Merge pull request #5964 from simonpasquier/rework-controller-configs

chore: reduce code duplication in components
2025-04-21 11:48:53 +00:00 · 2023-11-27 09:11:32 +01:00 · 2023-11-27 09:11:32 +01:00 · 34941afa1a
commit 34941afa1a
parent 9e9a7536a8 5e9eed43e4
25 changed files with 959 additions and 843 deletions
--- a/Documentation/operator.md
+++ b/Documentation/operator.md
@ -21,8 +21,8 @@ Usage of ./operator:
    	Alertmanager default base image (path without tag/version) (default "quay.io/prometheus/alertmanager")
  -alertmanager-instance-namespaces value
    	Namespaces where Alertmanager custom resources and corresponding StatefulSets are watched/created. If set this takes precedence over --namespaces or --deny-namespaces for Alertmanager custom resources.
-  -alertmanager-instance-selector string
-    	Label selector to filter AlertManager Custom Resources to watch.
+  -alertmanager-instance-selector value
+    	Label selector to filter Alertmanager Custom Resources to watch.
  -annotations value
    	Annotations to be add to all resources created by the operator
  -apiserver string
@ -49,7 +49,7 @@ Usage of ./operator:
    	Enable liveness and readiness for the config-reloader container. Default: false
  -key-file string
    	- NOT RECOMMENDED FOR PRODUCTION - Path to private TLS certificate file.
-  -kubelet-selector string
+  -kubelet-selector value
    	Label selector to filter nodes.
  -kubelet-service string
    	Service/Endpoints object to write kubelets into in format "namespace/name"
@ -69,9 +69,9 @@ Usage of ./operator:
    	Prometheus default base image (path without tag/version) (default "quay.io/prometheus/prometheus")
  -prometheus-instance-namespaces value
    	Namespaces where Prometheus and PrometheusAgent custom resources and corresponding Secrets, Configmaps and StatefulSets are watched/created. If set this takes precedence over --namespaces or --deny-namespaces for Prometheus custom resources.
-  -prometheus-instance-selector string
+  -prometheus-instance-selector value
    	Label selector to filter Prometheus and PrometheusAgent Custom Resources to watch.
-  -secret-field-selector string
+  -secret-field-selector value
    	Field selector to filter Secrets to watch
  -short-version
    	Print just the version number.
@ -79,26 +79,26 @@ Usage of ./operator:
    	Thanos default base image (path without tag/version) (default "quay.io/thanos/thanos")
  -thanos-ruler-instance-namespaces value
    	Namespaces where ThanosRuler custom resources and corresponding StatefulSets are watched/created. If set this takes precedence over --namespaces or --deny-namespaces for ThanosRuler custom resources.
-  -thanos-ruler-instance-selector string
+  -thanos-ruler-instance-selector value
    	Label selector to filter ThanosRuler Custom Resources to watch.
  -tls-insecure
    	- NOT RECOMMENDED FOR PRODUCTION - Don't verify API server's CA certificate.
  -version
    	Prints current version.
  -web.cert-file string
-    	Cert file to be used for operator web server endpoints. (default "/etc/tls/private/tls.crt")
+    	Certficate file to be used for the web server. (default "/etc/tls/private/tls.crt")
  -web.client-ca-file string
-    	Client CA certificate file to be used for operator web server endpoints. (default "/etc/tls/private/tls-ca.crt")
+    	Client CA certificate file to be used for the web server. (default "/etc/tls/private/tls-ca.crt")
  -web.enable-http2
    	Enable HTTP2 connections.
  -web.enable-tls
-    	Activate prometheus operator web server TLS.   This is useful for example when using the rule validation webhook.
+    	Enable TLS for the web server.
  -web.key-file string
-    	Private key matching the cert file to be used for operator web server endpoints. (default "/etc/tls/private/tls.key")
+    	Private key matching the cert file to be used for the web server. (default "/etc/tls/private/tls.key")
  -web.listen-address string
    	Address on which to expose metrics and web interface. (default ":8080")
-  -web.tls-cipher-suites string
-    	Comma-separated list of cipher suites for the server. Values are from tls package constants (https://golang.org/pkg/crypto/tls/#pkg-constants).If omitted, the default Go cipher suites will be used.Note that TLS 1.3 ciphersuites are not configurable.
+  -web.tls-cipher-suites value
+    	Comma-separated list of cipher suites for the server. Values are from tls package constants (https://golang.org/pkg/crypto/tls/#pkg-constants).If omitted, the default Go cipher suites will be used. Note that TLS 1.3 ciphersuites are not configurable.
  -web.tls-min-version string
    	Minimum TLS version supported. Value must match version names from https://golang.org/pkg/crypto/tls/#pkg-constants. (default "VersionTLS13")
  -web.tls-reload-interval duration
--- a/cmd/admission-webhook/main.go
+++ b/cmd/admission-webhook/main.go
@ -16,19 +16,13 @@ package main

 import (
 	"context"
-	"crypto/tls"
 	"flag"
-	"fmt"
 	stdlog "log"
-	"net"
 	"net/http"
 	"os"
 	"os/signal"
-	"strings"
 	"syscall"
-	"time"

-	rbacproxytls "github.com/brancz/kube-rbac-proxy/pkg/tls"
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
 	"github.com/prometheus/client_golang/prometheus"
@ -40,54 +34,28 @@ import (
 	logging "github.com/prometheus-operator/prometheus-operator/internal/log"
 	"github.com/prometheus-operator/prometheus-operator/pkg/admission"
 	"github.com/prometheus-operator/prometheus-operator/pkg/server"
-)
-
-const (
-	defaultTLSDir  = "/etc/tls/private"
-	defaultCrtFile = defaultTLSDir + "/tls.crt"
-	defaultKeyFile = defaultTLSDir + "/tls.key"
-	defaultCaCrt   = defaultTLSDir + "/tls-ca.crt"
-)
-
-var (
-	cfg     = config{}
-	flagset = flag.CommandLine
-
-	enableHTTP2        bool
-	serverTLS          bool
-	rawTLSCipherSuites string
+	"github.com/prometheus-operator/prometheus-operator/pkg/versionutil"
 )

 func main() {
-	flagset.StringVar(&cfg.ListenAddress, "web.listen-address", ":8443", "Address on which the admission webhook service listens")
-	// Mitigate CVE-2023-44487 by disabling HTTP2 by default until the Go
-	// standard library and golang.org/x/net are fully fixed.
-	// Right now, it is possible for authenticated and unauthenticated users to
-	// hold open HTTP2 connections and consume huge amounts of memory.
-	// See:
-	// * https://github.com/kubernetes/kubernetes/pull/121120
-	// * https://github.com/kubernetes/kubernetes/issues/121197
-	// * https://github.com/golang/go/issues/63417#issuecomment-1758858612
-	flagset.BoolVar(&enableHTTP2, "web.enable-http2", false, "Enable HTTP2 connections.")
-	flagset.BoolVar(&serverTLS, "web.enable-tls", true, "Enable TLS web server")
+	var (
+		serverConfig server.Config = server.DefaultConfig(":8443", true)
+		flagset                    = flag.CommandLine
+		logConfig    logging.Config
+	)

-	flagset.StringVar(&cfg.ServerTLSConfig.CertFile, "web.cert-file", defaultCrtFile, "Certificate file to be used for the web server.")
-	flagset.StringVar(&cfg.ServerTLSConfig.KeyFile, "web.key-file", defaultKeyFile, "Private key matching the certificate file to be used for the web server")
-	flagset.StringVar(&cfg.ServerTLSConfig.ClientCAFile, "web.client-ca-file", defaultCaCrt, "Client CA certificate file to be used for web server.")
-
-	flagset.DurationVar(&cfg.ServerTLSConfig.ReloadInterval, "web.tls-reload-interval", time.Minute, "The interval at which to watch for TLS certificate changes (default 1m).")
-	flagset.StringVar(&cfg.ServerTLSConfig.MinVersion, "web.tls-min-version", "VersionTLS13", fmt.Sprintf("Minimum TLS version supported. One of %s", validTLSVersions()))
-	flagset.StringVar(&rawTLSCipherSuites, "web.tls-cipher-suites", "", "Comma-separated list of cipher suites for the server."+
-		" Values are from tls package constants (https://golang.org/pkg/crypto/tls/#pkg-constants)."+
-		"If omitted, the default Go cipher suites will be used."+
-		"Note that TLS 1.3 ciphersuites are not configurable.")
-
-	flagset.StringVar(&cfg.LogLevel, "log-level", logging.LevelInfo, fmt.Sprintf("Log level to use. Possible values: %s", strings.Join(logging.AvailableLogLevels, ", ")))
-	flagset.StringVar(&cfg.LogFormat, "log-format", logging.FormatLogFmt, fmt.Sprintf("Log format to use. Possible values: %s", strings.Join(logging.AvailableLogFormats, ", ")))
+	server.RegisterFlags(flagset, &serverConfig)
+	versionutil.RegisterFlags(flagset)
+	logging.RegisterFlags(flagset, &logConfig)

 	_ = flagset.Parse(os.Args[1:])

-	logger, err := logging.NewLogger(cfg.LogLevel, cfg.LogFormat)
+	if versionutil.ShouldPrintVersion() {
+		versionutil.Print(os.Stdout, "admission-webhook")
+		return
+	}
+
+	logger, err := logging.NewLogger(logConfig)
 	if err != nil {
 		stdlog.Fatal(err)
 	}
@ -96,66 +64,6 @@ func main() {
 	defer cancel()
 	wg, ctx := errgroup.WithContext(ctx)

-	listener, err := net.Listen("tcp", cfg.ListenAddress)
-	if err != nil {
-		level.Error(logger).Log("msg", "failed to start required HTTP listener", "err", err)
-		os.Exit(1)
-	}
-
-	tlsConf, err := loadTLSConfigFromFlags(ctx, logger, wg)
-	if err != nil {
-		level.Error(logger).Log("msg", "failed to build TLS config", "err", err)
-		os.Exit(1)
-	}
-
-	server := newSrv(logger, tlsConf)
-	wg.Go(func() error {
-		return server.run(listener)
-	})
-
-	term := make(chan os.Signal, 1)
-	signal.Notify(term, os.Interrupt, syscall.SIGTERM)
-
-	select {
-	case sig := <-term:
-		level.Info(logger).Log("msg", "Received signal, exiting gracefully...", "signal", sig.String())
-	case <-ctx.Done():
-	}
-
-	if err := server.shutdown(ctx); err != nil {
-		level.Warn(logger).Log("msg", "Server shutdown error", "err", err)
-	}
-
-	cancel()
-	if err := wg.Wait(); err != nil {
-		level.Warn(logger).Log("msg", "Unhandled error received. Exiting...", "err", err)
-		os.Exit(1)
-	}
-}
-
-func (s *srv) run(listener net.Listener) error {
-	log := log.With(s.logger, "address", listener.Addr().String())
-
-	if s.s.TLSConfig != nil {
-		level.Info(log).Log("msg", "Starting TLS enabled server", "http2", enableHTTP2)
-		if err := s.s.ServeTLS(listener, "", ""); err != http.ErrServerClosed {
-			return err
-		}
-		return nil
-	}
-
-	level.Info(log).Log("msg", "Starting insecure server")
-	if err := s.s.Serve(listener); err != http.ErrServerClosed {
-		return err
-	}
-	return nil
-}
-
-func (s *srv) shutdown(ctx context.Context) error {
-	return s.s.Shutdown(ctx)
-}
-
-func newSrv(logger log.Logger, tlsConf *tls.Config) *srv {
 	mux := http.NewServeMux()
 	admit := admission.New(log.With(logger, "component", "admissionwebhook"))
 	admit.Register(mux)
@ -173,100 +81,32 @@ func newSrv(logger log.Logger, tlsConf *tls.Config) *srv {
 		w.Write([]byte(`{"status":"up"}`))
 	})

-	httpServer := http.Server{
-		Handler:           mux,
-		TLSConfig:         tlsConf,
-		ReadHeaderTimeout: 30 * time.Second,
-		ReadTimeout:       30 * time.Second,
-		// use flags on standard logger to align with base logger and get consistent parsed fields form adapter:
-		// use shortfile flag to get proper 'caller' field (avoid being wrongly parsed/extracted from message)
-		// and no datetime related flag to keep 'ts' field from base logger (with controlled format)
-		ErrorLog: stdlog.New(log.NewStdlibAdapter(logger), "", stdlog.Lshortfile),
-	}
-	if !enableHTTP2 {
-		httpServer.TLSNextProto = make(map[string]func(*http.Server, *tls.Conn, http.Handler))
+	srv, err := server.NewServer(logger, &serverConfig, mux)
+	if err != nil {
+		level.Error(logger).Log("msg", "failed to create web server", "err", err)
+		os.Exit(1)
 	}

-	return &srv{
-		logger: logger,
-		s:      &httpServer,
+	wg.Go(func() error {
+		return srv.Serve(ctx)
+	})
+
+	term := make(chan os.Signal, 1)
+	signal.Notify(term, os.Interrupt, syscall.SIGTERM)
+
+	select {
+	case sig := <-term:
+		level.Info(logger).Log("msg", "Received signal, exiting gracefully...", "signal", sig.String())
+	case <-ctx.Done():
+	}
+
+	if err := srv.Shutdown(ctx); err != nil {
+		level.Warn(logger).Log("msg", "Server shutdown error", "err", err)
+	}
+
+	cancel()
+	if err := wg.Wait(); err != nil {
+		level.Warn(logger).Log("msg", "Unhandled error received. Exiting...", "err", err)
+		os.Exit(1)
 	}
 }
-
-// loadTLSConfigFromFlags creates a tls.Config if configured and starts a watch on the dir to reload certs
-func loadTLSConfigFromFlags(ctx context.Context, logger log.Logger, wg *errgroup.Group) (*tls.Config, error) {
-	var (
-		tlsConfig *tls.Config
-		err       error
-	)
-	if serverTLS {
-		if _, ok := allowedTLSVersions[cfg.ServerTLSConfig.MinVersion]; !ok {
-			return nil, fmt.Errorf("unsupported TLS version %s provided", cfg.ServerTLSConfig.MinVersion)
-		}
-
-		if rawTLSCipherSuites != "" {
-			cfg.ServerTLSConfig.CipherSuites = strings.Split(rawTLSCipherSuites, ",")
-		}
-		tlsConfig, err = server.NewTLSConfig(
-			logger,
-			cfg.ServerTLSConfig.CertFile,
-			cfg.ServerTLSConfig.KeyFile,
-			cfg.ServerTLSConfig.ClientCAFile,
-			cfg.ServerTLSConfig.MinVersion,
-			cfg.ServerTLSConfig.CipherSuites,
-		)
-		if tlsConfig == nil || err != nil {
-			return nil, fmt.Errorf("invalid TLS config: %w", err)
-		}
-	}
-
-	if tlsConfig != nil {
-		r, err := rbacproxytls.NewCertReloader(
-			cfg.ServerTLSConfig.CertFile,
-			cfg.ServerTLSConfig.KeyFile,
-			cfg.ServerTLSConfig.ReloadInterval,
-		)
-		if err != nil {
-			return nil, fmt.Errorf("failed to initialize certificate reloader: %w", err)
-		}
-
-		tlsConfig.GetCertificate = r.GetCertificate
-		wg.Go(func() error {
-			for {
-				// r.Watch will wait ReloadInterval, so this is not
-				// a hot loop
-				if err := r.Watch(ctx); err != nil {
-					level.Warn(logger).Log("msg", "error watching certificate reloader", "err", err)
-				} else {
-					return nil
-				}
-			}
-		})
-	}
-	return tlsConfig, nil
-}
-
-type config struct {
-	ListenAddress   string
-	TLSInsecure     bool
-	ServerTLSConfig server.TLSServerConfig
-	LocalHost       string
-	LogLevel        string
-	LogFormat       string
-}
-
-type srv struct {
-	logger log.Logger
-	s      *http.Server
-}
-
-// any older versions won't allow a secure conn
-var allowedTLSVersions = map[string]bool{"VersionTLS13": true, "VersionTLS12": true}
-
-func validTLSVersions() string {
-	var out string
-	for validVersion := range allowedTLSVersions {
-		out += validVersion + ","
-	}
-	return strings.TrimRight(out, ",")
-}
--- a/cmd/operator/main.go
+++ b/cmd/operator/main.go
@ -16,21 +16,15 @@ package main

 import (
 	"context"
-	"crypto/tls"
-	"errors"
 	"flag"
 	"fmt"
 	stdlog "log"
-	"net"
 	"net/http"
 	"net/http/pprof"
 	"os"
 	"os/signal"
-	"strings"
 	"syscall"
-	"time"

