Add --opts-config-file flag

Add `--opts-config-file` flag to support suppling options from a config
file.

Signed-off-by: Pranshu Srivastava <rexagod@gmail.com>

main.go

@@ -19,12 +19,12 @@ package main
 import (
 	"context"
 	"fmt"
-	"os"
-	"strings"
-
 	"github.com/prometheus/common/version"
 	"gopkg.in/yaml.v3"
 	"k8s.io/klog/v2"
+	"os"
+	"strings"
+	"time"
 
 	"k8s.io/kube-state-metrics/v2/pkg/customresource"
 	"k8s.io/kube-state-metrics/v2/pkg/customresourcestate"
@@ -62,10 +62,57 @@ func main() {
 		factories = append(factories, crf...)
 	}
 
-	ctx := context.Background()
-	if err := app.RunKubeStateMetrics(ctx, opts, factories...); err != nil {
-		klog.ErrorS(err, "Failed to run kube-state-metrics")
-		klog.FlushAndExit(klog.ExitFlushTimeout, 1)
+	KSMRunOrDie := func(ctx context.Context) {
+		klog.Infoln("Starting kube-state-metrics")
+		if err := app.RunKubeStateMetricsWrapper(ctx, opts, factories...); err != nil {
+			klog.Errorln(err)
+			klog.FlushAndExit(klog.ExitFlushTimeout, 1)
+		}
+	}
+	changed := make(chan bool, 1)
+	go KSMWrapper(changed, KSMRunOrDie)
+	got := options.GetOptsConfigFile(*opts)
+	if got != "" {
+		initialStat, err := os.Stat(got)
+		if err != nil {
+			klog.Fatalf("Failed to get file stat: %v", err)
+		}
+		initialModTime := initialStat.ModTime()
+		go monitorChange(changed, got, initialModTime)
+	}
+	select {}
+}
+
+func KSMWrapper(changed chan bool, fn func(context.Context)) {
+	// start kube-state-metrics
+	ctx, cancel := context.WithCancel(context.Background())
+	go fn(ctx)
+	for {
+		// wait for any changes
+		<-changed
+
+		// stop kube-state-metrics
+		cancel()
+		klog.Infoln(ctx.Err())
+
+		// restart kube-state-metrics
+		ctx, cancel = context.WithCancel(context.Background())
+		go fn(ctx)
+	}
+}
+
+func monitorChange(changed chan bool, optsConfigFile string, initialModTime time.Time) {
+	for {
+		stat, err := os.Stat(optsConfigFile)
+		if err != nil {
+			klog.Fatalln(err)
+		}
+		newModTime := stat.ModTime()
+		if newModTime != initialModTime {
+			changed <- true
+			initialModTime = newModTime
+		}
+		<-time.After(3 * time.Second)
 	}
 }
 

pkg/app/server.go

@@ -19,6 +19,8 @@ package app
 import (
 	"context"
 	"fmt"
+	"gopkg.in/yaml.v3"
+	"io/ioutil"
 	"net"
 	"net/http"
 	"net/http/pprof"
@@ -66,10 +68,24 @@ func (pl promLogger) Log(v ...interface{}) error {
 	return nil
 }
 
-// RunKubeStateMetrics will build and run the kube-state-metrics.
+func RunKubeStateMetricsWrapper(ctx context.Context, opts *options.Options, factories ...customresource.RegistryFactory) error {
+	err := runKubeStateMetrics(ctx, opts, factories...)
+	for {
+		select {
+		case <-ctx.Done():
+			if ctx.Err() == context.Canceled {
+				return nil
+			}
+			return err
+		default:
+		}
+	}
+}
+
+// runKubeStateMetrics will build and run the kube-state-metrics.
 // Any out-of-tree custom resource metrics could be registered by newing a registry factory
 // which implements customresource.RegistryFactory and pass all factories into this function.
-func RunKubeStateMetrics(ctx context.Context, opts *options.Options, factories ...customresource.RegistryFactory) error {
+func runKubeStateMetrics(ctx context.Context, opts *options.Options, factories ...customresource.RegistryFactory) error {
 	promLogger := promLogger{}
 
 	storeBuilder := store.NewBuilder()
@@ -87,6 +103,18 @@ func RunKubeStateMetrics(ctx context.Context, opts *options.Options, factories .
 	)
 	storeBuilder.WithMetrics(ksmMetricsRegistry)
 
+	// TODO: Should the options config file override flags?
+	got := options.GetOptsConfigFile(*opts)
+	if got != "" {
+		optsConfigFile, err := ioutil.ReadFile(got)
+		if err != nil {
+			return fmt.Errorf("failed to read opts config file: %v", err)
+		}
+		err = yaml.Unmarshal(optsConfigFile, opts)
+		if err != nil {
+			return fmt.Errorf("failed to unmarshal opts config file: %v", err)
+		}
+	}
 	var resources []string
 	if len(opts.Resources) == 0 {
 		klog.InfoS("Used default resources")

pkg/options/options.go

@@ -43,8 +43,8 @@ type Options struct {
 	TotalShards          int
 	Pod                  string
 	Namespace            string
-	MetricDenylist       MetricSet
-	MetricAllowlist      MetricSet
+	MetricDenylist       MetricSet `yaml:"metric_denylist"`
+	MetricAllowlist      MetricSet `yaml:"metric_allowlist"`
 	MetricOptInList      MetricSet
 	Version              bool
 	AnnotationsAllowList LabelsAllowList
@@ -57,9 +57,15 @@ type Options struct {
 	CustomResourceConfig     string
 	CustomResourceConfigFile string
 
+	optsConfigFile string
+
 	flags *pflag.FlagSet
 }
 
+func GetOptsConfigFile(opt Options) string {
+	return opt.optsConfigFile
+}
+
 // NewOptions returns a new instance of `Options`.
 func NewOptions() *Options {
 	return &Options{
@@ -117,6 +123,7 @@ func (o *Options) AddFlags() {
 
 	o.flags.StringVar(&o.CustomResourceConfig, "custom-resource-state-config", "", "Inline Custom Resource State Metrics config YAML (experimental)")
 	o.flags.StringVar(&o.CustomResourceConfigFile, "custom-resource-state-config-file", "", "Path to a Custom Resource State Metrics config file (experimental)")
+	o.flags.StringVar(&o.optsConfigFile, "opts-config-file", "", "Path to the custom options config file (experimental)")
 }
 
 // Parse parses the flag definitions from the argument list.