feat: convenience method for ALB redirects (#9913)

After the feedback I received for my latest addition of the redirect method to the ÀpplicationLoadBalancerFargateService` I propose a convenience method for the ALB to create redirects.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-elasticloadbalancingv2/README.md

@@ -151,6 +151,19 @@ listener.addAction('DefaultAction', {
 });
 ```
 
+If you just want to redirect all incoming traffic on one port to another port, you can use the following code:
+
+```ts
+lb.addRedirect({
+  sourceProtocol: elbv2.ApplicationProtocol.HTTPS,
+  sourcePort: 8443,
+  targetProtocol: elbv2.ApplicationProtocol.HTTP,
+  targetPort: 8080,
+});
+```
+
+If you do not provide any options for this method, it redirects HTTP port 80 to HTTPS port 443.
+
 ### Defining a Network Load Balancer
 
 Network Load Balancers are defined in a similar way to Application Load

packages/@aws-cdk/aws-elasticloadbalancingv2/lib/alb/application-load-balancer.ts

@@ -2,8 +2,9 @@ import * as cloudwatch from '@aws-cdk/aws-cloudwatch';
 import * as ec2 from '@aws-cdk/aws-ec2';
 import { Construct, Duration, Lazy, Resource } from '@aws-cdk/core';
 import { BaseLoadBalancer, BaseLoadBalancerProps, ILoadBalancerV2 } from '../shared/base-load-balancer';
-import { IpAddressType } from '../shared/enums';
+import { IpAddressType, ApplicationProtocol } from '../shared/enums';
 import { ApplicationListener, BaseApplicationListenerProps } from './application-listener';
+import { ListenerAction } from './application-listener-action';
 
 /**
  * Properties for defining an Application Load Balancer
@@ -88,6 +89,24 @@ export class ApplicationLoadBalancer extends BaseLoadBalancer implements IApplic
     });
   }
 
+  /**
+   * Add a redirection listener to this load balancer
+   */
+  public addRedirect(props: ApplicationLoadBalancerRedirectConfig = {}): ApplicationListener {
+    const sourcePort = props.sourcePort ?? 80;
+    const targetPort = (props.targetPort ?? 443).toString();
+    return this.addListener(`Redirect${sourcePort}To${targetPort}`, {
+      protocol: props.sourceProtocol ?? ApplicationProtocol.HTTP,
+      port: sourcePort,
+      open: true,
+      defaultAction: ListenerAction.redirect({
+        port: targetPort,
+        protocol: props.targetProtocol ?? ApplicationProtocol.HTTPS,
+        permanent: true,
+      }),
+    });
+  }
+
   /**
    * Return the given named metric for this Application Load Balancer
    *
@@ -571,3 +590,38 @@ class ImportedApplicationLoadBalancer extends Resource implements IApplicationLo
     throw new Error(`'loadBalancerDnsName' was not provided when constructing Application Load Balancer ${this.node.path} from attributes`);
   }
 }
+
+/**
+ * Properties for a redirection config
+ */
+export interface ApplicationLoadBalancerRedirectConfig {
+
+  /**
+   * The protocol of the listener being created
+   *
+   * @default HTTP
+   */
+  readonly sourceProtocol?: ApplicationProtocol;
+
+  /**
+   * The port number to listen to
+   *
+   * @default 80
+   */
+  readonly sourcePort?: number;
+
+  /**
+   * The protocol of the redirection target
+   *
+   * @default HTTPS
+   */
+  readonly targetProtocol?: ApplicationProtocol;
+
+  /**
+   * The port number to redirect to
+   *
+   * @default 443
+   */
+  readonly targetPort?: number;
+
+}

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

@@ -661,6 +661,68 @@ describe('tests', () => {
     });
   });
 
+  test('Can add simple redirect responses', () => {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.Vpc(stack, 'VPC');
+    const lb = new elbv2.ApplicationLoadBalancer(stack, 'LoadBalancer', {
+      vpc,
+    });
+
+    // WHEN
+    lb.addRedirect();
+
+    // THEN
+    expect(stack).toHaveResource('AWS::ElasticLoadBalancingV2::Listener', {
+      Port: 80,
+      Protocol: 'HTTP',
+      DefaultActions: [
+        {
+          RedirectConfig: {
+            Port: '443',
+            Protocol: 'HTTPS',
+            StatusCode: 'HTTP_301',
+          },
+          Type: 'redirect',
+        },
+      ],
+    });
+  });
+
+  test('Can add simple redirect responses with custom values', () => {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.Vpc(stack, 'VPC');
+    const lb = new elbv2.ApplicationLoadBalancer(stack, 'LoadBalancer', {
+      vpc,
+    });
+
+    // WHEN
+    const listener = lb.addRedirect({
+      sourceProtocol: elbv2.ApplicationProtocol.HTTPS,
+      sourcePort: 8443,
+      targetProtocol: elbv2.ApplicationProtocol.HTTP,
+      targetPort: 8080,
+    });
+    listener.addCertificateArns('ListenerCertificateX', ['cert3']);
+
+    // THEN
+    expect(stack).toHaveResource('AWS::ElasticLoadBalancingV2::Listener', {
+      Port: 8443,
+      Protocol: 'HTTPS',
+      DefaultActions: [
+        {
+          RedirectConfig: {
+            Port: '8080',
+            Protocol: 'HTTP',
+            StatusCode: 'HTTP_301',
+          },
+          Type: 'redirect',
+        },
+      ],
+    });
+  });
+
   test('Can configure deregistration_delay for targets', () => {
     // GIVEN
     const stack = new cdk.Stack();