AWS CDK prevent creation of extra LogRetention Function

Question

I am using AWS CDK with typescript to create a lambda function. I am attempting to add a subscription filter to that lambda function to push logs to a kinesis stream.

Whenever i include the subscription filter it creates a new lambda function "LogRetention" which i dont want.

   const MyLFN = new NodejsFunction(this, "MyLFN", {...}) // We do not set any log* props here

   const FnbKinesisSF = new logs.SubscriptionFilter(this, "FnbKinesisSF", {
        logGroup: MyLFN.logGroup,
        destination: new destinations.KinesisDestination(FnbKinesis, {
            role: FnbKinesisRole,
        }),
        filterPattern: logs.FilterPattern.allEvents(),
    });

Is there a way to prevent the creation of the LogRetention Lambda function.

FYI: The LogRetention lambda does not show up in the CDK diff.

Answer 1

The solution is to create the LogGroup first before creating the Lambda Function. Then in your lambda function you reference an existing log group.

    const MyLfnLg = new logs.LogGroup(this, "MyLfnLg", {
        logGroupName: "/aws/lambda/ex-scheduler",
        retention: logs.RetentionDays.ONE_MONTH,
        removalPolicy: cdk.RemovalPolicy.DESTROY,
    });

    const MyLfn = new NodejsFunction(this, "RoboloxSchedulerLfn", {
        functionName: "ex-scheduler",
        logGroup: MyLfnLg,
    });

    MyLfnLg.addSubscriptionFilter("FnbKinesis-Subscription", {
        destination: new destinations.KinesisDestination(FnbKinesis, {
            role: FnbKinesisRole,
        }),
        filterPattern: logs.FilterPattern.allEvents(),
    });

This prevents the creation of the uncessary "LogRetention" Lambda function