Hello, I'm trying to replicate a behaviour that I have in SLS which is to have multiple SNS topics send messages to one Lambda. Effectively One Lambda Subscribing 2 topics. However this doesn't seem to be allowed?

Error: A subscription with id "Topic" already exists under the scope dev-*-metadata-stack/UpdateSnapshot
    at Topic.addSubscription (/home/dev/Documents/*/Github/*/node_modules/aws-cdk-lib/aws-sns/lib/topic-base.ts:61:13)
    at Topic.addFunctionSubscriber (/home/dev/Documents/*/Github/*/node_modules/@serverless-stack/resources/src/Topic.ts:231:19)
    at Topic.addSubscriber (/home/dev/Documents/*/Github/*/node_modules/@serverless-stack/resources/src/Topic.ts:176:12)
    at /home/dev/Documents/*/Github/*/node_modules/@serverless-stack/resources/src/Topic.ts:125:46
    at Array.forEach (<anonymous>)
    at Topic.addSubscribers (/home/dev/Documents/*/Github/*/node_modules/@serverless-stack/resources/src/Topic.ts:125:17)
    at new MetadataStack (/home/dev/Documents/*/Github/*/lib/metadataStack.js:231:22)
    at Object.main (/home/dev/Documents/*/Github/*/lib/index.js:125:39)
    at Object.<anonymous> (/home/dev/Documents/*/Github/*/.build/run.js:94:16)
    at Module._compile (node:internal/modules/cjs/loader:1101:14)

Any ideas of a work around? Thanks!

Can I see your cdk code

I've defined the Topics "lazily" and i'm adding subscribers in the stacks that define the functions (just because its easier and cleaner that way (i think).

props.topicA.addSubscribers(this, [
      {
        function: updateSnapshot,
        subscriberProps: {
          filterPolicy: {
            event_type: SubscriptionFilter.stringFilter({
              allowlist: ["file_created"],
            }),
          },
        },
      },
    ]);

    props.topicB.addSubscribers(this, [
      {
        function: updateSnapshot,
        subscriberProps: {
          filterPolicy: {
            event_type: SubscriptionFilter.stringFilter({
              allowlist: ["state_changed"],
            }),
          },
        },
      },
    ]);

This is a snippet that flags up. SST version @ latest.

I vaguely recall this being brought up and I think we maybe fixed it - @Frank?

Any updates on this? @thdxr thanks

Taking a look..

Sorry to ask again 🙈 but is there any update? I sort of have a work around so its not "urgent" just wondering if this was in any way fixed and not included in the patch notes.

Hey @Hubert, sorry about the delay. I just tried it out. I’m guess the two topics

props.topicA

and

props.topicB

have the same id ^^ ie. id is the 2nd parameter passed into the constructor

new sst.Topic(this, "topicId", {…});

Thanks for getting back to me! All my topics have a unique ID I've made sure that's the case for every single resource. This is only an issue when attaching one function to two topics as a subscriber. Hence why I assumed that the topics themselves aren't at fault because they work if I dont setup the subscribers.

Hey @Hubert, I dug into this a bit further, and it seems to be a case that’s not handled by CDK.

Thanks for that Frank, sorry for the late reply. I will keep an eye on the github page. I'm going to implement what you've suggested as a temporary solution 🙂 thanks!