fix(appmesh): fix circular dependency by removing virtual service nam…

…e reference for virtual node backends
aws · Jan 5, 2022 · 98c481c · 98c481c
1 parent 26ee826
commit 98c481c
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diff --git a/packages/@aws-cdk/aws-appmesh/README.md b/packages/@aws-cdk/aws-appmesh/README.md
@@ -236,6 +236,24 @@ The `backends` property can be added with `node.addBackend()`. In the example, w
 
 The `backendDefaults` property is added to the node while creating the virtual node. These are the virtual node's default settings for all backends.
 
+The `VirtualNode.addBackend()` method is especially useful if you want to create a circular traffic flow by having a Virtual Service as a backend whose provider is that same Virtual Node:
+
+```ts
+declare const mesh: appmesh.Mesh;
+
+const node = new appmesh.VirtualNode(this, 'node', {
+  mesh,
+  serviceDiscovery: appmesh.ServiceDiscovery.dns('node'),
+});
+
+const virtualService = new appmesh.VirtualService(this, 'service-1', {
+  virtualServiceProvider: appmesh.VirtualServiceProvider.virtualNode(node),
+  virtualServiceName: 'service1.domain.local',
+});
+
+node.addBackend(appmesh.Backend.virtualService(virtualService));
+```
+
 ### Adding TLS to a listener
 
 The `tls` property specifies TLS configuration when creating a listener for a virtual node or a virtual gateway. 

diff --git a/packages/@aws-cdk/aws-appmesh/lib/shared-interfaces.ts b/packages/@aws-cdk/aws-appmesh/lib/shared-interfaces.ts
@@ -238,7 +238,14 @@ class VirtualServiceBackend extends Backend {
     return {
       virtualServiceBackend: {
         virtualService: {
-          virtualServiceName: this.virtualService.virtualServiceName,
+          /**
+           * We want to use the name of the Virtual Service here directly instead of
+           * a `{ 'Fn::GetAtt' }` CFN expression. This avoids a circular dependency in
+           * the case where this Virtual Node is the Virtual Service's provider.
+           */
+          virtualServiceName: cdk.Token.isUnresolved(this.virtualService.virtualServiceName)
+            ? (this.virtualService as any).physicalName
+            : this.virtualService.virtualServiceName,
           clientPolicy: this.tlsClientPolicy
             ? {
               tls: renderTlsClientPolicy(scope, this.tlsClientPolicy),

diff --git a/packages/@aws-cdk/aws-appmesh/test/integ.mesh.expected.json b/packages/@aws-cdk/aws-appmesh/test/integ.mesh.expected.json
@@ -1040,22 +1040,12 @@
           "Backends": [
             {
               "VirtualService": {
-                "VirtualServiceName": {
-                  "Fn::GetAtt": [
-                    "service6D174F83",
-                    "VirtualServiceName"
-                  ]
-                }
+                "VirtualServiceName": "service1.domain.local"
               }
             },
             {
               "VirtualService": {
-                "VirtualServiceName": {
-                  "Fn::GetAtt": [
-                    "service27C65CF7D",
-                    "VirtualServiceName"
-                  ]
-                }
+                "VirtualServiceName": "service2.domain.local"
               }
             }
           ],
@@ -1111,12 +1101,7 @@
           "Backends": [
             {
               "VirtualService": {
-                "VirtualServiceName": {
-                  "Fn::GetAtt": [
-                    "service3859EB104",
-                    "VirtualServiceName"
-                  ]
-                }
+                "VirtualServiceName": "service3.domain.local"
               }
             }
           ],
@@ -1241,12 +1226,7 @@
           "Backends": [
             {
               "VirtualService": {
-                "VirtualServiceName": {
-                  "Fn::GetAtt": [
-                    "service4983B61EE",
-                    "VirtualServiceName"
-                  ]
-                }
+                "VirtualServiceName": "service4.domain.local"
               }
             }
           ],

