kustomize generator: add a builtin function kubernetesVersion

this builtin returns the deployment target cluster's server version
as a k8s version.Info struct

Author: cbarbian-sap

pkg/component/reconcile.go

@@ -43,6 +43,7 @@ import (
 // TODO: allow to override namespace auto-creation on a per-object level
 // TODO: allow some timeout feature, such that component will go into error state if not ready within the given timeout
 // (e.g. through a TimeoutConfiguration interface that components could optionally implement)
+// TODO: from time to time, enforce dependent updates even if digest is matching
 // TODO: run admission webhooks (if present) in reconcile (e.g. as post-read hook)
 // TODO: improve overall log output
 

pkg/component/reference.go

@@ -25,6 +25,8 @@ import (
 
 // TODO: should below reference actions be thread safe?
 // If not, it should be stated somewhere explicitly that they are not.
+// TODO: allow to skip loading of references upon deletion in general (e.g. by a tagLoadPolicy)
+// (currently it is only possible to ignore not-found errors upon deletion)
 
 const (
 	tagNotFoundPolicy = "notFoundPolicy"

pkg/manifests/kustomize/generator.go

@@ -20,14 +20,14 @@ import (
 
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	utilyaml "k8s.io/apimachinery/pkg/util/yaml"
+	"k8s.io/apimachinery/pkg/version"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/kustomize/api/konfig"
 	"sigs.k8s.io/kustomize/api/krusty"
 	kustypes "sigs.k8s.io/kustomize/api/types"
 	kustfsys "sigs.k8s.io/kustomize/kyaml/filesys"
 	kyaml "sigs.k8s.io/yaml"
 
-	"github.com/sap/component-operator-runtime/internal/cluster"
 	"github.com/sap/component-operator-runtime/internal/fileutils"
 	"github.com/sap/component-operator-runtime/internal/templatex"
 	"github.com/sap/component-operator-runtime/pkg/component"
@@ -165,6 +165,11 @@ func (g *KustomizeGenerator) Generate(ctx context.Context, namespace string, nam
 		return nil, err
 	}
 
+	serverInfo, err := clnt.DiscoveryClient().ServerVersion()
+	if err != nil {
+		return nil, err
+	}
+
 	data := parameters.ToUnstructured()
 	fsys := kustfsys.MakeFsInMemory()
 
@@ -183,7 +188,7 @@ func (g *KustomizeGenerator) Generate(ctx context.Context, namespace string, nam
 			}
 			t0.Option("missingkey=zero").
 				Funcs(templatex.FuncMapForClient(clnt)).
-				Funcs(funcMapForGenerateContext(clnt, component, namespace, name))
+				Funcs(funcMapForGenerateContext(serverInfo, component, namespace, name))
 		}
 		var buf bytes.Buffer
 		if err := t0.ExecuteTemplate(&buf, t.Name(), data); err != nil {
@@ -239,14 +244,14 @@ func (g *KustomizeGenerator) Generate(ctx context.Context, namespace string, nam
 	return objects, nil
 }
 
-func funcMapForGenerateContext(clnt cluster.Client, component component.Component, namespace string, name string) template.FuncMap {
-	// TODO: add accessors for Kubernetes version etc.
+func funcMapForGenerateContext(serverInfo *version.Info, component component.Component, namespace string, name string) template.FuncMap {
 	return template.FuncMap{
 		// TODO: maybe it would it be better to convert component to unstructured;
 		// then calling methods would no longer be possible, and attributes would be in lowercase
-		"component": makeFuncData(component),
-		"namespace": func() string { return namespace },
-		"name":      func() string { return name },
+		"component":         makeFuncData(component),
+		"namespace":         func() string { return namespace },
+		"name":              func() string { return name },
+		"kubernetesVersion": func() *version.Info { return serverInfo },
 	}
 }
 

website/content/en/docs/generators/kustomize.md

@@ -11,7 +11,9 @@ This generator allows to generate the manifests of the component's resources fro
 As a special case, one or more simple Kubernetes manifests (without a `kustomization.yaml`) are supported as well.
 In addition, all (or selected; see below) files in the kustomization directory can be templatized in a helm'ish way.
 That means, they will be considered as a common template group (where all templates are associated with each other),
-and the same template function set that is available on helm can be used; so, all the [sprig](http://masterminds.github.io/sprig) functions, and custom functions such as `include`, `tpl`, `lookup` can be used. In addition, parameterless functions `namespace` and `name` are defined, which return the corresponding arguments passed to `Generate()`.
+and the same template function set that is available on helm can be used; so, all the [sprig](http://masterminds.github.io/sprig) functions, and custom functions such as `include`, `tpl`, `lookup` can be used. In addition:
+- parameterless functions `namespace` and `name` are defined, which return the corresponding arguments passed to `Generate()`
+- a function `kubernetesVersion` is available, which returns the version information of the target cluster, as a [version.Info](https://pkg.go.dev/k8s.io/apimachinery/pkg/version#Info) structure.
 
 In the generation step, first, all the go templates will be rendered, and the result of this pre-step will be passed to kustomize.