From a3cbfb6605603db70b2fe96efcf5192afea26fbb Mon Sep 17 00:00:00 2001
From: Sebastian Florek <sebastian@plural.sh>
Date: Mon, 17 Jun 2024 12:27:37 -0500
Subject: [PATCH] feat: scrape minimum kubelet version from k8s nodes (#223)

* feat: scrape minimum kubelet version from k8s nodes

* log pinger errors
---
 pkg/ping/build.go  |  3 ++-
 pkg/ping/pinger.go | 51 ++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/pkg/ping/build.go b/pkg/ping/build.go
index 8991c7b7..7b0d88e7 100644
--- a/pkg/ping/build.go
+++ b/pkg/ping/build.go
@@ -8,10 +8,11 @@ import (
 	"k8s.io/apimachinery/pkg/version"
 )
 
-func pingAttributes(info *version.Info, pods []string) console.ClusterPing {
+func pingAttributes(info *version.Info, pods []string, minKubeletVersion *string) console.ClusterPing {
 	vs := strings.Split(info.GitVersion, "-")
 	return console.ClusterPing{
 		CurrentVersion: strings.TrimPrefix(vs[0], "v"),
 		Distro:         lo.ToPtr(findDistro(append(pods, info.GitVersion))),
+		KubeletVersion: minKubeletVersion,
 	}
 }
diff --git a/pkg/ping/pinger.go b/pkg/ping/pinger.go
index 3149e605..985c962f 100644
--- a/pkg/ping/pinger.go
+++ b/pkg/ping/pinger.go
@@ -3,12 +3,16 @@ package ping
 import (
 	"context"
 
-	"github.com/pluralsh/deployment-operator/pkg/client"
+	"github.com/Masterminds/semver/v3"
 	"github.com/samber/lo"
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/discovery"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/klog/v2"
 	"k8s.io/kubectl/pkg/cmd/util"
+
+	"github.com/pluralsh/deployment-operator/pkg/client"
 )
 
 type Pinger struct {
@@ -28,23 +32,27 @@ func New(console client.Client, discovery *discovery.DiscoveryClient, factory ut
 func (p *Pinger) Ping() error {
 	info, err := p.discoveryClient.ServerVersion()
 	if err != nil {
+		klog.ErrorS(err, "failed to get server version")
 		return err
 	}
 
 	cs, err := p.factory.KubernetesClientSet()
 	if err != nil {
+		klog.ErrorS(err, "failed to create kubernetes clientset")
 		return nil
 	}
 
-	podNames := []string{}
+	var podNames []string
 	// can find some distro information by checking what's running in kube-system
-	if pods, err := cs.CoreV1().Pods("kube-system").List(context.TODO(), metav1.ListOptions{}); err == nil {
+	if pods, err := cs.CoreV1().Pods("kube-system").List(context.Background(), metav1.ListOptions{}); err == nil {
 		podNames = lo.Map(pods.Items, func(pod corev1.Pod, ind int) string {
 			return pod.Name
 		})
 	}
 
-	attrs := pingAttributes(info, podNames)
+	minKubeletVersion := p.minimumKubeletVersion(cs)
+
+	attrs := pingAttributes(info, podNames, minKubeletVersion)
 	if err := p.consoleClient.PingCluster(attrs); err != nil {
 		attrs.Distro = nil
 		return p.consoleClient.PingCluster(attrs) // fallback to no distro to support old console servers
@@ -52,3 +60,38 @@ func (p *Pinger) Ping() error {
 
 	return nil
 }
+
+// minimumKubeletVersion tries to scrape a minimum kubelet version across all nodes in the cluster.
+// It is expected that the kubelet will report to the API a valid SemVer-ish version.
+// If no parsable version is found across all nodes, nil will be returned.
+func (p *Pinger) minimumKubeletVersion(client *kubernetes.Clientset) *string {
+	nodes, err := client.CoreV1().Nodes().List(context.Background(), metav1.ListOptions{})
+	if err != nil {
+		klog.ErrorS(err, "failed to list nodes")
+		return nil
+	}
+
+	minKubeletVersion := new(semver.Version)
+	for _, node := range nodes.Items {
+		kubeletVersion, _ := semver.NewVersion(node.Status.NodeInfo.KubeletVersion)
+		if kubeletVersion == nil {
+			continue
+		}
+
+		// Initialize with first correctly parsed version
+		if len(minKubeletVersion.Original()) == 0 {
+			minKubeletVersion = kubeletVersion
+			continue
+		}
+
+		if kubeletVersion.LessThan(minKubeletVersion) {
+			minKubeletVersion = kubeletVersion
+		}
+	}
+
+	if len(minKubeletVersion.Original()) == 0 {
+		return nil
+	}
+
+	return lo.ToPtr(minKubeletVersion.Original())
+}