SNS Lambda Subscription Conflict

When subscribing multiple SNS Topics to a single Lambda Function, if two of those Topics have the same id (scope-local - this could happen if those Topics are in different scopes) then the second subscription will fail to be created with:

A subscription with id "SomeId" already exists under the scope Stack/Resource

Reproduction Steps

See robwettach/sns-lambda-subscription-conflict

Error Log

A subscription with id "SomeId" already exists under the scope Stack/Resource

Environment

• CLI Version : 1.37.0 (build e4709de)
• Framework Version: 1.37.0
• OS : macOS Mojave 10.14.6
• Language : TypeScript (all)

Other

I believe changing this line from

subscriberId: topic.node.id,

to

subscriberId: topic.node.uniqueId,

will solve this issue.

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This is 🐛 Bug Report

[JelsB]

I just ran into the same problem. I also have an sns.Topic within a custom construct. @fwang, thanks for the PR!

[PatrykMilewski]

I have the same error message, but different setup. I’m importing the topic using:

const topic = sns.Topic.fromTopicArn(
  this,
  'topic-id'
  `arn-goes-here`,
);
this.addEventSource(new SnsEventSource(topic));

And then I’m getting this error message:

Error: A subscription with id “topic-id” already exists under the scope stack-name/lambda-id

My Lambda is wrapped over a custom construct, so I think it’s not only a problem of wrapping the Topic in a custom construct

I also managed to workaround it, by extracting the sns.Topic.fromTopicArn( [...] ) call out of custom Lambda construct to one level up and then passing it as props.