-	rbacproxytls "github.com/brancz/kube-rbac-proxy/pkg/tls"
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
 	"github.com/prometheus/client_golang/prometheus"
@ -38,10 +32,10 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/prometheus/common/version"
 	"golang.org/x/sync/errgroup"
-	v1 "k8s.io/api/core/v1"
 	storagev1 "k8s.io/api/storage/v1"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"

 	logging "github.com/prometheus-operator/prometheus-operator/internal/log"
 	"github.com/prometheus-operator/prometheus-operator/pkg/admission"
@ -57,45 +51,6 @@ import (
 	"github.com/prometheus-operator/prometheus-operator/pkg/versionutil"
 )

-const (
-	defaultOperatorTLSDir = "/etc/tls/private"
-)
-
-var (
-	ns                   = namespaces{}
-	deniedNs             = namespaces{}
-	prometheusNs         = namespaces{}
-	alertmanagerNs       = namespaces{}
-	alertmanagerConfigNs = namespaces{}
-	thanosRulerNs        = namespaces{}
-)
-
-type namespaces map[string]struct{}
-
-// Set implements the flag.Value interface.
-func (n namespaces) Set(value string) error {
-	if n == nil {
-		return errors.New("expected n of type namespaces to be initialized")
-	}
-	for _, ns := range strings.Split(value, ",") {
-		n[ns] = struct{}{}
-	}
-	return nil
-}
-
-// String implements the flag.Value interface.
-func (n namespaces) String() string {
-	return strings.Join(n.asSlice(), ",")
-}
-
-func (n namespaces) asSlice() []string {
-	var ns = make([]string, 0, len(n))
-	for k := range n {
-		ns = append(ns, k)
-	}
-	return ns
-}
-
 // checkPrerequisites verifies that the CRD is installed in the cluster and
 // that the operator has enough permissions to manage the resource.
 func checkPrerequisites(
@ -132,26 +87,6 @@ func checkPrerequisites(
 	return true, nil
 }

-func serve(srv *http.Server, listener net.Listener, logger log.Logger) func() error {
-	return func() error {
-		level.Info(logger).Log("msg", "Starting insecure server on "+listener.Addr().String())
-		if err := srv.Serve(listener); err != http.ErrServerClosed {
-			return err
-		}
-		return nil
-	}
-}
-
-func serveTLS(srv *http.Server, listener net.Listener, logger log.Logger) func() error {
-	return func() error {
-		level.Info(logger).Log("msg", "Starting secure server on "+listener.Addr().String(), "http2", enableHTTP2)
-		if err := srv.ServeTLS(listener, "", ""); err != http.ErrServerClosed {
-			return err
-		}
-		return nil
-	}
-}
-
 const (
 	defaultReloaderCPU    = "10m"
 	defaultReloaderMemory = "50Mi"
@ -160,95 +95,79 @@ const (
 var (
 	cfg = operator.DefaultConfig(defaultReloaderCPU, defaultReloaderMemory)

-	rawTLSCipherSuites string
-	enableHTTP2        bool
-	serverTLS          bool
+	logConfig logging.Config

-	flagset = flag.CommandLine
+	impersonateUser string
+	apiServer       string
+	tlsClientConfig rest.TLSClientConfig
+
+	serverConfig = server.DefaultConfig(":8080", false)
 )

-func init() {
-	flagset.StringVar(&cfg.ListenAddress, "web.listen-address", ":8080", "Address on which to expose metrics and web interface.")
-	// Mitigate CVE-2023-44487 by disabling HTTP2 by default until the Go
-	// standard library and golang.org/x/net are fully fixed.
-	// Right now, it is possible for authenticated and unauthenticated users to
-	// hold open HTTP2 connections and consume huge amounts of memory.
-	// See:
-	// * https://github.com/kubernetes/kubernetes/pull/121120
-	// * https://github.com/kubernetes/kubernetes/issues/121197
-	// * https://github.com/golang/go/issues/63417#issuecomment-1758858612
-	flagset.BoolVar(&enableHTTP2, "web.enable-http2", false, "Enable HTTP2 connections.")
-	flagset.BoolVar(&serverTLS, "web.enable-tls", false, "Activate prometheus operator web server TLS.  "+
-		" This is useful for example when using the rule validation webhook.")
-	flagset.StringVar(&cfg.ServerTLSConfig.CertFile, "web.cert-file", defaultOperatorTLSDir+"/tls.crt", "Cert file to be used for operator web server endpoints.")
-	flagset.StringVar(&cfg.ServerTLSConfig.KeyFile, "web.key-file", defaultOperatorTLSDir+"/tls.key", "Private key matching the cert file to be used for operator web server endpoints.")
-	flagset.StringVar(&cfg.ServerTLSConfig.ClientCAFile, "web.client-ca-file", defaultOperatorTLSDir+"/tls-ca.crt", "Client CA certificate file to be used for operator web server endpoints.")
-	flagset.DurationVar(&cfg.ServerTLSConfig.ReloadInterval, "web.tls-reload-interval", time.Minute, "The interval at which to watch for TLS certificate changes, by default set to 1 minute. (default 1m0s).")
-	flagset.StringVar(&cfg.ServerTLSConfig.MinVersion, "web.tls-min-version", "VersionTLS13",
-		"Minimum TLS version supported. Value must match version names from https://golang.org/pkg/crypto/tls/#pkg-constants.")
-	flagset.StringVar(&rawTLSCipherSuites, "web.tls-cipher-suites", "", "Comma-separated list of cipher suites for the server."+
-		" Values are from tls package constants (https://golang.org/pkg/crypto/tls/#pkg-constants)."+
-		"If omitted, the default Go cipher suites will be used."+
-		"Note that TLS 1.3 ciphersuites are not configurable.")
+func parseFlags(fs *flag.FlagSet) {
+	// Web server settings.
+	server.RegisterFlags(fs, &serverConfig)

-	flagset.StringVar(&cfg.ImpersonateUser, "as", "", "Username to impersonate. User could be a regular user or a service account in a namespace.")
-	flagset.StringVar(&cfg.Host, "apiserver", "", "API Server addr, e.g. ' - NOT RECOMMENDED FOR PRODUCTION - http://127.0.0.1:8080'. Omit parameter to run in on-cluster mode and utilize the service account token.")
-	flagset.StringVar(&cfg.TLSConfig.CertFile, "cert-file", "", " - NOT RECOMMENDED FOR PRODUCTION - Path to public TLS certificate file.")
-	flagset.StringVar(&cfg.TLSConfig.KeyFile, "key-file", "", "- NOT RECOMMENDED FOR PRODUCTION - Path to private TLS certificate file.")
-	flagset.StringVar(&cfg.TLSConfig.CAFile, "ca-file", "", "- NOT RECOMMENDED FOR PRODUCTION - Path to TLS CA file.")
+	// Kubernetes client-go settings.
+	fs.StringVar(&impersonateUser, "as", "", "Username to impersonate. User could be a regular user or a service account in a namespace.")
+	fs.StringVar(&apiServer, "apiserver", "", "API Server addr, e.g. ' - NOT RECOMMENDED FOR PRODUCTION - http://127.0.0.1:8080'. Omit parameter to run in on-cluster mode and utilize the service account token.")
+	fs.StringVar(&tlsClientConfig.CertFile, "cert-file", "", " - NOT RECOMMENDED FOR PRODUCTION - Path to public TLS certificate file.")
+	fs.StringVar(&tlsClientConfig.KeyFile, "key-file", "", "- NOT RECOMMENDED FOR PRODUCTION - Path to private TLS certificate file.")
+	fs.StringVar(&tlsClientConfig.CAFile, "ca-file", "", "- NOT RECOMMENDED FOR PRODUCTION - Path to TLS CA file.")
+	fs.BoolVar(&tlsClientConfig.Insecure, "tls-insecure", false, "- NOT RECOMMENDED FOR PRODUCTION - Don't verify API server's CA certificate.")

-	flagset.StringVar(&cfg.KubeletObject, "kubelet-service", "", "Service/Endpoints object to write kubelets into in format \"namespace/name\"")
-	flagset.StringVar(&cfg.KubeletSelector, "kubelet-selector", "", "Label selector to filter nodes.")
-	flagset.BoolVar(&cfg.TLSInsecure, "tls-insecure", false, "- NOT RECOMMENDED FOR PRODUCTION - Don't verify API server's CA certificate.")
+	fs.StringVar(&cfg.KubeletObject, "kubelet-service", "", "Service/Endpoints object to write kubelets into in format \"namespace/name\"")
+	fs.Var(&cfg.KubeletSelector, "kubelet-selector", "Label selector to filter nodes.")

 	// The Prometheus config reloader image is released along with the
 	// Prometheus Operator image, tagged with the same semver version. Default to
 	// the Prometheus Operator version if no Prometheus config reloader image is
 	// specified.
-	flagset.StringVar(&cfg.ReloaderConfig.Image, "prometheus-config-reloader", operator.DefaultPrometheusConfigReloaderImage, "Prometheus config reloader image")
-	flagset.Var(&cfg.ReloaderConfig.CPURequests, "config-reloader-cpu-request", "Config Reloader CPU requests. Value \"0\" disables it and causes no request to be configured.")
-	flagset.Var(&cfg.ReloaderConfig.CPULimits, "config-reloader-cpu-limit", "Config Reloader CPU limits. Value \"0\" disables it and causes no limit to be configured.")
-	flagset.Var(&cfg.ReloaderConfig.MemoryRequests, "config-reloader-memory-request", "Config Reloader memory requests. Value \"0\" disables it and causes no request to be configured.")
-	flagset.Var(&cfg.ReloaderConfig.MemoryLimits, "config-reloader-memory-limit", "Config Reloader memory limits. Value \"0\" disables it and causes no limit to be configured.")
-	flagset.BoolVar(&cfg.ReloaderConfig.EnableProbes, "enable-config-reloader-probes", false, "Enable liveness and readiness for the config-reloader container. Default: false")
+	fs.StringVar(&cfg.ReloaderConfig.Image, "prometheus-config-reloader", operator.DefaultPrometheusConfigReloaderImage, "Prometheus config reloader image")
+	fs.Var(&cfg.ReloaderConfig.CPURequests, "config-reloader-cpu-request", "Config Reloader CPU requests. Value \"0\" disables it and causes no request to be configured.")
+	fs.Var(&cfg.ReloaderConfig.CPULimits, "config-reloader-cpu-limit", "Config Reloader CPU limits. Value \"0\" disables it and causes no limit to be configured.")
+	fs.Var(&cfg.ReloaderConfig.MemoryRequests, "config-reloader-memory-request", "Config Reloader memory requests. Value \"0\" disables it and causes no request to be configured.")
+	fs.Var(&cfg.ReloaderConfig.MemoryLimits, "config-reloader-memory-limit", "Config Reloader memory limits. Value \"0\" disables it and causes no limit to be configured.")
+	fs.BoolVar(&cfg.ReloaderConfig.EnableProbes, "enable-config-reloader-probes", false, "Enable liveness and readiness for the config-reloader container. Default: false")

-	flagset.StringVar(&cfg.AlertmanagerDefaultBaseImage, "alertmanager-default-base-image", operator.DefaultAlertmanagerBaseImage, "Alertmanager default base image (path without tag/version)")
-	flagset.StringVar(&cfg.PrometheusDefaultBaseImage, "prometheus-default-base-image", operator.DefaultPrometheusBaseImage, "Prometheus default base image (path without tag/version)")
-	flagset.StringVar(&cfg.ThanosDefaultBaseImage, "thanos-default-base-image", operator.DefaultThanosBaseImage, "Thanos default base image (path without tag/version)")
+	fs.StringVar(&cfg.AlertmanagerDefaultBaseImage, "alertmanager-default-base-image", operator.DefaultAlertmanagerBaseImage, "Alertmanager default base image (path without tag/version)")
+	fs.StringVar(&cfg.PrometheusDefaultBaseImage, "prometheus-default-base-image", operator.DefaultPrometheusBaseImage, "Prometheus default base image (path without tag/version)")
+	fs.StringVar(&cfg.ThanosDefaultBaseImage, "thanos-default-base-image", operator.DefaultThanosBaseImage, "Thanos default base image (path without tag/version)")

-	flagset.Var(ns, "namespaces", "Namespaces to scope the interaction of the Prometheus Operator and the apiserver (allow list). This is mutually exclusive with --deny-namespaces.")
-	flagset.Var(deniedNs, "deny-namespaces", "Namespaces not to scope the interaction of the Prometheus Operator (deny list). This is mutually exclusive with --namespaces.")
-	flagset.Var(prometheusNs, "prometheus-instance-namespaces", "Namespaces where Prometheus and PrometheusAgent custom resources and corresponding Secrets, Configmaps and StatefulSets are watched/created. If set this takes precedence over --namespaces or --deny-namespaces for Prometheus custom resources.")
-	flagset.Var(alertmanagerNs, "alertmanager-instance-namespaces", "Namespaces where Alertmanager custom resources and corresponding StatefulSets are watched/created. If set this takes precedence over --namespaces or --deny-namespaces for Alertmanager custom resources.")
-	flagset.Var(alertmanagerConfigNs, "alertmanager-config-namespaces", "Namespaces where AlertmanagerConfig custom resources and corresponding Secrets are watched/created. If set this takes precedence over --namespaces or --deny-namespaces for AlertmanagerConfig custom resources.")
-	flagset.Var(thanosRulerNs, "thanos-ruler-instance-namespaces", "Namespaces where ThanosRuler custom resources and corresponding StatefulSets are watched/created. If set this takes precedence over --namespaces or --deny-namespaces for ThanosRuler custom resources.")
+	fs.Var(cfg.Namespaces.AllowList, "namespaces", "Namespaces to scope the interaction of the Prometheus Operator and the apiserver (allow list). This is mutually exclusive with --deny-namespaces.")
+	fs.Var(cfg.Namespaces.DenyList, "deny-namespaces", "Namespaces not to scope the interaction of the Prometheus Operator (deny list). This is mutually exclusive with --namespaces.")
+	fs.Var(cfg.Namespaces.PrometheusAllowList, "prometheus-instance-namespaces", "Namespaces where Prometheus and PrometheusAgent custom resources and corresponding Secrets, Configmaps and StatefulSets are watched/created. If set this takes precedence over --namespaces or --deny-namespaces for Prometheus custom resources.")
+	fs.Var(cfg.Namespaces.AlertmanagerAllowList, "alertmanager-instance-namespaces", "Namespaces where Alertmanager custom resources and corresponding StatefulSets are watched/created. If set this takes precedence over --namespaces or --deny-namespaces for Alertmanager custom resources.")
+	fs.Var(cfg.Namespaces.AlertmanagerConfigAllowList, "alertmanager-config-namespaces", "Namespaces where AlertmanagerConfig custom resources and corresponding Secrets are watched/created. If set this takes precedence over --namespaces or --deny-namespaces for AlertmanagerConfig custom resources.")
+	fs.Var(cfg.Namespaces.ThanosRulerAllowList, "thanos-ruler-instance-namespaces", "Namespaces where ThanosRuler custom resources and corresponding StatefulSets are watched/created. If set this takes precedence over --namespaces or --deny-namespaces for ThanosRuler custom resources.")

