feat(eks): default vpc (#3632)

When defining an EKS cluster, the `vpc` property is now
optional. If not specified, a VPC will be defined with
the default configuration for this environment.

It can then be accessed through `cluster.vpc`.

Fixes #3541

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

@@ -24,7 +24,7 @@ manifests within EKS clusters.
 This example defines an Amazon EKS cluster with a single pod:
 
 ```ts
-const cluster = new eks.Cluster(this, 'hello-eks', { vpc });
+const cluster = new eks.Cluster(this, 'hello-eks');
 
 cluster.addCapacity('default', {
   instanceType: new ec2.InstanceType('t2.medium'),
@@ -74,7 +74,6 @@ const clusterAdmin = new iam.Role(this, 'AdminRole', {
 
 // now define the cluster and map role to "masters" RBAC group
 new eks.Cluster(this, 'Cluster', {
-  vpc: vpc,
   mastersRole: clusterAdmin
 });
 ```
@@ -242,7 +241,6 @@ the cluster:
 
 ```ts
 new eks.Cluster(this, 'cluster', {
-  vpc: vpc,
   kubectlEnabled: false
 });
 ```

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

@@ -87,8 +87,10 @@ export interface ClusterAttributes {
 export interface ClusterProps {
   /**
    * The VPC in which to create the Cluster
+   *
+   * @default - a VPC with default configuration will be created and can be accessed through `cluster.vpc`.
    */
-  readonly vpc: ec2.IVpc;
+  readonly vpc?: ec2.IVpc;
 
   /**
    * Where to place EKS Control Plane ENIs
@@ -269,12 +271,12 @@ export class Cluster extends Resource implements ICluster {
    * @param name the name of the Construct to create
    * @param props properties in the IClusterProps interface
    */
-  constructor(scope: Construct, id: string, props: ClusterProps) {
+  constructor(scope: Construct, id: string, props: ClusterProps = { }) {
     super(scope, id, {
       physicalName: props.clusterName,
     });
 
-    this.vpc = props.vpc;
+    this.vpc = props.vpc || new ec2.Vpc(this, 'DefaultVpc');
     this.version = props.version;
 
     this.tagSubnets();
@@ -288,7 +290,7 @@ export class Cluster extends Resource implements ICluster {
     });
 
     const securityGroup = props.securityGroup || new ec2.SecurityGroup(this, 'ControlPlaneSecurityGroup', {
-      vpc: props.vpc,
+      vpc: this.vpc,
       description: 'EKS Control Plane Security Group',
     });
 
@@ -299,7 +301,7 @@ export class Cluster extends Resource implements ICluster {
 
     // Get subnetIds for all selected subnets
     const placements = props.vpcSubnets || [{ subnetType: ec2.SubnetType.PUBLIC }, { subnetType: ec2.SubnetType.PRIVATE }];
-    const subnetIds = [...new Set(Array().concat(...placements.map(s => props.vpc.selectSubnets(s).subnetIds)))];
+    const subnetIds = [...new Set(Array().concat(...placements.map(s => this.vpc.selectSubnets(s).subnetIds)))];
 
     const clusterProps: CfnClusterProps = {
       name: this.physicalName,