Circular dependency of defining APIGateway, ARecord, and Certificate - aws-api-gateway

Question

In CDK, I would like to define:
An APIGateway (backed by a Lambda)
An ARecord to resolve to the APIGateway
A Certificate associated with the ARecord
The code to do this would look something like:
let apig = new LambdaRestApi(this, 'api', {
handler: <some Lambda Function>,
proxy: true,
deploy: true,
domainName: {
domainName: aRecord.domainName,
certificate: cert
}
})
let aRecord = new ARecord(this, 'apiDNS', {
zone: zone,
recordName: props.recordName,
target: RecordTarget.fromAlias(new ApiGateway(apig))
})
let cert = new Certificate(this, 'cert', {
domainName: aRecord.domainName,
validation: CertificateValidation.fromDns(zone)
});
However, this appears to be impossible because of circular dependencies:
The APIGateway needs to have a domain name set at construction-time (there's an .addDomainName method, but even when that is called, I still get an error API does not define a default domain name when trying to call RecordTarget.fromAlias(...)), which requires that both the Certificate and the ARecord exist.
The ARecord needs to have a target, which requires that the ApiGateway exists.
The Certificate needs to have a DomainName set, which requires that the ARecord exists
I guess I could manually determine what the ARecord's domainName would be, and set that as the domainName for the Certificate and the APIGateway - but that feels like I'm doing something wrong. Is there a way to "lazily" set the APIGateway's domainName to "the domainName of the ARecord (that hasn't been created yet)?", or some other way to achieve this setup with explicit (rather than implicit) associations?

Answer 1

As already mentioned in ticket, it is not possible for CDK or CloudFormation to create resource which depends on each other.
Here is blog on Circular Dependency
Resource A is dependent on Resource B, and Resource B is dependent on
Resource A. When AWS CloudFormation assesses that this type of
condition exists, you will get a circular dependency error because AWS
CloudFormation is unable to clearly determine which resource should be
created first.
In this case, we can create a ACM Certificate for subDomain and then pass the domain and certificate to LambdaRestApi.
Here is the modified CDK.
const rootDomain = "mydomain.com";
const subDomain = "api-test";
const zone = route53.HostedZone.fromLookup(this, "baseZone", {
domainName: rootDomain,
});
let cert = new acm.Certificate(this, "cert", {
domainName: `${subDomain}.${rootDomain}`,
validation: acm.CertificateValidation.fromDns(zone),
});
const backend = new lambda.Function(this, "MyLayeredLambda", {
code: new lambda.InlineCode("foo"),
handler: "index.handler",
runtime: lambda.Runtime.NODEJS_10_X,
});
const restApi = new apigw.LambdaRestApi(this, "myapi", {
handler: backend,
domainName: {
domainName: `${subDomain}.${rootDomain}`,
certificate: cert,
endpointType: apigw.EndpointType.REGIONAL,
},
});
new route53.ARecord(this, "apiDNS", {
zone: zone,
recordName: `${subDomain}`,
target: route53.RecordTarget.fromAlias(
new route53Targets.ApiGateway(restApi)
),
});
}