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versilisversilis
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Add utilities for Injecting Kubernetes Deployments (#207)
This PR adds utilities for injecting Kubernetes deployments to be used with #206. The main component is the `Injector` interface which provides the functionality to traverse YAML files (including those with multiple resources using the `---` directive), and inject sidecar containers into any found Deployments.
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6 files changed

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‎cmd/internal/kube/injector/helper.go‎

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package injector
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import (
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"bytes"
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v1 "k8s.io/api/core/v1"
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kyaml "sigs.k8s.io/yaml"
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)
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// Calls the given injector's Inject method and returns the result as a YAML bytes.
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func ToRawYAML(injector Injector, sidecar v1.Container) ([]byte, error) {
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injectedObjects, err := injector.Inject(sidecar)
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if err != nil {
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return nil, err
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}
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out := new(bytes.Buffer)
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for _, obj := range injectedObjects {
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raw, err := kyaml.Marshal(obj)
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if err != nil {
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return nil, err
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}
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out.WriteString("---\n")
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out.Write(raw)
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}
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return out.Bytes(), nil
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}

‎cmd/internal/kube/injector/injector.go‎

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package injector
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import (
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"bufio"
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"bytes"
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"io"
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"os"
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"path/filepath"
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"github.com/akitasoftware/go-utils/sets"
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"github.com/akitasoftware/go-utils/slices"
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"github.com/pkg/errors"
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appsv1 "k8s.io/api/apps/v1"
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v1 "k8s.io/api/core/v1"
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"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
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"k8s.io/apimachinery/pkg/runtime"
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"k8s.io/apimachinery/pkg/runtime/schema"
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kyamlutil "k8s.io/apimachinery/pkg/util/yaml"
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)
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type (
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Injector interface {
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// Injects the given sidecar into all valid Deployment Objects and returns the result as a list of unstructured objects.
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Inject(sidecar v1.Container) ([]*unstructured.Unstructured, error)
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// Returns a list of namespaces that contain injectable objects.
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// This can be used to generate other Kuberenetes objects that need to be created in the same namespace.
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InjectableNamespaces() ([]string, error)
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}
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injectorImpl struct {
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// The list of Kubernetes objects to traverse during injection. This is a list of
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// unstructured objects because we likely won't know the type of all objects
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// ahead of time (e.g., when reading multiple objects from a YAML file).
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objects []*unstructured.Unstructured
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}
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)
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// Constructs a new Injector with Kubernetes objects derived from the given file path.
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func FromYAML(filePath string) (Injector, error) {
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var err error
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yamlContent, err := getFile(filePath)
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if err != nil {
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return nil, errors.Wrap(err, "failed to retrieve raw yaml file content")
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}
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// Read the YAML file into a list of unstructured objects.
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// This is necessary because the YAML file may contain multiple Kubernetes objects.
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// We only want to inject the sidecar into Deployment objects, but we still need to parse all resources.
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multidocReader := kyamlutil.NewYAMLReader(bufio.NewReader(bytes.NewReader(yamlContent)))
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var objList []*unstructured.Unstructured
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for {
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raw, err := multidocReader.Read()
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if err != nil {
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if errors.Is(err, io.EOF) {
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break
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}
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return nil, errors.Wrap(err, "failed to read raw yaml file")
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}
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obj, err := fromRawObject(raw)
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if err != nil {
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return nil, errors.Wrap(err, "failed to convert raw yaml resource to an unstructured object")
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}
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objList = append(objList, obj)
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}
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return &injectorImpl{objects: objList}, nil
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}
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func (i *injectorImpl) InjectableNamespaces() ([]string, error) {
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set := sets.NewSet[string]()
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for _, obj := range i.objects {
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gvk := obj.GetObjectKind().GroupVersionKind()
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if !isInjectable(gvk) {
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continue
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}
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deployment, err := toDeployment(obj)
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if err != nil {
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return nil, errors.Wrap(err, "failed to convert object to deployment during namespace discovery")
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}
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if deployment.Namespace == "" {
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set.Insert("default")
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} else {
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set.Insert(deployment.Namespace)
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}
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}
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return set.AsSlice(), nil
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}
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func (i *injectorImpl) Inject(sidecar v1.Container) ([]*unstructured.Unstructured, error) {
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onMap := func(obj *unstructured.Unstructured) (*unstructured.Unstructured, error) {
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gvk := obj.GetObjectKind().GroupVersionKind()
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if !isInjectable(gvk) {
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return obj, nil
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}
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deployment, err := toDeployment(obj)
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if err != nil {
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return nil, errors.Wrap(err, "failed to convert object to deployment during injection")
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}
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containers := deployment.Spec.Template.Spec.Containers
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deployment.Spec.Template.Spec.Containers = append(containers, sidecar)
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obj.Object, err = runtime.DefaultUnstructuredConverter.ToUnstructured(deployment)
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if err != nil {
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return nil, errors.Wrap(err, "failed to convert injected deployment to unstructured object")
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}
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return obj, nil
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}
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return slices.MapWithErr(i.objects, onMap)
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}
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func isInjectable(kind schema.GroupVersionKind) bool {
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acceptedKind := schema.GroupVersionKind{
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Group: "apps",
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Version: "v1",
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Kind: "Deployment",
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}
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return kind == acceptedKind
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}
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// Converts a generic Kubernetes object into a Deployment Object.
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func toDeployment(obj *unstructured.Unstructured) (*appsv1.Deployment, error) {
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var deployment *appsv1.Deployment
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err := runtime.DefaultUnstructuredConverter.FromUnstructured(obj.Object, &deployment)
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if err != nil {
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return nil, errors.Wrap(err, "failed to convert object to deployment during injection")
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}
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return deployment, nil
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}
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// fromRawObject converts raw bytes into an unstructured.Unstrucutred object.
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// unstructured.Unstructured is used to represent a Kubernetes object that is not known ahead of time.
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func fromRawObject(raw []byte) (*unstructured.Unstructured, error) {
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jConfigMap, err := kyamlutil.ToJSON(raw)
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if err != nil {
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return nil, err
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}
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object, err := runtime.Decode(unstructured.UnstructuredJSONScheme, jConfigMap)
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if err != nil {
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return nil, err
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}
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unstruct, ok := object.(*unstructured.Unstructured)
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if !ok {
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return nil, errors.New("unstructured conversion failed")
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}
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return unstruct, nil
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}
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func getFile(filePath string) ([]byte, error) {
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fileDir, fileName := filepath.Split(filePath)
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absOutputDir, err := filepath.Abs(fileDir)
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if err != nil {
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return nil, err
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}
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// Check for directory existence
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if _, staterr := os.Stat(absOutputDir); os.IsNotExist(staterr) {
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return nil, errors.Wrapf(staterr, "directory %s does not exist", absOutputDir)
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}
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absPath := filepath.Join(absOutputDir, fileName)
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// Check for existence of file
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if _, staterr := os.Stat(absPath); os.IsNotExist(staterr) {
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return nil, errors.Wrapf(staterr, "file %s does not exist", absPath)
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}
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return os.ReadFile(absPath)
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}

