fix(ecs): fix memoryReservationLimit in LoadBalancedEcsService (#2463)

Previously, only `memoryLimitMiB` was being set in the constructor. This would cause an unexpected validation error when a LoadBalancedEcsService was instantiated with `memoryReservationMiB` only specified. This fix correctly sets both fields.

Fixes #2263

Author: piradeepk

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

@@ -42,17 +42,18 @@ export class LoadBalancedEc2Service extends LoadBalancedServiceBase {
     const container = taskDefinition.addContainer('web', {
       image: props.image,
       memoryLimitMiB: props.memoryLimitMiB,
-      environment: props.environment,
+      memoryReservationMiB: props.memoryReservationMiB,
+      environment: props.environment
     });
 
     container.addPortMappings({
-      containerPort: props.containerPort || 80,
+      containerPort: props.containerPort || 80
     });
 
     const service = new Ec2Service(this, "Service", {
       cluster: props.cluster,
       desiredCount: props.desiredCount || 1,
-      taskDefinition,
+      taskDefinition
     });
 
     this.addServiceAsTarget(service);

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

@@ -26,7 +26,7 @@ export = {
       }
     });
 
-    // THEN - stack containers a load balancer and a service
+    // THEN - stack contains a load balancer and a service
     expect(stack).to(haveResource('AWS::ElasticLoadBalancingV2::LoadBalancer'));
 
     expect(stack).to(haveResource("AWS::ECS::Service", {
@@ -47,6 +47,35 @@ export = {
               Value: "test environment variable 2 value"
             }
           ],
+          Memory: 1024
+        }
+      ]
+    }));
+
+    test.done();
+  },
+
+  'test ECS loadbalanced construct with memoryReservationMiB'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.VpcNetwork(stack, 'VPC');
+    const cluster = new ecs.Cluster(stack, 'Cluster', { vpc });
+    cluster.addCapacity('DefaultAutoScalingGroup', { instanceType: new ec2.InstanceType('t2.micro') });
+
+    // WHEN
+    new ecs.LoadBalancedEc2Service(stack, 'Service', {
+      cluster,
+      memoryReservationMiB: 1024,
+      image: ecs.ContainerImage.fromRegistry('test')
+    });
+
+    // THEN - stack contains a load balancer and a service
+    expect(stack).to(haveResource('AWS::ElasticLoadBalancingV2::LoadBalancer'));
+
+    expect(stack).to(haveResourceLike('AWS::ECS::TaskDefinition', {
+      ContainerDefinitions: [
+        {
+          MemoryReservation: 1024
         }
       ]
     }));