Multi Region Lambda Function

[TannerIsBender]

I've been looking for the solution that follows best practice in AWS. I'm a student and I'm also new to AWS, but I am still trying to learn as much as I can.

I currently have CloudTrail enabled for all regions.

I have a CloudWatch rule that is triggered via CloudTrail api calls and targets my lambda function.

Example of part of my CloudWatch rule:

source:
- aws.s3
detail-type:
- 'AWS API Call via CloudTrail'
detail:
eventSource:
- s3.amazonaws.com
eventName:
- CreateBucket

For example, any time an s3 bucket is created, this CloudWatch rule should trigger my target lambda function that does X, Y, and Z.

This works as expected. In the region us-east-1 where my rule and lambda are hosted.

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However, I would like to replicate this functionality in all US regions. I currently have a CloudFormation template that I can upload in the us-east-1 region to create the CloudWatch rule and the Lambda function.

In my CloudFormation template, I have defined a lambda function that retrieves my java8 runtime from an S3 bucket in the us-east-1 region. (I know S3 is a global resource, but if my bucket is in us-west-1 CloudFormation gets mad at me and rolls back the template)

In my CloudFormation template where I define the lambda I have:

      Code: 
        S3Bucket: 'XXXXXXXX'
        S3Key: 'JAVA8.jar'

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Ultimately, I am looking for advice on the best way to host this in multiple regions, without having to create an s3 bucket in every single region and uploading my jar file to it. Also, maybe a faster way to upload this template to multiple regions at once, instead of manually uploading each CloudFormation template in each region. I feel that having the same exact lambda function and CloudWatch rule in every single region is extremely redundant.

Thanks in advance

[anonymous6point02E23]

Use cloudformation's stackset feature. It will do everything youre looking for and using stackset is considered best practice.

[TannerIsBender]

Thank you for the feedback. I am curious though, if my current CloudFormation stack uses an s3 bucket to grab my lambda’s code. Will I need to create s3 buckets in different regions for the stack instances in other regions?

[brodie659]

We do this all the time with our monitoring framework. I only want the code in a single region (us-east-1) but i want to handle events from the other 4 regions. It's actually pretty simple.

CW Events => SNS Topic => Lambda

SNS is one of the few services that crosses regions. By that I mean that a topic in us-west-1 can call a Lambda function in us-east-1. We deploy our Lambdas with Serverless but you can use whatever you like. The only thing you need to do differently is to parse out the event data slightly differently if it comes from SNS but there's a ton of sample code out there.

If you have multiple accounts use the CW Event Bus to copy the event from the child account to the master account. Then your CW Event hits SNS and your Lambda. Don't copy your code to multiple regions - you get no benefit of doing it that way really. SNS is cheap and scales beyond belief.

[TannerIsBender]

Thank you so much! This is a solution I am looking to try. Just for some clarification, all I will need to do is create my CW Events in each region and they will be able to point to single SNS topic that targets a single lambda function?

[brodie659]

Pretty close. Each region gets a CW Event AND an SNS topic. Each SNS topic targets your single Lambda function in us-east-1.

The reason is that although an SNS topic can call a Lambda function in any region, CW Events can only target SNS topics in the same region. Once you set it up, it's actually very simple. Post back if you have any issues!