kubernetes/kops · error

error while hashing resource: %v

Error message

error while hashing resource: %v

What it means

HashAlgorithm.Hash streams an io.Reader through the algorithm's hasher; this error wraps any failure that occurs while copying the reader's data into the hasher. Because hashing itself cannot fail for in-memory data, the cause is almost always an I/O read error from the underlying source (network body, pipe, file reader).

Source

Thrown at util/pkg/hashing/hash.go:132

	switch len(s) {
	case 32:
		ha = HashAlgorithmMD5
	case 40:
		ha = HashAlgorithmSHA1
	case 64:
		ha = HashAlgorithmSHA256
	default:
		return nil, fmt.Errorf("cannot determine algorithm for hash length: %d", len(s))
	}

	return ha.FromString(s)
}

func (ha HashAlgorithm) Hash(r io.Reader) (*Hash, error) {
	hasher := ha.NewHasher()
	_, err := copyToHasher(hasher, r)
	if err != nil {
		return nil, fmt.Errorf("error while hashing resource: %v", err)
	}
	return &Hash{Algorithm: ha, HashValue: hasher.Sum(nil)}, nil
}

func (ha HashAlgorithm) HashFile(p string) (*Hash, error) {
	f, err := os.OpenFile(p, os.O_RDONLY, 0)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, err
		}
		return nil, fmt.Errorf("error opening file %q: %v", p, err)
	}
	defer try.CloseFile(f)
	return ha.Hash(f)
}

func copyToHasher(dest io.Writer, src io.Reader) (int64, error) {
	n, err := io.Copy(dest, src)

View on GitHub (pinned to 4c8573c808)

Solutions

1. Retry the operation; transient reader/network errors usually clear on re-run
2. Verify the source of the reader is fully available before hashing (e.g. download completes first)
3. Inspect the wrapped %v cause to identify the underlying read failure
4. Read the source fully into memory (io.ReadAll) first to separate download errors from hashing

Example fix

// before
h, err := algo.Hash(resp.Body)
// after
data, err := io.ReadAll(resp.Body)
if err != nil { return fmt.Errorf("downloading asset: %w", err) }
h, err := algo.Hash(bytes.NewReader(data))

null

null

h, err := algo.Hash(r)
if err != nil {
	var netErr net.Error
	if errors.As(err, &netErr) || isRetryable(err) {
		return retryHash(r)
	}
	return fmt.Errorf("hashing failed: %w", err)
}

When it happens

Trigger: Calling HashAlgorithm.Hash(r) with a reader whose Read fails mid-stream — e.g. an HTTP response body cut off during transferFile, a closed file, or a broken pipe from a subprocess.

Common situations: Network flakiness while hashing a downloaded CNI/utility asset; reading from a file being concurrently truncated; disk I/O errors on the node running the tool.

Related errors

• error hashing data: %v
• reading data: %v
• error hashing manifest: %v
• error hashing manifest location: %v
• error writing to output: %v

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/82515574b65ed81a. Report an issue: GitHub.