-	flagset.Var(&cfg.Annotations, "annotations", "Annotations to be add to all resources created by the operator")
-	flagset.Var(&cfg.Labels, "labels", "Labels to be add to all resources created by the operator")
+	fs.Var(&cfg.Annotations, "annotations", "Annotations to be add to all resources created by the operator")
+	fs.Var(&cfg.Labels, "labels", "Labels to be add to all resources created by the operator")

-	flagset.StringVar(&cfg.LocalHost, "localhost", "localhost", "EXPERIMENTAL (could be removed in future releases) - Host used to communicate between local services on a pod. Fixes issues where localhost resolves incorrectly.")
-	flagset.StringVar(&cfg.ClusterDomain, "cluster-domain", "", "The domain of the cluster. This is used to generate service FQDNs. If this is not specified, DNS search domain expansion is used instead.")
+	fs.StringVar(&cfg.LocalHost, "localhost", "localhost", "EXPERIMENTAL (could be removed in future releases) - Host used to communicate between local services on a pod. Fixes issues where localhost resolves incorrectly.")
+	fs.StringVar(&cfg.ClusterDomain, "cluster-domain", "", "The domain of the cluster. This is used to generate service FQDNs. If this is not specified, DNS search domain expansion is used instead.")

-	flagset.StringVar(&cfg.LogLevel, "log-level", "info", fmt.Sprintf("Log level to use. Possible values: %s", strings.Join(logging.AvailableLogLevels, ", ")))
-	flagset.StringVar(&cfg.LogFormat, "log-format", "logfmt", fmt.Sprintf("Log format to use. Possible values: %s", strings.Join(logging.AvailableLogFormats, ", ")))
+	fs.Var(&cfg.PromSelector, "prometheus-instance-selector", "Label selector to filter Prometheus and PrometheusAgent Custom Resources to watch.")
+	fs.Var(&cfg.AlertmanagerSelector, "alertmanager-instance-selector", "Label selector to filter Alertmanager Custom Resources to watch.")
+	fs.Var(&cfg.ThanosRulerSelector, "thanos-ruler-instance-selector", "Label selector to filter ThanosRuler Custom Resources to watch.")
+	fs.Var(&cfg.SecretListWatchSelector, "secret-field-selector", "Field selector to filter Secrets to watch")

-	flagset.StringVar(&cfg.PromSelector, "prometheus-instance-selector", "", "Label selector to filter Prometheus and PrometheusAgent Custom Resources to watch.")
-	flagset.StringVar(&cfg.AlertManagerSelector, "alertmanager-instance-selector", "", "Label selector to filter AlertManager Custom Resources to watch.")
-	flagset.StringVar(&cfg.ThanosRulerSelector, "thanos-ruler-instance-selector", "", "Label selector to filter ThanosRuler Custom Resources to watch.")
-	flagset.StringVar(&cfg.SecretListWatchSelector, "secret-field-selector", "", "Field selector to filter Secrets to watch")
+	logging.RegisterFlags(fs, &logConfig)
+	versionutil.RegisterFlags(fs)
+
+	// No need to check for errors because Parse would exit on error.
+	_ = fs.Parse(os.Args[1:])
 }

-func run() int {
-	versionutil.RegisterFlags()
-	// No need to check for errors because Parse would exit on error.
-	_ = flagset.Parse(os.Args[1:])
+func run(fs *flag.FlagSet) int {
+	parseFlags(fs)

 	if versionutil.ShouldPrintVersion() {
 		versionutil.Print(os.Stdout, "prometheus-operator")
 		return 0
 	}

-	logger, err := logging.NewLogger(cfg.LogLevel, cfg.LogFormat)
+	logger, err := logging.NewLogger(logConfig)
 	if err != nil {
 		stdlog.Fatal(err)
 	}
@ -256,41 +175,16 @@ func run() int {
 	level.Info(logger).Log("msg", "Starting Prometheus Operator", "version", version.Info())
 	level.Info(logger).Log("build_context", version.BuildContext())

-	if len(ns) > 0 && len(deniedNs) > 0 {
+	if len(cfg.Namespaces.AllowList) > 0 && len(cfg.Namespaces.DenyList) > 0 {
 		level.Error(logger).Log(
 			"msg", "--namespaces and --deny-namespaces are mutually exclusive, only one should be provided",
-			"namespaces", ns,
-			"deny_namespaces", deniedNs,
+			"namespaces", cfg.Namespaces.AllowList,
+			"deny_namespaces", cfg.Namespaces.DenyList,
 		)
 		return 1
 	}
-
-	cfg.Namespaces.AllowList = ns
-	if len(cfg.Namespaces.AllowList) == 0 {
-		cfg.Namespaces.AllowList[v1.NamespaceAll] = struct{}{}
-	}
-
-	cfg.Namespaces.DenyList = deniedNs
-	cfg.Namespaces.PrometheusAllowList = prometheusNs
-	cfg.Namespaces.AlertmanagerAllowList = alertmanagerNs
-	cfg.Namespaces.AlertmanagerConfigAllowList = alertmanagerConfigNs
-	cfg.Namespaces.ThanosRulerAllowList = thanosRulerNs
-
-	if len(cfg.Namespaces.PrometheusAllowList) == 0 {
-		cfg.Namespaces.PrometheusAllowList = cfg.Namespaces.AllowList
-	}
-
-	if len(cfg.Namespaces.AlertmanagerAllowList) == 0 {
-		cfg.Namespaces.AlertmanagerAllowList = cfg.Namespaces.AllowList
-	}
-
-	if len(cfg.Namespaces.AlertmanagerConfigAllowList) == 0 {
-		cfg.Namespaces.AlertmanagerConfigAllowList = cfg.Namespaces.AllowList
-	}
-
-	if len(cfg.Namespaces.ThanosRulerAllowList) == 0 {
-		cfg.Namespaces.ThanosRulerAllowList = cfg.Namespaces.AllowList
-	}
+	cfg.Namespaces.Finalize()
+	level.Info(logger).Log("msg", "namespaces filtering configuration ", "config", cfg.Namespaces.String())

 	ctx, cancel := context.WithCancel(context.Background())
 	wg, ctx := errgroup.WithContext(ctx)
@ -298,7 +192,7 @@ func run() int {

 	k8sutil.MustRegisterClientGoMetrics(r)

-	restConfig, err := k8sutil.NewClusterConfig(cfg.Host, cfg.TLSInsecure, &cfg.TLSConfig, cfg.ImpersonateUser)
+	restConfig, err := k8sutil.NewClusterConfig(apiServer, tlsClientConfig, impersonateUser)
 	if err != nil {
 		level.Error(logger).Log("msg", "failed to create Kubernetes client configuration", "err", err)
 		cancel()
@ -346,7 +240,7 @@ func run() int {
 		ctx,
 		logger,
 		kclient,
-		namespaces(cfg.Namespaces.AllowList).asSlice(),
+		cfg.Namespaces.AllowList.Slice(),
 		monitoringv1alpha1.SchemeGroupVersion,
 		monitoringv1alpha1.ScrapeConfigName,
 		k8sutil.ResourceAttribute{
@ -373,7 +267,7 @@ func run() int {
 		ctx,
 		logger,
 		kclient,
-		namespaces(cfg.Namespaces.PrometheusAllowList).asSlice(),
+		cfg.Namespaces.PrometheusAllowList.Slice(),
 		monitoringv1alpha1.SchemeGroupVersion,
 		monitoringv1alpha1.PrometheusAgentName,
 		k8sutil.ResourceAttribute{
@ -419,30 +313,11 @@ func run() int {
 		return 1
 	}

+	// Setup the web server.
 	mux := http.NewServeMux()

 	admit := admission.New(log.With(logger, "component", "admissionwebhook"))
 	admit.Register(mux)
-	l, err := net.Listen("tcp", cfg.ListenAddress)
-	if err != nil {
-		level.Error(logger).Log("msg", "listening failed", "address", cfg.ListenAddress, "err", err)
-		cancel()
-		return 1
-	}
-
-	var tlsConfig *tls.Config
-	if serverTLS {
-		if rawTLSCipherSuites != "" {
-			cfg.ServerTLSConfig.CipherSuites = strings.Split(rawTLSCipherSuites, ",")
-		}
-		tlsConfig, err = server.NewTLSConfig(logger, cfg.ServerTLSConfig.CertFile, cfg.ServerTLSConfig.KeyFile,
-			cfg.ServerTLSConfig.ClientCAFile, cfg.ServerTLSConfig.MinVersion, cfg.ServerTLSConfig.CipherSuites)
-		if tlsConfig == nil || err != nil {
-			level.Error(logger).Log("msg", "invalid TLS config", "err", err)
-			cancel()
-			return 1
-		}
-	}

 	r.MustRegister(
 		collectors.NewGoCollector(),
@ -460,6 +335,17 @@ func run() int {
 		w.WriteHeader(http.StatusOK)
 	}))

+	srv, err := server.NewServer(logger, &serverConfig, mux)
+	if err != nil {
+		level.Error(logger).Log("msg", "failed to create web server", "err", err)
+		cancel()
+		return 1
+	}
+
+	// Start the web server.
+	wg.Go(func() error { return srv.Serve(ctx) })
+
+	// Start the controllers.
 	wg.Go(func() error { return po.Run(ctx) })
 	if pao != nil {
 		wg.Go(func() error { return pao.Run(ctx) })
@ -467,68 +353,22 @@ func run() int {
 	wg.Go(func() error { return ao.Run(ctx) })
 	wg.Go(func() error { return to.Run(ctx) })

-	if tlsConfig != nil {
-		r, err := rbacproxytls.NewCertReloader(
-			cfg.ServerTLSConfig.CertFile,
-			cfg.ServerTLSConfig.KeyFile,
-			cfg.ServerTLSConfig.ReloadInterval,
-		)
-		if err != nil {
-			level.Error(logger).Log("msg", "failed to initialize certificate reloader", "err", err)
-			cancel()
-			return 1
-		}
-
-		tlsConfig.GetCertificate = r.GetCertificate
-
-		wg.Go(func() error {
-			for {
-				// r.Watch will wait ReloadInterval, so this is not
-				// a hot loop
-				if err := r.Watch(ctx); err != nil {
-					level.Warn(logger).Log("msg", "error watching certificate reloader",
-						"err", err)
-				} else {
-					return nil
-				}
-			}
-		})
-	}
-	srv := &http.Server{
-		Handler:           mux,
-		TLSConfig:         tlsConfig,
-		ReadHeaderTimeout: 30 * time.Second,
-		ReadTimeout:       30 * time.Second,
-		// use flags on standard logger to align with base logger and get consistent parsed fields form adapter:
-		// use shortfile flag to get proper 'caller' field (avoid being wrongly parsed/extracted from message)
-		// and no datetime related flag to keep 'ts' field from base logger (with controlled format)
-		ErrorLog: stdlog.New(log.NewStdlibAdapter(logger), "", stdlog.Lshortfile),
-	}
-	if !enableHTTP2 {
-		srv.TLSNextProto = make(map[string]func(*http.Server, *tls.Conn, http.Handler))
-	}
-	if srv.TLSConfig == nil {
-		wg.Go(serve(srv, l, logger))
-	} else {
-		wg.Go(serveTLS(srv, l, logger))
-	}
-
 	term := make(chan os.Signal, 1)
 	signal.Notify(term, os.Interrupt, syscall.SIGTERM)

 	select {
 	case <-term:
-		level.Info(logger).Log("msg", "Received SIGTERM, exiting gracefully...")
+		level.Info(logger).Log("msg", "received SIGTERM, exiting gracefully...")
 	case <-ctx.Done():
 	}

 	if err := srv.Shutdown(ctx); err != nil {
-		level.Warn(logger).Log("msg", "Server shutdown error", "err", err)
+		level.Warn(logger).Log("msg", "server shutdown error", "err", err)
 	}

 	cancel()
 	if err := wg.Wait(); err != nil {
-		level.Warn(logger).Log("msg", "Unhandled error received. Exiting...", "err", err)
+		level.Warn(logger).Log("msg", "unhandled error received. Exiting...", "err", err)
 		return 1
 	}

@ -536,5 +376,5 @@ func run() int {
 }

 func main() {
-	os.Exit(run())
+	os.Exit(run(flag.CommandLine))
 }
--- a/cmd/operator/main_test.go
+++ b/cmd/operator/main_test.go
@ -1,46 +0,0 @@
-// Copyright 2020 The prometheus-operator 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 (
-	"strings"
-	"testing"
-)
-
-func TestNamespacesType(t *testing.T) {
-	var ns namespaces
-	if ns.String() != "" {
-		t.Errorf("incorrect string value for nil namespaces, want: empty string, got %v", ns.String())
-	}
-
-	val := "a,b,c"
-	err := ns.Set(val)
-	if err == nil {
-		t.Error("expected error for nil namespaces")
-	}
-
-	ns = namespaces{}
-	ns.Set(val)
-	if len(ns) != 3 {
-		t.Errorf("incorrect length of namespaces, want: %v, got: %v", 3, len(ns))
-	}
-
-	for _, next := range strings.Split(val, ",") {
-		if _, ok := ns[next]; !ok {
-			t.Errorf("namespace not in map, want: %v, not in map: %v", next, map[string]struct{}(ns))
-		}
-	}
-
-}
--- a/cmd/po-rule-migration/main.go
+++ b/cmd/po-rule-migration/main.go
@ -34,11 +34,14 @@ import (
 )

 func main() {
-	versionutil.RegisterFlags()
+	fs := flag.CommandLine
+	versionutil.RegisterFlags(fs)

 	var ruleConfigMapName = flag.String("rule-config-map", "", "path to rule ConfigMap")
 	var ruleCRDSDestination = flag.String("rule-crds-destination", "", "destination new crds should be created in")
-	flag.Parse()
+
+	// No need to check for errors because Parse would exit on error.
+	_ = fs.Parse(os.Args[1:])

 	if versionutil.ShouldPrintVersion() {
 		versionutil.Print(os.Stdout, "po-rule-migration")
--- a/cmd/prometheus-config-reloader/main.go
+++ b/cmd/prometheus-config-reloader/main.go
@ -82,15 +82,16 @@ func main() {
 		"[EXPERIMENTAL] Path to configuration file that can enable TLS or authentication. See: https://prometheus.io/docs/prometheus/latest/configuration/https/",
 	).Default("").String()

-	logFormat := app.Flag(
+	var logConfig logging.Config
+	app.Flag(
 		"log-format",
 		fmt.Sprintf("log format to use. Possible values: %s", strings.Join(logging.AvailableLogFormats, ", "))).
-		Default(logging.FormatLogFmt).String()
+		Default(logging.FormatLogFmt).StringVar(&logConfig.Format)

-	logLevel := app.Flag(
+	app.Flag(
 		"log-level",
 		fmt.Sprintf("log level to use. Possible values: %s", strings.Join(logging.AvailableLogLevels, ", "))).
-		Default(logging.LevelInfo).String()
+		Default(logging.LevelInfo).StringVar(&logConfig.Level)

 	reloadURL := app.Flag("reload-url", "reload URL to trigger Prometheus reload on").
 		Default("http://127.0.0.1:9090/-/reload").URL()
@ -107,7 +108,7 @@ func main() {
 		os.Exit(0)
 	}

-	logger, err := logging.NewLogger(*logLevel, *logFormat)
+	logger, err := logging.NewLogger(logConfig)
 	if err != nil {
 		stdlog.Fatal(err)
 	}
--- a/internal/log/log.go
+++ b/internal/log/log.go
@ -16,6 +16,7 @@
 package log

 import (
+	"flag"
 	"fmt"
 	"os"
 	"strings"
@ -39,9 +40,19 @@ const (
 	FormatJSON   = "json"
 )

+type Config struct {
+	Level  string
+	Format string
+}
+
+func RegisterFlags(fs *flag.FlagSet, c *Config) {
+	fs.StringVar(&c.Level, "log-level", "info", fmt.Sprintf("Log level to use. Possible values: %s", strings.Join(AvailableLogLevels, ", ")))
+	fs.StringVar(&c.Format, "log-format", "logfmt", fmt.Sprintf("Log format to use. Possible values: %s", strings.Join(AvailableLogFormats, ", ")))
+}
+
 // NewLogger returns a log.Logger that prints in the provided format at the
 // provided level with a UTC timestamp and the caller of the log entry.
-func NewLogger(level string, format string) (log.Logger, error) {
+func NewLogger(c Config) (log.Logger, error) {
 	var (
 		logger    log.Logger
 		lvlOption loglevel.Option
@ -49,7 +60,7 @@ func NewLogger(level string, format string) (log.Logger, error) {

