CODEWITHSUNDEEP
amazon-web-servicesautoscaling
Darren Oakey
Darren Oakey

Reputation: 3594

Automatically terminate Auto Scaling instances after a time period

We use Amazon EC2 Auto Scaling groups for a bunch of apps - as everyone knows, while you try your hardest not to have memory leaks and other "been up for a while problems" - it's still possible.

We'd like to protect against such possibilities by just bouncing the servers - ie make sure an instance only lasts, say, 24 hours before killing it. However, we want the killing to be "safe" - eg - even if there's only one instance in the group, we want to start up another instance to a working state, then kill the old box.

Is there any support for this? eg a time-to-live property on an instance?

Upvotes: 3

Views: 1636

Answers (2)

Robin Houston
Robin Houston

Reputation: 299

Since 2019, there has been a Maximum Instance Lifetime parameter, that almost does what you wanted.

Unfortunately, though, it isn’t possible to set the maximum instance lifetime to 24 hours (86400 seconds): the minimum is a week.

Maximum instance lifetime must be equal to 0, between 604800 and 31536000 seconds (inclusive), or not specified.

Upvotes: 3

John Rotenstein
John Rotenstein

Reputation: 269171

There is no such property in Amazon EC2 nor in Auto Scaling.

You could manually set the instance health to Unhealthy, which would cause Auto Scaling to terminate and replace the instance. However, if you have only one instance then there will likely be a period where there are no instances.

You could set the Auto Scaling termination policy to OldestInstance, which means that when Auto scaling needs to terminate an instance, it will terminate the oldest instance within the AZ that has the most instances. This gets rid of old instances, but only when the group is scaled-in.

Therefore, you could supplement the Termination Policy with a script that scales-out the group and then causes it to scale-in again. For example, double the number of instances, wait for them to launch, and then halve the number of instances. This should cause them all to refresh (with a few edge conditions if your instances are spread across multiple AZs, causing non-even counts).

Another option is to restart the instance(s). This will not cause them to appear unhealthy to Auto Scaling, but they will appear unhealthy to a Load Balancer. (If you have activated ELB Health Checks within Auto Scaling, then Auto Scaling would actually terminate instances the fail the health check.) You can use Scheduled Events for Your Instances to have Amazon CloudWatch Events restart your instance(s) at certain intervals, or even have a script on the instance tell the Operating System to restart at certain intervals.

However, there is no automatic option to do exactly what you asked.

Upvotes: 3

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