Add trailing dot to KubernetesClusterInfo::cluster_domain

Author: sbernauer

crates/stackable-operator/src/utils/cluster_info.rs

@@ -2,18 +2,22 @@ use std::str::FromStr;
 
 use crate::commons::networking::DomainName;
 
-const KUBERNETES_CLUSTER_DOMAIN_DEFAULT: &str = "cluster.local";
+const KUBERNETES_CLUSTER_DOMAIN_DEFAULT: &str = "cluster.local.";
 
 /// Some information that we know about the Kubernetes cluster.
 #[derive(Debug, Clone)]
 pub struct KubernetesClusterInfo {
-    /// The Kubernetes cluster domain, typically `cluster.local`.
+    /// The Kubernetes cluster domain, typically `cluster.local.`.
     pub cluster_domain: DomainName,
 }
 
 #[derive(clap::Parser, Debug, Default, PartialEq, Eq)]
 pub struct KubernetesClusterInfoOpts {
-    /// Kubernetes cluster domain, usually this is `cluster.local`.
+    /// Kubernetes cluster domain, usually this is `cluster.local.`.
+    ///
+    /// Please note that we recommend adding a trailing dot (".") for performance reasons, see
+    /// <https://github.com/stackabletech/issues/issues/656> for details.
+    //
     // We are not using a default value here, as operators will probably do an more advanced
     // auto-detection of the cluster domain in case it is not specified in the future.
     #[arg(long, env)]
@@ -25,6 +29,9 @@ impl KubernetesClusterInfo {
         let cluster_domain = match &cluster_info_opts.kubernetes_cluster_domain {
             Some(cluster_domain) => {
                 tracing::info!(%cluster_domain, "Using configured Kubernetes cluster domain");
+                if !cluster_domain.ends_with('.') {
+                    tracing::warn!(%cluster_domain, "Your configured Kubernetes cluster domain does not end with a dot (\".\"). We recommend to add a trailing dot for performance reasons, see https://github.com/stackabletech/issues/issues/656 for details");
+                }
 
                 cluster_domain.clone()
             }