grafana/k6 · error

fetching response body: %w

Error message

fetching response body: %w

What it means

Response bodies are fetched lazily over CDP with Network.getResponseBody on the frame manager's session. fetchBody first returns any cached body, then retries up to 5 times with 100ms sleeps specifically for 'No data found for resource with given identifier' (body not yet flushed). This error means the final attempt still failed: the body is genuinely unavailable or the session is gone.

Source

Thrown at internal/js/modules/k6/browser/common/http.go:610

	var body []byte
	var err error
	maxRetries := 5
	for i := 0; i <= maxRetries; i++ {
		body, err = action.Do(cdp.WithExecutor(r.ctx, r.request.frame.manager.session))
		if err == nil {
			break
		}
		if strings.Contains(err.Error(), "No data found for resource with given identifier") {
			if i == maxRetries {
				break
			}
			time.Sleep(100 * time.Millisecond)
			continue
		}
		break
	}
	if err != nil {
		return fmt.Errorf("fetching response body: %w", err)
	}
	r.bodyMu.Lock()
	r.body = body
	r.bodyMu.Unlock()

	return nil
}

func (r *Response) headersSize() int64 {
	size := 4 // 4 = 2 spaces + 2 line breaks (HTTP/1.1 200 OK\r\n)
	size += 8 // httpVersion
	size += 3 // statusCode
	size += len(r.statusText)
	r.extraHeadersMu.RLock()
	if len(r.extraHeaders) != 0 {
		for name, values := range r.extraHeaders {
			for _, value := range values {
				size += len(name) + len(value) + 4 // 4 = ': ' + '\r\n'

View on GitHub (pinned to 93accf6570)

Solutions

1. Read the response body immediately after obtaining the Response, before further navigation or closing the page
2. For intercepted/fulfilled requests, use the content you supplied to fulfill() instead of reading it back through the browser API
3. Check the response status and whether the request was cached before attempting a body read
4. Keep the browser/context alive until all assertions on bodies complete

Example fix

// before
const res = await page.goto('https://app.example.com');
await page.goto('https://app.example.com/next');
const body = await res.body(); // frame may be gone

// after
const res = await page.goto('https://app.example.com');
const body = await res.body(); // read immediately
await page.goto('https://app.example.com/next');

// read bodies before navigating further
const res = await page.goto(url);
const body = await res.body(); // immediate read

let body;
for (let i = 0; i < 2; i++) {
  try { body = await res.body(); break; }
  catch (e) {
    if (i === 1 || !/fetching response body/.test(String(e.message))) throw e;
    await page.waitForTimeout(200);
  }
}

When it happens

Trigger: The frame's manager session cannot serve GetResponseBody: the page navigated away or closed before the body was read, the request was fulfilled by route.fulfill() so no network data exists, the response came from cache/service worker without retrievable body, or the target/browser died.

Common situations: Reading res.body()/text()/json() late in the iteration after further navigation; intercepted requests handled with page.route; service-worker-backed responses; calling body accessors after context/page teardown; heavy parallelism causing the browser to drop.

Related errors

• getting response body: %w
• getting response body as text: %w
• errorText
• updating extra HTTP headers: %w
• updating offline mode for frame %v: %w

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/87cfeea60d66bc41. Report an issue: GitHub.