grafana/k6 · error

unknown compressionType %s

Error message

unknown compressionType %s

What it means

Raised by compressBody when a requested compression algorithm falls through the switch on CompressionType without matching gzip, deflate, zstd or brotli. In practice this indicates an unparseable or unsupported value in the setCompression / compression option.

Source

Thrown at lib/netext/httpext/compression.go:64

		}
		buf = new(bytes.Buffer)

		if contentEncoding != "" {
			contentEncoding += ", "
		}
		contentEncoding += compressionType.String()
		var w io.WriteCloser
		switch compressionType {
		case CompressionTypeGzip:
			w = gzip.NewWriter(buf)
		case CompressionTypeDeflate:
			w = zlib.NewWriter(buf)
		case CompressionTypeZstd:
			w, _ = zstd.NewWriter(buf)
		case CompressionTypeBr:
			w = brotli.NewWriter(buf)
		default:
			return nil, "", fmt.Errorf("unknown compressionType %s", compressionType)
		}
		// we don't close in defer because zlib will write it's checksum again if it closes twice :(
		_, err := io.Copy(w, prevBuf)
		if err != nil {
			_ = w.Close()
			return nil, "", err
		}

		if err = w.Close(); err != nil {
			return nil, "", err
		}
	}

	return buf, contentEncoding, body.Close()
}

//nolint:gochecknoglobals
var decompressionErrors = [...]error{

View on GitHub (pinned to 01ffac6f24)

Solutions

1. Use only supported compression keywords: gzip, deflate, zstd, brotli (or their Content-Encoding names)
2. Check the spelling of values passed to setCompression or the compression option

When it happens

Trigger: Thrown at lib/netext/httpext/compression.go:64 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/227ca2e16b918e3f. Report an issue: GitHub.