This is now supported in cloudformation, however, you have to add target region within cfn. Example: ` SNSSampleSubscription: Type: AWS::SNS::Subscription

Properties:
  Endpoint: !Sub 'arn:aws:lambda:us-east-2:2222222:function:sample_lambda'
  Protocol: lambda
  TopicArn: !Sub 'arn:aws:sns:us-east-1:1111111:osbf-pull-ami'
  Region: !Sub 'us-east-1'`

In above example, lambda is in us-east-2, and it is subscribing to an sns in us-east-1. The “Region” allows you to do that.

I have created a Gist showing how to implement the custom resource with SLS:

https://gist.github.com/jscattergood/00a2ea6a80fe41a74c5c7efed1b238b4

Hey all - sorry if this is just me being dense, but this took me a while to figure out and I want to add a couple clarifications in case they help out others who run into this issue.

My lambda functions are in us-east-2, but I wanted to use a SNS queue in us-east-1 as a trigger.

I originally tried this in my serverless.yml file, but I got the “invalid parameter: TopicArn” error (like the original poster).

handleBounceOrComplaintEmailSNS:
  handler: server.handleBounceOrComplaintEmailSNS
  events:
    - sns:
        arn: arn:aws:sns:us-east-1:0005555555555:email-bounces-complaints

I didn’t know enough about serverless or cloudformation to know what @Imran99 meant by SubNameFromGeneratedCfn, so it took a lot of head scratching and searching.
After staring at my .serverless/cloudformation-template-update-stack.json for a while (and several failed attempts), I finally sorted it out. By searching for my SNS’s ARN in .serverless/cloudformation-template-update-stack.json, I found that the SubNameFromGeneratedCfn Imran99 was referring to was HandleBounceOrComplaintEmailSNSSnsSubscriptionemailbouncescomplaints (in my template). By using that name under resources, I was able get it working! So these two components of my serverless.yml file are:

handleBounceOrComplaintEmailSNS:
  handler: server.handleBounceOrComplaintEmailSNS
  events:
    - sns:
        arn: arn:aws:sns:us-east-1:0005555555555:email-bounces-complaints

resources:  
  Resources:
    HandleBounceOrComplaintEmailSNSSnsSubscriptionemailbouncescomplaints:
      Type: AWS::SNS::Subscription
      Properties:
        Region: us-east-1

Bottom line: use Imran99’s workaround, but note you’ll need to search .serverless/cloudformation-template-update-stack.json to figure out SubNameFromGeneratedCfn. Thank you all for the workaround!

Whilst there is now a workaround available it would be great if there was first class support for this on the sns event in serverless.

@dschep why was this issue closed? I do not see any messages from maintainers as to whether this issue will be addressed. There isn’t a pending PR either.

This is now supported in cloudformation, however, you have to add target region within cfn.

I was able to modify my serverless.yml with the Region parameter and I can see that the subscription is created successfully against the correct topic.

serverless.yml

resources:
  Resources
    SubNameFromGeneratedCfn:
      Properties:
        Region: eu-west-1

I also had to ensure that serverless-psuedo-parameters didn’t auto replace the region so just a heads up if you are using that:

custom:
  pseudoParameters:
    skipRegionReplace: true

I have the same problem. I need to subscribe to an us-east-1 ARN for the AWS marketplace but my whole infrastructure runs in us-west-2

Whilst there is now a workaround available it would be great if there was first class support for this on the sns event in serverless.

@srg-avai Yes, you can subscribe cross-region like the FAQ says. However, you can not do it (or could not at the time that I wrote that post) via CloudFormation. Thus, I ended up having to make a custom resource that did the cross-region subscription, and using that custom CloudFormation resource rather than using the built-in CF SNS subscription resource. Obviously, that’s not an option for the SLS team (since we’d all have to deploy custom resources to use SLS), but maybe their connections / weight with AWS could get the issue noticed if someone on their team reported it to AWS.

@jthomerson Q: Do my AWS Lambda functions need to be in the same region as my Amazon SNS usage? You can subscribe your AWS Lambda functions to an Amazon SNS topic in any region. https://aws.amazon.com/sns/faqs/

We need this on our project. What are the next steps for follow up with AWS? I’m sure you guys can pull more strings than we can to get this worked out with CloudFormation

In Account1 we subscribe SNS in region us-west-1, it will fail with error “Error code: InvalidParameter - Error message: Invalid parameter: TopicArn”

We need to switch Account1 to region us-east-1 to do the subscription, it will success.

Try the longer form for the event

    events:
      - sns: 
          arn: ${self:provider.TopicArn}

I’ll look into why the short form is not adding it.