grafana/k6 · error

the Protobuf message is too large to be handled by Snappy en

Error message

the Protobuf message is too large to be handled by Snappy encoder; size: %d, limit: %d

What it means

In newRequestBody, snappy.MaxEncodedLen returned a negative value for the marshalled Protobuf message, meaning the message exceeds the maximum size the Snappy encoder can handle (~2GB). A single batched MetricSet payload grew beyond the encoder's representable limit.

Source

Thrown at output/cloud/expv2/metrics_client.go:103

	err = mc.httpClient.Do(req, nil)
	if err != nil {
		return err
	}

	return nil
}

func newRequestBody(data *pbcloud.MetricSet) ([]byte, error) {
	b, err := proto.Marshal(data)
	if err != nil {
		return nil, fmt.Errorf("encoding metrics as Protobuf write request failed: %w", err)
	}
	// TODO: use the framing format
	// https://github.com/google/snappy/blob/main/framing_format.txt
	// It can be done replacing the encode with
	// https://pkg.go.dev/github.com/klauspost/compress/snappy#NewBufferedWriter
	if snappy.MaxEncodedLen(len(b)) < 0 {
		return nil, fmt.Errorf("the Protobuf message is too large to be handled by Snappy encoder; "+
			"size: %d, limit: %d", len(b), 0xffffffff)
	}
	return snappy.Encode(nil, b), nil
}

View on GitHub (pinned to 01ffac6f24)

Solutions

1. Reduce the volume of metrics emitted per aggregation window (fewer tags, fewer custom metrics)
2. Shorten the aggregation period so batches stay small
3. Report to grafana/k6 — the client should split oversized payloads rather than fail

When it happens

Trigger: Thrown at output/cloud/expv2/metrics_client.go:103 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grafana/k6@01ffac6f24 (2026-08-18). Data as JSON: /api/errors/24df9cfe13bdcbd5. Report an issue: GitHub.