MWAA Webserver IPs on CDK

Question

I'm creating an Amazon Managed Airflow (MWAA) using CDK with the setting of webserver_access_mode='PRIVATE_ONLY'. In this mode, AWS creates a VPC interface endpoint and binds an IP address, from the selected VPC private subnets, to them as explained here: https://docs.aws.amazon.com/mwaa/latest/userguide/configuring-networking.html

Now, I want to use those IPs to add a listener to an existing load balancer that I can then use to connect to a VPN, but this doesn't seem to be available as an output attribute/property of aws_cdk.aws_mwaa.CfnEnvironment: https://docs.aws.amazon.com/cdk/api/v1/python/aws_cdk.aws_mwaa/CfnEnvironment.html#aws_cdk.aws_mwaa.CfnEnvironment.NetworkConfigurationProperty

My question is, is there a way to obtain those IPs associated with the aws_cdk.aws_mwaa.CfnEnvironment? Right now I am looking up the results manually after the deployment with CDK and creating the listener but I would prefer to fully automate it in the same CDK construct.

user_18268762 · Answer

I struggled with this same problem for some time. In the end I used a Custom Resource in my CFN template, passing it the URL of the MWAA webserver. In the Python code associated with the Custom Resource (Lambda) I do a socket.gethostbyname_ex() call, passing the URL as an argument. This call will return a tuple that that you'll have to parse to extract the endpoint addresses.

I made good use of the crhelper libraries (https://aws.amazon.com/blogs/infrastructure-and-automation/aws-cloudformation-custom-resource-creation-with-python-aws-lambda-and-crhelper/), which made things a lot easier.

user_3193886 · Answer

In the end, I used a lambda function to resolve the webserver URL and register the IP addresses to the target group. The approach is described in the following AWS blog post: https://aws.amazon.com/blogs/networking-and-content-delivery/hostname-as-target-for-network-load-balancers/

The implementation of the lambda function is also available through the following AWS sample code: https://github.com/aws-samples/hostname-as-target-for-elastic-load-balancer

MWAA Webserver IPs on CDK

2 Answers