[Quick Tip] I Tried Sending Data to a Lambda Function in a Different Region Using a CloudWatch Logs Subscription Filter

Conclusion First

In the console, you cannot specify a Lambda function in another region for a CloudWatch Logs subscription filter, but by using the put-subscription-filter command, you can specify a Lambda function in a different region within the same account.

Trying It Out

① Based on the following blog, create an SNS topic and a Lambda function (testLambda) in the Tokyo region

I Tried Detecting Strings in CloudWatch Logs and Sending the Log Contents by Email: Subscription Filter Version

• I set the following environment variables for the Lambda function

SNS_TOPIC_ARN: ARN of the created SNS topic
ALARM_SUBJECT: OtherRegionSubscriptionFilterTest 

• I set the following resource policy on the Lambda function

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Statement1",
      "Effect": "Allow",
      "Principal": {
        "Service": "logs.amazonaws.com"
      },
      "Action": "lambda:InvokeFunction",
      "Resource": "arn:aws:lambda:ap-northeast-1:XXXXXXXXXXXX:function:testLambda"
    }
  ]
}

• I added permission for the sns:publish action to the Lambda function's role

② Create a log group (testOtherRegionLambdaLog) in the N. Virginia region

③ Set a subscription filter on the log group

Since the Lambda function is not displayed in the console, specify the Lambda function in the Tokyo region using the following aws cli command

aws logs put-subscription-filter \
--log-group-name "testOtherRegionLambdaLog" \
--filter-name "testLambda" \
--filter-pattern "Error" \
--destination-arn "arn:aws:lambda:ap-northeast-1:XXXXXXXXXXXX:function:testLambda"

④ Put logs into the log group

aws logs put-log-events --log-group-name testOtherRegionLambdaLog \
--log-stream-name testOtherRegionLambdaLogStream \
--log-events timestamp=`date +%s%3N`,message="This is Error" 

⑤ The Lambda function was executed, and an email was received from the SNS topic

Notes

In the "destination-arn" option of the command executed in ③, the Lambda function is specified directly,
but please note that it must be a Lambda function within the same account.

PutSubscriptionFilter - Request Parameters

destinationArn
The ARN of the destination to deliver matching log events to. Currently, the supported destinations are:
...
A Lambda function belonging to the same account as the subscription filter, for same-account delivery.

In Closing

If you have a requirement to integrate data across regions, I hope this blog is helpful.

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