How can I assign a IAM role to a resolver?

[chstrong]

I'm using a VTL resolver with 3 DynamoDB databases and TransactWriteItems.

As only one datasource can be assigned to a resolver I assume I need to create an IAM role, grant access to all the tables with the role and assign it to the resolver. However this doesn't work as it seems that "role" doesn't exist as attribute of the Resolver (role: resolverRole).

How can I configure CDK correctly so that the VTL resolver can access all 3 datasources?

CDK Stack Config

Even though suggested in examples, "role: resolverRole" isn't a valid attribute. I have no clue how to accomplish this. I've searched and read my but off but can't find a solution.

const resolver = new Resolver(this, 'Resolver', {
            api: api,
            typeName: 'Mutation',
            fieldName: 'like',
            dataSource: new DynamoDbDataSource(this, 'LikeTableDs', {
                api: api,
                table: props.likeTable,
            }),
            requestMappingTemplate: MappingTemplate.fromFile(
                path.join(__dirname, '../graphql/mapping-templates/Mutation.like.request.vtl')
            ),
            responseMappingTemplate: MappingTemplate.fromFile(
                path.join(__dirname, '../graphql/mapping-templates/Mutation.like.response.vtl')
            ),
            role: resolverRole,
});

VTL Request File

  "version": "2018-05-29",
  "operation": "TransactWriteItems",
  "transactItems": [
    {
      "table": "twitterapp-like-dev",
      "operation": "PutItem",
      "key": {
        "userId": $util.dynamodb.toDynamoDBJson($context.identity.username),
        "tweetId": $util.dynamodb.toDynamoDBJson($context.arguments.tweetId)
      },
      "condition": {
        "expression": "attribute_not_exists(tweetId)"
      }
    },
    {
      "table": "twitterapp-tweet-dev",
      "operation": "UpdateItem",
      "key": {
        "id": $util.dynamodb.toDynamoDBJson($context.arguments.tweetId)
      },
      "update": {
        "expression": "ADD likes :one",
        "expressionValues": {
          ":one": $util.dynamodb.toDynamoDBJson(1)
        }
      },
      "condition": {
        "expression": "attribute_exists(id)"
      }
    },
    {
      "table": "twitterapp-user-dev",
      "operation": "UpdateItem",
      "key": {
        "id": $util.dynamodb.toDynamoDBJson($context.identity.username)
      },
      "update": {
        "expression": "ADD likesCounts :one",
        "expressionValues": {
          ":one": $util.dynamodb.toDynamoDBJson(1)
        }
      },
      "condition": {
        "expression": "attribute_exists(id)"
      }
    }
  ]
}```

[peterwoodworth]

Hey @chstrong, I'm not familiar with AppSync really so apologies in advance for my lack of knowledge here - but I can't find any references to associating a role with a resolver in CloudFormation or AppSync documentation.

Do you know how this use case is normally achieved without CDK?