Support for cluster context name in kube_config function (#122)

This patch introduces support for cluster context name when
declaring kubeernetes configuration using the kube_config starlark script
function. Now, command functions such as kube_get and kube_capture
can create connection to the API server using the local kubectl CLI
cluster context name.

Signed-off-by: Vladimir Vivien <[email protected]>

docs/README.md

@@ -145,6 +145,7 @@ This configuration function declares and stores configuration needed to connect
 | Param | Description | Required |
 | -------- | -------- | ------- |
 | `path` | Path to the local Kubernetes config file. Default: `$HOME/.kube/config`| No |
+| `cluster_context` | The name of a context to use when accessing the cluster. Default: (empty) | No |
 | `capi_provider` | A Cluster-API provider (see providers below) to obtain Kubernetes configurations | No |
 
 #### Output
@@ -153,11 +154,12 @@ This configuration function declares and stores configuration needed to connect
 | Field | Description |
 | --------| --------- |
 | `path` | The path to the local Kubernetes config that was set |
+| `cluster_context` | The name of a context that was set for the cluster |
 | `capi_provider`|A provider that was set for Cluster-API usage|
 
 #### Example
 ```python
-kube_config(path=args.kube_conf)
+kube_config(path=args.kube_conf, cluster_context="my-cluster")
 ```
 ### `ssh_config()`
 This function creates configuration that can be used to connect via SSH to remote machines.

k8s/client.go

@@ -36,11 +36,17 @@ type Client struct {
  JsonPrinter printers.JSONPrinter
 }
 
-// New returns a *Client
-func New(kubeconfig string) (*Client, error) {
+// New returns a *Client built with the kubecontext file path
+// and an optional (at most one) K8s CLI context name.
+func New(kubeconfig string, clusterContextOptions ...string) (*Client, error) {
+ var clusterCtxName string
+ if len(clusterContextOptions) > 0 {
+ clusterCtxName = clusterContextOptions[0]
+ }
+
  // creating cfg for each client type because each
- // setup its own cfg default which may not be compatible
- dynCfg, err := clientcmd.BuildConfigFromFlags("", kubeconfig)
+ // setup needs its own cfg default which may not be compatible
+ dynCfg, err := makeRESTConfig(kubeconfig, clusterCtxName)
  if err != nil {
  return nil, err
  }
@@ -49,7 +55,7 @@ func New(kubeconfig string) (*Client, error) {
  return nil, err
  }
 
- discoCfg, err := clientcmd.BuildConfigFromFlags("", kubeconfig)
+ discoCfg, err := makeRESTConfig(kubeconfig, clusterCtxName)
  if err != nil {
  return nil, err
  }
@@ -64,7 +70,7 @@ func New(kubeconfig string) (*Client, error) {
  }
  mapper := restmapper.NewDiscoveryRESTMapper(resources)
 
- restCfg, err := clientcmd.BuildConfigFromFlags("", kubeconfig)
+ restCfg, err := makeRESTConfig(kubeconfig, clusterCtxName)
  if err != nil {
  return nil, err
  }
@@ -77,6 +83,27 @@ func New(kubeconfig string) (*Client, error) {
  return &Client{Client: client, Disco: disco, CoreRest: restc, Mapper: mapper}, nil
 }
 
+// makeRESTConfig creates a new *rest.Config with a k8s context name if one is provided.
+func makeRESTConfig(fileName, contextName string) (*rest.Config, error) {
+ if fileName == "" {
+ return nil, fmt.Errorf("kubeconfig file path required")
+ }
+
+ if contextName != "" {
+ // create the config object from k8s config path and context
+ return clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
+ &clientcmd.ClientConfigLoadingRules{ExplicitPath: fileName},
+ &clientcmd.ConfigOverrides{
+ CurrentContext: contextName,
+ }).ClientConfig()
+ }
+
+ return clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
+ &clientcmd.ClientConfigLoadingRules{ExplicitPath: fileName},
+ &clientcmd.ConfigOverrides{},
+ ).ClientConfig()
+}
+
 func (k8sc *Client) Search(ctx context.Context, params SearchParams) ([]SearchResult, error) {
  return k8sc._search(ctx, strings.Join(params.Groups, " "),
  strings.Join(params.Categories, " "),

k8s/client_test.go

@@ -8,6 +8,56 @@ import (
  "testing"
 )
 
