monitoring aws ec2 instance ports

Question

I have an application running in EC2 that listen to many ports, some external devices connect to those ports to send data to my application. This is fine, but my client has a requirement that i must monitoring those ports and if one of them stop listening, the instance must be terminated and a new one started.

I was reading about couldwatch, but i didn't found an alarm that i can customize like this (doing requests to ports). Is it possible to do this using cloudwatch ? i'm looking for a direction to create this monitoring, using internal aws services or develop a new solution (maybe a sheel script).

thanks!

Answer 1

I'm not aware of any AWS provided EC2 healthcheck monitoring system for custom checks.

You could write an AWS lambda function which sends requests to the ports on the EC2 instance you require. You can then schedule that lambda to run periodically with whatever frequency you want with Cloudwatch Events. The lambda function could publish this as a metric to cloudwatch which would then make it possible for you to use it in an alarm and thus take action when whatever threshold you deem reasonable to spin up a new replacement instance.

One part of AWS that does have basically what you are looking for built-in though is ECS. Instead of an EC2 instance, you'd have a Docker instance (running on an EC2 instance or Fargate) which can have healthchecks defined .

Answer 2

There are many ways to do what you are asking for.

• Simplest solution: I will write a boto3/shell script to monitor the port and call TerminateInstance API or use AWS CLI to terminate the current instance. Needless to say, you need to pass AWS credentials or attach instance profile with sufficient privileges to terminate the instance.
• Using Cloudwatch: Have a script to check port status and send 1 or 0 (Dimension: Count) to Cloudwatch. Set a threshold in Cloudwatch if there is consecutive 0s or NoData, then terminate the instance. Or do not send any data to Cloudwatch if the port is not available and NoData in Cloudwatch can trigger TerminateInstance. See: Cloudwatch - AddingTerminateActions