fix(appmesh): allow the virtualServiceName field for virtual node backends to be supplied as a string

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

@@ -196,16 +196,19 @@ const node = new appmesh.VirtualNode(this, 'node', {
 cdk.Tags.of(node).add('Environment', 'Dev');
 ```
 
-Create a `VirtualNode` with the constructor and add backend virtual service.
+Create a `VirtualNode` with the constructor, specifying a backend, and adding another backend virtual service later.
 
 ```ts
 declare const mesh: appmesh.Mesh;
 declare const router: appmesh.VirtualRouter;
 declare const service: cloudmap.Service;
 
+const virtualServiceName1 = 'service1.domain.local';
+const virtualServiceName2 = 'service2.domain.local';
 const node = new appmesh.VirtualNode(this, 'node', {
   mesh,
   serviceDiscovery: appmesh.ServiceDiscovery.cloudMap(service),
+  backends: [appmesh.Backend.virtualServiceName(virtualServiceName1)],
   listeners: [appmesh.VirtualNodeListener.http({
     port: 8080,
     healthCheck: appmesh.HealthCheck.http({
@@ -222,17 +225,21 @@ const node = new appmesh.VirtualNode(this, 'node', {
   accessLog: appmesh.AccessLog.fromFilePath('/dev/stdout'),
 });
 
-const virtualService = new appmesh.VirtualService(this, 'service-1', {
+const virtualService1 = new appmesh.VirtualService(this, 'service-1', {
   virtualServiceProvider: appmesh.VirtualServiceProvider.virtualRouter(router),
-  virtualServiceName: 'service1.domain.local',
+  virtualServiceName: virtualServiceName1,
+});
+const virtualService2 = new appmesh.VirtualService(this, 'service-2', {
+  virtualServiceProvider: appmesh.VirtualServiceProvider.virtualRouter(router),
+  virtualServiceName: virtualServiceName2,
 });
 
-node.addBackend(appmesh.Backend.virtualService(virtualService));
+node.addBackend(appmesh.Backend.virtualServiceName(virtualServiceName2));
 ```
 
 The `listeners` property can be left blank and added later with the `node.addListener()` method. The `serviceDiscovery` property must be specified when specifying a listener.
 
-The `backends` property can be added with `node.addBackend()`. In the example, we define a virtual service and add it to the virtual node to allow egress traffic to other nodes.
+The `backends` property can be added in the constructor or with `node.addBackend()`. In the example, we define two virtual services and add one to the virtual node in the constructor and one via `addBackend` to allow egress traffic to other nodes.
 
 The `backendDefaults` property is added to the node while creating the virtual node. These are the virtual node's default settings for all backends.
 

packages/@aws-cdk/aws-appmesh/lib/shared-interfaces.ts

@@ -215,6 +215,13 @@ export abstract class Backend {
     return new VirtualServiceBackend(virtualService, props.tlsClientPolicy);
   }
 
+  /**
+   * Construct a Virtual Service backend via a Virtual Service name
+   */
+  public static virtualServiceName(virtualServiceName: string, props: VirtualServiceBackendOptions = {}): Backend {
+    return new VirtualServiceNameBackend(virtualServiceName, props.tlsClientPolicy);
+  }
+
   /**
    * Return backend config
    */
@@ -250,6 +257,35 @@ class VirtualServiceBackend extends Backend {
   }
 }
 
+/**
+ * Represents the properties needed to define a Virtual Service backend via a Virtual Service name
+ */
+class VirtualServiceNameBackend extends Backend {
+
+  constructor (private readonly virtualServiceName: string,
+    private readonly tlsClientPolicy: TlsClientPolicy | undefined) {
+    super();
+  }
+
+  /**
+   * Return config for a Virtual Service backend
+   */
+  public bind(scope: Construct): BackendConfig {
+    return {
+      virtualServiceBackend: {
+        virtualService: {
+          virtualServiceName: this.virtualServiceName,
+          clientPolicy: this.tlsClientPolicy
+            ? {
+              tls: renderTlsClientPolicy(scope, this.tlsClientPolicy),
+            }
+            : undefined,
+        },
+      },
+    };
+  }
+}
+
 /**
  * Connection pool properties for HTTP listeners
  */

packages/@aws-cdk/aws-appmesh/test/virtual-node.test.ts

@@ -57,8 +57,53 @@ describe('virtual node', () => {
           },
           MeshOwner: ABSENT,
         });
+      });
+
+      test('should add resource with service backends via virtual service names', () => {
+        // GIVEN
+        const stack = new cdk.Stack();
+
+        // WHEN
+        const mesh = new appmesh.Mesh(stack, 'mesh', {
+          meshName: 'test-mesh',
+        });
+
+        const service1Name = 'service1.domain.local';
+        new appmesh.VirtualService(stack, 'service-1', {
+          virtualServiceName: service1Name,
+          virtualServiceProvider: appmesh.VirtualServiceProvider.none(mesh),
+        });
+        const service2Name = 'service2.domain.local';
+        new appmesh.VirtualService(stack, 'service-2', {
+          virtualServiceName: service2Name,
+          virtualServiceProvider: appmesh.VirtualServiceProvider.none(mesh),
+        });
+
+        const node = new appmesh.VirtualNode(stack, 'test-node', {
+          mesh,
+          serviceDiscovery: appmesh.ServiceDiscovery.dns('test'),
+          backends: [appmesh.Backend.virtualServiceName(service1Name)],
+        });
 
+        node.addBackend(appmesh.Backend.virtualServiceName(service2Name));
 
+        // THEN
+        expect(stack).toHaveResourceLike('AWS::AppMesh::VirtualNode', {
+          Spec: {
+            Backends: [
+              {
+                VirtualService: {
+                  VirtualServiceName: service1Name,
+                },
+              },
+              {
+                VirtualService: {
+                  VirtualServiceName: service2Name,
+                },
+              },
+            ],
+          },
+        });
       });
     });