Implement metric-gen tool

Implements the metric-gen tool which could get used to create custom resource
configurations directly from code, similar to what controller-gen does.

exp/metric-gen/go.mod

@@ -0,0 +1,59 @@
+module k8s.io/kube-state-metrics/exp/metric-gen
+
+go 1.19
+
+replace k8s.io/kube-state-metrics/v2 => ../..
+
+require (
+	github.com/spf13/cobra v1.6.1
+	k8s.io/apimachinery v0.26.0
+	k8s.io/klog/v2 v2.80.1
+	k8s.io/kube-state-metrics/v2 v2.0.0-00010101000000-000000000000
+	k8s.io/utils v0.0.0-20221128185143-99ec85e7a448
+	sigs.k8s.io/controller-tools v0.11.1
+)
+
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/blang/semver/v4 v4.0.0 // indirect
+	github.com/cespare/xxhash/v2 v2.1.2 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/fatih/color v1.13.0 // indirect
+	github.com/go-logr/logr v1.2.3 // indirect
+	github.com/gobuffalo/flect v0.3.0 // indirect
+	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/golang/protobuf v1.5.2 // indirect
+	github.com/google/go-cmp v0.5.9 // indirect
+	github.com/google/gofuzz v1.1.0 // indirect
+	github.com/inconshreveable/mousetrap v1.0.1 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/mattn/go-colorable v0.1.9 // indirect
+	github.com/mattn/go-isatty v0.0.14 // indirect
+	github.com/matttproud/golang_protobuf_extensions v1.0.2 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/prometheus/client_golang v1.14.0 // indirect
+	github.com/prometheus/client_model v0.3.0 // indirect
+	github.com/prometheus/common v0.38.0 // indirect
+	github.com/prometheus/procfs v0.8.0 // indirect
+	github.com/rogpeppe/go-internal v1.9.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+	golang.org/x/mod v0.7.0 // indirect
+	golang.org/x/net v0.4.0 // indirect
+	golang.org/x/oauth2 v0.0.0-20221014153046-6fdb5e3db783 // indirect
+	golang.org/x/sys v0.3.0 // indirect
+	golang.org/x/term v0.3.0 // indirect
+	golang.org/x/text v0.5.0 // indirect
+	golang.org/x/time v0.0.0-20220609170525-579cf78fd858 // indirect
+	golang.org/x/tools v0.4.0 // indirect
+	google.golang.org/appengine v1.6.7 // indirect
+	google.golang.org/protobuf v1.28.1 // indirect
+	gopkg.in/inf.v0 v0.9.1 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
+	k8s.io/apiextensions-apiserver v0.26.0 // indirect
+	k8s.io/client-go v0.26.0 // indirect
+	k8s.io/component-base v0.26.0 // indirect
+	sigs.k8s.io/json v0.0.0-20220713155537-f223a00ba0e2 // indirect
+	sigs.k8s.io/structured-merge-diff/v4 v4.2.3 // indirect
+	sigs.k8s.io/yaml v1.3.0 // indirect
+)