+func TestClientNew(t *testing.T) {
+ tests := []struct {
+ name string
+ test func(*testing.T)
+ }{
+ {
+ name: "client with no cluster context",
+ test: func(t *testing.T) {
+ client, err := New(support.KindKubeConfigFile())
+ if err != nil {
+ t.Fatal(err)
+ }
+ results, err := client.Search(context.TODO(), SearchParams{Kinds: []string{"pods"}})
+ if err != nil {
+ t.Fatal(err)
+ }
+ count := 0
+ for _, result := range results {
+ count = len(result.List.Items) + count
+ }
+ t.Logf("found %d objects", count)
+ },
+ },
+ {
+ name: "client with cluster context",
+ test: func(t *testing.T) {
+ client, err := New(support.KindKubeConfigFile(), support.KindClusterContextName())
+ if err != nil {
+ t.Fatal(err)
+ }
+ results, err := client.Search(context.TODO(), SearchParams{Kinds: []string{"pods"}})
+ if err != nil {
+ t.Fatal(err)
+ }
+ count := 0
+ for _, result := range results {
+ count = len(result.List.Items) + count
+ }
+ t.Logf("found %d objects", count)
+ },
+ },
+ }
+
+ for _, test := range tests {
+ t.Run(test.name, func(t *testing.T) {
+ test.test(t)
+ })
+ }
+}
+
 func TestClient_Search(t *testing.T) {
  tests := []struct {
  name string

starlark/capa_provider.go

@@ -47,7 +47,7 @@ func CapaProviderFn(thread *starlark.Thread, _ *starlark.Builtin, args starlark.
  if mgmtKubeConfig == nil {
  mgmtKubeConfig = thread.Local(identifiers.kubeCfg).(*starlarkstruct.Struct)
  }
- mgmtKubeConfigPath, err := getKubeConfigFromStruct(mgmtKubeConfig)
+ mgmtKubeConfigPath, err := getKubeConfigPathFromStruct(mgmtKubeConfig)
  if err != nil {
  return starlark.None, errors.Wrap(err, "failed to extract management kubeconfig")
  }

starlark/capv_provider.go

@@ -47,7 +47,7 @@ func CapvProviderFn(thread *starlark.Thread, _ *starlark.Builtin, args starlark.
  if mgmtKubeConfig == nil {
  mgmtKubeConfig = thread.Local(identifiers.kubeCfg).(*starlarkstruct.Struct)
  }
- mgmtKubeConfigPath, err := getKubeConfigFromStruct(mgmtKubeConfig)
+ mgmtKubeConfigPath, err := getKubeConfigPathFromStruct(mgmtKubeConfig)
  if err != nil {
  return starlark.None, errors.Wrap(err, "failed to extract management kubeconfig")
  }

starlark/kube_capture.go

@@ -47,11 +47,13 @@ func KubeCaptureFn(thread *starlark.Thread, _ *starlark.Builtin, args starlark.T
  if kubeConfig == nil {
  kubeConfig = thread.Local(identifiers.kubeCfg).(*starlarkstruct.Struct)
  }
- path, err := getKubeConfigFromStruct(kubeConfig)
+ path, err := getKubeConfigPathFromStruct(kubeConfig)
  if err != nil {
  return starlark.None, errors.Wrap(err, "failed to kubeconfig")
  }
- client, err := k8s.New(path)
+ clusterCtxName := getKubeConfigContextNameFromStruct(kubeConfig)
+
+ client, err := k8s.New(path, clusterCtxName)
  if err != nil {
  return starlark.None, errors.Wrap(err, "could not initialize search client")
  }

starlark/kube_capture_test.go

@@ -346,6 +346,7 @@ func TestKubeCapture(t *testing.T) {
 func TestKubeCaptureScript(t *testing.T) {
  workdir := testSupport.TmpDirRoot()
  k8sconfig := testSupport.KindKubeConfigFile()
+ clusterCtxName := testSupport.KindClusterContextName()
 