 	// For log levels other than debug, the klog verbosity level is 0.
 	klogv2.ClampLevel(0)
-	switch strings.ToLower(level) {
+	switch strings.ToLower(c.Level) {
 	case LevelAll:
 		lvlOption = loglevel.AllowAll()
 	case LevelDebug:
@ -66,16 +77,16 @@ func NewLogger(level string, format string) (log.Logger, error) {
 	case LevelNone:
 		lvlOption = loglevel.AllowNone()
 	default:
-		return nil, fmt.Errorf("log log_level %s unknown, %v are possible values", level, AvailableLogLevels)
+		return nil, fmt.Errorf("log log_level %s unknown, %v are possible values", c.Level, AvailableLogLevels)
 	}

-	switch format {
+	switch c.Format {
 	case FormatLogFmt:
 		logger = log.NewLogfmtLogger(log.NewSyncWriter(os.Stdout))
 	case FormatJSON:
 		logger = log.NewJSONLogger(log.NewSyncWriter(os.Stdout))
 	default:
-		return nil, fmt.Errorf("log format %s unknown, %v are possible values", format, AvailableLogFormats)
+		return nil, fmt.Errorf("log format %s unknown, %v are possible values", c.Format, AvailableLogFormats)
 	}

 	logger = loglevel.NewFilter(logger, lvlOption)
--- a/pkg/alertmanager/operator.go
+++ b/pkg/alertmanager/operator.go
@ -35,7 +35,6 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/fields"
 	"k8s.io/apimachinery/pkg/labels"
-	"k8s.io/apimachinery/pkg/version"
 	"k8s.io/client-go/kubernetes"
 	authv1 "k8s.io/client-go/kubernetes/typed/authorization/v1"
 	"k8s.io/client-go/metadata"
@ -68,8 +67,20 @@ var (
 	}
 )

-// Operator manages life cycle of Alertmanager deployments and
-// monitoring configurations.
+// Config defines the operator's parameters for the Alertmanager controller.
+// Whenever the value of one of these parameters is changed, it triggers an
+// update of the managed statefulsets.
+type Config struct {
+	LocalHost                    string
+	ClusterDomain                string
+	ReloaderConfig               operator.ContainerConfig
+	AlertmanagerDefaultBaseImage string
+	Annotations                  operator.Map
+	Labels                       operator.Map
+}
+
+// Operator manages the lifecycle of the Alertmanager statefulsets and their
+// configurations.
 type Operator struct {
 	kclient    kubernetes.Interface
 	mdClient   metadata.Interface
@ -97,19 +108,6 @@ type Operator struct {
 	config Config
 }

-type Config struct {
-	KubernetesVersion            version.Info
-	LocalHost                    string
-	ClusterDomain                string
-	ReloaderConfig               operator.ContainerConfig
-	AlertmanagerDefaultBaseImage string
-	Namespaces                   operator.Namespaces
-	Annotations                  operator.Map
-	Labels                       operator.Map
-	AlertManagerSelector         string
-	SecretListWatchSelector      string
-}
-
 // New creates a new controller.
 func New(ctx context.Context, restConfig *rest.Config, c operator.Config, logger log.Logger, r prometheus.Registerer, canReadStorageClass bool) (*Operator, error) {
 	client, err := kubernetes.NewForConfig(restConfig)
@ -142,17 +140,14 @@ func New(ctx context.Context, restConfig *rest.Config, c operator.Config, logger
 		metrics:             operator.NewMetrics(r),
 		reconciliations:     &operator.ReconciliationTracker{},
 		canReadStorageClass: canReadStorageClass,
+
 		config: Config{
-			KubernetesVersion:            c.KubernetesVersion,
 			LocalHost:                    c.LocalHost,
 			ClusterDomain:                c.ClusterDomain,
 			ReloaderConfig:               c.ReloaderConfig,
 			AlertmanagerDefaultBaseImage: c.AlertmanagerDefaultBaseImage,
-			Namespaces:                   c.Namespaces,
 			Annotations:                  c.Annotations,
 			Labels:                       c.Labels,
-			AlertManagerSelector:         c.AlertManagerSelector,
-			SecretListWatchSelector:      c.SecretListWatchSelector,
 		},
 	}

@ -164,30 +159,25 @@ func New(ctx context.Context, restConfig *rest.Config, c operator.Config, logger
 		r,
 	)

-	if err := o.bootstrap(ctx); err != nil {
+	if err := o.bootstrap(ctx, c); err != nil {
 		return nil, err
 	}

 	return o, nil
 }

-func (c *Operator) bootstrap(ctx context.Context) error {
-	var err error
-
-	if _, err := labels.Parse(c.config.AlertManagerSelector); err != nil {
-		return fmt.Errorf("can not parse alertmanager selector value: %w", err)
-	}
-
+func (c *Operator) bootstrap(ctx context.Context, config operator.Config) error {
 	c.metrics.MustRegister(c.reconciliations)

+	var err error
 	c.alrtInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			c.config.Namespaces.AlertmanagerAllowList,
-			c.config.Namespaces.DenyList,
+			config.Namespaces.AlertmanagerAllowList,
+			config.Namespaces.DenyList,
 			c.mclient,
 			resyncPeriod,
 			func(options *metav1.ListOptions) {
-				options.LabelSelector = c.config.AlertManagerSelector
+				options.LabelSelector = config.AlertmanagerSelector.String()
 			},
 		),
 		monitoringv1.SchemeGroupVersion.WithResource(monitoringv1.AlertmanagerName),
@ -204,8 +194,8 @@ func (c *Operator) bootstrap(ctx context.Context) error {

 	c.alrtCfgInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			c.config.Namespaces.AlertmanagerConfigAllowList,
-			c.config.Namespaces.DenyList,
+			config.Namespaces.AlertmanagerConfigAllowList,
+			config.Namespaces.DenyList,
 			c.mclient,
 			resyncPeriod,
 			nil,
@ -216,19 +206,14 @@ func (c *Operator) bootstrap(ctx context.Context) error {
 		return fmt.Errorf("error creating alertmanagerconfig informers: %w", err)
 	}

-	secretListWatchSelector, err := fields.ParseSelector(c.config.SecretListWatchSelector)
-	if err != nil {
-		return fmt.Errorf("can not parse secrets selector value: %w", err)
-	}
-
 	c.secrInfs, err = informers.NewInformersForResourceWithTransform(
 		informers.NewMetadataInformerFactory(
-			c.config.Namespaces.AlertmanagerConfigAllowList,
-			c.config.Namespaces.DenyList,
+			config.Namespaces.AlertmanagerConfigAllowList,
+			config.Namespaces.DenyList,
 			c.mdClient,
 			resyncPeriod,
 			func(options *metav1.ListOptions) {
-				options.FieldSelector = secretListWatchSelector.String()
+				options.FieldSelector = config.SecretListWatchSelector.String()
 			},
 		),
 		v1.SchemeGroupVersion.WithResource("secrets"),
@ -240,8 +225,8 @@ func (c *Operator) bootstrap(ctx context.Context) error {

 	c.ssetInfs, err = informers.NewInformersForResource(
 		informers.NewKubeInformerFactories(
-			c.config.Namespaces.AlertmanagerAllowList,
-			c.config.Namespaces.DenyList,
+			config.Namespaces.AlertmanagerAllowList,
+			config.Namespaces.DenyList,
 			c.kclient,
 			resyncPeriod,
 			nil,
@ -256,11 +241,11 @@ func (c *Operator) bootstrap(ctx context.Context) error {
 		lw, privileged, err := listwatch.NewNamespaceListWatchFromClient(
 			ctx,
 			o.logger,
-			o.config.KubernetesVersion,
+			config.KubernetesVersion,
 			o.kclient.CoreV1(),
 			o.ssarClient,
 			allowList,
-			o.config.Namespaces.DenyList,
+			config.Namespaces.DenyList,
 		)
 		if err != nil {
 			return nil, fmt.Errorf("failed to create namespace lister/watcher: %w", err)
@ -274,15 +259,15 @@ func (c *Operator) bootstrap(ctx context.Context) error {
 			cache.Indexers{},
 		), nil
 	}
-	c.nsAlrtCfgInf, err = newNamespaceInformer(c, c.config.Namespaces.AlertmanagerConfigAllowList)
+	c.nsAlrtCfgInf, err = newNamespaceInformer(c, config.Namespaces.AlertmanagerConfigAllowList)
 	if err != nil {
 		return err
 	}

-	if listwatch.IdenticalNamespaces(c.config.Namespaces.AlertmanagerConfigAllowList, c.config.Namespaces.AlertmanagerAllowList) {
+	if listwatch.IdenticalNamespaces(config.Namespaces.AlertmanagerConfigAllowList, config.Namespaces.AlertmanagerAllowList) {
 		c.nsAlrtInf = c.nsAlrtCfgInf
 	} else {
-		c.nsAlrtInf, err = newNamespaceInformer(c, c.config.Namespaces.AlertmanagerAllowList)
+		c.nsAlrtInf, err = newNamespaceInformer(c, config.Namespaces.AlertmanagerAllowList)
 		if err != nil {
 			return err
 		}
@ -733,7 +718,7 @@ func (c *Operator) sync(ctx context.Context, key string) error {
 			failMsg[i] = cause.Message
 		}

-		level.Info(logger).Log("msg", "recreating AlertManager StatefulSet because the update operation wasn't possible", "reason", strings.Join(failMsg, ", "))
+		level.Info(logger).Log("msg", "recreating Alertmanager StatefulSet because the update operation wasn't possible", "reason", strings.Join(failMsg, ", "))
 		propagationPolicy := metav1.DeletePropagationForeground
 		if err := ssetClient.Delete(ctx, sset.GetName(), metav1.DeleteOptions{PropagationPolicy: &propagationPolicy}); err != nil {
 			return fmt.Errorf("failed to delete StatefulSet to avoid forbidden action: %w", err)
@ -1171,14 +1156,14 @@ func checkHTTPConfig(hc *monitoringv1alpha1.HTTPConfig, amVersion semver.Version

 	if hc.Authorization != nil && !amVersion.GTE(semver.MustParse("0.22.0")) {
 		return fmt.Errorf(
-			"'authorization' config set in 'httpConfig' but supported in AlertManager >= 0.22.0 only - current %s",
+			"'authorization' config set in 'httpConfig' but supported in Alertmanager >= 0.22.0 only - current %s",
 			amVersion.String(),
 		)
 	}

 	if hc.OAuth2 != nil && !amVersion.GTE(semver.MustParse("0.22.0")) {
 		return fmt.Errorf(
-			"'oauth2' config set in 'httpConfig' but supported in AlertManager >= 0.22.0 only - current %s",
+			"'oauth2' config set in 'httpConfig' but supported in Alertmanager >= 0.22.0 only - current %s",
 			amVersion.String(),
 		)
 	}
@ -1329,7 +1314,7 @@ func checkOpsGenieResponder(opsgenieResponder []monitoringv1alpha1.OpsGenieConfi
 	lessThanV0_24 := amVersion.LT(semver.MustParse("0.24.0"))
 	for _, resp := range opsgenieResponder {
 		if resp.Type == "teams" && lessThanV0_24 {
-			return fmt.Errorf("'teams' set in 'opsgenieResponder' but supported in AlertManager >= 0.24.0 only")
+			return fmt.Errorf("'teams' set in 'opsgenieResponder' but supported in Alertmanager >= 0.24.0 only")
 		}
 	}
 	return nil
--- a/pkg/alertmanager/operator_test.go
+++ b/pkg/alertmanager/operator_test.go
@ -1239,7 +1239,11 @@ func TestProvisionAlertmanagerConfiguration(t *testing.T) {
 				ssarClient: &alwaysAllowed{},
 				logger:     level.NewFilter(log.NewLogfmtLogger(os.Stdout), level.AllowInfo()),
 				metrics:    operator.NewMetrics(prometheus.NewRegistry()),
-				config: Config{
+			}
+
+			err := o.bootstrap(
+				context.Background(),
+				operator.Config{
 					Namespaces: operator.Namespaces{
 						AlertmanagerConfigAllowList: map[string]struct{}{
 							v1.NamespaceAll: {},
@ -1249,9 +1253,7 @@ func TestProvisionAlertmanagerConfiguration(t *testing.T) {
 						},
 					},
 				},
-			}
-
-			err := o.bootstrap(context.Background())
+			)
 			if err != nil {
 				t.Fatalf("unexpected error: %v", err)
 			}
--- a/pkg/k8sutil/k8sutil.go
+++ b/pkg/k8sutil/k8sutil.go
@ -79,7 +79,7 @@ func PodRunningAndReady(pod v1.Pod) (bool, error) {
 	return false, nil
 }

-func NewClusterConfig(host string, tlsInsecure bool, tlsConfig *rest.TLSClientConfig, asUser string) (*rest.Config, error) {
+func NewClusterConfig(host string, tlsConfig rest.TLSClientConfig, asUser string) (*rest.Config, error) {
 	var cfg *rest.Config
 	var err error

@ -104,8 +104,7 @@ func NewClusterConfig(host string, tlsInsecure bool, tlsConfig *rest.TLSClientCo
 				return nil, fmt.Errorf("error parsing host url %s: %w", host, err)
 			}
 			if hostURL.Scheme == "https" {
-				cfg.TLSClientConfig = *tlsConfig
-				cfg.Insecure = tlsInsecure
+				cfg.TLSClientConfig = tlsConfig
 			}
 		}
 	}
--- a/pkg/operator/config.go
+++ b/pkg/operator/config.go
@ -16,48 +16,56 @@ package operator

 import (
 	"fmt"
+	"slices"
 	"sort"
 	"strings"

 	"golang.org/x/exp/maps"
 	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
+	"k8s.io/apimachinery/pkg/fields"
+	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/version"
-	"k8s.io/client-go/rest"
-
-	"github.com/prometheus-operator/prometheus-operator/pkg/server"
 )

 // Config defines configuration parameters for the Operator.
 type Config struct {
-	// Kubernetes client configuration.
-	Host              string
-	TLSInsecure       bool
-	TLSConfig         rest.TLSClientConfig
-	ImpersonateUser   string
+	// Version reported by the Kubernetes API.
 	KubernetesVersion version.Info

-	ClusterDomain                string
-	KubeletObject                string
-	KubeletSelector              string
-	ListenAddress                string
-	ServerTLSConfig              server.TLSServerConfig
-	ReloaderConfig               ContainerConfig
+	// Parameters for the kubelet endpoint controller.
+	KubeletObject   string
+	KubeletSelector LabelSelector
+
+	// Cluster domain for Kubernetes services managed by the operator.
+	ClusterDomain string
+
+	// Global configuration for the reloader config sidecar.
+	ReloaderConfig ContainerConfig
+
+	// Base container images for operands.
 	AlertmanagerDefaultBaseImage string
 	PrometheusDefaultBaseImage   string
 	ThanosDefaultBaseImage       string
-	Namespaces                   Namespaces
-	Annotations                  Map
-	Labels                       Map
-	LocalHost                    string
-	LogLevel                     string
-	LogFormat                    string
-	PromSelector                 string
-	AlertManagerSelector         string
-	ThanosRulerSelector          string
-	SecretListWatchSelector      string
+
+	// Allow and deny lists for namespace watchers.
+	Namespaces Namespaces
+
+	// Metadata applied to all resources managed by the operator.
+	Annotations Map
+	Labels      Map
+
+	// Custom name to use for "localhost".
+	LocalHost string
+
+	// Label and field selectors for resource watchers.
+	PromSelector            LabelSelector
+	AlertmanagerSelector    LabelSelector
+	ThanosRulerSelector     LabelSelector
+	SecretListWatchSelector FieldSelector
 }

