How can I send a variables from cloudwatch service to Lambda function using SNS Topic


I have CloudWatch Alarm the count the traffic if the traffic is below the threshold then to send a notification via SNS message and the SNS message trigger A lambda function, and the lambda function trigger a python code to decrees the ASG Instance number. it works for me when I but hardcoded the ASG name And the CloudWatch name inside the lambda, auto_scaling_group_name = 'PRD-WEB-ADS-ASG' cloudwatch_alarm_name = 'ASG_Traffic_TO_ADS_WEB' but now I want it to be generic and dynamic and I want to send the cloudwatch name and the ASG name from the CloudWatch as a variable the lambda can get, I have tried to google it , it suggest me to configure it on the sns / CloudWatch notification section (but I don't see any way to configure the message in cloud watch and I don't see an action section inside the SNS topic, so please help me what I should do and how to get it to lambda. (what I have to write in lambda if I am using python 3.10 where can I configure the notification inside the CloudWatch and what should I write there, and what should I configure on the SNS topic if I already have lambda to trigger

  • Side note: Why do you want to go through all of these steps you have to manually create instead of just using a scaling policy on the ASG?

1 Answer

The CloudWatch alarm embeds a Json payload in the context when sending the SNS notification, which is automatically extracted to the event variable of the Lambda - did you try reading that information? You should get the alarm name from it at the very least. For example, if you take a look at the following blog post (, you'll see that you can get the alarm name with alarmName=event['detail']['alarmName']

Likewise, you can get from event['detail'] the alarm configuration, which will give you extra information that you may need/want?

profile pictureAWS
answered 9 months ago

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