  execute := func(t *testing.T, script string) *starlarkstruct.Struct {
  executor := New()
@@ -369,11 +370,11 @@ func TestKubeCaptureScript(t *testing.T) {
  eval func(t *testing.T, script string)
  }{
  {
- name: "simple search with namespaced objects",
+ name: "simple search with namespaced objects with cluster context",
  script: fmt.Sprintf(`
 crashd_config(workdir="%s")
-set_defaults(kube_config(path="%s"))
-kube_data = kube_capture(what="objects", groups=["core"], kinds=["services"], namespaces=["default", "kube-system"])`, workdir, k8sconfig),
+set_defaults(kube_config(path="%s", cluster_context="%s"))
+kube_data = kube_capture(what="objects", groups=["core"], kinds=["services"], namespaces=["default", "kube-system"])`, workdir, k8sconfig, clusterCtxName),
  eval: func(t *testing.T, script string) {
  data := execute(t, script)
 
@@ -511,11 +512,11 @@ kube_data = kube_capture(what="objects", groups=["core"], categories=["all"], na
  },
  },
  {
- name: "search for all logs in a namespace",
+ name: "search for all logs in a namespace with cluster context",
  script: fmt.Sprintf(`
 crashd_config(workdir="%s")
-set_defaults(kube_config(path="%s"))
-kube_data = kube_capture(what="logs", namespaces=["kube-system"])`, workdir, k8sconfig),
+set_defaults(kube_config(path="%s", cluster_context="%s"))
+kube_data = kube_capture(what="logs", namespaces=["kube-system"])`, workdir, k8sconfig, clusterCtxName),
  eval: func(t *testing.T, script string) {
  data := execute(t, script)
 

starlark/kube_config.go

@@ -14,13 +14,14 @@ import (
 
 // KubeConfigFn is built-in starlark function that wraps the kwargs into a dictionary value.
 // The result is also added to the thread for other built-in to access.
-// Starlark: kube_config(path=kubecf/path)
+// Starlark: kube_config(path=kubecf/path, [cluster_context=context_name])
 func KubeConfigFn(_ *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
- var path string
+ var path, clusterCtxName string
  var provider *starlarkstruct.Struct
 
  if err := starlark.UnpackArgs(
  identifiers.kubeCfg, args, kwargs,
+ "cluster_context?", &clusterCtxName,
  "path?", &path,
  "capi_provider?", &provider,
  ); err != nil {
@@ -58,7 +59,8 @@ func KubeConfigFn(_ *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple,
  }
 
  structVal := starlarkstruct.FromStringDict(starlark.String(identifiers.kubeCfg), starlark.StringDict{
- "path": starlark.String(path),
+ "cluster_context": starlark.String(clusterCtxName),
+ "path": starlark.String(path),
  })
 
  return structVal, nil
@@ -79,14 +81,29 @@ func addDefaultKubeConf(thread *starlark.Thread) error {
  return nil
 }
 
-func getKubeConfigFromStruct(kubeConfigStructVal *starlarkstruct.Struct) (string, error) {
+func getKubeConfigPathFromStruct(kubeConfigStructVal *starlarkstruct.Struct) (string, error) {
  kvPathVal, err := kubeConfigStructVal.Attr("path")
  if err != nil {
  return "", errors.Wrap(err, "failed to extract kubeconfig path")
  }
  kvPathStrVal, ok := kvPathVal.(starlark.String)
  if !ok {
- return "", errors.New("failed to extract management kubeconfig")
+ return "", errors.New("failed to extract kubeconfig")
  }
  return kvPathStrVal.GoString(), nil
 }
+
+// getKubeConfigContextNameFromStruct returns the cluster name from the KubeConfig struct
+// provided. If filed cluster_context not provided or unable to convert, it is returned
+// as an empty context.
+func getKubeConfigContextNameFromStruct(kubeConfigStructVal *starlarkstruct.Struct) string {
+ ctxVal, err := kubeConfigStructVal.Attr("cluster_context")
+ if err != nil {
+ return ""
+ }
+ ctxName, ok := ctxVal.(starlark.String)
+ if !ok {
+ return ""
+ }
+ return ctxName.GoString()
+}

starlark/kube_config_test.go

@@ -44,7 +44,6 @@ var _ = Describe("kube_config", func() {
  Expect(kubeConfigData).To(BeAssignableToTypeOf(&starlarkstruct.Struct{}))
 
  cfg, _ := kubeConfigData.(*starlarkstruct.Struct)
- Expect(cfg.AttrNames()).To(HaveLen(1))
 
