optimize the manifest conversion from bytes to unstructured

[smira]

See the code in

talos/internal/app/machined/pkg/adapters/k8s/manifest.go

Lines 35 to 76 in 7d688cc

	func (a manifest) SetYAML(yamlBytes []byte) error {
	a.Manifest.TypedSpec().Items = nil
	reader := yaml.NewYAMLReader(bufio.NewReader(bytes.NewReader(yamlBytes)))
	for {
	yamlManifest, err := reader.Read()
	if err != nil {
	if err == io.EOF {
	break
	}
	return err
	}
	yamlManifest = bytes.TrimSpace(yamlManifest)
	if len(yamlManifest) == 0 {
	continue
	}
	jsonManifest, err := yaml.ToJSON(yamlManifest)
	if err != nil {
	return fmt.Errorf("error converting manifest to JSON: %w", err)
	}
	if bytes.Equal(jsonManifest, []byte("null")) || bytes.Equal(jsonManifest, []byte("{}")) {
	// skip YAML docs which contain only comments
	continue
	}
	var obj unstructured.Unstructured
	if err = json.Unmarshal(jsonManifest, &obj); err != nil {
	return fmt.Errorf("error loading JSON manifest into unstructured: %w", err)
	}
	a.Manifest.TypedSpec().Items = append(a.Manifest.TypedSpec().Items, k8s.SingleManifest{Object: obj.Object})
	}
	return nil
	}

There are many copies over:

• first the YAML document is split into sub-documents with inefficient bufio
• second, the YAML is re-marshalled to JSON
• third, JSON is unmarshalled to object.Object

We could look if we could go directly from YAML to unstructured.Unstructured (performing all required conversions on the fly).

[github-actions]

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