elasticache: Serverless cache attr_endpoint returning aws_cdk.Reference

[Jmevorach]

Describe the bug

The attr_endpoint attribute of the CfnServerlessCache should be a string or be resolvable to a string but instead it's aws_cdk.Reference instead.

Expected Behavior

I expected that this script should be able to run:

import aws_cdk as cdk
from aws_cdk import (
    Stack,
    aws_elasticache as elasticache,
    aws_ssm as ssm
)
from constructs import Construct
import os

class test_stack(Stack):

    def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
        super().__init__(scope, construct_id, **kwargs)

        self.redis_cluster = elasticache.CfnServerlessCache(
            self,
            "RedisCluster",
            engine="redis",
            serverless_cache_name="ServerlessCache",
        )

        self.redis_endpoint = ssm.StringParameter(
            self,
            "redis-endpoint",
            parameter_name="redis_endpoint",
            string_value=self.redis_cluster.attr_endpoint
        )

if __name__ == "__main__":
    app = cdk.App()
    test_stack(app, "test",
    env=cdk.Environment(
        account=os.getenv('CDK_DEFAULT_ACCOUNT'),
        region=os.getenv('CDK_DEFAULT_REGION')
    ))
    app.synth()

Current Behavior

Instead of running successfully this traceback is returned: Traceback (most recent call last): File "/Users/home/test.py", line 32, in test_stack(app, "test", File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/jsii/_runtime.py", line 118, in call inst = super(JSIIMeta, cast(JSIIMeta, cls)).call(*args, *kwargs) File "/Users/home/test.py", line 22, in init self.redis_endpoint = ssm.StringParameter( File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/jsii/_runtime.py", line 118, in call inst = super(JSIIMeta, cast(JSIIMeta, cls)).call(args, **kwargs) File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/aws_cdk/aws_ssm/init.py", line 8397, in init props = StringParameterProps( File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/aws_cdk/aws_ssm/init.py", line 8924, in init check_type(argname="argument string_value", value=string_value, expected_type=type_hints["string_value"]) File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/typeguard/init.py", line 785, in check_type raise TypeError( TypeError: type of argument string_value must be str; got aws_cdk.Reference instead

Reproduction Steps

Running this script below should reproduce the bug:

import aws_cdk as cdk
from aws_cdk import (
    Stack,
    aws_elasticache as elasticache,
    aws_ssm as ssm
)
from constructs import Construct
import os

class test_stack(Stack):

    def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
        super().__init__(scope, construct_id, **kwargs)

        self.redis_cluster = elasticache.CfnServerlessCache(
            self,
            "RedisCluster",
            engine="redis",
            serverless_cache_name="ServerlessCache",
        )

        self.redis_endpoint = ssm.StringParameter(
            self,
            "redis-endpoint",
            parameter_name="redis_endpoint",
            string_value=self.redis_cluster.attr_endpoint
        )

if __name__ == "__main__":
    app = cdk.App()
    test_stack(app, "test",
    env=cdk.Environment(
        account=os.getenv('CDK_DEFAULT_ACCOUNT'),
        region=os.getenv('CDK_DEFAULT_REGION')
    ))
    app.synth()

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.113.0

Framework Version

No response

Node.js Version

v18.2.0

OS

MacOS 13.5.2

Language

Python

Language Version

3.10

Other information

No response

[Jmevorach]

If I change string_value=self.redis_cluster.attr_endpoint to string_value=self.redis_cluster.attr_endpoint.to_string() and run cdk deploy the stack fails to deploy with ...

| CREATE_FAILED        | AWS::SSM::Parameter                         | redisendpointA956750C
Properties validation failed for resource redisendpointA956750C with message:
#/Value: expected type: String, found: JSONObject

[pahud]

I haven't deployed this resource before it's pretty new but according to the CFN doc

Endpoint Represents the information required for client programs to connect to a cache node.

And JS SDK https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/ElastiCache.html#createServerlessCache-property

I guess it should be a json object that contains both Address and Port.

Are you able to return its address by self.redis_cluster.attr_endpoint.address or attr_endpoint.get('Address') ?

[vktrl]

Having the same issue with the TS CDK. Haven't found a way to extract the address property from the JSON nor verify that it has it.

[Jmevorach]

Using self.redis_cluster.attr_endpoint.address gives AttributeError: 'Reference' object has no attribute 'address'.

Using self.redis_cluster.attr_endpoint.get('Address') gives AttributeError: 'Reference' object has no attribute 'get'.

[CEVO-MatheusJGSantos]

Same issue here. Oddly if I do print("{}".format(self.resolve(myElasticache.get_att('Endpoint')))) I will get a function that should work, but I can't use the actual object anywhere in my stack: {'Fn::GetAtt': ['serverlessRedisCache', 'Endpoint']}

[jayhilden]

+1. If I try to export the address I get an error using the TS client on 2.113.0

Code

const redisServerlessCluster = new CfnServerlessCache(this, cacheName, {
            ...
        })

this.redisServerlessURI = "rediss://" + redisServerlessCluster.attrEndpoint
new CfnOutput(this,  'redisServerlessURI', {
    exportName: 'redisServerlessURI',
    value: this.redisServerlessURI,
})

CFN Error

Requested attribute Endpoint must be a readonly property in schema for AWS::ElastiCache::ServerlessCache

[MatheusAfinovicz]

Having the same issue here with TS CDK. Did a workaround with the SDK to get the DB using its name, and then accessing the endpoint:

        const client = new ElastiCacheClient({
        region
    });

    const describeServerlessCachesCommand = new DescribeServerlessCachesCommand({
        MaxResults: 20,
        ServerlessCacheName: your-db-name
    });

    const redis = await client.send(describeServerlessCachesCommand);

    if (!redis || !redis.ServerlessCaches) throw new Error('No redis found');

    const endpoint = redis.ServerlessCaches[0].Endpoint;

    if (!endpoint) throw new Error('No redis endpoint found');

    return `${endpoint.Address}:${endpoint.Port}`;

[ChadMoran]

I found a workaround.

const cluster = new elasticache.CfnServerlessCache(this, 'RedisCluster', {
  serverlessCacheName: 'redis',
  engine: 'redis',
});

new cdk.CfnOutput(this, 'RedisEndpoint', {
  value: cluster.getAtt('Endpoint.Address').toString(),
});

You can also access Endpoint.Port as seen from aws elasticache describe-serverless-caches

It looks like the docs are out of date or incorrect. It seems that .attr_Endpoint should return the CfnServerlessCache.Endpoint type.