Aws-cdk: [@aws-cdk/aws-apigatewayv2] Httpapi not deploying when new stack created when using custom domain

[dave-graham]

Httpapi not deploying when new stack created when using custom domain, and not accepting base path of '/'

I tried to follow the description of how to setup a base path mapping here:

https://docs.aws.amazon.com/cdk/api/latest/docs/aws-apigatewayv2-readme.html#custom-domain

My actual code was:

const domainName = "test.testdomain.com";

const dn = new apigw.DomainName(this, "DN", {
  domainName,
  certificate: certificate,
});

const httpApi = new apigw.HttpApi(this, "HttpApi", {
  defaultDomainMapping: {
    domainName: dn,
    mappingKey: "hello",
  },
});

When I run this with a stack that has never been deployed before, I get the following error:

Invalid stage identifier specified (Service: AmazonApiGatewayV2; Status Code: 400; Error Code: BadRequestException;

Secondly if I try to change mappingKey to '/' I get the following:

An ApiMapping key may contain only letters, numbers and one of $-_.+!*'(), (Service: AmazonApiGatewayV2; Status Code: 400; Error Code: BadRequestException;

Any help you can give is really appreciated, as this is such a great feature, and when it's possible to get authentication in there too, that will be icing on the cake!

Error Log

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This is :bug: Bug Report

[ggrandes]

In the aws console the error also appears...

[pahud]

We probably need to improve the validation on the mapping key.

Let me pick this up. Will try reproduce it in my environment and create a PR when necessary.

[dave-graham]

thanks @pahud you may also want to change the docs too, as I got the idea to add a "/" from https://docs.aws.amazon.com/cdk/api/latest/docs/aws-apigatewayv2-readme.html#custom-domain

[nakedible]

Empty string for mappingKey will achieve wanted behavior - however, just not passing the value would be preferable.

[pahud]

Appreciated the bug report. I am still working on it. Yes, we probably should leave it as an empty string for mappingKey as the default root base path which is the expected behavior from cloudformation's perspective and mappingkey containing the '/' character is not allowed. However, I noticed there's a condition which API Gateway returns 400 errors with ConflictException error and I am still trying to get it sorted internally before we can fix this issue with another PR.

I will post more details in the following comments later.

[dave-graham]

👍 thanks for looking into it @pahud

[pahud]

OK this is what we already know:

1. empty ApiMappingKey is allowed, which indicates the root path of the custom domain
2. multiple ApiMappingKeys are allowed, but none of them is allowed to be empty

In this case, let's say our custom domain is abc.com:

If the $default stage is having an empty ApiMappingKey, https://abc.com will go to the $default stage of this API but no more additional ApiMapping would be allowed for this custom domain.

If we need multiple ApiMapping resources, they should all have non-empty ApiMappingKey which expands to different base paths e.g.

'foo' -> /foo
'bar' -> /bar

Let me know if I was wrong and I will start a new PR to fix according to this.

@dave-graham

[dave-graham]

👍 @pahud that looks good to me

[pahud]

@dave-graham PR underway

[ggrandes]

And how about "/foo/bar"? how this case is mapped in ApiMapping?

[pahud]

And how about "/foo/bar"? how this case is mapped in ApiMapping?

Looks like the api mapping key only support the 1-level bath path mapping at this moment.

Unfortunately, the character '/' is not allowed for the mapping key.

[dave-graham]

@ggrandes I may be missing something, but a path that has 2 levels can be achieved by mapping the domain to an api at one level e.g. /foo, then adding a route for the next level e.g. /bar.

I don't have the exact code, but would look something like:

const domainName = "test.testdomain.com";

const dn = new apigw.DomainName(this, "DN", {
  domainName,
  certificate: certificate,
});

const httpApi = new apigw.HttpApi(this, "HttpApi", {
  defaultDomainMapping: {
    domainName: dn,
    mappingKey: "foo",
  },
});

httpApi.addRoutes({
      path: "/bar",
      methods: [HttpMethod.GET],
      integration: booksDefaultIntegration,
    });

[pahud]

Hi @dave-graham

CDK v1.54.0 released and the fix is available now. Please let me know if it works. thanks.

[Shamshiel]

The following mapping works for me now:

defaultDomainMapping: {
     domainName: domainName,
     mappingKey: 'v1'
}

But how would I add an empty mappingKey? Both '/' and '' don't work.

[pahud]

The following mapping works for me now:

defaultDomainMapping: {
     domainName: domainName,
     mappingKey: 'v1'
}

But how would I add an empty mappingKey? Both '/' and '' don't work.

Hi

At this moment, custom domain only allows to create root base path mapping when there is only one api mapping for this domain. Starting from v1.54.0 in AWS CDK, simply leave the mappingKey undefined and behind the scene an api mapping with empty api mapping key will be created.

However, please note if you create a root path mapping, you can't create any more api mapping key. This is what we can do with current apigateway v2 custom domain now.

[kay-is]

This is the best I could get going:

const proxy = new apigatewayv2.HttpApi(this, "DemoProxy", {
  defaultDomainMapping: { domainName, mappingKey: "graphql" },
});

const integration = new apigatewayv2.HttpProxyIntegration({ url: api.graphqlUrl });

proxy.addRoutes({ path: "/", methods: [apigateway.HttpMethod.POST], integration });

mappingKey could neither be "" nor "/".

path couldn't be empty, so the "/" at the end of the URL is required now.

I have the feeling this should work better, but don't know how.