fix(aws-elasticloadbalancingv2): target group metrics

packages/@aws-cdk/aws-autoscaling/test/integ.asg-w-elbv2.expected.json

@@ -495,15 +495,7 @@
                         "Fn::Split": [
                           "/",
                           {
-                            "Fn::Select": [
-                              0,
-                              {
-                                "Fn::GetAtt": [
-                                  "LBListenerTargetGroupF04FCF6D",
-                                  "LoadBalancerArns"
-                                ]
-                              }
-                            ]
+                            "Ref": "LBListener49E825B4"
                           }
                         ]
                       }
@@ -517,15 +509,7 @@
                         "Fn::Split": [
                           "/",
                           {
-                            "Fn::Select": [
-                              0,
-                              {
-                                "Fn::GetAtt": [
-                                  "LBListenerTargetGroupF04FCF6D",
-                                  "LoadBalancerArns"
-                                ]
-                              }
-                            ]
+                            "Ref": "LBListener49E825B4"
                           }
                         ]
                       }
@@ -539,15 +523,7 @@
                         "Fn::Split": [
                           "/",
                           {
-                            "Fn::Select": [
-                              0,
-                              {
-                                "Fn::GetAtt": [
-                                  "LBListenerTargetGroupF04FCF6D",
-                                  "LoadBalancerArns"
-                                ]
-                              }
-                            ]
+                            "Ref": "LBListener49E825B4"
                           }
                         ]
                       }

packages/@aws-cdk/aws-autoscaling/test/test.scaling.ts

@@ -94,10 +94,7 @@ export = {
       const arnParts = {
         "Fn::Split": [
           "/",
-          { "Fn::Select": [
-            0,
-            { "Fn::GetAtt": [ "ALBListenerTargetsGroup01D7716A", "LoadBalancerArns" ] }
-          ]}
+          { Ref: "ALBListener3B99FF85" }
         ]};
 
       expect(stack).to(haveResource('AWS::AutoScaling::ScalingPolicy', {

packages/@aws-cdk/aws-elasticloadbalancingv2/lib/alb/application-target-group.ts

@@ -1,7 +1,8 @@
 import cloudwatch = require('@aws-cdk/aws-cloudwatch');
 import ec2 = require('@aws-cdk/aws-ec2');
 import cdk = require('@aws-cdk/cdk');
-import { BaseTargetGroup, BaseTargetGroupProps, ITargetGroup, LoadBalancerTargetProps, TargetGroupRefProps } from '../shared/base-target-group';
+import { BaseTargetGroup, BaseTargetGroupProps, ITargetGroup, loadBalancerNameFromListenerArn,
+         LoadBalancerTargetProps, TargetGroupRefProps } from '../shared/base-target-group';
 import { ApplicationProtocol } from '../shared/enums';
 import { BaseImportedTargetGroup } from '../shared/imported';
 import { determineProtocolAndPort, LazyDependable } from '../shared/util';
@@ -149,6 +150,16 @@ export class ApplicationTargetGroup extends BaseTargetGroup {
     this.loadBalancerAssociationDependencies.push(dependable || listener);
   }
 
+  /**
+   * Full name of first load balancer
+   */
+  public get firstLoadBalancerFullName(): string {
+    if (this.listeners.length === 0) {
+      throw new Error('The TargetGroup needs to be attached to a LoadBalancer before you can call this method');
+    }
+    return loadBalancerNameFromListenerArn(this.listeners[0].listenerArn);
+  }
+
   /**
    * Return the given named metric for this Application Load Balancer Target Group
    *

packages/@aws-cdk/aws-elasticloadbalancingv2/lib/nlb/network-target-group.ts

@@ -1,5 +1,6 @@
 import cdk = require('@aws-cdk/cdk');
-import { BaseTargetGroup, BaseTargetGroupProps, ITargetGroup, LoadBalancerTargetProps, TargetGroupRefProps } from '../shared/base-target-group';
+import { BaseTargetGroup, BaseTargetGroupProps, ITargetGroup, loadBalancerNameFromListenerArn,
+         LoadBalancerTargetProps, TargetGroupRefProps } from '../shared/base-target-group';
 import { Protocol } from '../shared/enums';
 import { BaseImportedTargetGroup } from '../shared/imported';
 import { LazyDependable } from '../shared/util';
@@ -42,12 +43,16 @@ export class NetworkTargetGroup extends BaseTargetGroup {
     return new ImportedNetworkTargetGroup(parent, id, props);
   }
 
+  private readonly listeners: INetworkListener[];
+
   constructor(parent: cdk.Construct, id: string, props: NetworkTargetGroupProps) {
     super(parent, id, props, {
       protocol: Protocol.Tcp,
       port: props.port,
     });
 
