt.Sprintf("projects/%s/locations/-", s.ProjectID()),
		Filter:   filter,
		PageSize: int32(pageSize),
		OrderBy:  orderBy,
	}

	it := s.GetDataScanClient().ListDataScans(ctx, req)

	var results []*dataplexpb.DataScan
	for len(results) < pageSize {
		scan, err := it.Next()
		if err == iterator.Done {
			break
		}
		if err != nil {
			if st, ok := grpcstatus.FromError(err); ok {
				return nil, fmt.Errorf("failed to list data scans: code=%s message=%s", st.Code(), st.Message())
			}
			return nil, fmt.Errorf("failed to list data scans: %w", err)
		}
		results = append(results, scan)
	}
	return results, nil
}

type DataProductSummary struct {
	LocationID    string   `json:"locationId"`
	DataProductID string   `json:"dataProductId"`
	DisplayName   string   `json:"displayName"`
	OwnerEmails   []string `json:"ownerEmails"`
	AssetCount    int32    `json:"assetCount"`
}

func (s *Source) ListDataProducts(
	ctx context.Context,
	filter string,
	pageSize int,

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Inspect the wrapped cause with errors.Is/errors.Unwrap to identify the underlying transport, context, or auth error.
2. Check that the context passed to SearchDataQualityScans is not cancelled or near its deadline before/during pagination.
3. Verify network connectivity to the Dataplex endpoint (dataplex.googleapis.com:443) and retry the call.
4. Regenerate/refresh Application Default Credentials and retry in case of transient auth refresh failure.

Example fix

// before
ctx := context.Background()
scans, err := src.SearchDataQualityScans(ctx, ...)
// after
ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
defer cancel()
scans, err := src.SearchDataQualityScans(ctx, ...)
if err != nil {
	if errors.Is(err, context.DeadlineExceeded) { /* retry with larger timeout */ }
}

if err := ctx.Err(); err != nil { return nil, fmt.Errorf("context already done: %w", err) }

func asGRPCStatus(err error) (code string, msg string, ok bool) {
	if st, ok := status.FromError(err); ok {
		return st.Code().String(), st.Message(), true
	}
	return "", "", false
}

scans, err := src.SearchDataQualityScans(ctx, query, pageSize)
if err != nil {
	var ctxErr error
	switch {
	case errors.Is(err, context.Canceled), errors.Is(err, context.DeadlineExceeded):
		ctxErr = err // retry with fresh context
	default:
		return fmt.Errorf("scan search failed: %w", err)
	}
	_ = ctxErr
}

When it happens

Trigger: Calling SearchDataQualityScans when iterator.Next() returns a non-gRPC error: a cancelled or deadline-exceeded context that surfaces as a plain context error, a network disconnect producing a wrapped transport error, or a client construction/serialization failure inside the paging loop.

Common situations: Short-lived HTTP clients losing connectivity mid-pagination; callers passing a context that is cancelled while iterating many pages; proxy or firewall dropping the long-lived gRPC/HTTP stream; go-auth library token refresh failures surfaced as plain errors.

Related errors

• failed to list data products: %w
• failed to list data assets: %w
• failed to create Dataplex client for project %q: %w
• failed to list tables: %w
• failed to create Dataplex client for project %q: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/84ae608c0abe0f32. Report an issue: GitHub.