Function parseThresholdExpression

metrics/thresholds_parser.go:72–104

parseThresholdExpression parses a threshold condition expression, as defined in a JS script (for instance p(95)<1000), into a thresholdExpression instance. It is expected to be of the form: `aggregation_method operator value`. As defined by the following BNF: ``` assertion -> aggregation_

(input string)

// whitespace          -> " "
// ```
func parseThresholdExpression(input string) (*thresholdExpression, error) {
	// Scanning makes no assumption on the underlying values, and only
	// checks that the expression has the right format.
	method, operator, value, err := scanThresholdExpression(input)
	if err != nil {
		return nil, fmt.Errorf("failed parsing threshold expression %q; reason: %w", input, err)
	}

	parsedMethod, parsedMethodValue, err := parseThresholdAggregationMethod(method)
	if err != nil {
		err = fmt.Errorf("failed parsing threshold expression's %q left hand side; "+
			"reason: %w", input, err,
		)
		return nil, err
	}

	parsedValue, err := strconv.ParseFloat(value, 64)
	if err != nil {
		err = fmt.Errorf("failed parsing threshold expresion's %q right hand side; "+
			"reason: %w", input, err,
		)
		return nil, err
	}

	condition := &thresholdExpression{
		AggregationMethod: parsedMethod,
		AggregationValue:  parsedMethodValue,
		Operator:          operator,
		Value:             parsedValue,
	}

	return condition, nil
}

// Define accepted threshold expression operators tokens
const (