Feat(py/alb): Add example for adding redirect from port 80 to 443

Fixes: #305

Author: Michael Kaiser

python/application-load-balancer/app.py

@@ -4,6 +4,7 @@
     aws_autoscaling as autoscaling,
     aws_ec2 as ec2,
     aws_elasticloadbalancingv2 as elbv2,
+    aws_certificatemanager as acm,
     App, CfnOutput, Stack
 )
 
@@ -12,13 +13,15 @@ class LoadBalancerStack(Stack):
     def __init__(self, app: App, id: str) -> None:
         super().__init__(app, id)
 
+        # Create a VPC for our infrastructure
         vpc = ec2.Vpc(self, "VPC")
 
+        # Read and prepare user data script for EC2 instances
         data = open("./httpd.sh", "rb").read()
         httpd=ec2.UserData.for_linux()
         httpd.add_commands(str(data,'utf-8'))
 
-
+        # Create an Auto Scaling Group with EC2 instances
         asg = autoscaling.AutoScalingGroup(
             self,
             "ASG",
@@ -30,19 +33,46 @@ def __init__(self, app: App, id: str) -> None:
             user_data=httpd,
         )
 
+        # Create an Application Load Balancer
         lb = elbv2.ApplicationLoadBalancer(
             self, "LB",
             vpc=vpc,
             internet_facing=True)
 
-        listener = lb.add_listener("Listener", port=80)
-        listener.add_targets("Target", port=80, targets=[asg])
-        listener.connections.allow_default_port_from_any_ipv4("Open to the world")
+        # Create HTTP listener with redirect
+        http_listener = lb.add_listener(
+            "HttpListener", 
+            port=80,
+            default_action=elbv2.ListenerAction.redirect(
+                port="443",
+                protocol="HTTPS",
+                permanent=True,
+                host="#{host}",
+                path="/#{path}",
+                query="#{query}"
+            )
+        )
+
+        # Create HTTPS listener
+        https_listener = lb.add_listener(
+            "HttpsListener",
+            port=443,
+            certificates=[elbv2.ListenerCertificate.from_arn("certificate_arn")],
+            ssl_policy=elbv2.SslPolicy.RECOMMENDED
+        )
+
+        # Add target group to HTTPS listener
+        https_listener.add_targets("Target", port=80, targets=[asg])
+        https_listener.connections.allow_default_port_from_any_ipv4("Open to the world")
 
+        # Configure Auto Scaling based on request count
         asg.scale_on_request_count("AModestLoad", target_requests_per_minute=60)
+        
+        # Output the Load Balancer DNS name
         CfnOutput(self,"LoadBalancer",export_name="LoadBalancer",value=lb.load_balancer_dns_name)
 
 
+# Initialize the CDK app and create the stack
 app = App()
 LoadBalancerStack(app, "LoadBalancerStack")
 app.synth()