warn about performance for certain versions of kubernetes

cmd/minikube/cmd/start.go

@@ -394,7 +394,7 @@ func startWithDriver(cmd *cobra.Command, starter node.Starter, existing *config.
 }
 
 func warnAboutMultiNodeCNI() {
-	out.WarningT("Cluster was created without any CNI, adding node to it might cause broken network.")
+	out.WarningT("Cluster was created without any CNI, adding a node to it might cause broken networking.")
 }
 
 func updateDriver(driverName string) {
@@ -1370,6 +1370,14 @@ func validateKubernetesVersion(old *config.ClusterConfig) {
 		exitIfNotForced(reason.KubernetesTooOld, "Kubernetes {{.version}} is not supported by this release of minikube", out.V{"version": nvs})
 	}
 
+	// If the version of Kubernetes has a known issue, print a warning out to the screen
+	if issue := reason.ProblematicK8sVersion(nvs); issue != nil {
+		out.WarningT(issue.Description, out.V{"version": nvs.String()})
+		if issue.URL != "" {
+			out.WarningT("For more information, see: {{.url}}", out.V{"url": issue.URL})
+		}
+	}
+
 	if old == nil || old.KubernetesConfig.KubernetesVersion == "" {
 		return
 	}

pkg/minikube/reason/k8s.go

@@ -0,0 +1,58 @@
+/*
+Copyright 2021 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package reason
+
+import "github.com/blang/semver"
+
+// K8sIssue represents a known issue with a particular version of Kubernetes
+type K8sIssue struct {
+	// VersionAffected is the list of Kubernetes versions that has a particular issue
+	VersionsAffected []string
+	// Description is what will be printed to the user describing the issue
+	Description string
+	// URL is a link to an issue or documentation about the issue, optional.
+	URL string
+}
+
+var k8sIssues = []K8sIssue{
+	{
+		VersionsAffected: []string{
+			"1.18.16",
+			"1.18.17",
+			"1.19.8",
+			"1.19.9",
+			"1.20.3",
+			"1.20.4",
+			"1.20.5",
+			"1.21.0",
+		},
+		Description: "Kubernetes {{.version}} has a known performance issue on cluster startup. It might take 2 to 3 minutes for a cluster to start.",
+		URL:         "https://github.com/kubernetes/kubeadm/issues/2395",
+	},
+}
+
+// ProblematicK8sVersion checks for the supplied Kubernetes version and checks if there's a known issue with it.
+func ProblematicK8sVersion(v semver.Version) *K8sIssue {
+	for _, issue := range k8sIssues {
+		for _, va := range issue.VersionsAffected {
+			if va == v.String() {
+				return &issue
+			}
+		}
+	}
+	return nil
+}

pkg/minikube/reason/reason.go

@@ -14,22 +14,6 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-/*
-Copyright 2020 The Kubernetes Authors All rights reserved.
-
-Licensed under the Apache License, Version 2.0 (the Kind{ID: "License", ExitCode: });
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an Kind{ID: "AS IS", ExitCode: } BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
 package reason
 
 import (