  val, err := cfg.Attr("path")
  Expect(err).To(BeNil())
@@ -66,7 +65,6 @@ var _ = Describe("kube_config", func() {
  Expect(kubeConfigData).NotTo(BeNil())
 
  cfg, _ := kubeConfigData.(*starlarkstruct.Struct)
- Expect(cfg.AttrNames()).To(HaveLen(1))
 
  val, err := cfg.Attr("path")
  Expect(err).To(BeNil())
@@ -111,7 +109,6 @@ var _ = Describe("KubeConfigFn", func() {
  Expect(err).NotTo(HaveOccurred())
 
  cfg, _ := val.(*starlarkstruct.Struct)
- Expect(cfg.AttrNames()).To(HaveLen(1))
 
  path, err := cfg.Attr("path")
  Expect(err).To(BeNil())

starlark/kube_get.go

@@ -42,12 +42,13 @@ func KubeGetFn(thread *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple
  if kubeConfig == nil {
  kubeConfig = thread.Local(identifiers.kubeCfg).(*starlarkstruct.Struct)
  }
- path, err := getKubeConfigFromStruct(kubeConfig)
+ path, err := getKubeConfigPathFromStruct(kubeConfig)
  if err != nil {
- return starlark.None, errors.Wrap(err, "failed to kubeconfig")
+ return starlark.None, errors.Wrap(err, "failed to get kubeconfig")
  }
+ clusterCtxName := getKubeConfigContextNameFromStruct(kubeConfig)
 
- client, err := k8s.New(path)
+ client, err := k8s.New(path, clusterCtxName)
  if err != nil {
  return starlark.None, errors.Wrap(err, "could not initialize search client")
  }

starlark/kube_get_test.go

@@ -149,6 +149,7 @@ func TestKubeGet(t *testing.T) {
 
 func TestKubeGetScript(t *testing.T) {
  k8sconfig := testSupport.KindKubeConfigFile()
+ clusterName := testSupport.KindClusterContextName()
 
  execute := func(t *testing.T, script string) *starlarkstruct.Struct {
  executor := New()
@@ -172,11 +173,11 @@ func TestKubeGetScript(t *testing.T) {
  eval func(t *testing.T, script string)
  }{
  {
- name: "namespaced objects as starlark objects",
+ name: "namespaced objects as starlark objects with context",
  script: fmt.Sprintf(`
-set_defaults(kube_config(path="%s"))
+set_defaults(kube_config(path="%s", cluster_context="%s"))
 kube_data = kube_get(groups=["core"], kinds=["services"], namespaces=["default", "kube-system"])
-`, k8sconfig),
+`, k8sconfig, clusterName),
  eval: func(t *testing.T, script string) {
  data := execute(t, script)
 
@@ -234,11 +235,11 @@ kube_data = kube_get(groups=["core"], kinds=["nodes"])
  },
  },
  {
- name: "different categories of objects as starlark objects",
+ name: "different categories of objects as starlark objects with context",
  script: fmt.Sprintf(`
-set_defaults(kube_config(path="%s"))
+set_defaults(kube_config(path="%s", cluster_context="%s"))
 kube_data = kube_get(categories=["all"])
-`, k8sconfig),
+`, k8sconfig, clusterName),
  eval: func(t *testing.T, script string) {
  data := execute(t, script)
 

starlark/kube_nodes_provider.go

@@ -39,7 +39,7 @@ func KubeNodesProviderFn(thread *starlark.Thread, _ *starlark.Builtin, args star
  if kubeConfig == nil {
  kubeConfig = thread.Local(identifiers.kubeCfg).(*starlarkstruct.Struct)
  }
- path, err := getKubeConfigFromStruct(kubeConfig)
+ path, err := getKubeConfigPathFromStruct(kubeConfig)
  if err != nil {
  return starlark.None, errors.Wrap(err, "failed to kubeconfig")
  }

testing/setup.go

@@ -200,6 +200,10 @@ func (t *TestSupport) KindKubeConfigFile() string {
  return t.kindKubeCfg
 }
 
+func (t *TestSupport) KindClusterContextName() string {
+ return t.kindCluster.GetKubeCtlContext()
+}
+
 func (t *TestSupport) TearDown() error {
  var errs []error