grafana/k6 · error

invalid method type '%#v'

Error message

invalid method type '%#v'

What it means

In an array-form batch entry like [method, url, ...], the first element was not a string, so it cannot be an HTTP method. parseBatchRequest type-asserts data[0] to string after the array-length check passed; e.g. http.batch([42, 'http://example.com']) triggers it.

Source

Thrown at js/modules/k6/http/request.go:566

func (c *Client) parseBatchRequest(key any, val any) (*httpext.ParsedHTTPRequest, error) {
	var (
		method       = http.MethodGet
		ok           bool
		body, reqURL any
		params       sobek.Value
		rt           = c.moduleInstance.vu.Runtime()
	)

	switch data := val.(type) {
	case []any:
		// Handling of ["GET", "http://example.com/"]
		dataLen := len(data)
		if dataLen < 2 {
			return nil, fmt.Errorf("invalid batch request '%#v'", data)
		}
		method, ok = data[0].(string)
		if !ok {
			return nil, fmt.Errorf("invalid method type '%#v'", data[0])
		}
		reqURL = data[1]
		if dataLen > 2 {
			body = data[2]
		}
		if dataLen > 3 {
			params = rt.ToValue(data[3])
		}

	case map[string]any:
		// Handling of {method: "GET", url: "https://test.k6.io"}
		if _, ok := data["url"]; !ok {
			return nil, fmt.Errorf("batch request %v doesn't have a url key", key)
		}

		reqURL = data["url"]
		body = data["body"] // It's fine if it's missing, the map lookup will return

View on GitHub (pinned to 01ffac6f24)

Solutions

1. Make the first element of each array-form batch entry a string HTTP method, e.g. ['GET', 'http://example.com']
2. Use the object form {method: 'GET', url: '...'} where the method value is also a string

When it happens

Trigger: Thrown at js/modules/k6/http/request.go:566 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/953af4413dbcb945. Report an issue: GitHub.