feat(eks): bottlerocket versoin follows the cluster k8s versoin (#10189)

This PR will implicitly select correct bottlerocket variant in consist with the  cluster k8s version. For example, if the cluster k8s version is `1.17`, previously only bottlerocket `aws-k8s-1.15` variant is available. Now the variant will be `aws-k8s-1.17`

BREAKING CHANGE: Clusters previously running k8s version other than `1.15` and bottlerocket AMI(`aws-k8s-1.15` variant) will trigger AMI and node replacement.

Closes: #10188 

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-eks/README.md

@@ -726,7 +726,7 @@ chart2.node.addDependency(chart1);
 
 [Bottlerocket](https://aws.amazon.com/bottlerocket/) is a Linux-based open-source operating system that is purpose-built by Amazon Web Services for running containers on virtual machines or bare metal hosts. At this moment the managed nodegroup only supports Amazon EKS-optimized AMI but it's possible to create a capacity of self-managed `AutoScalingGroup` running with bottlerocket Linux AMI.
 
-> **NOTICE**: Bottlerocket is in public preview and only available in [some supported AWS regions](https://github.com/bottlerocket-os/bottlerocket/blob/develop/QUICKSTART.md#finding-an-ami).
+> **NOTICE**: Bottlerocket is only available in [some supported AWS regions](https://github.com/bottlerocket-os/bottlerocket/blob/develop/QUICKSTART-EKS.md#finding-an-ami).
 
 The following example will create a capacity with self-managed Amazon EC2 capacity of 2 `t3.small` Linux instances running with `Bottlerocket` AMI.
 
@@ -739,6 +739,10 @@ cluster.addCapacity('BottlerocketNodes', {
 });
 ```
 
+The Bottlerocket AMI will be auto selected with the variant of different k8s version for the `x86_64` architecture.
+For example, if the Amazon EKS cluster version is `1.17`, the Bottlerocket AMI variant will be auto selected as
+`aws-k8s-1.17` behind the scene. See [Variants](https://github.com/bottlerocket-os/bottlerocket/blob/develop/README.md#variants) for more details.
+
 To define only Bottlerocket capacity in your cluster, set `defaultCapacity` to `0` when you define the cluster as described above.
 
 Please note Bottlerocket does not allow to customize bootstrap options and `bootstrapOptions` properties is not supported when you create the `Bottlerocket` capacity.

packages/@aws-cdk/aws-eks/lib/cluster.ts

@@ -18,6 +18,7 @@ import { KubernetesObjectValue } from './k8s-object-value';
 import { KubernetesPatch } from './k8s-patch';
 import { KubectlProvider } from './kubectl-provider';
 import { Nodegroup, NodegroupOptions } from './managed-nodegroup';
+import { BottleRocketImage } from './private/bottlerocket';
 import { ServiceAccount, ServiceAccountOptions } from './service-account';
 import { LifecycleLabel, renderAmazonLinuxUserData, renderBottlerocketUserData } from './user-data';
 
@@ -1045,7 +1046,9 @@ export class Cluster extends ClusterBase {
       ...options,
       vpc: this.vpc,
       machineImage: options.machineImageType === MachineImageType.BOTTLEROCKET ?
-        new BottleRocketImage() :
+        new BottleRocketImage({
+          kubernetesVersion: this.version.version,
+        }) :
         new EksOptimizedImage({
           nodeType: nodeTypeForInstanceType(options.instanceType),
           cpuArch: cpuArchForInstanceType(options.instanceType),
@@ -1695,38 +1698,6 @@ export class EksOptimizedImage implements ec2.IMachineImage {
   }
 }
 
-/**
- * Construct an Bottlerocket image from the latest AMI published in SSM
- */
-class BottleRocketImage implements ec2.IMachineImage {
-  private readonly kubernetesVersion?: string;
-
-  private readonly amiParameterName: string;
-
-  /**
-   * Constructs a new instance of the BottleRocketImage class.
-   */
-  public constructor() {
-    // only 1.15 is currently available
-    this.kubernetesVersion = '1.15';
-
-    // set the SSM parameter name
-    this.amiParameterName = `/aws/service/bottlerocket/aws-k8s-${this.kubernetesVersion}/x86_64/latest/image_id`;
-  }
-
-  /**
-   * Return the correct image
-   */
-  public getImage(scope: Construct): ec2.MachineImageConfig {
-    const ami = ssm.StringParameter.valueForStringParameter(scope, this.amiParameterName);
-    return {
-      imageId: ami,
-      osType: ec2.OperatingSystemType.LINUX,
-      userData: ec2.UserData.custom(''),
-    };
-  }
-}
-
 // MAINTAINERS: use ./scripts/kube_bump.sh to update LATEST_KUBERNETES_VERSION
 const LATEST_KUBERNETES_VERSION = '1.14';
 

packages/@aws-cdk/aws-eks/lib/private/bottlerocket.ts

@@ -0,0 +1,44 @@
+import * as ec2 from '@aws-cdk/aws-ec2';
+import * as ssm from '@aws-cdk/aws-ssm';
+import { Construct } from '@aws-cdk/core';
+
+/**
+ * Properties for BottleRocketImage
+ */
+export interface BottleRocketImageProps {
+  /**
+   * The Kubernetes version to use
+   */
+  readonly kubernetesVersion: string;
+}
+
+/**
+ * Construct an Bottlerocket image from the latest AMI published in SSM
+ */
+export class BottleRocketImage implements ec2.IMachineImage {
+  private readonly kubernetesVersion: string;
+
+  private readonly amiParameterName: string;
+
+  /**
+   * Constructs a new instance of the BottleRocketImage class.
+   */
+  public constructor(props: BottleRocketImageProps) {
+    this.kubernetesVersion = props.kubernetesVersion;
+
+    // set the SSM parameter name
+    this.amiParameterName = `/aws/service/bottlerocket/aws-k8s-${this.kubernetesVersion}/x86_64/latest/image_id`;
+  }
+
+  /**
+   * Return the correct image
+   */
+  public getImage(scope: Construct): ec2.MachineImageConfig {
+    const ami = ssm.StringParameter.valueForStringParameter(scope, this.amiParameterName);
+    return {
+      imageId: ami,
+      osType: ec2.OperatingSystemType.LINUX,
+      userData: ec2.UserData.custom(''),
+    };
+  }
+}