+// DefaultConfig returns a default operator configuration.
 func DefaultConfig(cpu, memory string) Config {
 	return Config{
 		ReloaderConfig: ContainerConfig{
@ -66,6 +74,14 @@ func DefaultConfig(cpu, memory string) Config {
 			MemoryRequests: Quantity{q: resource.MustParse(memory)},
 			MemoryLimits:   Quantity{q: resource.MustParse(memory)},
 		},
+		Namespaces: Namespaces{
+			AllowList:                   StringSet{},
+			DenyList:                    StringSet{},
+			PrometheusAllowList:         StringSet{},
+			AlertmanagerAllowList:       StringSet{},
+			AlertmanagerConfigAllowList: StringSet{},
+			ThanosRulerAllowList:        StringSet{},
+		},
 	}
 }

@ -196,8 +212,126 @@ func (m *Map) SortedKeys() []string {
 }

 type Namespaces struct {
-	// Allow list/deny list for common custom resources.
-	AllowList, DenyList map[string]struct{}
-	// Allow list for prometheus/alertmanager custom resources.
-	PrometheusAllowList, AlertmanagerAllowList, AlertmanagerConfigAllowList, ThanosRulerAllowList map[string]struct{}
+	// Allow list for common custom resources.
+	AllowList StringSet
+	// Deny list for common custom resources.
+	DenyList StringSet
+	// Allow list for Prometheus custom resources.
+	PrometheusAllowList StringSet
+	// Allow list for Alertmanager custom resources.
+	AlertmanagerAllowList StringSet
+	// Allow list for AlertmanagerConfig custom resources.
+	AlertmanagerConfigAllowList StringSet
+	// Allow list for ThanosRuler custom resources.
+	ThanosRulerAllowList StringSet
+}
+
+func (n *Namespaces) String() string {
+	return fmt.Sprintf("{allow_list=%q,deny_list=%q,prometheus_allow_list=%q,alertmanager_allow_list=%q,alertmanagerconfig_allow_list=%q,thanosruler_allow_list=%q}",
+		n.AllowList,
+		n.DenyList,
+		n.PrometheusAllowList,
+		n.AlertmanagerAllowList,
+		n.AlertmanagerConfigAllowList,
+		n.ThanosRulerAllowList,
+	)
+}
+
+func (n *Namespaces) Finalize() {
+	if len(n.AllowList) == 0 {
+		n.AllowList.Insert(v1.NamespaceAll)
+	}
+
+	if len(n.PrometheusAllowList) == 0 {
+		n.PrometheusAllowList = n.AllowList
+	}
+
+	if len(n.AlertmanagerAllowList) == 0 {
+		n.AlertmanagerAllowList = n.AllowList
+	}
+
+	if len(n.AlertmanagerConfigAllowList) == 0 {
+		n.AlertmanagerConfigAllowList = n.AllowList
+	}
+
+	if len(n.ThanosRulerAllowList) == 0 {
+		n.ThanosRulerAllowList = n.AllowList
+	}
+}
+
+type LabelSelector string
+
+// String implements the flag.Value interface
+func (ls *LabelSelector) String() string {
+	if ls == nil {
+		return ""
+	}
+
+	return string(*ls)
+}
+
+// Set implements the flag.Value interface.
+func (ls *LabelSelector) Set(value string) error {
+	if _, err := labels.Parse(value); err != nil {
+		return err
+	}
+
+	*ls = LabelSelector(value)
+	return nil
+}
+
+type FieldSelector string
+
+// String implements the flag.Value interface
+func (fs *FieldSelector) String() string {
+	if fs == nil {
+		return ""
+	}
+
+	return string(*fs)
+}
+
+// Set implements the flag.Value interface.
+func (fs *FieldSelector) Set(value string) error {
+	if _, err := fields.ParseSelector(value); err != nil {
+		return err
+	}
+
+	*fs = FieldSelector(value)
+	return nil
+}
+
+// StringSet represents a list of comma-separated strings.
+type StringSet map[string]struct{}
+
+// Set implements the flag.Value interface.
+func (s StringSet) Set(value string) error {
+	if s == nil {
+		return fmt.Errorf("expected StringSet variable to be initialized")
+	}
+
+	for _, v := range strings.Split(value, ",") {
+		s[v] = struct{}{}
+	}
+
+	return nil
+}
+
+// String implements the flag.Value interface.
+func (s StringSet) String() string {
+	return strings.Join(s.Slice(), ",")
+}
+
+func (s StringSet) Insert(value string) {
+	s[value] = struct{}{}
+}
+
+func (s StringSet) Slice() []string {
+	ss := make([]string, 0, len(s))
+	for k := range s {
+		ss = append(ss, k)
+	}
+
+	slices.Sort(ss)
+	return ss
 }
--- a/pkg/operator/config_test.go
+++ b/pkg/operator/config_test.go
@ -34,3 +34,79 @@ func TestMap(t *testing.T) {

 	require.Equal(t, map[string]string{"foo": "bar", "foo2": "bar2", "foo3": "bar3"}, m.Merge(map[string]string{"foo": "xxx", "foo3": "bar3"}))
 }
+
+func TestFieldSelector(t *testing.T) {
+	for _, tc := range []struct {
+		value string
+		fail  bool
+	}{
+		{
+			value: "",
+		},
+		{
+			value: "foo = bar",
+		},
+		{
+			value: "foo",
+			fail:  true,
+		},
+	} {
+		t.Run(tc.value, func(t *testing.T) {
+			fs := new(FieldSelector)
+
+			err := fs.Set(tc.value)
+			if tc.fail {
+				require.Error(t, err)
+				return
+			}
+
+			require.NoError(t, err)
+		})
+	}
+}
+
+func TestLabelSelector(t *testing.T) {
+	for _, tc := range []struct {
+		value string
+		fail  bool
+	}{
+		{
+			value: "",
+		},
+		{
+			value: "foo in (bar)",
+		},
+		{
+			value: "foo in",
+			fail:  true,
+		},
+	} {
+		t.Run(tc.value, func(t *testing.T) {
+			ls := new(LabelSelector)
+
+			err := ls.Set(tc.value)
+			if tc.fail {
+				require.Error(t, err)
+				return
+			}
+
+			require.NoError(t, err)
+		})
+	}
+}
+
+func TestStringSet(t *testing.T) {
+	var s StringSet
+
+	require.Error(t, s.Set("a,b,c"))
+
+	s = StringSet{}
+
+	require.NoError(t, s.Set("a,b,c"))
+	require.Equal(t, len(s), 3)
+	require.Equal(t, s.String(), "a,b,c")
+	for _, k := range []string{"a", "b", "c"} {
+		_, found := s[k]
+		require.True(t, found)
+	}
+}
--- a/pkg/prometheus/agent/operator.go
+++ b/pkg/prometheus/agent/operator.go
@ -79,7 +79,7 @@ type Operator struct {
 	metrics         *operator.Metrics
 	reconciliations *operator.ReconciliationTracker

-	config                 operator.Config
+	config                 prompkg.Config
 	endpointSliceSupported bool
 	scrapeConfigSupported  bool
 	canReadStorageClass    bool
@ -88,7 +88,7 @@ type Operator struct {
 }

 // New creates a new controller.
-func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, logger log.Logger, r prometheus.Registerer, scrapeConfigSupported bool, canReadStorageClass bool) (*Operator, error) {
+func New(ctx context.Context, restConfig *rest.Config, c operator.Config, logger log.Logger, r prometheus.Registerer, scrapeConfigSupported bool, canReadStorageClass bool) (*Operator, error) {
 	client, err := kubernetes.NewForConfig(restConfig)
 	if err != nil {
 		return nil, fmt.Errorf("instantiating kubernetes client failed: %w", err)
@ -104,49 +104,47 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("instantiating monitoring client failed: %w", err)
 	}

-	if _, err := labels.Parse(conf.PromSelector); err != nil {
-		return nil, fmt.Errorf("can not parse prometheus-agent selector value: %w", err)
-	}
-
-	secretListWatchSelector, err := fields.ParseSelector(conf.SecretListWatchSelector)
-	if err != nil {
-		return nil, fmt.Errorf("can not parse secrets selector value: %w", err)
-	}
-
 	// All the metrics exposed by the controller get the controller="prometheus-agent" label.
 	r = prometheus.WrapRegistererWith(prometheus.Labels{"controller": "prometheus-agent"}, r)

-	c := &Operator{
-		kclient:               client,
-		mdClient:              mdClient,
-		mclient:               mclient,
-		logger:                logger,
-		config:                conf,
+	o := &Operator{
+		kclient:  client,
+		mdClient: mdClient,
+		mclient:  mclient,
+		logger:   logger,
+		config: prompkg.Config{
+			LocalHost:                  c.LocalHost,
+			ReloaderConfig:             c.ReloaderConfig,
+			PrometheusDefaultBaseImage: c.PrometheusDefaultBaseImage,
+			ThanosDefaultBaseImage:     c.ThanosDefaultBaseImage,
+			Annotations:                c.Annotations,
+			Labels:                     c.Labels,
+		},
 		metrics:               operator.NewMetrics(r),
 		reconciliations:       &operator.ReconciliationTracker{},
 		scrapeConfigSupported: scrapeConfigSupported,
 		canReadStorageClass:   canReadStorageClass,
 	}
-	c.metrics.MustRegister(
-		c.reconciliations,
+	o.metrics.MustRegister(
+		o.reconciliations,
 	)

-	c.rr = operator.NewResourceReconciler(
-		c.logger,
-		c,
-		c.metrics,
+	o.rr = operator.NewResourceReconciler(
+		o.logger,
+		o,
+		o.metrics,
 		monitoringv1alpha1.PrometheusAgentsKind,
 		r,
 	)

-	c.promInfs, err = informers.NewInformersForResource(
+	o.promInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			c.config.Namespaces.PrometheusAllowList,
-			c.config.Namespaces.DenyList,
+			c.Namespaces.PrometheusAllowList,
+			c.Namespaces.DenyList,
 			mclient,
 			resyncPeriod,
 			func(options *metav1.ListOptions) {
-				options.LabelSelector = c.config.PromSelector
+				options.LabelSelector = c.PromSelector.String()
 			},
 		),
 		monitoringv1alpha1.SchemeGroupVersion.WithResource(monitoringv1alpha1.PrometheusAgentName),
@ -156,16 +154,16 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 	}

 	var promStores []cache.Store
-	for _, informer := range c.promInfs.GetInformers() {
+	for _, informer := range o.promInfs.GetInformers() {
 		promStores = append(promStores, informer.Informer().GetStore())
 	}

-	c.metrics.MustRegister(prompkg.NewCollectorForStores(promStores...))
+	o.metrics.MustRegister(prompkg.NewCollectorForStores(promStores...))

-	c.smonInfs, err = informers.NewInformersForResource(
+	o.smonInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			c.config.Namespaces.AllowList,
-			c.config.Namespaces.DenyList,
+			c.Namespaces.AllowList,
+			c.Namespaces.DenyList,
 			mclient,
 			resyncPeriod,
 			nil,
@ -176,10 +174,10 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("error creating servicemonitor informers: %w", err)
 	}

-	c.pmonInfs, err = informers.NewInformersForResource(
+	o.pmonInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			c.config.Namespaces.AllowList,
-			c.config.Namespaces.DenyList,
+			c.Namespaces.AllowList,
+			c.Namespaces.DenyList,
 			mclient,
 			resyncPeriod,
 			nil,
@ -190,10 +188,10 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("error creating podmonitor informers: %w", err)
 	}

-	c.probeInfs, err = informers.NewInformersForResource(
+	o.probeInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			c.config.Namespaces.AllowList,
-			c.config.Namespaces.DenyList,
+			c.Namespaces.AllowList,
+			c.Namespaces.DenyList,
 			mclient,
 			resyncPeriod,
 			nil,
@ -204,11 +202,11 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("error creating probe informers: %w", err)
 	}

-	if c.scrapeConfigSupported {
-		c.sconInfs, err = informers.NewInformersForResource(
+	if o.scrapeConfigSupported {
+		o.sconInfs, err = informers.NewInformersForResource(
 			informers.NewMonitoringInformerFactories(
-				c.config.Namespaces.AllowList,
-				c.config.Namespaces.DenyList,
+				c.Namespaces.AllowList,
+				c.Namespaces.DenyList,
 				mclient,
 				resyncPeriod,
 				nil,
@ -220,11 +218,11 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		}
 	}

-	c.cmapInfs, err = informers.NewInformersForResourceWithTransform(
+	o.cmapInfs, err = informers.NewInformersForResourceWithTransform(
 		informers.NewMetadataInformerFactory(
-			c.config.Namespaces.PrometheusAllowList,
-			c.config.Namespaces.DenyList,
-			c.mdClient,
+			c.Namespaces.PrometheusAllowList,
+			c.Namespaces.DenyList,
+			o.mdClient,
 			resyncPeriod,
 			func(options *metav1.ListOptions) {
 				options.LabelSelector = prompkg.LabelPrometheusName
@ -237,14 +235,14 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("error creating configmap informers: %w", err)
 	}

-	c.secrInfs, err = informers.NewInformersForResourceWithTransform(
+	o.secrInfs, err = informers.NewInformersForResourceWithTransform(
 		informers.NewMetadataInformerFactory(
-			c.config.Namespaces.PrometheusAllowList,
-			c.config.Namespaces.DenyList,
-			c.mdClient,
+			c.Namespaces.PrometheusAllowList,
+			c.Namespaces.DenyList,
+			o.mdClient,
 			resyncPeriod,
 			func(options *metav1.ListOptions) {
-				options.FieldSelector = secretListWatchSelector.String()
+				options.FieldSelector = c.SecretListWatchSelector.String()
 			},
 		),
 		v1.SchemeGroupVersion.WithResource(string(v1.ResourceSecrets)),
@ -254,11 +252,11 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("error creating secrets informers: %w", err)
 	}

-	c.ssetInfs, err = informers.NewInformersForResource(
+	o.ssetInfs, err = informers.NewInformersForResource(
 		informers.NewKubeInformerFactories(
-			c.config.Namespaces.PrometheusAllowList,
-			c.config.Namespaces.DenyList,
-			c.kclient,
+			c.Namespaces.PrometheusAllowList,
+			c.Namespaces.DenyList,
+			o.kclient,
 			resyncPeriod,
 			nil,
 		),
@ -272,55 +270,55 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		lw, privileged, err := listwatch.NewNamespaceListWatchFromClient(
 			ctx,
 			o.logger,
-			o.config.KubernetesVersion,
+			c.KubernetesVersion,
 			o.kclient.CoreV1(),
 			o.kclient.AuthorizationV1().SelfSubjectAccessReviews(),
 			allowList,
-			o.config.Namespaces.DenyList,
+			c.Namespaces.DenyList,
 		)
 		if err != nil {
 			return nil, err
 		}

-		level.Debug(c.logger).Log("msg", "creating namespace informer", "privileged", privileged)
+		level.Debug(o.logger).Log("msg", "creating namespace informer", "privileged", privileged)
 		return cache.NewSharedIndexInformer(
 			o.metrics.NewInstrumentedListerWatcher(lw),
 			&v1.Namespace{}, resyncPeriod, cache.Indexers{},
 		), nil
 	}

-	c.nsMonInf, err = newNamespaceInformer(c, c.config.Namespaces.AllowList)
+	o.nsMonInf, err = newNamespaceInformer(o, c.Namespaces.AllowList)
 	if err != nil {
 		return nil, err
 	}

-	if listwatch.IdenticalNamespaces(c.config.Namespaces.AllowList, c.config.Namespaces.PrometheusAllowList) {
-		c.nsPromInf = c.nsMonInf
+	if listwatch.IdenticalNamespaces(c.Namespaces.AllowList, c.Namespaces.PrometheusAllowList) {
+		o.nsPromInf = o.nsMonInf
 	} else {
-		c.nsPromInf, err = newNamespaceInformer(c, c.config.Namespaces.PrometheusAllowList)
+		o.nsPromInf, err = newNamespaceInformer(o, c.Namespaces.PrometheusAllowList)
 		if err != nil {
 			return nil, err
 		}
 	}

