feat: automatic cluster detection

Cargo.toml

@@ -25,6 +25,7 @@ educe =  { version = "0.6.0", default-features = false, features = ["Clone", "De
 either = "1.13.0"
 futures = "0.3.30"
 futures-util = "0.3.30"
+http = "1.3.1"
 indexmap = "2.5.0"
 indoc = "2.0.6"
 insta = { version= "1.40", features = ["glob"] }

crates/stackable-operator/CHANGELOG.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+### Added
+
+- The default Kubernetes cluster domain name is now fetched from the kubelet API unless explicitely configured ([#1068]).
+
 ### Changed
 
 - Update `kube` to `1.1.0` ([#1049]).
@@ -23,6 +27,7 @@ All notable changes to this project will be documented in this file.
 [#1058]: https://github.com/stackabletech/operator-rs/pull/1058
 [#1060]: https://github.com/stackabletech/operator-rs/pull/1060
 [#1064]: https://github.com/stackabletech/operator-rs/pull/1064
+[#1068]: https://github.com/stackabletech/operator-rs/pull/1068
 
 ## [0.93.2] - 2025-05-26
 

crates/stackable-operator/Cargo.toml

@@ -28,6 +28,7 @@ dockerfile-parser.workspace = true
 either.workspace = true
 educe.workspace = true
 futures.workspace = true
+http.workspace = true
 indexmap.workspace = true
 json-patch.workspace = true
 k8s-openapi.workspace = true

crates/stackable-operator/src/client.rs

@@ -21,7 +21,10 @@ use tracing::trace;
 
 use crate::{
     kvp::LabelSelectorExt,
-    utils::cluster_info::{KubernetesClusterInfo, KubernetesClusterInfoOpts},
+    utils::{
+        cluster_info::{KubernetesClusterInfo, KubernetesClusterInfoOpts},
+        kubelet,
+    },
 };
 
 pub type Result<T, E = Error> = std::result::Result<T, E>;
@@ -84,6 +87,9 @@ pub enum Error {
 
     #[snafu(display("unable to create kubernetes client"))]
     CreateKubeClient { source: kube::Error },
+
+    #[snafu(display("unable to fetch kubelet config"))]
+    KubeletConfig { source: kubelet::Error },
 }
 
 /// This `Client` can be used to access Kubernetes.
@@ -651,7 +657,25 @@ pub async fn initialize_operator(
         .context(InferKubeConfigSnafu)?;
     let default_namespace = kubeconfig.default_namespace.clone();
     let client = kube::Client::try_from(kubeconfig).context(CreateKubeClientSnafu)?;
-    let cluster_info = KubernetesClusterInfo::new(cluster_info_opts);
+
+    let local_cluster_info_opts = match cluster_info_opts.kubernetes_cluster_domain {
+        None => {
+            trace!("Cluster domain not set, fetching kubelet config to determine cluster domain.");
+
+            let kubelet_config = kubelet::KubeletConfig::fetch(&client)
+                .await
+                .context(KubeletConfigSnafu)?;
+
+            KubernetesClusterInfoOpts {
+                kubernetes_cluster_domain: Some(kubelet_config.cluster_domain),
+            }
+        }
+        _ => KubernetesClusterInfoOpts {
+            kubernetes_cluster_domain: cluster_info_opts.kubernetes_cluster_domain.clone(),
+        },
+    };
+
+    let cluster_info = KubernetesClusterInfo::new(&local_cluster_info_opts);
 
     Ok(Client::new(
         client,

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

@@ -0,0 +1,69 @@
+use http;
+use k8s_openapi::api::core::v1::Node;
+use kube::{
+    Api,
+    api::{ListParams, ResourceExt},
+    client::Client,
+};
+use serde::Deserialize;
+use snafu::{OptionExt, ResultExt, Snafu};
+
+use crate::commons::networking::DomainName;
+
+#[derive(Debug, Snafu)]
+pub enum Error {
+    #[snafu(display("failed to list nodes"))]
+    ListNodes { source: kube::Error },
+    #[snafu(display("failed to build proxy/configz request"))]
+    ConfigzRequest { source: http::Error },
+
+    #[snafu(display("failed to fetch kubelet config from node {node}"))]
+    FetchNodeKubeletConfig { source: kube::Error, node: String },
+
+    #[snafu(display("failed to fetch `kubeletconfig` JSON key from configz response"))]
+    KubeletConfigJsonKey,
+
+    #[snafu(display("failed to deserialize kubelet config JSON"))]
+    KubeletConfigJson { source: serde_json::Error },
+
+    #[snafu(display("empty Kubernetes nodes list"))]
+    EmptyKubernetesNodesList,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct ProxyConfigResponse {
+    kubeletconfig: KubeletConfig,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct KubeletConfig {
+    pub cluster_domain: DomainName,
+}
+
+impl KubeletConfig {
+    /// Fetches the kubelet configuration from the "first" node in the Kubernetes cluster.
+    pub async fn fetch(client: &Client) -> Result<Self, Error> {
+        let api: Api<Node> = Api::all(client.clone());
+        let nodes = api
+            .list(&ListParams::default())
+            .await
+            .context(ListNodesSnafu)?;
+        let node = nodes.iter().next().context(EmptyKubernetesNodesListSnafu)?;
+
+        let name = node.name_any();
+
+        let url = format!("/api/v1/nodes/{}/proxy/configz", name);
+        let req = http::Request::get(url)
+            .body(Default::default())
+            .context(ConfigzRequestSnafu)?;
+
+        let resp = client
+            .request::<ProxyConfigResponse>(req)
+            .await
+            .context(FetchNodeKubeletConfigSnafu { node: name })?;
+
+        Ok(resp.kubeletconfig)
+    }
+}

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

@@ -1,6 +1,7 @@
 pub mod bash;
 pub mod cluster_info;
 pub mod crds;
+pub mod kubelet;
 pub mod logging;
 mod option;
 mod url;