hashicorp/packer · error

failed to fetch release index: %w

Error message

failed to fetch release index: %w

What it means

The HTTP GET to the Packer releases index endpoint failed at the transport layer: `client.Do(req)` returned an error before any HTTP response was produced. This wraps the underlying net/http error (DNS failure, TCP connect error, TLS handshake failure, or the request context being canceled/timed out).

Source

Thrown at provisioner/hcp-sbom/packer_release_fetch.go:65

	Arch     string `json:"arch"`
	Filename string `json:"filename"`
	URL      string `json:"url"`
}

// fetchLatestPackerVersion queries the HashiCorp releases index, sorts all
// stable (non-prerelease) versions with semver, and returns the highest one.
func fetchLatestPackerVersion(ctx context.Context, client *http.Client) (string, error) {
	indexURL := getReleaseBaseURL() + "/packer/index.json"
	var indexData releaseIndex

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, indexURL, nil)
	if err != nil {
		return "", fmt.Errorf("failed to build index request: %w", err)
	}

	resp, err := client.Do(req)
	if err != nil {
		return "", fmt.Errorf("failed to fetch release index: %w", err)
	}
	defer func() { _ = resp.Body.Close() }()

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("HTTP %d for %s", resp.StatusCode, indexURL)
	}

	err = json.NewDecoder(resp.Body).Decode(&indexData)
	if err != nil {
		return "", fmt.Errorf("failed to retrieve packer release index from %s: %w", indexURL, err)
	}

	var semverList []*semver.Version
	for vStr := range indexData.Versions {
		v, parseErr := semver.NewVersion(vStr)
		if parseErr != nil {
			continue
		}

View on GitHub (pinned to eb36e3c3e4)

Solutions

1. Read the wrapped error to distinguish DNS/connect/TLS/timeout and confirm network egress to https://releases.hashicorp.com/packer/index.json.
2. Configure proxy settings (HTTPS_PROXY) if the environment requires a proxy for outbound HTTPS.
3. Retry the build — transient network/DNS blips commonly cause this; the caller may already wrap this in packer's retry helper.
4. Check status.hashicorp.com for an ongoing releases endpoint outage.
5. Ensure the context passed into the provisioner has an adequate deadline.

Example fix

// before: blocked by corporate proxy, no egress
export HTTPS_PROXY=http://proxy.corp.example:3128
// after: request succeeds via configured proxy

// Pre-flight connectivity check
req, _ := http.NewRequestWithContext(ctx, http.MethodHead, "https://releases.hashicorp.com/packer/index.json", nil)
resp, err := client.Do(req)
if err != nil {
	return fmt.Errorf("no egress to releases.hashicorp.com: %w", err)
}
resp.Body.Close()

func isNetworkError(err error) bool {
	var ne net.Error
	return err != nil && (errors.As(err, &ne) || errors.Is(err, context.DeadlineExceeded) || errors.Is(err, syscall.ECONNREFUSED))
}

var latest string
err := retry.Config{Tries: 3, ShouldRetry: func(err error) bool { return isNetworkError(err) }}.Run(ctx, func(ctx context.Context) error {
	var e error
	latest, e = fetchLatestPackerVersion(ctx, client)
	return e
})

When it happens

Trigger: fetchLatestPackerVersion calls client.Do on the index request; the error fires when there is no network connectivity to releases.hashicorp.com, DNS resolution fails, a proxy/firewall blocks the connection, TLS fails, or ctx is canceled/deadline exceeded mid-request.

Common situations: CI runner or air-gapped machine without internet egress; corporate proxy required but unset (HTTP(S)_PROXY); transient DNS outage; releases.hashicorp.com incident; build context deadline canceled before the request finished.

Understand the failure class

Background: 'Something went wrong' / 'Request failed (500)' / 'HTTP error! status: 404' — what failed HTTP requests actually mean and how to find the real cause — this error's family across 28 libraries.

Related errors

• HTTP request failed: %w
• failed to download %s: %w
• request GitHub OIDC token: %w
• Error reading checksum file: %s
• failed to build index request: %w

AI-assisted analysis of hashicorp/packer@eb36e3c3e4 (2026-09-05). Data as JSON: /api/errors/a8f4b7ce5e673c6f. Report an issue: GitHub.