-	endpointSliceSupported, err := k8sutil.IsAPIGroupVersionResourceSupported(c.kclient.Discovery(), schema.GroupVersion{Group: "discovery.k8s.io", Version: "v1"}, "endpointslices")
+	endpointSliceSupported, err := k8sutil.IsAPIGroupVersionResourceSupported(o.kclient.Discovery(), schema.GroupVersion{Group: "discovery.k8s.io", Version: "v1"}, "endpointslices")
 	if err != nil {
-		level.Warn(c.logger).Log("msg", "failed to check if the API supports the endpointslice resources", "err ", err)
+		level.Warn(o.logger).Log("msg", "failed to check if the API supports the endpointslice resources", "err ", err)
 	}
-	level.Info(c.logger).Log("msg", "Kubernetes API capabilities", "endpointslices", endpointSliceSupported)
+	level.Info(o.logger).Log("msg", "Kubernetes API capabilities", "endpointslices", endpointSliceSupported)
 	// The operator doesn't yet support the endpointslices API.
 	// See https://github.com/prometheus-operator/prometheus-operator/issues/3862
 	// for details.
-	c.endpointSliceSupported = false
+	o.endpointSliceSupported = false

-	c.statusReporter = prompkg.StatusReporter{
-		Kclient:         c.kclient,
-		Reconciliations: c.reconciliations,
-		SsetInfs:        c.ssetInfs,
-		Rr:              c.rr,
+	o.statusReporter = prompkg.StatusReporter{
+		Kclient:         o.kclient,
+		Reconciliations: o.reconciliations,
+		SsetInfs:        o.ssetInfs,
+		Rr:              o.rr,
 	}

-	return c, nil
+	return o, nil
 }

 // Run the controller.
@ -752,7 +750,7 @@ func (c *Operator) createOrUpdateConfigurationSecret(ctx context.Context, p *mon
 	return k8sutil.CreateOrUpdateSecret(ctx, sClient, s)
 }

-func createSSetInputHash(p monitoringv1alpha1.PrometheusAgent, c operator.Config, tlsAssets *operator.ShardedSecret, ssSpec appsv1.StatefulSetSpec) (string, error) {
+func createSSetInputHash(p monitoringv1alpha1.PrometheusAgent, c prompkg.Config, tlsAssets *operator.ShardedSecret, ssSpec appsv1.StatefulSetSpec) (string, error) {
 	var http2 *bool
 	if p.Spec.Web != nil && p.Spec.Web.WebConfigFileFields.HTTPConfig != nil {
 		http2 = p.Spec.Web.WebConfigFileFields.HTTPConfig.HTTP2
@ -768,7 +766,7 @@ func createSSetInputHash(p monitoringv1alpha1.PrometheusAgent, c operator.Config
 		PrometheusAnnotations map[string]string
 		PrometheusGeneration  int64
 		PrometheusWebHTTP2    *bool
-		Config                operator.Config
+		Config                prompkg.Config
 		StatefulSetSpec       appsv1.StatefulSetSpec
 		Assets                []string `hash:"set"`
 	}{
--- a/pkg/prometheus/agent/statefulset.go
+++ b/pkg/prometheus/agent/statefulset.go
@ -41,7 +41,7 @@ const (
 func makeStatefulSet(
 	name string,
 	p monitoringv1.PrometheusInterface,
-	config *operator.Config,
+	config *prompkg.Config,
 	cg *prompkg.ConfigGenerator,
 	inputHash string,
 	shard int32,
@ -166,7 +166,7 @@ func makeStatefulSet(

 func makeStatefulSetSpec(
 	p monitoringv1.PrometheusInterface,
-	c *operator.Config,
+	c *prompkg.Config,
 	cg *prompkg.ConfigGenerator,
 	shard int32,
 	tlsAssetSecrets []string,
@ -426,7 +426,7 @@ func makeStatefulSetSpec(
 	}, nil
 }

-func makeStatefulSetService(p *monitoringv1alpha1.PrometheusAgent, config operator.Config) *v1.Service {
+func makeStatefulSetService(p *monitoringv1alpha1.PrometheusAgent, config prompkg.Config) *v1.Service {
 	p = p.DeepCopy()

 	if p.Spec.PortName == "" {
--- a/pkg/prometheus/agent/statefulset_test.go
+++ b/pkg/prometheus/agent/statefulset_test.go
@ -33,7 +33,7 @@ import (
 )

 var (
-	defaultTestConfig = &operator.Config{
+	defaultTestConfig = &prompkg.Config{
 		LocalHost:                  "localhost",
 		ReloaderConfig:             operator.DefaultReloaderTestConfig.ReloaderConfig,
 		PrometheusDefaultBaseImage: operator.DefaultPrometheusBaseImage,
--- a/pkg/prometheus/operator.go
+++ b/pkg/prometheus/operator.go
@ -38,6 +38,18 @@ import (
 var prometheusKeyInShardStatefulSet = regexp.MustCompile("^(.+)/prometheus-(.+)-shard-[1-9][0-9]*$")
 var prometheusKeyInStatefulSet = regexp.MustCompile("^(.+)/prometheus-(.+)$")

+// Config defines the operator's parameters for the Prometheus controllers.
+// Whenever the value of one of these parameters is changed, it triggers an
+// update of the managed statefulsets.
+type Config struct {
+	LocalHost                  string
+	ReloaderConfig             operator.ContainerConfig
+	PrometheusDefaultBaseImage string
+	ThanosDefaultBaseImage     string
+	Annotations                operator.Map
+	Labels                     operator.Map
+}
+
 type StatusReporter struct {
 	Kclient         kubernetes.Interface
 	Reconciliations *operator.ReconciliationTracker
--- a/pkg/prometheus/server/operator.go
+++ b/pkg/prometheus/server/operator.go
@ -61,6 +61,7 @@ type Operator struct {

 	logger   log.Logger
 	accessor *operator.Accessor
+	config   prompkg.Config

 	nsPromInf cache.SharedIndexInformer
 	nsMonInf  cache.SharedIndexInformer
@ -79,6 +80,7 @@ type Operator struct {

 	metrics         *operator.Metrics
 	reconciliations *operator.ReconciliationTracker
+	statusReporter  prompkg.StatusReporter

 	nodeAddressLookupErrors prometheus.Counter
 	nodeEndpointSyncs       prometheus.Counter
@ -86,17 +88,16 @@ type Operator struct {

 	kubeletObjectName      string
 	kubeletObjectNamespace string
+	kubeletSelector        string
 	kubeletSyncEnabled     bool
-	config                 operator.Config
+
 	endpointSliceSupported bool
 	scrapeConfigSupported  bool
 	canReadStorageClass    bool
-
-	statusReporter prompkg.StatusReporter
 }

 // New creates a new controller.
-func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, logger log.Logger, r prometheus.Registerer, scrapeConfigSupported bool, canReadStorageClass bool) (*Operator, error) {
+func New(ctx context.Context, restConfig *rest.Config, c operator.Config, logger log.Logger, r prometheus.Registerer, scrapeConfigSupported bool, canReadStorageClass bool) (*Operator, error) {
 	client, err := kubernetes.NewForConfig(restConfig)
 	if err != nil {
 		return nil, fmt.Errorf("instantiating kubernetes client failed: %w", err)
@ -112,21 +113,12 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("instantiating monitoring client failed: %w", err)
 	}

-	if _, err := labels.Parse(conf.PromSelector); err != nil {
-		return nil, fmt.Errorf("can not parse prometheus selector value: %w", err)
-	}
-
-	secretListWatchSelector, err := fields.ParseSelector(conf.SecretListWatchSelector)
-	if err != nil {
-		return nil, fmt.Errorf("can not parse secrets selector value: %w", err)
-	}
-
 	kubeletObjectName := ""
 	kubeletObjectNamespace := ""
 	kubeletSyncEnabled := false

-	if conf.KubeletObject != "" {
-		parts := strings.Split(conf.KubeletObject, "/")
+	if c.KubeletObject != "" {
+		parts := strings.Split(c.KubeletObject, "/")
 		if len(parts) != 2 {
 			return nil, fmt.Errorf("malformatted kubelet object string, must be in format \"namespace/name\"")
 		}
@ -138,18 +130,28 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 	// All the metrics exposed by the controller get the controller="prometheus" label.
 	r = prometheus.WrapRegistererWith(prometheus.Labels{"controller": "prometheus"}, r)

-	c := &Operator{
-		kclient:                client,
-		mdClient:               mdClient,
-		mclient:                mclient,
-		logger:                 logger,
-		accessor:               operator.NewAccessor(logger),
+	o := &Operator{
+		kclient:  client,
+		mdClient: mdClient,
+		mclient:  mclient,
+		logger:   logger,
+		accessor: operator.NewAccessor(logger),
+
 		kubeletObjectName:      kubeletObjectName,
 		kubeletObjectNamespace: kubeletObjectNamespace,
 		kubeletSyncEnabled:     kubeletSyncEnabled,
-		config:                 conf,
-		metrics:                operator.NewMetrics(r),
-		reconciliations:        &operator.ReconciliationTracker{},
+		kubeletSelector:        c.KubeletSelector.String(),
+
+		config: prompkg.Config{
+			LocalHost:                  c.LocalHost,
+			ReloaderConfig:             c.ReloaderConfig,
+			PrometheusDefaultBaseImage: c.PrometheusDefaultBaseImage,
+			ThanosDefaultBaseImage:     c.ThanosDefaultBaseImage,
+			Annotations:                c.Annotations,
+			Labels:                     c.Labels,
+		},
+		metrics:         operator.NewMetrics(r),
+		reconciliations: &operator.ReconciliationTracker{},
 		nodeAddressLookupErrors: prometheus.NewCounter(prometheus.CounterOpts{
 			Name: "prometheus_operator_node_address_lookup_errors_total",
 			Help: "Number of times a node IP address could not be determined",
@ -165,29 +167,29 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		scrapeConfigSupported: scrapeConfigSupported,
 		canReadStorageClass:   canReadStorageClass,
 	}
-	c.metrics.MustRegister(
-		c.nodeAddressLookupErrors,
-		c.nodeEndpointSyncs,
-		c.nodeEndpointSyncErrors,
-		c.reconciliations,
+	o.metrics.MustRegister(
+		o.nodeAddressLookupErrors,
+		o.nodeEndpointSyncs,
+		o.nodeEndpointSyncErrors,
+		o.reconciliations,
 	)

-	c.rr = operator.NewResourceReconciler(
-		c.logger,
-		c,
-		c.metrics,
+	o.rr = operator.NewResourceReconciler(
+		o.logger,
+		o,
+		o.metrics,
 		monitoringv1.PrometheusesKind,
 		r,
 	)

-	c.promInfs, err = informers.NewInformersForResource(
+	o.promInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			c.config.Namespaces.PrometheusAllowList,
-			c.config.Namespaces.DenyList,
+			c.Namespaces.PrometheusAllowList,
+			c.Namespaces.DenyList,
 			mclient,
 			resyncPeriod,
 			func(options *metav1.ListOptions) {
-				options.LabelSelector = c.config.PromSelector
+				options.LabelSelector = c.PromSelector.String()
 			},
 		),
 		monitoringv1.SchemeGroupVersion.WithResource(monitoringv1.PrometheusName),
@ -197,15 +199,15 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 	}

 	var promStores []cache.Store
-	for _, informer := range c.promInfs.GetInformers() {
+	for _, informer := range o.promInfs.GetInformers() {
 		promStores = append(promStores, informer.Informer().GetStore())
 	}
-	c.metrics.MustRegister(prompkg.NewCollectorForStores(promStores...))
+	o.metrics.MustRegister(prompkg.NewCollectorForStores(promStores...))

-	c.smonInfs, err = informers.NewInformersForResource(
+	o.smonInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			c.config.Namespaces.AllowList,
-			c.config.Namespaces.DenyList,
+			c.Namespaces.AllowList,
+			c.Namespaces.DenyList,
 			mclient,
 			resyncPeriod,
 			nil,
@ -216,10 +218,10 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("error creating servicemonitor informers: %w", err)
 	}

-	c.pmonInfs, err = informers.NewInformersForResource(
+	o.pmonInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			c.config.Namespaces.AllowList,
-			c.config.Namespaces.DenyList,
+			c.Namespaces.AllowList,
+			c.Namespaces.DenyList,
 			mclient,
 			resyncPeriod,
 			nil,
@ -230,10 +232,10 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("error creating podmonitor informers: %w", err)
 	}

-	c.probeInfs, err = informers.NewInformersForResource(
+	o.probeInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			c.config.Namespaces.AllowList,
-			c.config.Namespaces.DenyList,
+			c.Namespaces.AllowList,
+			c.Namespaces.DenyList,
 			mclient,
 			resyncPeriod,
 			nil,
@ -244,11 +246,11 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("error creating probe informers: %w", err)
 	}

-	if c.scrapeConfigSupported {
-		c.sconInfs, err = informers.NewInformersForResource(
+	if o.scrapeConfigSupported {
+		o.sconInfs, err = informers.NewInformersForResource(
 			informers.NewMonitoringInformerFactories(
-				c.config.Namespaces.AllowList,
-				c.config.Namespaces.DenyList,
+				c.Namespaces.AllowList,
+				c.Namespaces.DenyList,
 				mclient,
 				resyncPeriod,
 				nil,
@ -259,10 +261,10 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 			return nil, fmt.Errorf("error creating scrapeconfigs informers: %w", err)
 		}
 	}
-	c.ruleInfs, err = informers.NewInformersForResource(
+	o.ruleInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			c.config.Namespaces.AllowList,
-			c.config.Namespaces.DenyList,
+			c.Namespaces.AllowList,
+			c.Namespaces.DenyList,
 			mclient,
 			resyncPeriod,
 			nil,
@ -273,11 +275,11 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("error creating prometheusrule informers: %w", err)
 	}

-	c.cmapInfs, err = informers.NewInformersForResourceWithTransform(
+	o.cmapInfs, err = informers.NewInformersForResourceWithTransform(
 		informers.NewMetadataInformerFactory(
-			c.config.Namespaces.PrometheusAllowList,
-			c.config.Namespaces.DenyList,
-			c.mdClient,
+			c.Namespaces.PrometheusAllowList,
+			c.Namespaces.DenyList,
+			o.mdClient,
 			resyncPeriod,
 			func(options *metav1.ListOptions) {
 				options.LabelSelector = prompkg.LabelPrometheusName
@ -290,14 +292,14 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("error creating configmap informers: %w", err)
 	}

-	c.secrInfs, err = informers.NewInformersForResourceWithTransform(
+	o.secrInfs, err = informers.NewInformersForResourceWithTransform(
 		informers.NewMetadataInformerFactory(
-			c.config.Namespaces.PrometheusAllowList,
-			c.config.Namespaces.DenyList,
-			c.mdClient,
+			c.Namespaces.PrometheusAllowList,
+			c.Namespaces.DenyList,
+			o.mdClient,
 			resyncPeriod,
 			func(options *metav1.ListOptions) {
-				options.FieldSelector = secretListWatchSelector.String()
+				options.FieldSelector = c.SecretListWatchSelector.String()
 			},
 		),
 		v1.SchemeGroupVersion.WithResource(string(v1.ResourceSecrets)),
@ -307,11 +309,11 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("error creating secrets informers: %w", err)
 	}

-	c.ssetInfs, err = informers.NewInformersForResource(
+	o.ssetInfs, err = informers.NewInformersForResource(
 		informers.NewKubeInformerFactories(
-			c.config.Namespaces.PrometheusAllowList,
-			c.config.Namespaces.DenyList,
-			c.kclient,
+			c.Namespaces.PrometheusAllowList,
+			c.Namespaces.DenyList,
+			o.kclient,
 			resyncPeriod,
 			nil,
 		),
@ -325,55 +327,55 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		lw, privileged, err := listwatch.NewNamespaceListWatchFromClient(
 			ctx,
 			o.logger,
-			o.config.KubernetesVersion,
+			c.KubernetesVersion,
 			o.kclient.CoreV1(),
 			o.kclient.AuthorizationV1().SelfSubjectAccessReviews(),
 			allowList,
-			o.config.Namespaces.DenyList,
+			c.Namespaces.DenyList,
 		)
 		if err != nil {
 			return nil, err
 		}

-		level.Debug(c.logger).Log("msg", "creating namespace informer", "privileged", privileged)
+		level.Debug(o.logger).Log("msg", "creating namespace informer", "privileged", privileged)
 		return cache.NewSharedIndexInformer(
 			o.metrics.NewInstrumentedListerWatcher(lw),
 			&v1.Namespace{}, resyncPeriod, cache.Indexers{},
 		), nil
 	}