+    this.listeners = [];
+
     if (props.proxyProtocolV2) {
       this.setAttribute('proxy_protocol_v2.enabled', 'true');
     }
@@ -72,6 +77,17 @@ export class NetworkTargetGroup extends BaseTargetGroup {
    */
   public registerListener(listener: INetworkListener) {
     this.loadBalancerAssociationDependencies.push(listener);
+    this.listeners.push(listener);
+  }
+
+  /**
+   * Full name of first load balancer
+   */
+  public get firstLoadBalancerFullName(): string {
+    if (this.listeners.length === 0) {
+      throw new Error('The TargetGroup needs to be attached to a LoadBalancer before you can call this method');
+    }
+    return loadBalancerNameFromListenerArn(this.listeners[0].listenerArn);
   }
 }
 

packages/@aws-cdk/aws-elasticloadbalancingv2/lib/shared/base-target-group.ts

@@ -160,7 +160,7 @@ export abstract class BaseTargetGroup extends cdk.Construct implements ITargetGr
    *
    * @example app/my-load-balancer/123456789
    */
-  public readonly firstLoadBalancerFullName: string;
+  public abstract readonly firstLoadBalancerFullName: string;
 
   /**
    * Health check for the members of this target group
@@ -240,11 +240,6 @@ export abstract class BaseTargetGroup extends cdk.Construct implements ITargetGr
     this.loadBalancerArns = this.resource.targetGroupLoadBalancerArns.toString();
     this.targetGroupName = this.resource.targetGroupName;
     this.defaultPort = `${additionalProps.port}`;
-
-    const firstLoadBalancerArn = new cdk.FnSelect(0, this.targetGroupLoadBalancerArns);
-    // arn:aws:elasticloadbalancing:us-west-2:123456789012:loadbalancer/app/my-internal-load-balancer/50dc6c495c0c9188
-    const arnParts = new cdk.FnSplit('/', firstLoadBalancerArn);
-    this.firstLoadBalancerFullName = `${new cdk.FnSelect(1, arnParts)}/${new cdk.FnSelect(2, arnParts)}/${new cdk.FnSelect(3, arnParts)}`;
   }
 
   /**
@@ -365,3 +360,19 @@ export interface LoadBalancerTargetProps {
    */
   targetJson?: any;
 }
+
+/**
+ * Extract the full load balancer name (used for metrics) from the listener ARN:
+ *
+ * Turns
+ *
+ *     arn:aws:elasticloadbalancing:us-west-2:123456789012:listener/app/my-load-balancer/50dc6c495c0c9188/f2f7dc8efc522ab2
+ *
+ * Into
+ *
+ *     app/my-load-balancer/50dc6c495c0c9188
+ */
+export function loadBalancerNameFromListenerArn(listenerArn: string) {
+    const arnParts = new cdk.FnSplit('/', listenerArn);
+    return `${new cdk.FnSelect(1, arnParts)}/${new cdk.FnSelect(2, arnParts)}/${new cdk.FnSelect(3, arnParts)}`;
+}

packages/@aws-cdk/aws-elasticloadbalancingv2/test/alb/test.listener.ts

@@ -389,7 +389,12 @@ export = {
     // GIVEN
     const stack = new cdk.Stack();
     const vpc = new ec2.VpcNetwork(stack, 'VPC');
+    const lb = new elbv2.ApplicationLoadBalancer(stack, 'LB', { vpc });
     const group = new elbv2.ApplicationTargetGroup(stack, 'TargetGroup', { vpc, port: 80 });
+    lb.addListener('SomeListener', {
+      port: 80,
+      defaultTargetGroups: [group]
+    });
 
     // WHEN
     const metrics = [];
@@ -404,16 +409,17 @@ export = {
 
     for (const metric of metrics) {
       test.equal('AWS/ApplicationELB', metric.namespace);
-      const firstArn = { "Fn::Select": [0, { "Fn::GetAtt": ["TargetGroup3D7CD9B8", "LoadBalancerArns"] }] };
+      const loadBalancerArn = { Ref: "LBSomeListenerCA01F1A0" };
+
       test.deepEqual(cdk.resolve(metric.dimensions), {
          TargetGroup: { 'Fn::GetAtt': [ 'TargetGroup3D7CD9B8', 'TargetGroupFullName' ] },
          LoadBalancer: { 'Fn::Join':
             [ '',
-              [ { 'Fn::Select': [ 1, { 'Fn::Split': [ '/', firstArn ] } ] },
+              [ { 'Fn::Select': [ 1, { 'Fn::Split': [ '/', loadBalancerArn ] } ] },
                 '/',
-                { 'Fn::Select': [ 2, { 'Fn::Split': [ '/', firstArn ] } ] },
+                { 'Fn::Select': [ 2, { 'Fn::Split': [ '/', loadBalancerArn ] } ] },
                 '/',
-                { 'Fn::Select': [ 3, { 'Fn::Split': [ '/', firstArn ] } ] }
+                { 'Fn::Select': [ 3, { 'Fn::Split': [ '/', loadBalancerArn ] } ] }
               ]
             ]
          }