Function extractMediaType

model/textparse/interface.go:93–123

extractMediaType returns the mediaType of a required parser. It tries first to extract a valid and supported mediaType from contentType. If that fails, the provided fallbackType (possibly an empty string) is returned, together with an error. fallbackType is used as-is without further validation.

(contentType, fallbackType string)

// the provided fallbackType (possibly an empty string) is returned, together with
// an error. fallbackType is used as-is without further validation.
func extractMediaType(contentType, fallbackType string) (string, error) {
	if contentType == "" {
		if fallbackType == "" {
			return "", errors.New("non-compliant scrape target sending blank Content-Type and no fallback_scrape_protocol specified for target")
		}
		return fallbackType, fmt.Errorf("non-compliant scrape target sending blank Content-Type, using fallback_scrape_protocol %q", fallbackType)
	}

	// We have a contentType, parse it.
	mediaType, _, err := mime.ParseMediaType(contentType)
	if err != nil {
		if fallbackType == "" {
			retErr := fmt.Errorf("cannot parse Content-Type %q and no fallback_scrape_protocol for target", contentType)
			return "", errors.Join(retErr, err)
		}
		retErr := fmt.Errorf("could not parse received Content-Type %q, using fallback_scrape_protocol %q", contentType, fallbackType)
		return fallbackType, errors.Join(retErr, err)
	}

	// We have a valid media type, either we recognise it and can use it
	// or we have to error.
	switch mediaType {
	case "application/openmetrics-text", "application/vnd.google.protobuf", "text/plain":
		return mediaType, nil
	}
	// We're here because we have no recognised mediaType.
	if fallbackType == "" {
		return "", fmt.Errorf("received unsupported Content-Type %q and no fallback_scrape_protocol specified for target", contentType)
	}
	return fallbackType, fmt.Errorf("received unsupported Content-Type %q, using fallback_scrape_protocol %q", contentType, fallbackType)
}

type ParserOptions struct {
	// EnableTypeAndUnitLabels enables parsing and inclusion of type and unit labels