(batch): Batch Compute on Fargate with CfnComputeEnvironment requires instance_role and instance_types

AWS Batch on Fargate does not allow instanceRole and instanceType in the API. However, CDK requires this parameter to be present.

Reproduction Steps

from aws_cdk import aws_iam as iam
from aws_cdk import aws_ecs as ecs
from aws_cdk import aws_batch as batch

class FaultBatchStack(core.Stack):

    def __init__(
        self,
        scope: core.Construct,
        construct_id: str,
        **kwargs
    ) -> None:
        super().__init__(scope, construct_id, **kwargs)
        batch_service_role = iam.Role(
            self,
            "BatchServiceRole",
            assumed_by=iam.ServicePrincipal('batch.amazonaws.com'),
        )
        batch_service_role.add_managed_policy(iam.ManagedPolicy.from_aws_managed_policy_name("service-role/AWSBatchServiceRole"))

        batch_ecs_role = iam.Role(
            self,
            "BatchFargateRole",
            assumed_by=iam.ServicePrincipal('ecs.amazonaws.com'),
        )

        batch_cfn_compute = batch.CfnComputeEnvironment(
            self,
            "RdsBatchCompute",
            type='MANAGED',
            service_role = batch_service_role.role_arn,
            compute_resources= batch.CfnComputeEnvironment.ComputeResourcesProperty(
                type = 'FARGATE',
                maxv_cpus=50,
                minv_cpus=0,
                # instance_role = batch_ecs_role.role_arn,
                # instance_types = ['m5.large'],
                subnets = [vpc.private_subnets[0].subnet_id, vpc.private_subnets[1].subnet_id, vpc.private_subnets[2].subnet_id],
            security_group_ids=[rds_sec_group_id]) 
            
        )

The above will fail on synth/diff However, if you uncomment instance_Type and instance_role it will deploy but fail at CFN level.

What did you expect to happen?

Allow Fargate task to get created without need for instance_type or instance_role

What actually happened?

CDK stack deployed but failed in CloudFormation console with An error occurred (ClientException) when calling the CreateComputeEnvironment operation: Error executing request, Exception : instanceRole is not applicable for Fargate.,

Environment

• CDK CLI Version : 1.77.0 (build a941c53)
• Framework Version:
• Node.js Version: 14.9.0
• OS : mac 10.15.7
• Language (Version): Python 3.8.6

Other

---

This is 🐛 Bug Report

[iliapolo]

Should be resolved once we merge https://github.com/aws/aws-cdk/pull/12204.

[iliapolo]

@nagmesh Thanks for reporting this.

The underlying problem is that the CloudFormation schema says its required at the same time it says it shouldn’t be supplied when using fargate.

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-batch-computeenvironment-computeresources.html#cfn-batch-computeenvironment-computeresources-instancerole

We will address it.

In the meantime, you can remove those two properties:

batch_cfn_compute.add_property_deletion_override('ComputeResources.InstanceRole')
batch_cfn_compute.add_property_deletion_override('ComputeResources.InstanceTypes')

cc @dsudduth