Do not remove the generated app-config if fluentd resource updated

pkg/resources/fluentd/appconfigmap.go

@@ -17,15 +17,23 @@
 package fluentd
 
 import (
+	"context"
+
 	"github.com/banzaicloud/logging-operator/pkg/resources/templates"
 	"github.com/banzaicloud/logging-operator/pkg/util"
 	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/types"
 )
 
 func (r *Reconciler) appconfigMap() runtime.Object {
-	return &corev1.ConfigMap{
-		ObjectMeta: templates.FluentdObjectMeta(appConfigMapName, util.MergeLabels(r.Fluentd.Labels, labelSelector), r.Fluentd),
-		Data:       map[string]string{},
+	current := &corev1.ConfigMap{}
+	err := r.Client.Get(context.TODO(), types.NamespacedName{Namespace: r.Fluentd.Namespace, Name: appConfigMapName}, current)
+	if err != nil {
+		return &corev1.ConfigMap{
+			ObjectMeta: templates.FluentdObjectMeta(appConfigMapName, util.MergeLabels(r.Fluentd.Labels, labelSelector), r.Fluentd),
+			Data:       map[string]string{},
+		}
 	}
+	return current
 }