diff --git a/packages/@aws-cdk/aws-appmesh/test/mesh.test.ts b/packages/@aws-cdk/aws-appmesh/test/mesh.test.ts
@@ -314,9 +314,7 @@ describe('mesh', () => {
               Backends: [
                 {
                   VirtualService: {
-                    VirtualServiceName: {
-                      'Fn::GetAtt': ['service1A48078CF', 'VirtualServiceName'],
-                    },
+                    VirtualServiceName: 'service1.domain.local',
                   },
                 },
               ],

diff --git a/packages/@aws-cdk/aws-appmesh/test/virtual-node.test.ts b/packages/@aws-cdk/aws-appmesh/test/virtual-node.test.ts
@@ -41,24 +41,18 @@ describe('virtual node', () => {
             Backends: [
               {
                 VirtualService: {
-                  VirtualServiceName: {
-                    'Fn::GetAtt': ['service1A48078CF', 'VirtualServiceName'],
-                  },
+                  VirtualServiceName: 'service1.domain.local',
                 },
               },
               {
                 VirtualService: {
-                  VirtualServiceName: {
-                    'Fn::GetAtt': ['service27C65CF7D', 'VirtualServiceName'],
-                  },
+                  VirtualServiceName: 'service2.domain.local',
                 },
               },
             ],
           },
           MeshOwner: ABSENT,
         });
-
-
       });
     });
 
@@ -458,9 +452,7 @@ describe('virtual node', () => {
             Backends: [
               {
                 VirtualService: {
-                  VirtualServiceName: {
-                    'Fn::GetAtt': ['service1A48078CF', 'VirtualServiceName'],
-                  },
+                  VirtualServiceName: 'service1.domain.local',
                   ClientPolicy: {
                     TLS: {
                       Ports: [8080, 8081],
@@ -478,8 +470,75 @@ describe('virtual node', () => {
             ],
           },
         });
+      });
+
+      test('you can add a Virtual Service as a backend to a Virtual Node which is the provider for that Virtual Service', () => {
+        // GIVEN
+        const stack = new cdk.Stack();
+
+        // WHEN
+        const mesh = new appmesh.Mesh(stack, 'mesh', {
+          meshName: 'test-mesh',
+        });
+
+        const node = new appmesh.VirtualNode(stack, 'test-node', {
+          mesh,
+          serviceDiscovery: appmesh.ServiceDiscovery.dns('test'),
+        });
+
+        const myVirtualService = new appmesh.VirtualService(stack, 'service-1', {
+          virtualServiceProvider: appmesh.VirtualServiceProvider.virtualNode(node),
+          virtualServiceName: 'service1.domain.local',
+        });
+
+        node.addBackend(appmesh.Backend.virtualService(myVirtualService));
+
+        // THEN
+        expect(stack).toHaveResourceLike('AWS::AppMesh::VirtualNode', {
+          Spec: {
+            Backends: [
+              {
+                VirtualService: {
+                  VirtualServiceName: 'service1.domain.local',
+                },
+              },
+            ],
+          },
+        });
+      });
+
+      test('you can add a Virtual Service with an automated name as a backend to a Virtual Node which is the provider for that Virtual Service, ', () => {
+        // GIVEN
+        const stack = new cdk.Stack();
 
+        // WHEN
+        const mesh = new appmesh.Mesh(stack, 'mesh', {
+          meshName: 'test-mesh',
+        });
 
+        const node = new appmesh.VirtualNode(stack, 'test-node', {
+          mesh,
+          serviceDiscovery: appmesh.ServiceDiscovery.dns('test'),
+        });
+
+        const myVirtualService = new appmesh.VirtualService(stack, 'service-1', {
+          virtualServiceProvider: appmesh.VirtualServiceProvider.virtualNode(node),
+        });
+
+        node.addBackend(appmesh.Backend.virtualService(myVirtualService));
+
+        // THEN
+        expect(stack).toHaveResourceLike('AWS::AppMesh::VirtualNode', {
+          Spec: {
+            Backends: [
+              {
+                VirtualService: {
+                  VirtualServiceName: 'service1',
+                },
+              },
+            ],
+          },
+        });
       });
     });