chore(kubernetes): deduplicate warning logs from the API

Signed-off-by: machine424 <ayoubmrini424@gmail.com>

cmd/prometheus/main.go

@@ -55,6 +55,7 @@ import (
 	toolkit_web "github.com/prometheus/exporter-toolkit/web"
 	"go.uber.org/atomic"
 	"go.uber.org/automaxprocs/maxprocs"
+	"k8s.io/client-go/rest"
 	"k8s.io/klog"
 	klogv2 "k8s.io/klog/v2"
 
@@ -836,6 +837,9 @@ func main() {
 
 	klogv2.SetSlogLogger(logger.With("component", "k8s_client_runtime"))
 	klog.SetOutputBySeverity("INFO", klogv1Writer{})
+	// Avoid duplicate API deprecation warnings (e.g., "v1 Endpoints is deprecated in v1.33+...")
+	// that can pollute the logs.
+	rest.SetDefaultWarningHandlerWithContext(logging.NewDedupDeprecationWarningLogger())
 
 	modeAppName := "Prometheus Server"
 	mode := "server"

util/logging/dedupe.go

@@ -18,6 +18,9 @@ import (
 	"log/slog"
 	"sync"
 	"time"
+
+	"github.com/grafana/regexp"
+	"k8s.io/client-go/rest"
 )
 
 const (
@@ -134,3 +137,44 @@ func (d *Deduper) run() {
 		}
 	}
 }
+
+// deprecationRegex matches the format of Kubernetes API deprecation warnings:
+// See https://github.com/kubernetes/kubernetes/blob/da663405beb487d66c27a0220ea4073305ae9077/staging/src/k8s.io/apiserver/pkg/endpoints/deprecation/deprecation.go#L117.
+var deprecationRegex = regexp.MustCompile(`\S+ \S+ is deprecated in v\d+\.\d+\+`)
+
+// Even though deprecation warnings should be bounded in number, this safeguard should help prevent leaks.
+const maxDeprecationWarnings = 32
+
+// DedupDeprecationWarningLogger deduplicates Kube API deprecation warnings by message before logging them.
+// Inspired by https://github.com/kubernetes/kubernetes/blob/3edae6c1c49958fd10a708d9cc8c4c9e7f5fb6e8/staging/src/k8s.io/client-go/rest/warnings.go#L113
+type DedupDeprecationWarningLogger struct {
+	logger rest.WarningHandlerWithContext
+	lock   sync.Mutex
+	logged map[string]struct{}
+}
+
+func NewDedupDeprecationWarningLogger() *DedupDeprecationWarningLogger {
+	return &DedupDeprecationWarningLogger{
+		logger: rest.WarningLogger{},
+		logged: make(map[string]struct{}),
+	}
+}
+
+func (w *DedupDeprecationWarningLogger) HandleWarningHeaderWithContext(ctx context.Context, code int, agent, message string) {
+	if code != 299 || message == "" {
+		return
+	}
+
+	w.lock.Lock()
+	defer w.lock.Unlock()
+
+	if _, seen := w.logged[message]; seen {
+		return
+	}
+
+	if deprecationRegex.MatchString(message) && len(w.logged) < maxDeprecationWarnings {
+		w.logged[message] = struct{}{}
+	}
+
+	w.logger.HandleWarningHeaderWithContext(ctx, code, agent, message)
+}

util/logging/dedupe_test.go

@@ -15,6 +15,8 @@ package logging
 
 import (
 	"bytes"
+	"context"
+	"fmt"
 	"log/slog"
 	"strings"
 	"testing"
@@ -80,3 +82,33 @@ func TestDedupeConcurrent(t *testing.T) {
 
 	require.NotPanics(t, func() { concurrentWriteFunc() })
 }
+
+type fakeWarningLogger struct {
+	logs []string
+}
+
+func (fl *fakeWarningLogger) HandleWarningHeaderWithContext(_ context.Context, _ int, _, message string) {
+	fl.logs = append(fl.logs, message)
+}
+
+func TestDedupeDeprecationWarningLogger(t *testing.T) {
+	wl := DedupDeprecationWarningLogger{
+		logger: &fakeWarningLogger{},
+		logged: make(map[string]struct{}),
+	}
+
+	deprecationMessage := "v1 Endpoints is deprecated in v1.33+; use [discovery.k8s.io/v1](http://discovery.k8s.io/v1) EndpointSlice"
+	for range 10 {
+		wl.HandleWarningHeaderWithContext(context.Background(), 299, "", deprecationMessage)
+	}
+	require.Len(t, wl.logger.(*fakeWarningLogger).logs, 1)
+	require.Len(t, wl.logged, 1)
+	require.Equal(t, wl.logger.(*fakeWarningLogger).logs[0], deprecationMessage)
+
+	for i := range 10 {
+		wl.HandleWarningHeaderWithContext(context.Background(), 299, "", fmt.Sprintf("some other warning %d", i+1))
+	}
+	require.Len(t, wl.logger.(*fakeWarningLogger).logs, 11)
+	require.Len(t, wl.logged, 1)
+	require.Equal(t, "some other warning 10", wl.logger.(*fakeWarningLogger).logs[10])
+}