-	c.nsMonInf, err = newNamespaceInformer(c, c.config.Namespaces.AllowList)
+	o.nsMonInf, err = newNamespaceInformer(o, c.Namespaces.AllowList)
 	if err != nil {
 		return nil, err
 	}

-	if listwatch.IdenticalNamespaces(c.config.Namespaces.AllowList, c.config.Namespaces.PrometheusAllowList) {
-		c.nsPromInf = c.nsMonInf
+	if listwatch.IdenticalNamespaces(c.Namespaces.AllowList, c.Namespaces.PrometheusAllowList) {
+		o.nsPromInf = o.nsMonInf
 	} else {
-		c.nsPromInf, err = newNamespaceInformer(c, c.config.Namespaces.PrometheusAllowList)
+		o.nsPromInf, err = newNamespaceInformer(o, c.Namespaces.PrometheusAllowList)
 		if err != nil {
 			return nil, err
 		}
 	}

-	endpointSliceSupported, err := k8sutil.IsAPIGroupVersionResourceSupported(c.kclient.Discovery(), schema.GroupVersion{Group: "discovery.k8s.io", Version: "v1"}, "endpointslices")
+	endpointSliceSupported, err := k8sutil.IsAPIGroupVersionResourceSupported(o.kclient.Discovery(), schema.GroupVersion{Group: "discovery.k8s.io", Version: "v1"}, "endpointslices")
 	if err != nil {
-		level.Warn(c.logger).Log("msg", "failed to check if the API supports the endpointslice resources", "err ", err)
+		level.Warn(o.logger).Log("msg", "failed to check if the API supports the endpointslice resources", "err ", err)
 	}
-	level.Info(c.logger).Log("msg", "Kubernetes API capabilities", "endpointslices", endpointSliceSupported)
+	level.Info(o.logger).Log("msg", "Kubernetes API capabilities", "endpointslices", endpointSliceSupported)
 	// The operator doesn't yet support the endpointslices API.
 	// See https://github.com/prometheus-operator/prometheus-operator/issues/3862
 	// for details.
-	c.endpointSliceSupported = false
+	o.endpointSliceSupported = false

-	c.statusReporter = prompkg.StatusReporter{
-		Kclient:         c.kclient,
-		Reconciliations: c.reconciliations,
-		SsetInfs:        c.ssetInfs,
-		Rr:              c.rr,
+	o.statusReporter = prompkg.StatusReporter{
+		Kclient:         o.kclient,
+		Reconciliations: o.reconciliations,
+		SsetInfs:        o.ssetInfs,
+		Rr:              o.rr,
 	}

-	return c, nil
+	return o, nil
 }

 // waitForCacheSync waits for the informers' caches to be synced.
@ -635,7 +637,7 @@ func (c *Operator) syncNodeEndpoints(ctx context.Context) error {
 		},
 	}

-	nodes, err := c.kclient.CoreV1().Nodes().List(ctx, metav1.ListOptions{LabelSelector: c.config.KubeletSelector})
+	nodes, err := c.kclient.CoreV1().Nodes().List(ctx, metav1.ListOptions{LabelSelector: c.kubeletSelector})
 	if err != nil {
 		return fmt.Errorf("listing nodes failed: %w", err)
 	}
@ -1408,7 +1410,7 @@ func logDeprecatedFields(logger log.Logger, p *monitoringv1.Prometheus) {
 	}
 }

-func createSSetInputHash(p monitoringv1.Prometheus, c operator.Config, ruleConfigMapNames []string, tlsAssets *operator.ShardedSecret, ssSpec appsv1.StatefulSetSpec) (string, error) {
+func createSSetInputHash(p monitoringv1.Prometheus, c prompkg.Config, ruleConfigMapNames []string, tlsAssets *operator.ShardedSecret, ssSpec appsv1.StatefulSetSpec) (string, error) {
 	var http2 *bool
 	if p.Spec.Web != nil && p.Spec.Web.WebConfigFileFields.HTTPConfig != nil {
 		http2 = p.Spec.Web.WebConfigFileFields.HTTPConfig.HTTP2
@ -1424,7 +1426,7 @@ func createSSetInputHash(p monitoringv1.Prometheus, c operator.Config, ruleConfi
 		PrometheusAnnotations map[string]string
 		PrometheusGeneration  int64
 		PrometheusWebHTTP2    *bool
-		Config                operator.Config
+		Config                prompkg.Config
 		StatefulSetSpec       appsv1.StatefulSetSpec
 		RuleConfigMaps        []string `hash:"set"`
 		Assets                []string `hash:"set"`
--- a/pkg/prometheus/server/operator_test.go
+++ b/pkg/prometheus/server/operator_test.go
@ -26,7 +26,7 @@ import (
 	"k8s.io/utils/ptr"

 	monitoringv1 "github.com/prometheus-operator/prometheus-operator/pkg/apis/monitoring/v1"
-	"github.com/prometheus-operator/prometheus-operator/pkg/operator"
+	prompkg "github.com/prometheus-operator/prometheus-operator/pkg/prometheus"
 )

 func TestListOptions(t *testing.T) {
@ -207,7 +207,7 @@ func TestCreateStatefulSetInputHash(t *testing.T) {
 		},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
-			c := operator.Config{}
+			c := prompkg.Config{}

 			p1Hash, err := createSSetInputHash(tc.a, c, []string{}, nil, appsv1.StatefulSetSpec{})
 			if err != nil {
--- a/pkg/prometheus/server/statefulset.go
+++ b/pkg/prometheus/server/statefulset.go
@ -41,7 +41,7 @@ const (
 )

 // TODO(ArthurSens): generalize it enough to be used by both server and agent.
-func makeStatefulSetService(p *monitoringv1.Prometheus, config operator.Config) *v1.Service {
+func makeStatefulSetService(p *monitoringv1.Prometheus, config prompkg.Config) *v1.Service {
 	p = p.DeepCopy()

 	if p.Spec.PortName == "" {
@ -103,7 +103,7 @@ func makeStatefulSet(
 	queryLogFile string,
 	thanos *monitoringv1.ThanosSpec,
 	disableCompaction bool,
-	config *operator.Config,
+	config *prompkg.Config,
 	cg *prompkg.ConfigGenerator,
 	ruleConfigMapNames []string,
 	inputHash string,
@ -239,7 +239,7 @@ func makeStatefulSetSpec(
 	thanos *monitoringv1.ThanosSpec,
 	disableCompaction bool,
 	p monitoringv1.PrometheusInterface,
-	c *operator.Config,
+	c *prompkg.Config,
 	cg *prompkg.ConfigGenerator,
 	shard int32,
 	ruleConfigMapNames []string,
@ -647,7 +647,7 @@ func createThanosContainer(
 	disableCompaction *bool,
 	p monitoringv1.PrometheusInterface,
 	thanos *monitoringv1.ThanosSpec,
-	c *operator.Config,
+	c *prompkg.Config,
 	prometheusURIScheme, webRoutePrefix string) (*v1.Container, error) {

 	var container *v1.Container
--- a/pkg/prometheus/server/statefulset_test.go
+++ b/pkg/prometheus/server/statefulset_test.go
@ -39,7 +39,7 @@ import (
 )

 var (
-	defaultTestConfig = &operator.Config{
+	defaultTestConfig = &prompkg.Config{
 		LocalHost:                  "localhost",
 		ReloaderConfig:             operator.DefaultReloaderTestConfig.ReloaderConfig,
 		PrometheusDefaultBaseImage: operator.DefaultPrometheusBaseImage,
@ -874,7 +874,7 @@ func TestTagAndShaAndVersion(t *testing.T) {
 }

 func TestPrometheusDefaultBaseImageFlag(t *testing.T) {
-	operatorConfig := &operator.Config{
+	operatorConfig := &prompkg.Config{
 		ReloaderConfig:             defaultTestConfig.ReloaderConfig,
 		PrometheusDefaultBaseImage: "nondefaultuseflag/quay.io/prometheus/prometheus",
 		ThanosDefaultBaseImage:     "nondefaultuseflag/quay.io/thanos/thanos",
@ -926,7 +926,7 @@ func TestPrometheusDefaultBaseImageFlag(t *testing.T) {
 }

 func TestThanosDefaultBaseImageFlag(t *testing.T) {
-	thanosBaseImageConfig := &operator.Config{
+	thanosBaseImageConfig := &prompkg.Config{
 		ReloaderConfig:             defaultTestConfig.ReloaderConfig,
 		PrometheusDefaultBaseImage: "nondefaultuseflag/quay.io/prometheus/prometheus",
 		ThanosDefaultBaseImage:     "nondefaultuseflag/quay.io/thanos/thanos",
@ -1534,7 +1534,7 @@ func TestRetentionAndRetentionSize(t *testing.T) {
 }

 func TestReplicasConfigurationWithSharding(t *testing.T) {
-	testConfig := &operator.Config{
+	testConfig := &prompkg.Config{
 		ReloaderConfig:             defaultTestConfig.ReloaderConfig,
 		PrometheusDefaultBaseImage: "quay.io/prometheus/prometheus",
 		ThanosDefaultBaseImage:     "quay.io/thanos/thanos:v0.7.0",
@ -1596,7 +1596,7 @@ func TestReplicasConfigurationWithSharding(t *testing.T) {

 func TestSidecarResources(t *testing.T) {
 	operator.TestSidecarsResources(t, func(reloaderConfig operator.ContainerConfig) *appsv1.StatefulSet {
-		testConfig := &operator.Config{
+		testConfig := &prompkg.Config{
 			ReloaderConfig:             reloaderConfig,
 			PrometheusDefaultBaseImage: defaultTestConfig.PrometheusDefaultBaseImage,
 			ThanosDefaultBaseImage:     defaultTestConfig.ThanosDefaultBaseImage,
--- a/pkg/prometheus/statefulset.go
+++ b/pkg/prometheus/statefulset.go
@ -119,7 +119,7 @@ func compress(data []byte) ([]byte, error) {
 	return buf.Bytes(), nil
 }

-func MakeConfigurationSecret(p monitoringv1.PrometheusInterface, config operator.Config, data []byte) (*v1.Secret, error) {
+func MakeConfigurationSecret(p monitoringv1.PrometheusInterface, config Config, data []byte) (*v1.Secret, error) {
 	promConfig, err := compress(data)
 	if err != nil {
 		return nil, err
--- a/pkg/server/server.go
+++ b/pkg/server/server.go
@ -15,49 +15,132 @@
 package server

 import (
+	"context"
 	"crypto/tls"
 	"crypto/x509"
+	"flag"
 	"fmt"
+	stdlog "log"
+	"net"
+	"net/http"
 	"os"
+	"path/filepath"
 	"time"

+	rbacproxytls "github.com/brancz/kube-rbac-proxy/pkg/tls"
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
-	"k8s.io/component-base/cli/flag"
+	kflag "k8s.io/component-base/cli/flag"
+
+	"github.com/prometheus-operator/prometheus-operator/pkg/operator"
 )

-// TLSServerConfig contains the necessary fields to configure
-// web server TLS
-type TLSServerConfig struct {
+const (
+	defaultTLSDir     = "/etc/tls/private"
+	defaultTLSVersion = "VersionTLS13"
+)
+
+func DefaultConfig(listenAddress string, enableTLS bool) Config {
+	return Config{
+		ListenAddress: listenAddress,
+		// Mitigate CVE-2023-44487 by disabling HTTP2 by default until the Go
+		// standard library and golang.org/x/net are fully fixed.
+		// Right now, it is possible for authenticated and unauthenticated users to
+		// hold open HTTP2 connections and consume huge amounts of memory.
+		// See:
+		// * https://github.com/kubernetes/kubernetes/pull/121120
+		// * https://github.com/kubernetes/kubernetes/issues/121197
+		// * https://github.com/golang/go/issues/63417#issuecomment-1758858612
+		EnableHTTP2: false,
+		TLSConfig: TLSConfig{
+			Enabled:        enableTLS,
+			CertFile:       filepath.Join(defaultTLSDir, "tls.crt"),
+			KeyFile:        filepath.Join(defaultTLSDir, "tls.key"),
+			ClientCAFile:   filepath.Join(defaultTLSDir, "tls-ca.crt"),
+			MinVersion:     defaultTLSVersion,
+			CipherSuites:   operator.StringSet{},
+			ReloadInterval: time.Minute,
+		},
+	}
+}
+
+func RegisterFlags(fs *flag.FlagSet, c *Config) {
+	fs.StringVar(&c.ListenAddress, "web.listen-address", c.ListenAddress, "Address on which to expose metrics and web interface.")
+
+	fs.BoolVar(&c.EnableHTTP2, "web.enable-http2", c.EnableHTTP2, "Enable HTTP2 connections.")
+
+	fs.BoolVar(&c.TLSConfig.Enabled, "web.enable-tls", c.TLSConfig.Enabled, "Enable TLS for the web server.")
+	fs.StringVar(&c.TLSConfig.CertFile, "web.cert-file", c.TLSConfig.CertFile, "Certficate file to be used for the web server.")
+	fs.StringVar(&c.TLSConfig.KeyFile, "web.key-file", c.TLSConfig.KeyFile, "Private key matching the cert file to be used for the web server.")
+	fs.StringVar(&c.TLSConfig.ClientCAFile, "web.client-ca-file", c.TLSConfig.ClientCAFile, "Client CA certificate file to be used for the web server.")
+
+	fs.DurationVar(&c.TLSConfig.ReloadInterval, "web.tls-reload-interval", c.TLSConfig.ReloadInterval, "The interval at which to watch for TLS certificate changes, by default set to 1 minute. (default 1m0s).")
+
+	fs.StringVar(&c.TLSConfig.MinVersion, "web.tls-min-version", c.TLSConfig.MinVersion,
+		"Minimum TLS version supported. Value must match version names from https://golang.org/pkg/crypto/tls/#pkg-constants.")
+	fs.Var(&c.TLSConfig.CipherSuites, "web.tls-cipher-suites", "Comma-separated list of cipher suites for the server."+
+		" Values are from tls package constants (https://golang.org/pkg/crypto/tls/#pkg-constants)."+
+		"If omitted, the default Go cipher suites will be used. "+
+		"Note that TLS 1.3 ciphersuites are not configurable.")
+}
+
+// Config defines the web server configuration.
+type Config struct {
+	ListenAddress string
+	EnableHTTP2   bool
+	TLSConfig     TLSConfig
+}
+
+// TLSConfig defines the TLS settings of the web server.
+type TLSConfig struct {
+	Enabled        bool
 	CertFile       string
 	KeyFile        string
 	ClientCAFile   string
 	MinVersion     string
-	CipherSuites   []string
+	CipherSuites   operator.StringSet
 	ReloadInterval time.Duration
 }

-// NewTLSConfig provides new server TLS configuration.
-func NewTLSConfig(logger log.Logger, certFile, keyFile, clientCAFile, minVersion string, cipherSuites []string) (*tls.Config, error) {
-	if certFile == "" && keyFile == "" {
-		if clientCAFile != "" {
-			return nil, fmt.Errorf("when a client CA is used a server key and certificate must also be provided")
+// Convert returns a *tls.Config from the given TLSConfig.
+func (tc *TLSConfig) Convert(logger log.Logger) (*tls.Config, error) {
+	if logger == nil {
+		logger = log.NewNopLogger()
+	}
+
+	if !tc.Enabled {
+		return nil, nil
+	}
+
+	if tc.CertFile == "" && tc.KeyFile == "" {
+		if tc.ClientCAFile != "" {
+			return nil, fmt.Errorf("server key and certificate must be provided when a client CA is configured")
 		}
-		return nil, fmt.Errorf("TLS disabled. key and cert must be set to enable")
+
+		// Disable TLS.
+		level.Warn(logger).Log("msg", "server key and certificate not provided, TLS disabled")
+		return nil, nil
 	}

 	tlsCfg := &tls.Config{}
-
-	version, err := flag.TLSVersion(minVersion)
+	version, err := kflag.TLSVersion(tc.MinVersion)
 	if err != nil {
-		return nil, fmt.Errorf("TLS version invalid: %w", err)
+		return nil, fmt.Errorf("invalid TLS version: %w", err)
+	}
+
+	// Any older versions won't allow a secure connection.
+	switch version {
+	case tls.VersionTLS12:
+	case tls.VersionTLS13:
+	default:
+		return nil, fmt.Errorf("TLS version %q isn't supported", tls.VersionName(version))
 	}

 	tlsCfg.MinVersion = version

-	cipherSuiteIDs, err := flag.TLSCipherSuites(cipherSuites)
+	cipherSuiteIDs, err := kflag.TLSCipherSuites(tc.CipherSuites.Slice())
 	if err != nil {
-		return nil, fmt.Errorf("TLS cipher suite name to ID conversion: %w", err)
+		return nil, fmt.Errorf("failed to convert TLS cipher suite name to ID: %w", err)
 	}

