fix(aws-ecs): handle long ARN formats for services

Due to a bug in Cloudformation, Fn::GetAtt for service name on an ECS
service was returning the cluster name instead of the service name. This
was causing the ResourceId on AWS::ApplicationAutoScaling::ScalableTarget to be set incorrectly.

Fixes aws#1849.

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

@@ -62,6 +62,21 @@ export interface BaseServiceProps {
    * Options for enabling AWS Cloud Map service discovery for the service
    */
   readonly serviceDiscoveryOptions?: ServiceDiscoveryOptions;
+
+  /**
+   * Whether the new long ARN format has been enabled on ECS services.
+   * NOTE: This assumes customer has opted into the new format for the IAM role used for the service, and is a
+   * workaround for a current bug in Cloudformation in which the service name is not correctly returned when long ARN is
+   * enabled.
+   *
+   * Old ARN format: arn:aws:ecs:region:aws_account_id:service/service-name
+   * New ARN format: arn:aws:ecs:region:aws_account_id:service/cluster-name/service-name
+   *
+   * See: https://docs.aws.amazon.com/AmazonECS/latest/userguide/ecs-resource-ids.html
+   *
+   * @default false
+   */
+  readonly longArnEnabled?: boolean;
 }
 
 /**
@@ -95,6 +110,11 @@ export abstract class BaseService extends cdk.Construct
    */
   public readonly taskDefinition: TaskDefinition;
 
+  /**
+   * Whether the new long ARN format has been enabled on ECS services.
+   */
+  public readonly longArnEnabled: boolean;
+
   protected cloudmapService?: cloudmap.Service;
   protected cluster: ICluster;
   protected loadBalancers = new Array<CfnService.LoadBalancerProperty>();
@@ -128,15 +148,22 @@ export abstract class BaseService extends cdk.Construct
       serviceRegistries: new cdk.Token(() => this.serviceRegistries),
       ...additionalProps
     });
+
+    this.longArnEnabled = props.longArnEnabled !== undefined ? props.longArnEnabled : false;
     this.serviceArn = this.resource.serviceArn;
-    this.serviceName = this.resource.serviceName;
+
+    // This is a workaround for CFN bug that returns the cluster name instead of the service name when long ARN formats
+    // are enabled for the principal in a given region.
+    this.serviceName = this.longArnEnabled
+      ? cdk.Fn.select(2, cdk.Fn.split('/', this.serviceArn))
+      : this.resource.serviceName;
+
     this.clusterName = clusterName;
     this.cluster = props.cluster;
 
     if (props.serviceDiscoveryOptions) {
       this.enableServiceDiscovery(props.serviceDiscoveryOptions);
     }
-
   }
 
   /**
@@ -177,7 +204,7 @@ export abstract class BaseService extends cdk.Construct
 
     return this.scalableTaskCount = new ScalableTaskCount(this, 'TaskCount', {
       serviceNamespace: appscaling.ServiceNamespace.Ecs,
-      resourceId: `service/${this.clusterName}/${this.resource.serviceName}`,
+      resourceId: `service/${this.clusterName}/${this.serviceName}`,
       dimension: 'ecs:service:DesiredCount',
       role: this.makeAutoScalingRole(),
       ...props

packages/@aws-cdk/aws-ecs/test/fargate/integ.lb-awsvpc-nw.expected.json

@@ -522,9 +522,16 @@
               },
               "/",
               {
-                "Fn::GetAtt": [
-                  "ServiceD69D759B",
-                  "Name"
+                "Fn::Select": [
+                  2,
+                  {
+                    "Fn::Split": [
+                      "/",
+                      {
+                        "Ref": "ServiceD69D759B"
+                      }
+                    ]
+                  }
                 ]
               }
             ]
@@ -682,4 +689,4 @@
       }
     }
   }
-}
+}

packages/@aws-cdk/aws-ecs/test/fargate/integ.lb-awsvpc-nw.ts

@@ -27,6 +27,7 @@ container.addPortMappings({
 const service = new ecs.FargateService(stack, "Service", {
   cluster,
   taskDefinition,
+  longArnEnabled: true
 });
 
 const scaling = service.autoScaleTaskCount({ maxCapacity: 10 });

packages/@aws-cdk/aws-ecs/test/fargate/test.fargate-service.ts

@@ -216,7 +216,25 @@ export = {
       // THEN
       expect(stack).to(haveResource('AWS::ApplicationAutoScaling::ScalableTarget', {
         MaxCapacity: 10,
-        MinCapacity: 1
+        MinCapacity: 1,
+        ResourceId: {
+          "Fn::Join": [
+            "",
+            [
+              "service/",
+              {
+                Ref: "EcsCluster97242B84"
+              },
+              "/",
+              {
+                "Fn::GetAtt": [
+                  "ServiceD69D759B",
+                  "Name"
+                ]
+              }
+            ]
+          ]
+        },
       }));
 
       expect(stack).to(haveResource('AWS::ApplicationAutoScaling::ScalingPolicy', {
@@ -236,6 +254,71 @@ export = {
         }
       }));
 
+      test.done();
+    },
+
+    'allows auto scaling by ALB with new service arn format'(test: Test) {
+      // GIVEN
+      const stack = new cdk.Stack();
+      const vpc = new ec2.VpcNetwork(stack, 'MyVpc', {});
+      const cluster = new ecs.Cluster(stack, 'EcsCluster', { vpc });
+      const taskDefinition = new ecs.FargateTaskDefinition(stack, 'FargateTaskDef');
+      const container = taskDefinition.addContainer('MainContainer', {
+        image: ContainerImage.fromRegistry('hello'),
+      });
+      container.addPortMappings({ containerPort: 8000 });
+
+      const service = new ecs.FargateService(stack, 'Service', {
+        cluster,
+        taskDefinition,
+        longArnEnabled: true
+      });
+
+      const lb = new elbv2.ApplicationLoadBalancer(stack, "lb", { vpc });
+      const listener = lb.addListener("listener", { port: 80 });
+      const targetGroup = listener.addTargets("target", {
+        port: 80,
+        targets: [service]
+      });
+
+      // WHEN
+      const capacity = service.autoScaleTaskCount({ maxCapacity: 10, minCapacity: 1 });
+      capacity.scaleOnRequestCount("ScaleOnRequests", {
+        requestsPerTarget: 1000,
+        targetGroup
+      });
+
+      // THEN
+      expect(stack).to(haveResource('AWS::ApplicationAutoScaling::ScalableTarget', {
+        MaxCapacity: 10,
+        MinCapacity: 1,
+        ResourceId: {
+          "Fn::Join": [
+            "",
+            [
+              "service/",
+              {
+                Ref: "EcsCluster97242B84"
+              },
+              "/",
+              {
+                "Fn::Select": [
+                  2,
+                  {
+                    "Fn::Split": [
+                      "/",
+                      {
+                        Ref: "ServiceD69D759B"
+                      }
+                    ]
+                  }
+                ]
+              }
+            ]
+          ]
+        },
+      }));
+
       test.done();
     }
   },