aws_cdk.aws_route53_targets: ElasticBeanstalkEnvironmentEndpointTarget throwing an error

[agusavior]

What is the problem?

Creating a object of ElasticBeanstalkEnvironmentEndpointTarget is throwing a Exception.

I think this could be an bug because I'm just using this class in the way that it's supposed to be used.
This class receive an environment_endpoint, and that's what I give it to it.

Reproduction Steps

Just execute this with cdk deploy:

  # EB Enviroment
  enviroment = elasticbeanstalk.CfnEnvironment(self, 'Enviroment', 
      environment_name='MySampleEnviroment',
      application_name=application.application_name or application_name,
      solution_stack_name=SOLUTION_STACK_NAME,
      option_settings=self.get_option_setting_properties(),
      version_label=app_version_props.ref,
  )

  # Attach Domain to DNS Domain of the Load Balancer of the Enviroment
  route53.ARecord(self, f'{construct_label}AliasRecord',
      target=route53.RecordTarget.from_alias(
          targets.ElasticBeanstalkEnvironmentEndpointTarget(     # <-- Here is the problem
              enviroment.attr_endpoint_url,
          ),
      ),
      zone=domain_configuration.hosted_zone,
  )

What did you expect to happen?

I shouldn't have had an exception using that instance with the URL of the enviroment.

If I can't use that class with the url of the enviroment: Why that class exists.

I opened the link that appears on the exception but: That means that I can't do it without using the console? I want to use CDK and not the console.

What actually happened?

The exception:

jsii.errors.JSIIError: Cannot use an EBS alias as environmentEndpoint. You must find your EBS environment endpoint via the AWS console. See the Elastic Beanstalk developer guide: https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/customdomains.html

CDK CLI Version

2.1.0 (build f4f18b1)

Framework Version

No response

Node.js Version

v16.13.0

OS

Ubuntu 20.04 on WSL

Language

Python

Language Version

Python 3.7.2

Other information

I do not know how to create an AliasRecordTarget to point to my Load Balancer of my Elastic Beanstalk Enviroment.

I'm trying a lot of stuff.

I tried something like this: https://stackoverflow.com/questions/56164141/aws-cdk-how-to-target-an-elastic-beanstalk-environment-with-a-route53-alias-rec

But I couldn't do it with Python.

So I found out that there is a class ( ElasticBeanstalkEnvironmentEndpointTarget ) that seems to be right what I wanted.

Also: This is my first issue reported on GitHub. Sorry if I make a mistake with this.

[agusavior]

I was reading the code. It's interesting.
I do not understand why the url has to be resolved.
I think it has to be resolved because you can't manipulate a string if it has tokens inside.
So, that gives me another question: Do I can workaround this by resolving the URL first?
In order to resolve it, I tried to add addDependsOn to the ARecord (to resolve frist the Enviroment with its url). But ARecord has no addDependsOn method.

[agusavior]

[ Little bit off topic ]
Oh, I just realiced that Elastic Beanstalk has many problems with CDK because the enviroment of Elastic Beanstalk creates another Cloudformation template and creates a Stack for its own.

It were be nice if we could, in some way, reference the Stack and read all the resources of the Stack created by the enviroment of Elastic Beanstalk. The object of CfnEnviroment would has a function called "getStack" or something like that. That function would return the Stack created by the enviroment. Then, we would get the load balancer of the Stack. And then, with the load balancer we would create RecordTarget to point to the Load Balancer of that Stack.

Or shorter: A object of CfnEnviroment stores the URL of the load balancer, so: Why not store the Load Balancer ARN? So, we could get the load balancer and modify it.

MAYBE.

[njlynch]

This was noted in the initial implementation, but the original author didn't have the cycles to do the (more complicated) Token-safe implementation. The trick here is resolving the correct HostedZone for the correct region, based on the region from the (Elastic Beanstalk) environment. Contributions welcome!

[nicfix]

The current implementation has another problem as well.

Even if you create the beanstalk environment in advance (say in a previously run cdk deploy), and customize the CNAME_PREFIX, the ElasticBeanstalkEnvironmentEndpointTarget is not able to read correctly the region from the generated url.

Consider this scenario:

# app1.py
# EB Enviroment
enviroment = elasticbeanstalk.CfnEnvironment(self, 'Enviroment', 
    environment_name='MySampleEnviroment',
    application_name=application.application_name or application_name,
    solution_stack_name=SOLUTION_STACK_NAME,
    option_settings=self.get_option_setting_properties(),
    version_label=app_version_props.ref,
    cname_prefix='myapp'
)

This generates an elastic beanstalk environment with url myapp.eu-west-1.elasticbeanstalk.com (supposing one it's deploying in eu-west-1).

Then a following cdk app tries to create a DNS record for it

# app2.py
route53.ARecord(self, f'{construct_label}AliasRecord',
    target=route53.RecordTarget.from_alias(
        targets.ElasticBeanstalkEnvironmentEndpointTarget(     
            'myapp.eu-west-1.elasticbeanstalk.com',
        ),
    ),
    zone=domain_configuration.hosted_zone,
)

At this point the command cdk diff returns the following error:

jsii.errors.JSIIError: Elastic Beanstalk environment target is not supported for the "elasticbeanstalk" region.

Looking at the documentation ElasticBeanstalkEnvironmentEndpointTarget expects instead a URL similar to this:

myapp.xyz.eu-west-1.elasticbeanstalk.com

but the CNAME_PREFIX cannot contain . when created from cdk.

My guess is that the URL is split with . and then the 3rd group from the start is taken while it might be more robust to take the 3rd group from the end of the URL.

============

CDK CLI Version
2.10.0 (build e5b301f)

Framework Version
No response

Node.js Version
v14.18.3

OS
macOS 11.6

Language
Python

Language Version
Python 3.9.5

[altso]

Is there a workaround for this issue that could be used in .NET? I tried implementing IAliasRecordTarget but that didn't work and throws at runtime:

Unhandled exception. System.ArgumentException: Could not convert argument 'MyAliasRecordTarget' to Jsii (Parameter 'arguments')
   at Amazon.JSII.Runtime.Deputy.DeputyBase.<>c__DisplayClass20_0.<ConvertArguments>b__0(Parameter parameter, Object frameworkArgument)
   at System.Linq.Enumerable.ZipIterator[TFirst,TSecond,TResult](IEnumerable`1 first, IEnumerable`1 second, Func`3 resultSelector)+MoveNext()
   at System.Collections.Generic.LargeArrayBuilder`1.AddRange(IEnumerable`1 items)
   at System.Collections.Generic.EnumerableHelpers.ToArray[T](IEnumerable`1 source)
   at Amazon.JSII.Runtime.Deputy.DeputyBase.<InvokeMethodCore>g__GetResult|18_0[T](<>c__DisplayClass18_0`1& )
   at Amazon.JSII.Runtime.Deputy.DeputyBase.InvokeMethodCore[T](JsiiMethodAttribute methodAttribute, Object[] arguments, Func`3 beginFunc, Func`3 invokeFunc)
   at Amazon.JSII.Runtime.Deputy.DeputyBase.InvokeStaticMethod[T](Type type, Type[] parameterTypes, Object[] arguments, String methodName)
   at Amazon.CDK.AWS.Route53.RecordTarget.FromAlias(IAliasRecordTarget aliasTarget)

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