 	// A list of supported cipher suites for TLS versions up to TLS 1.2.
@ -65,24 +148,124 @@ func NewTLSConfig(logger log.Logger, certFile, keyFile, clientCAFile, minVersion
 	// Note that TLS 1.3 ciphersuites are not configurable.
 	tlsCfg.CipherSuites = cipherSuiteIDs

-	if clientCAFile != "" {
-		if info, err := os.Stat(clientCAFile); err == nil && info.Mode().IsRegular() {
-			caPEM, err := os.ReadFile(clientCAFile)
-			if err != nil {
-				return nil, fmt.Errorf("reading client CA: %w", err)
-			}
+	if tc.ClientCAFile == "" {
+		return tlsCfg, nil
+	}

-			certPool := x509.NewCertPool()
-			if !certPool.AppendCertsFromPEM(caPEM) {
-				return nil, fmt.Errorf("building client CA: %w", err)
-			}
+	info, err := os.Stat(tc.ClientCAFile)
+	switch {
+	case err != nil:
+		level.Warn(logger).Log("msg", "server TLS client verification disabled", "err", err, "client_ca_file", tc.ClientCAFile)

-			tlsCfg.ClientCAs = certPool
-			tlsCfg.ClientAuth = tls.RequireAndVerifyClientCert
+	case !info.Mode().IsRegular():
+		level.Warn(logger).Log("msg", "server TLS client verification disabled", "client_ca_file", tc.ClientCAFile, "file_mode", info.Mode().String())

-			level.Info(logger).Log("msg", "server TLS client verification enabled")
+	default:
+		caPEM, err := os.ReadFile(tc.ClientCAFile)
+		if err != nil {
+			return nil, fmt.Errorf("reading client CA %q: %w", tc.ClientCAFile, err)
 		}
+
+		certPool := x509.NewCertPool()
+		if !certPool.AppendCertsFromPEM(caPEM) {
+			return nil, fmt.Errorf("client CA %q: failed to parse certificate", tc.ClientCAFile)
+		}
+
+		tlsCfg.ClientCAs = certPool
+		tlsCfg.ClientAuth = tls.RequireAndVerifyClientCert
+		level.Info(logger).Log("msg", "server TLS client verification enabled", "client_ca_file", tc.ClientCAFile)
 	}

 	return tlsCfg, nil
 }
+
+// Server is a web server.
+type Server struct {
+	logger   log.Logger
+	srv      *http.Server
+	listener net.Listener
+	cfg      *Config
+}
+
+// NewServer initializes a web server with the given handler (typically an http.MuxServe).
+func NewServer(logger log.Logger, c *Config, handler http.Handler) (*Server, error) {
+	tlsConfig, err := c.TLSConfig.Convert(logger)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create TLS configuration: %w", err)
+	}
+
+	listener, err := net.Listen("tcp", c.ListenAddress)
+	if err != nil {
+		return nil, err
+	}
+
+	srv := &http.Server{
+		Handler:           handler,
+		TLSConfig:         tlsConfig,
+		ReadHeaderTimeout: 30 * time.Second,
+		ReadTimeout:       30 * time.Second,
+		// use flags on standard logger to align with base logger and get consistent parsed fields form adapter:
+		// use shortfile flag to get proper 'caller' field (avoid being wrongly parsed/extracted from message)
+		// and no datetime related flag to keep 'ts' field from base logger (with controlled format)
+		ErrorLog: stdlog.New(log.NewStdlibAdapter(logger), "", stdlog.Lshortfile),
+	}
+
+	if !c.EnableHTTP2 {
+		srv.TLSNextProto = make(map[string]func(*http.Server, *tls.Conn, http.Handler))
+	}
+
+	return &Server{
+		logger:   logger,
+		srv:      srv,
+		listener: listener,
+		cfg:      c,
+	}, nil
+}
+
+// Serve starts the web server. It will block until the server is shutted down
+// or an error occurs.
+func (s *Server) Serve(ctx context.Context) error {
+	if s.srv.TLSConfig == nil {
+		level.Info(s.logger).Log("msg", "starting insecure server", "address", s.listener.Addr().String())
+		if err := s.srv.Serve(s.listener); err != http.ErrServerClosed {
+			return err
+		}
+
+		return nil
+	}
+
+	r, err := rbacproxytls.NewCertReloader(
+		s.cfg.TLSConfig.CertFile,
+		s.cfg.TLSConfig.KeyFile,
+		s.cfg.TLSConfig.ReloadInterval,
+	)
+	if err != nil {
+		return fmt.Errorf("failed to initialize certificate reloader: %w", err)
+	}
+
+	s.srv.TLSConfig.GetCertificate = r.GetCertificate
+	go func() {
+		for {
+			// r.Watch will wait ReloadInterval, so this is not
+			// a hot loop
+			if err := r.Watch(ctx); err != nil {
+				level.Warn(s.logger).Log(
+					"msg", "error watching certificate reloader",
+					"err", err)
+			}
+		}
+	}()
+
+	level.Info(s.logger).Log("msg", "starting secure server", "address", s.listener.Addr().String(), "http2", s.cfg.EnableHTTP2)
+	if err := s.srv.ServeTLS(s.listener, "", ""); err != http.ErrServerClosed {
+		return err
+	}
+
+	return nil
+}
+
+// Shutdown closes gracefully all active connections.
+func (s *Server) Shutdown(ctx context.Context) error {
+	level.Info(s.logger).Log("msg", "shutting down web server")
+	return s.srv.Shutdown(ctx)
+}
--- a/pkg/server/server_test.go
+++ b/pkg/server/server_test.go
@ -15,12 +15,101 @@
 package server

 import (
+	"crypto/tls"
 	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/prometheus-operator/prometheus-operator/pkg/operator"
 )

-func TestNewTLSConfig(t *testing.T) {
-	_, err := NewTLSConfig(nil, "", "", "foo.txt", "", nil)
-	if err == nil {
-		t.Errorf("expected tls err when client CA set without key and cert files")
+func TestConvertTLSConfig(t *testing.T) {
+	for _, tc := range []struct {
+		c TLSConfig
+
+		err    bool
+		assert func(*testing.T, *tls.Config)
+	}{
+		{
+			c: TLSConfig{},
+
+			assert: func(t *testing.T, c *tls.Config) {
+				require.Nil(t, c)
+			},
+		},
+		{
+			c: TLSConfig{
+				Enabled:      true,
+				ClientCAFile: "ca.crt",
+			},
+			err: true,
+		},
+		{
+			c: TLSConfig{
+				Enabled: true,
+			},
+
+			assert: func(t *testing.T, c *tls.Config) {
+				require.Nil(t, c)
+			},
+		},
+		{
+			c: TLSConfig{
+				Enabled:    true,
+				CertFile:   "server.crt",
+				KeyFile:    "server.key",
+				MinVersion: "VersionTLSXX",
+			},
+
+			err: true,
+		},
+		{
+			c: TLSConfig{
+				Enabled:  true,
+				CertFile: "server.crt",
+				KeyFile:  "server.key",
+			},
+
+			assert: func(t *testing.T, c *tls.Config) {
+				require.NotNil(t, c)
+				require.Equal(t, tls.VersionTLS12, int(c.MinVersion))
+			},
+		},
+		{
+			c: TLSConfig{
+				Enabled:      true,
+				CertFile:     "server.crt",
+				KeyFile:      "server.key",
+				CipherSuites: operator.StringSet(map[string]struct{}{"foo": {}}),
+			},
+
+			err: true,
+		},
+		{
+			c: TLSConfig{
+				Enabled:      true,
+				CertFile:     "server.crt",
+				KeyFile:      "server.key",
+				CipherSuites: operator.StringSet(map[string]struct{}{"TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA": {}}),
+			},
+
+			assert: func(t *testing.T, c *tls.Config) {
+				require.NotNil(t, c)
+				require.Equal(t, []uint16{tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA}, c.CipherSuites)
+			},
+		},
+	} {
+		t.Run("", func(t *testing.T) {
+			c, err := tc.c.Convert(nil)
+			if tc.err {
+				require.Error(t, err)
+				return
+			}
+
+			require.NoError(t, err)
+			if tc.assert != nil {
+				tc.assert(t, c)
+			}
+		})
 	}
 }
--- a/pkg/thanos/operator.go
+++ b/pkg/thanos/operator.go
@ -30,7 +30,6 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/fields"
 	"k8s.io/apimachinery/pkg/labels"
-	"k8s.io/apimachinery/pkg/version"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/metadata"
 	"k8s.io/client-go/rest"
@ -76,22 +75,19 @@ type Operator struct {
 	config Config
 }

-// Config defines configuration parameters for the Operator.
+// Config defines the operator's parameters for the Thanos controller.
+// Whenever the value of one of these parameters is changed, it triggers an
+// update of the managed statefulsets.
 type Config struct {
-	KubernetesVersion      version.Info
+	LocalHost              string
 	ReloaderConfig         operator.ContainerConfig
 	ThanosDefaultBaseImage string
-	Namespaces             operator.Namespaces
 	Annotations            operator.Map
 	Labels                 operator.Map
-	LocalHost              string
-	LogLevel               string
-	LogFormat              string
-	ThanosRulerSelector    string
 }

 // New creates a new controller.
-func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, logger log.Logger, r prometheus.Registerer, canReadStorageClass bool) (*Operator, error) {
+func New(ctx context.Context, restConfig *rest.Config, c operator.Config, logger log.Logger, r prometheus.Registerer, canReadStorageClass bool) (*Operator, error) {
 	client, err := kubernetes.NewForConfig(restConfig)
 	if err != nil {
 		return nil, fmt.Errorf("instantiating kubernetes client failed: %w", err)
@ -107,10 +103,6 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		return nil, fmt.Errorf("instantiating monitoring client failed: %w", err)
 	}

-	if _, err := labels.Parse(conf.ThanosRulerSelector); err != nil {
-		return nil, fmt.Errorf("can not parse thanos ruler selector value: %w", err)
-	}
-
 	// All the metrics exposed by the controller get the controller="thanos" label.
 	r = prometheus.WrapRegistererWith(prometheus.Labels{"controller": "thanos"}, r)

@ -124,16 +116,11 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		reconciliations:     &operator.ReconciliationTracker{},
 		canReadStorageClass: canReadStorageClass,
 		config: Config{
-			KubernetesVersion:      conf.KubernetesVersion,
-			ReloaderConfig:         conf.ReloaderConfig,
-			ThanosDefaultBaseImage: conf.ThanosDefaultBaseImage,
-			Namespaces:             conf.Namespaces,
-			Annotations:            conf.Annotations,
-			Labels:                 conf.Labels,
-			LocalHost:              conf.LocalHost,
-			LogLevel:               conf.LogLevel,
-			LogFormat:              conf.LogFormat,
-			ThanosRulerSelector:    conf.ThanosRulerSelector,
+			ReloaderConfig:         c.ReloaderConfig,
+			ThanosDefaultBaseImage: c.ThanosDefaultBaseImage,
+			Annotations:            c.Annotations,
+			Labels:                 c.Labels,
+			LocalHost:              c.LocalHost,
 		},
 	}

@ -147,8 +134,8 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log

 	o.cmapInfs, err = informers.NewInformersForResource(
 		informers.NewMetadataInformerFactory(
-			o.config.Namespaces.ThanosRulerAllowList,
-			o.config.Namespaces.DenyList,
+			c.Namespaces.ThanosRulerAllowList,
+			c.Namespaces.DenyList,
 			o.mdClient,
 			resyncPeriod,
 			func(options *metav1.ListOptions) {
@ -163,12 +150,12 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log

 	o.thanosRulerInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			o.config.Namespaces.ThanosRulerAllowList,
-			o.config.Namespaces.DenyList,
+			c.Namespaces.ThanosRulerAllowList,
+			c.Namespaces.DenyList,
 			mclient,
 			resyncPeriod,
 			func(options *metav1.ListOptions) {
-				options.LabelSelector = o.config.ThanosRulerSelector
+				options.LabelSelector = c.ThanosRulerSelector.String()
 			},
 		),
 		monitoringv1.SchemeGroupVersion.WithResource(monitoringv1.ThanosRulerName),
@ -185,8 +172,8 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log

 	o.ruleInfs, err = informers.NewInformersForResource(
 		informers.NewMonitoringInformerFactories(
-			o.config.Namespaces.AllowList,
-			o.config.Namespaces.DenyList,
+			c.Namespaces.AllowList,
+			c.Namespaces.DenyList,
 			mclient,
 			resyncPeriod,
 			nil,
@ -199,8 +186,8 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log

 	o.ssetInfs, err = informers.NewInformersForResource(
 		informers.NewKubeInformerFactories(
-			o.config.Namespaces.ThanosRulerAllowList,
-			o.config.Namespaces.DenyList,
+			c.Namespaces.ThanosRulerAllowList,
+			c.Namespaces.DenyList,
 			o.kclient,
 			resyncPeriod,
 			nil,
@ -215,11 +202,11 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		lw, privileged, err := listwatch.NewNamespaceListWatchFromClient(
 			ctx,
 			o.logger,
-			o.config.KubernetesVersion,
+			c.KubernetesVersion,
 			o.kclient.CoreV1(),
 			o.kclient.AuthorizationV1().SelfSubjectAccessReviews(),
 			allowList,
-			o.config.Namespaces.DenyList)
+			c.Namespaces.DenyList)
 		if err != nil {
 			return nil, err
 		}
@ -233,15 +220,15 @@ func New(ctx context.Context, restConfig *rest.Config, conf operator.Config, log
 		), nil
 	}

-	o.nsRuleInf, err = newNamespaceInformer(o, o.config.Namespaces.AllowList)
+	o.nsRuleInf, err = newNamespaceInformer(o, c.Namespaces.AllowList)
 	if err != nil {
 		return nil, err
 	}

-	if listwatch.IdenticalNamespaces(o.config.Namespaces.AllowList, o.config.Namespaces.ThanosRulerAllowList) {
+	if listwatch.IdenticalNamespaces(c.Namespaces.AllowList, c.Namespaces.ThanosRulerAllowList) {
 		o.nsThanosRulerInf = o.nsRuleInf
 	} else {
-		o.nsThanosRulerInf, err = newNamespaceInformer(o, o.config.Namespaces.ThanosRulerAllowList)
+		o.nsThanosRulerInf, err = newNamespaceInformer(o, c.Namespaces.ThanosRulerAllowList)
 		if err != nil {
 			return nil, err
 		}
--- a/pkg/versionutil/cli.go
+++ b/pkg/versionutil/cli.go
@ -31,14 +31,14 @@ var (

 // RegisterParseFlags registers and parses version related flags.
 func RegisterParseFlags() {
-	RegisterFlags()
+	RegisterFlags(flag.CommandLine)
 	flag.Parse()
 }

 // RegisterFlags registers version related flags to core.
-func RegisterFlags() {
-	flag.BoolVar(&printVer, "version", false, "Prints current version.")
-	flag.BoolVar(&printShort, "short-version", false, "Print just the version number.")
+func RegisterFlags(fs *flag.FlagSet) {
+	fs.BoolVar(&printVer, "version", false, "Prints current version.")
+	fs.BoolVar(&printShort, "short-version", false, "Print just the version number.")
 }

 // RegisterIntoKingpinFlags registers version related flags in kingpin framework.