read existing redis elasticache properties in CDK

Question

Hi team,

I have an existing Amazon ElastiCache Redis cluster set up via CDK in our AWS account with the following configuration

```
const redis = new elasticache.CfnReplicationGroup(this, 'cache', {
      replicationGroupDescription: 'xxxxxxxx',
      atRestEncryptionEnabled: true,
      multiAzEnabled: true,
      cacheNodeType: 'cache.t2.micro',
      cacheSubnetGroupName: sng.cacheSubnetGroupName,
      engine: "redis",
      engineVersion: '7.1',
      numNodeGroups: 1, 
      replicasPerNodeGroup: 1, 
      securityGroupIds: [sg_id],
      transitEncryptionEnabled: true, 
    })

```

In a completely separate CDK project, I need my Lambda function to connect to this existing Redis cluster.

I couldn’t find a way to retrieve the Redis cluster’s host and port using methods like `.fromName() `or `.fromArn()`.

Is there a way to access the Redis cluster’s endpoint and port in my CDK project so I can inject them as environment variables in my Lambda function?

(The Redis cluster was created way before in another project and now it's running in AWS)

in this new CDK project, I just need to grab it so I can retrieve its host and port to use them in my lambda code to connect to the Elasticache cluster.

Thanks!

Didier_Durand · Answer

Hi,

The proper way to read properties of an AWS resource is not from CDK (which could be out of sync from reality) but from the AWS service API itself via the SDK of your preferred languages.

So, for Python, it would be those in https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/elasticache.html

Best,

Didier

Riku_Kobayashi · Answer

Hello.

Looking at the properties in the document below, it seems that you can get the endpoint and port number with "attrPrimaryEndPointAddress" and "attrPrimaryEndPointPort".  
https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_elasticache.CfnReplicationGroup.html

Therefore, if you add the code as shown below, you can output it from the stack, so I think it is possible to reference it from other stacks.  
```
new cdk.CfnOutput(this, 'RedisEndpoint', {
  value: redis.attrPrimaryEndPointAddress
});

new cdk.CfnOutput(this, 'RedisPort', {
  value: redis.attrPrimaryEndPointPort
});
```
If Lambda is in the same stack, I think you can set the environment variables as follows.  
https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_lambda.Function.html  
```
const fn = new lambda.Function(this, 'MyFunction', {
  runtime: lambda.Runtime.NODEJS_18_X,
  handler: 'index.handler',
  code: lambda.Code.fromAsset(path.join(__dirname, 'lambda-handler')),
  environment:{
    "ENDPOINT": redis.attrPrimaryEndPointAddress,
    "PORT": redis.attrPrimaryEndPointPort
  }
});
```

read existing redis elasticache properties in CDK

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