sns: topic.addSubscription should create the subscription on the consumer's stack to avoid cycles

[eladb]

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• I'm submitting a ...

  • 🪲 bug report

• What is the current behavior?
  If the current behavior is a 🪲bug🪲: Please provide the steps to reproduce

topic.addSubscription currently creates the SNS::Subscription resource in the scope of the SNS topic (this), but since in most cases the consumer will need to reference the topic in their e.g. resource policy, if the topic and the subscriber are from different stacks, that will surely create a cyclic reference.

• What is the expected behavior (or behavior of feature suggested)?

TopicSubscriptionConfig should return the scope in which the subscription should be created and addSubscription should use that instead of this when creating a Subscription object.

• What is the motivation / use case for changing the behavior or adding this feature?

Avoid cyclic references.

• Please tell us about your environment:

  • CDK CLI Version: 0.36.0
  • Module Version: 0.36.0
  • OS: all
  • Language: all

[eladb]

Workaround is to create an sns.Subscription manually (not through topic.addSubscription):

function addSubscription(scope, topic, subscription) {
    const config = subscription.bind(topic);

    new sns.Subscription(scope, 'Subscription', {
        topic: topic,
        endpoint: config.endpoint,
        filterPolicy: config.filterPolicy,
        protocol: config.protocol,
        rawMessageDelivery: config.rawMessageDelivery
    });
}

[eladb]

See grapl-security/grapl#25