‎cmd/internal/kube/injector/injector_test.go‎

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package injector
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import (
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"github.com/stretchr/testify/assert"
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appsv1 "k8s.io/api/apps/v1"
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v1 "k8s.io/api/core/v1"
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metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
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"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
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"k8s.io/apimachinery/pkg/runtime"
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"testing"
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)
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func Test_Inject(t *testing.T) {
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toUnstructured := func(obj runtime.Object) *unstructured.Unstructured {
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u, err := runtime.DefaultUnstructuredConverter.ToUnstructured(&obj)
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if err != nil {
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panic(err)
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}
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return &unstructured.Unstructured{Object: u}
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}
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appendContainer := func(deployment *appsv1.Deployment, container v1.Container) *appsv1.Deployment {
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injectedDeployment := deployment.DeepCopy()
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containers := injectedDeployment.Spec.Template.Spec.Containers
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injectedDeployment.Spec.Template.Spec.Containers = append(containers, container)
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return injectedDeployment
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}
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// GIVEN
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dummyDeployment1 := &appsv1.Deployment{
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TypeMeta: metav1.TypeMeta{
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Kind: "Deployment",
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APIVersion: "apps/v1",
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},
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ObjectMeta: metav1.ObjectMeta{
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Name: "test-deploy-1",
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},
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Spec: appsv1.DeploymentSpec{
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Template: v1.PodTemplateSpec{
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Spec: v1.PodSpec{
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Containers: []v1.Container{
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{
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Name: "nginx",
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Image: "nginx",
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},
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},
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},
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},
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},
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}
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dummyDeployment2 := &appsv1.Deployment{
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TypeMeta: metav1.TypeMeta{
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Kind: "Deployment",
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APIVersion: "apps/v1",
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},
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ObjectMeta: metav1.ObjectMeta{
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Name: "test-deploy-2",
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},
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Spec: appsv1.DeploymentSpec{
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Template: v1.PodTemplateSpec{
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Spec: v1.PodSpec{
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Containers: []v1.Container{
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{
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Name: "echo-server",
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Image: "ghcr.io/wzshiming/echoserver/echoserver:v0.0.1",
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},
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},
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},
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},
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},
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}
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sidecar := v1.Container{Name: "sidecar", Image: "fake-image"}
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expectedDeployment1 := appendContainer(dummyDeployment1, sidecar)
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expectedDeployment2 := appendContainer(dummyDeployment2, sidecar)
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injector := injectorImpl{
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objects: []*unstructured.Unstructured{
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toUnstructured(dummyDeployment1),
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toUnstructured(dummyDeployment2),
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},
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}
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expected := []*unstructured.Unstructured{
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toUnstructured(expectedDeployment1),
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toUnstructured(expectedDeployment2),
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}
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// WHEN
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actual, err := injector.Inject(sidecar)
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// THEN
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if assert.NoError(t, err) {
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assert.Equal(t, expected, actual)
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}
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}

‎cmd/internal/kube/test_resource/resources.yaml‎

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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: test-deploy
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namespace: default
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spec:
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replicas: 1
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selector:
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matchLabels:
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app: test-pod
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template:
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metadata:
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labels:
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app: test-pod
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spec:
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containers:
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- name: test-container
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image: ghcr.io/wzshiming/echoserver/echoserver:v0.0.1
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---
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: patch-demo
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namespace: ns1
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spec:
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replicas: 2
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selector:
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matchLabels:
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app: nginx
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template:
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metadata:
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labels:
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app: nginx
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spec:
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containers:
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- name: patch-demo-ctr
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image: nginx
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tolerations:
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- effect: NoSchedule
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key: dedicated
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value: test-team

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