exp/metric-gen/main.go

@@ -0,0 +1,124 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/spf13/pflag"
+	"k8s.io/kube-state-metrics/exp/metric-gen/metric"
+	"sigs.k8s.io/controller-tools/pkg/genall"
+	"sigs.k8s.io/controller-tools/pkg/genall/help"
+	prettyhelp "sigs.k8s.io/controller-tools/pkg/genall/help/pretty"
+	"sigs.k8s.io/controller-tools/pkg/loader"
+	"sigs.k8s.io/controller-tools/pkg/markers"
+)
+
+const (
+	generatorName = "metric"
+)
+
+var (
+	// optionsRegistry contains all the marker definitions used to process command line options
+	optionsRegistry = &markers.Registry{}
+)
+
+func main() {
+	var whichMarkersFlag bool
+
+	pflag.CommandLine.BoolVarP(&whichMarkersFlag, "which-markers", "w", false, "print out all markers available with the requested generators")
+
+	pflag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage of %s:\n\n", os.Args[0])
+		fmt.Fprintf(os.Stderr, "  metric-gen [flags] /path/to/package [/path/to/package]\n\n")
+		fmt.Fprintf(os.Stderr, "Flags:\n")
+		pflag.PrintDefaults()
+		fmt.Fprintf(os.Stderr, "\n")
+	}
+
+	pflag.Parse()
+
+	// Register the metric generator itself as marker so genall.FromOptions is able to initialize the runtime properly.
+	// This also registers the markers inside the optionsRegistry so its available to print the marker docs.
+	metricGenerator := metric.Generator{}
+	defn := markers.Must(markers.MakeDefinition(generatorName, markers.DescribesPackage, metricGenerator))
+	if err := optionsRegistry.Register(defn); err != nil {
+		panic(err)
+	}
+
+	if whichMarkersFlag {
+		printMarkerDocs()
+		return
+	}
+
+	// Check if package paths got passed as input parameters.
+	if len(os.Args[1:]) == 0 {
+		fmt.Fprint(os.Stderr, "error: Please provide package paths as parameters\n\n")
+		pflag.Usage()
+		os.Exit(1)
+	}
+
+	// Load the passed packages as roots.
+	roots, err := loader.LoadRoots(os.Args[1:]...)
+	if err != nil {
+		fmt.Fprint(os.Stderr, fmt.Sprintf("error: loading packages %v\n", err))
+		os.Exit(1)
+	}
+
+	// Set up the generator runtime using controller-tools and passing our optionsRegistry.
+	rt, err := genall.FromOptions(optionsRegistry, []string{generatorName})
+	if err != nil {
+		fmt.Fprint(os.Stderr, fmt.Sprintf("error: %v\n", err))
+		os.Exit(1)
+	}
+
+	// Setup the generation context with the loaded roots.
+	rt.GenerationContext.Roots = roots
+	// Setup the runtime to output to stdout.
+	rt.OutputRules = genall.OutputRules{Default: genall.OutputToStdout}
+
+	// Run the generator using the runtime.
+	if hadErrs := rt.Run(); hadErrs {
+		fmt.Fprint(os.Stderr, "generator did not run successfully\n")
+		os.Exit(1)
+	}
+}
+
+// printMarkerDocs prints out marker help for the given generators specified in
+// the rawOptions
+func printMarkerDocs() error {
+	// just grab a registry so we don't lag while trying to load roots
+	// (like we'd do if we just constructed the full runtime).
+	reg, err := genall.RegistryFromOptions(optionsRegistry, []string{generatorName})
+	if err != nil {
+		return err
+	}
+
+	helpInfo := help.ByCategory(reg, help.SortByCategory)
+
+	for _, cat := range helpInfo {
+		if cat.Category == "" {
+			continue
+		}
+		contents := prettyhelp.MarkersDetails(false, cat.Category, cat.Markers)
+		if err := contents.WriteTo(os.Stderr); err != nil {
+			return err
+		}
+	}
+	return nil
+}

exp/metric-gen/metric/generator.go

@@ -0,0 +1,117 @@
+package metric
+
+import (
+	"fmt"
+	"sort"
+
+	"k8s.io/klog/v2"
+	"sigs.k8s.io/controller-tools/pkg/crd"
+	"sigs.k8s.io/controller-tools/pkg/genall"
+	"sigs.k8s.io/controller-tools/pkg/loader"
+	"sigs.k8s.io/controller-tools/pkg/markers"
+
+	"k8s.io/kube-state-metrics/v2/pkg/customresourcestate"
+)
+
+type Generator struct{}
+
+func (Generator) CheckFilter() loader.NodeFilter {
+	// Re-use controller-tools filter to filter out unrelated nodes that aren't used
+	// in CRD generation, like interfaces and struct fields without JSON tag.
+	return crd.Generator{}.CheckFilter()
+}
+
+func (g Generator) Generate(ctx *genall.GenerationContext) error {
+	// Create the parser which is specific to the metric generator.
+	parser := newParser(
+		&crd.Parser{
+			Collector: ctx.Collector,
+			Checker:   ctx.Checker,
+		},
+	)
+
+	// Loop over all passed packages.
+	for _, root := range ctx.Roots {
+		// skip packages which don't import metav1 because they can't define a CRD without meta v1.
+		metav1 := root.Imports()["k8s.io/apimachinery/pkg/apis/meta/v1"]
+		if metav1 == nil {
+			continue
+		}
+
+		// parse the given package to feed crd.FindKubeKinds to find CRD objects.
+		parser.NeedPackage(root)
+		kubeKinds := crd.FindKubeKinds(parser.Parser, metav1)
+		if len(kubeKinds) == 0 {
+			klog.Fatalf("no objects in the roots")
+		}
+
+		for _, gv := range kubeKinds {
+			// Create customresourcestate.Resource for each CRD which contains all metric
+			// definitions for the CRD.
+			parser.NeedResourceFor(gv)
+		}
+	}
+
+	// Build customresourcestate configuration file from generated data.
+	metrics := customresourcestate.Metrics{
+		Spec: customresourcestate.MetricsSpec{
+			Resources: []customresourcestate.Resource{},
+		},
+	}
+
+	// Sort the resources to get a deterministic output.
+
+	for _, resource := range parser.CustomResourceStates {
+		if len(resource.Metrics) > 0 {
+			// sort the metrics
+			sort.Slice(resource.Metrics, func(i, j int) bool {
+				return resource.Metrics[i].Name < resource.Metrics[j].Name
+			})
+
+			metrics.Spec.Resources = append(metrics.Spec.Resources, resource)
+		}
+	}
+
+	sort.Slice(metrics.Spec.Resources, func(i, j int) bool {
+		if metrics.Spec.Resources[i].MetricNamePrefix == nil && metrics.Spec.Resources[j].MetricNamePrefix == nil {
+			a := metrics.Spec.Resources[i].GroupVersionKind.Group + "/" + metrics.Spec.Resources[i].GroupVersionKind.Version + "/" + metrics.Spec.Resources[i].GroupVersionKind.Kind
+			b := metrics.Spec.Resources[j].GroupVersionKind.Group + "/" + metrics.Spec.Resources[j].GroupVersionKind.Version + "/" + metrics.Spec.Resources[j].GroupVersionKind.Kind
+			return a < b
+		}
+
+		// Either a or b will not be the empty string, so we can compare them.
+		var a, b string
+		if metrics.Spec.Resources[i].MetricNamePrefix == nil {
+			a = *metrics.Spec.Resources[i].MetricNamePrefix
+		}
+		if metrics.Spec.Resources[j].MetricNamePrefix != nil {
+			b = *metrics.Spec.Resources[j].MetricNamePrefix
+		}
+		return a < b
+	})
+
+	// Write the rendered yaml to the context which will result in stdout.
+	filePath := "metrics.yaml"
+	if err := ctx.WriteYAML(filePath, []interface{}{metrics}, genall.WithTransform(addCustomResourceStateKind)); err != nil {
+		return fmt.Errorf("WriteYAML to %s: %w", filePath, err)
+	}
+
+	return nil
+}
+
+// addCustomResourceStateKind adds the correct kind because we don't have a correct
+// kubernetes-style object as configuration definition.
+func addCustomResourceStateKind(obj map[string]interface{}) error {
+	obj["kind"] = "CustomResourceStateMetrics"
+	return nil
+}
+
+func (g Generator) RegisterMarkers(into *markers.Registry) error {
+	for _, m := range markerDefinitions {
+		if err := m.Register(into); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

