VictoriaMetrics/VictoriaMetrics · error

cannot write series count to vmselect: %w

Error message

cannot write series count to vmselect: %w

What it means

Fires in processSeriesCount after the series count was successfully fetched: the binary write of the count to the vmselect RPC connection failed. This is a transport-level failure on the vmstorage<->vmselect connection (broken pipe, reset, timeout), meaning the successful query result could not be delivered.

Source

Thrown at lib/vmselectapi/server.go:847

	if err := s.beginConcurrentRequest(ctx); err != nil {
		return ctx.writeErrorMessage(err)
	}
	defer s.endConcurrentRequest()

	// Execute the request
	n, err := s.api.SeriesCount(ctx.qt, accountID, projectID, ctx.deadline)
	if err != nil {
		return ctx.writeErrorMessage(err)
	}

	// Send an empty error message to vmselect.
	if err := ctx.writeString(""); err != nil {
		return fmt.Errorf("cannot send empty error message: %w", err)
	}

	// Send series count to vmselect.
	if err := ctx.writeUint64(n); err != nil {
		return fmt.Errorf("cannot write series count to vmselect: %w", err)
	}
	return nil
}

func (s *Server) processTSDBStatus(ctx *vmselectRequestCtx) error {
	s.tsdbStatusRequests.Inc()

	// Read request
	if err := ctx.readSearchQuery(); err != nil {
		return err
	}
	if err := ctx.readDataBufBytes(maxLabelValueSize); err != nil {
		return fmt.Errorf("cannot read focusLabel: %w", err)
	}
	focusLabel := string(ctx.dataBuf)
	topN, err := ctx.readUint32()
	if err != nil {
		return fmt.Errorf("cannot read topN: %w", err)

View on GitHub (pinned to 5079fb58f1)

Solutions

1. Check network stability between vmstorage and vmselect
2. Look for earlier log lines indicating the connection was closed or timed out
3. Verify vmselect is alive and not restarting/OOM-killed
4. Increase RPC timeouts if large responses or slow links are involved
5. Retry the query; the failure is usually transient connection loss

When it happens

Trigger: Thrown at lib/vmselectapi/server.go:847 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of VictoriaMetrics/VictoriaMetrics@5079fb58f1 (2026-09-03). Data as JSON: /api/errors/1f51c8d1e6e1fba6. Report an issue: GitHub.