From 5d7800f7fdf720c7fe31d0c2055c3082f6549e79 Mon Sep 17 00:00:00 2001
From: Moritz Sanft <58110325+msanft@users.noreply.github.com>
Date: Tue, 21 May 2024 17:31:48 +0200
Subject: [PATCH] bootstrapper: only run disk prioritizer on control plane join

---
 bootstrapper/internal/kubernetes/BUILD.bazel   |  1 +
 bootstrapper/internal/kubernetes/kubernetes.go | 16 +++++++++-------
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/bootstrapper/internal/kubernetes/BUILD.bazel b/bootstrapper/internal/kubernetes/BUILD.bazel
index 935c3fefd..86ef3966e 100644
--- a/bootstrapper/internal/kubernetes/BUILD.bazel
+++ b/bootstrapper/internal/kubernetes/BUILD.bazel
@@ -31,6 +31,7 @@ go_test(
     srcs = ["kubernetes_test.go"],
     embed = [":kubernetes"],
     deps = [
+        "//bootstrapper/internal/etcdio",
         "//bootstrapper/internal/kubernetes/k8sapi",
         "//bootstrapper/internal/kubernetes/kubewaiter",
         "//internal/cloud/metadata",
diff --git a/bootstrapper/internal/kubernetes/kubernetes.go b/bootstrapper/internal/kubernetes/kubernetes.go
index a2c2ec1e9..1081bfe30 100644
--- a/bootstrapper/internal/kubernetes/kubernetes.go
+++ b/bootstrapper/internal/kubernetes/kubernetes.go
@@ -263,13 +263,15 @@ func (k *KubeWrapper) JoinCluster(ctx context.Context, args *kubeadm.BootstrapTo
 		return fmt.Errorf("joining cluster: %v; %w ", string(joinConfigYAML), err)
 	}
 
-	k.log.Info("Prioritizing etcd I/O")
-	err = k.etcdIOPrioritizer.PrioritizeIO()
-	if errors.Is(err, etcdio.ErrNoEtcdProcess) {
-		k.log.Warn("Skipping etcd I/O prioritization as etcd process is not running. " +
-			"This is expected if this node is a non-control-plane node.")
-	} else if err != nil {
-		return fmt.Errorf("prioritizing etcd I/O: %w", err)
+	// If on control plane (and thus with etcd), try to prioritize etcd I/O.
+	if peerRole == role.ControlPlane {
+		k.log.Info("Prioritizing etcd I/O")
+		err = k.etcdIOPrioritizer.PrioritizeIO()
+		if errors.Is(err, etcdio.ErrNoEtcdProcess) {
+			k.log.Warn("No etcd process found, skipping I/O prioritization. Is this a single-node cluster?")
+		} else if err != nil {
+			return fmt.Errorf("prioritizing etcd I/O: %w", err)
+		}
 	}
 
 	return nil