exp/metric-gen/metric/marker_gauge.go

@@ -0,0 +1,67 @@
+package metric
+
+import (
+	"sigs.k8s.io/controller-tools/pkg/markers"
+
+	"k8s.io/klog/v2"
+	"k8s.io/kube-state-metrics/v2/pkg/customresourcestate"
+)
+
+const (
+	// GaugeMarkerName is a marker for defining metric definitions.
+	GaugeMarkerName = "Metrics:gauge"
+)
+
+func init() {
+	markerDefinitions = append(
+		markerDefinitions,
+		must(markers.MakeDefinition(GaugeMarkerName, markers.DescribesField, GaugeMarker{})).
+			help(GaugeMarker{}.help()),
+		must(markers.MakeDefinition(GaugeMarkerName, markers.DescribesType, GaugeMarker{})).
+			help(GaugeMarker{}.help()),
+	)
+}
+
+type GaugeMarker struct {
+	Name         string
+	Help         string   `marker:"help,optional"`
+	NilIsZero    bool     `marker:"nilIsZero,optional"`
+	JSONPath     JSONPath `marker:"JSONPath,optional"`
+	LabelFromKey string   `marker:"labelFromKey,optional"`
+}
+
+func (GaugeMarker) help() *markers.DefinitionHelp {
+	return &markers.DefinitionHelp{
+		Category: "Metrics",
+		DetailedHelp: markers.DetailedHelp{
+			Summary: "Defines a Gauge metric and uses the implicit path to the field joined by the provided JSONPath as path for the metric configuration.",
+			Details: "",
+		},
+		FieldHelp: map[string]markers.DetailedHelp{},
+	}
+}
+
+func (g GaugeMarker) ToGenerator(basePath ...string) *customresourcestate.Generator {
+	valueFrom, err := g.JSONPath.Parse()
+	if err != nil {
+		klog.Fatal(err)
+	}
+
+	path := append(basePath, valueFrom...)
+
+	return &customresourcestate.Generator{
+		Name: g.Name,
+		Help: g.Help,
+		Each: customresourcestate.Metric{
+			Type: customresourcestate.MetricTypeGauge,
+			Gauge: &customresourcestate.MetricGauge{
+				NilIsZero: g.NilIsZero,
+				MetricMeta: customresourcestate.MetricMeta{
+					Path: path,
+				},
+				LabelFromKey: g.LabelFromKey,
+				ValueFrom:    nil,
+			},
+		},
+	}
+}