add ability to print default values for all operator variables (#675) (…

…#742)

* add ability to print default values for all operator variables (#675)

* fix review comment

docs/CHANGELOG.MD

@@ -8,7 +8,7 @@
 
 ### Features
 
-- TODO
+- [vmoperator](https://docs.victoriametrics.com/operator/) add ability to print default values for all [operator variables](https://docs.victoriametrics.com/operator/vars.html). See [this issue](https://github.com/VictoriaMetrics/operator/issues/675) for details.
 
 <a name="v0.37.1"></a>
 ## [v0.37.1](https://github.com/VictoriaMetrics/operator/releases/tag/v0.37.1) - 02 Sep 2023

e2e/suite/suite.go

@@ -6,6 +6,7 @@ import (
 	"path/filepath"
 
 	victoriametricsv1beta1 "github.com/VictoriaMetrics/operator/api/v1beta1"
+	"github.com/VictoriaMetrics/operator/internal/config"
 	"github.com/VictoriaMetrics/operator/internal/manager"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
@@ -89,7 +90,8 @@ func Before() {
 		ctx, cancel := context.WithCancel(context.Background())
 		go func(ctx context.Context) {
 			defer GinkgoRecover()
-			err := manager.RunManager(ctx)
+			baseConfig := config.MustGetBaseConfig()
+			err := manager.RunManager(ctx, baseConfig)
 			close(stopped)
 			Expect(err).NotTo(HaveOccurred())
 		}(ctx)

internal/config/config.go

@@ -6,6 +6,7 @@ import (
 	"regexp"
 	"strings"
 	"sync"
+	"text/tabwriter"
 	"time"
 
 	"github.com/kelseyhightower/envconfig"
@@ -325,6 +326,33 @@ func (boc BaseOperatorConf) Validate() error {
 	return nil
 }
 
+// PrintDefaults prints default values for all config variables.
+// format can be one of: table, list, json, yaml.
+func (boc BaseOperatorConf) PrintDefaults(format string) error {
+	tabs := tabwriter.NewWriter(os.Stdout, 1, 0, 4, ' ', 0)
+
+	var formatter = "unknown"
+	switch format {
+	case "table":
+		formatter = envconfig.DefaultTableFormat
+	case "list":
+		formatter = envconfig.DefaultListFormat
+	case "json":
+		formatter = `{{$last := (len (slice . 1))}}{
+{{range $index, $item := .}}	'{{usage_key $item}}': '{{usage_default $item}}'{{ if lt $index $last}},{{end}}
+{{end}}}`
+	case "yaml":
+		formatter = `{{range $index, $item := .}}{{usage_key $item}}: '{{usage_default $item}}'
+{{end}}`
+	default:
+		return fmt.Errorf("unknown print format %q", format)
+	}
+
+	err := envconfig.Usagef(prefixVar, &boc, tabs, formatter)
+	_ = tabs.Flush()
+	return err
+}
+
 func MustGetBaseConfig() *BaseOperatorConf {
 	initConf.Do(func() {
 		c := &BaseOperatorConf{}

internal/manager/manager.go

@@ -72,7 +72,7 @@ func init() {
 
 }
 
-func RunManager(ctx context.Context) error {
+func RunManager(ctx context.Context, baseConfig *config.BaseOperatorConf) error {
 	// Add flags registered by imported packages (e.g. glog and
 	// controller-runtime)
 	opts := zap.Options{}
@@ -170,7 +170,6 @@ func RunManager(ctx context.Context) error {
 			return err
 		}
 	}
-	baseConfig := config.MustGetBaseConfig()
 	victoriametricsv1beta1.SetLabelAndAnnotationPrefixes(baseConfig.FilterChildLabelPrefixes, baseConfig.FilterChildAnnotationPrefixes)
 
 	if err = (&controllers.VMAgentReconciler{

main.go

@@ -18,16 +18,20 @@ package main
 
 import (
 	"context"
+	"flag"
 	"os"
 
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/manager/signals"
 
+	"github.com/VictoriaMetrics/operator/internal/config"
 	"github.com/VictoriaMetrics/operator/internal/manager"
 )
 
 var (
-	setupLog = ctrl.Log.WithName("setup")
+	setupLog      = ctrl.Log.WithName("setup")
+	printDefaults = flag.Bool("printDefaults", false, "print all variables with their default values and exit")
+	printFormat   = flag.String("printFormat", "table", "output format for --printDefaults. Can be table, json, yaml or list")
 )
 
 func main() {
@@ -38,7 +42,18 @@ func main() {
 		cancel()
 	}()
 
-	err := manager.RunManager(ctx)
+	flag.Parse()
+	baseConfig := config.MustGetBaseConfig()
+	if *printDefaults {
+		err := baseConfig.PrintDefaults(*printFormat)
+		if err != nil {
+			setupLog.Error(err, "cannot print variables")
+			os.Exit(1)
+		}
+		return
+	}
+
+	err := manager.RunManager(ctx, baseConfig)
 	if err != nil {
 		setupLog.Error(err, "cannot setup manager")
 		os.Exit(1)