Elasticache.CfnParameterGroup cannot be initialized with a parameter_group_name

[tonyhammainen]

I wanted to initialize an Elasticache.CfnCacheCluster with a specific Elasticache.CfnParameterGroup. Elasticache.CfnCacheCluster has an optional init parameter called cache_parameter_group_name. However, Elasticache.CfnParameterGroup does not allow defining its name in its initialization. Furthermore, it does not have an attribute called parameter_group_name, which would be intuitive.

Not being able to define parameter_group_name results in having a gibberish name visible in AWS Console under the view: Elasticache > Parameter Groups.

It also makes the initialization of Elasticache.CfnCacheCluster with a Elasticache.CfnParameterGroup very unintuitive.

Reproduction Steps

redis_parameter_group = elasticache.CfnParameterGroup(
    self,
    "RedisParameterGroup",
    description="Redis parameter group for ...",
    cache_parameter_group_family="redis5.0",
    properties={ },
)

redis_subnet_group = elasticache.CfnSubnetGroup(
    self,
    "RedisClusterPrivateSubnetGroup",
    cache_subnet_group_name="redis-subnet-group",
    description="Redis subnet for ...",
    subnet_ids=[subnet.subnet_id for subnet in vpc.private_subnets],
)

self.redis = elasticache.CfnCacheCluster(
    self,
    "RedisCacheCluster",
    engine="redis",
    cache_node_type="cache.r5.xlarge",
    num_cache_nodes=1,
    cluster_name="redis",
    vpc_security_group_ids=[self.redis_security_group.security_group_id],
    cache_subnet_group_name=redis_subnet_group.cache_subnet_group_name,
    cache_parameter_group_name=redis_parameter_group.????????,
)

Workaround for inputting into CfnCacheCluster:

One needs to figure out that .ref resolves to the name

ref | string | Return a string that will be resolved to a CloudFormation { Ref } for this element.
-- | -- | --

Which with further digging resolves to

Return Values
Ref
When the logical ID of this resource is provided to the Ref intrinsic function, Ref returns the resource name.

so
cache_parameter_group_name=redis_parameter_group.ref
works

Environment

• CLI Version : 1.32.2 (build e19e206)
• Framework Version:
• OS : MacOS Catalina
• Language : Python

Suggestion

Elasticache.CfnParameterGroup should take parameter_group_name in its initialization, and it should be a callable attribute.

---

This is 🐛 Bug Report

[iliapolo]

Hi @tonyhammainen

It seems the configuring the group name isn't supported by CloudFormation.

See: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-elasticache-parameter-group.html

Regarding your suggestion:

Elasticache.CfnParameterGroup should take parameter_group_name in its initialization, and it should be a callable attribute.

While this intuitively makes sense, all the Cfn* resources are actually auto-generated from the CloudFormation spec, so as long as its not supported, the Cfn* will remain the same.

To that end, I suggest you also open a feature request for CloudFormation.

In the meantime, we have an issue for implementing higher level constructs in the aws-elasticache module, where you can keep track of possibly a native CDK workaround for this issue.

[tonyhammainen]

Thanks for the speedy reply!

Opened a CFN feature request: aws-cloudformation/cloudformation-coverage-roadmap#484

Wishing to see a higher level construct soon!

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