@aws-cdk/aws-appsync: Add ability to create resolvers with "operation": "BatchInvoke"

[asnaseer-resilient]

I want to setup an AppSync resolver using the CDK to use "operation": "BatchInvoke" as described here https://docs.aws.amazon.com/appsync/latest/devguide/tutorial-lambda-resolvers.html#advanced-use-case-batching

I am currently using the createResolver function to create my resolvers but cannot see a way to specify this type of operation - see here: https://docs.aws.amazon.com/cdk/api/latest/docs/@aws-cdk_aws-appsync.LambdaDataSource.html#createwbrresolverpropsspan-[…]y-change-without-noticespan

Use Case

The link above describes my use case.

Proposed Solution

None

Other

N/A

• 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change

---

This is a 🚀 Feature Request

[asnaseer-resilient]

Any chance of this getting implemented in the near future?

[MrArnoldPalmer]

@asnaseer-resilient the core team is not actively working on adding features to appsync right now. PRs from the community are always welcome or you may be able to implement this by extending the BaseDataSource.

I don't have any experience using BatchInvoke in CFN, @BryanPan342 you have any guidance to add here for implementing?

[BryanPan342]

I also don't have experience with BatchInvoke, but it looks like a Mapping Template issue that I honestly don't have that good of an answer for 😔

I know @duarten created an RFC for mapping templates and I think that would be nice to have even though JS is looking like an alternative.. would definitely require more thought

[duarten]

Most of that effort is in https://github.com/umani/ribosome, which works but isn't pretty (the API was designed to be compatible with the constraints of jsii, in case it would ever be merged into the cdk). But yeah, looking forward to JS resolvers :)

[asnaseer-resilient]

I have had a look around the code base and I think the change would need to be made in mapping-template.ts in this method:

aws-cdk/packages/@aws-cdk/aws-appsync/lib/mapping-template.ts

Line 95 in a75d52f

public static lambdaRequest(payload: string = '$util.toJson($ctx)'): MappingTemplate {

That method currently seems to hardwire the operation to "Invoke" as follows:

  public static lambdaRequest(payload: string = '$util.toJson($ctx)'): MappingTemplate {
    return this.fromString(`{"version": "2017-02-28", "operation": "Invoke", "payload": ${payload}}`);
  }

So maybe you could introduce an additional optional parameter as follows for backwards compatibility:

  public static lambdaRequest(payload: string = '$util.toJson($ctx)', operation: string = 'Invoke'): MappingTemplate {
    return this.fromString(`{"version": "2017-02-28", "operation": "${operation}", "payload": ${payload}}`);
  }

and then expose the ability to set this in the CDK. I am not really familiar enough with any of the CDK codebase to attempt to make any changes to it myself.

[BryanPan342]

@asnaseer-resilient I'm currently working on the schema validation PR, but ill see what I can do. It does seem pretty straightforward but I want to make sure I read more about mapping templates before I implement anything that will change the API.

[asnaseer-resilient]

@BryanPan342 - Any updates on this?

[BryanPan342]

@BryanPan342 - Any updates on this?

I'm finishing up my school quarter atm so don't have the bandwidth atm, but will look to implement it sometime in the summer

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