feat(ecs): make cluster and vpc optional for higher level constructs

packages/@aws-cdk/aws-ecs-patterns/lib/base/load-balanced-service-base.ts

@@ -1,4 +1,5 @@
 import { ICertificate } from '@aws-cdk/aws-certificatemanager';
+import ec2 = require('@aws-cdk/aws-ec2');
 import ecs = require('@aws-cdk/aws-ecs');
 import elbv2 = require('@aws-cdk/aws-elasticloadbalancingv2');
 import { AddressRecordTarget, ARecord, IHostedZone } from '@aws-cdk/aws-route53';
@@ -16,8 +17,19 @@ export enum LoadBalancerType {
 export interface LoadBalancedServiceBaseProps {
   /**
    * The cluster where your service will be deployed
+   * You can only specify either vpc or cluster. Alternatively, you can leave both blank
+   *
+   * @default - create a new cluster; if you do not specify a cluster nor a vpc, a new VPC will be created for you as well
+   */
+  readonly cluster?: ecs.ICluster;
+
+  /**
+   * VPC that the cluster instances or tasks are running in
+   * You can only specify either vpc or cluster. Alternatively, you can leave both blank
+   *
+   * @default - use vpc of cluster or create a new one
    */
-  readonly cluster: ecs.ICluster;
+  readonly vpc?: ec2.IVpc;
 
   /**
    * The image to start.
@@ -108,11 +120,18 @@ export abstract class LoadBalancedServiceBase extends cdk.Construct {
 
   public readonly targetGroup: elbv2.ApplicationTargetGroup | elbv2.NetworkTargetGroup;
 
+  public readonly cluster: ecs.ICluster;
+
   public readonly logDriver?: ecs.LogDriver;
 
   constructor(scope: cdk.Construct, id: string, props: LoadBalancedServiceBaseProps) {
     super(scope, id);
 
+    if (props.cluster && props.vpc) {
+      throw new Error(`You can only specify either vpc or cluster. Alternatively, you can leave both blank`);
+    }
+    this.cluster = props.cluster || this.getDefaultCluster(this, props.vpc);
+
     // Create log driver if logging is enabled
     const enableLogging = props.enableLogging !== undefined ? props.enableLogging : true;
     this.logDriver = enableLogging ? this.createAWSLogDriver(this.node.id) : undefined;
@@ -127,7 +146,7 @@ export abstract class LoadBalancedServiceBase extends cdk.Construct {
     const internetFacing = props.publicLoadBalancer !== undefined ? props.publicLoadBalancer : true;
 
     const lbProps = {
-      vpc: props.cluster.vpc,
+      vpc: this.cluster.vpc,
       internetFacing
     };
 
@@ -176,6 +195,13 @@ export abstract class LoadBalancedServiceBase extends cdk.Construct {
     new cdk.CfnOutput(this, 'LoadBalancerDNS', { value: this.loadBalancer.loadBalancerDnsName });
   }
 
+  protected getDefaultCluster(scope: cdk.Construct, vpc?: ec2.IVpc): ecs.Cluster {
+    // magic string to avoid collision with user-defined constructs
+    const DEFAULT_CLUSTER_ID = `EcsDefaultClusterMnL3mNNYN${vpc ? vpc.node.id : ''}`;
+    const stack = cdk.Stack.of(scope);
+    return stack.node.tryFindChild(DEFAULT_CLUSTER_ID) as ecs.Cluster || new ecs.Cluster(stack, DEFAULT_CLUSTER_ID, { vpc });
+  }
+
   protected addServiceAsTarget(service: ecs.BaseService) {
     if (this.loadBalancerType === LoadBalancerType.APPLICATION) {
       (this.targetGroup as elbv2.ApplicationTargetGroup).addTarget(service);

packages/@aws-cdk/aws-ecs-patterns/lib/ecs/load-balanced-ecs-service.ts

@@ -62,7 +62,7 @@ export class LoadBalancedEc2Service extends LoadBalancedServiceBase {
 
     const assignPublicIp = props.publicTasks !== undefined ? props.publicTasks : false;
     const service = new ecs.Ec2Service(this, "Service", {
-      cluster: props.cluster,
+      cluster: this.cluster,
       desiredCount: props.desiredCount || 1,
       taskDefinition,
       assignPublicIp

packages/@aws-cdk/aws-ecs-patterns/lib/fargate/load-balanced-fargate-service.ts

@@ -106,7 +106,7 @@ export class LoadBalancedFargateService extends LoadBalancedServiceBase {
     });
     const assignPublicIp = props.publicTasks !== undefined ? props.publicTasks : false;
     const service = new ecs.FargateService(this, "Service", {
-      cluster: props.cluster,
+      cluster: this.cluster,
       desiredCount: props.desiredCount || 1,
       taskDefinition,
       assignPublicIp,

packages/@aws-cdk/aws-ecs-patterns/test/ec2/test.l3s.ts

@@ -56,6 +56,48 @@ export = {
     test.done();
   },
 
+  'set vpc instead of cluster'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.Vpc(stack, 'VPC');
+
+    // WHEN
+    new ecsPatterns.LoadBalancedEc2Service(stack, 'Service', {
+      vpc,
+      memoryLimitMiB: 1024,
+      image: ecs.ContainerImage.fromRegistry('test'),
+      desiredCount: 2,
+      environment: {
+        TEST_ENVIRONMENT_VARIABLE1: "test environment variable 1 value",
+        TEST_ENVIRONMENT_VARIABLE2: "test environment variable 2 value"
+      }
+    });
+
+    // THEN - stack does not contain a LaunchConfiguration
+    expect(stack, true).notTo(haveResource("AWS::AutoScaling::LaunchConfiguration"));
+
+    test.throws(() => expect(stack));
+
+    test.done();
+  },
+
+  'setting vpc and cluster throws error'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.Vpc(stack, 'VPC');
+    const cluster = new ecs.Cluster(stack, 'Cluster', { vpc });
+
+    // WHEN
+    test.throws(() => new ecsPatterns.LoadBalancedEc2Service(stack, 'Service', {
+      cluster,
+      vpc,
+      loadBalancerType: ecsPatterns.LoadBalancerType.NETWORK,
+      image: ecs.ContainerImage.fromRegistry("/aws/aws-example-app")
+    }));
+
+    test.done();
+  },
+
   'test ECS loadbalanced construct with memoryReservationMiB'(test: Test) {
     // GIVEN
     const stack = new cdk.Stack();