Amazon SNS notification options for Amazon EC2 Auto Scaling - Amazon EC2 Auto Scaling
Amazon SNS and Amazon EC2 Auto Scaling

Amazon SNS notification options for Amazon EC2 Auto Scaling

You can configure your Auto Scaling group to notify you of important events that affect your application. With notifications, you can also eliminate polling, and you won't encounter the RequestLimitExceeded error that sometimes results from polling.

There are two ways to receive notifications about Amazon EC2 Auto Scaling:

  • Amazon Simple Notification Service – Amazon SNS can notify you when your Auto Scaling group launches or terminates instances. You can only turn Amazon SNS notifications on or off. For more information, see Amazon SNS and Amazon EC2 Auto Scaling.

  • Amazon EventBridge – EventBridge provides more advanced, event-driven notifications matched to specified criteria and sent to a variety of targets, including Amazon SNS. EventBridge can also monitor a wider range of Auto Scaling events for more precise monitoring. For more information, see Use EventBridge to handle Auto Scaling events.

You can optionally use notifications with lifecycle hooks to perform custom actions on instances during launch or termination. For more information on how to configure the notifications to use with lifecycle hooks, see Amazon EC2 Auto Scaling lifecycle hooks.

Amazon SNS and Amazon EC2 Auto Scaling

This section shows how to use Amazon SNS to monitor when your Auto Scaling group launches or terminates instances.

For example, if you configure your Auto Scaling group to use the autoscaling: EC2_INSTANCE_TERMINATE notification type, and your Auto Scaling group terminates an instance, it sends an email notification. This email contains the details of the terminated instance, such as the instance ID and the reason that the instance was terminated.

Note that as Amazon EC2 Auto Scaling adds or removes instances from the group, notifications about these changes are sent to you, with one notification sent per instance. However, delivery of these notifications is on a best-effort basis, and your instances could still fail after the initial notification, for example, if a later health check fails. For more information about the health check process, see Health checks for instances in an Auto Scaling group.

For more information about Amazon SNS generally, see the Amazon Simple Notification Service Developer Guide.

SNS notifications

Amazon EC2 Auto Scaling supports sending Amazon SNS notifications when the following events occur.

Event Description

autoscaling:EC2_INSTANCE_LAUNCH

Successful instance launch

autoscaling:EC2_INSTANCE_LAUNCH_ERROR

Failed instance launch

autoscaling:EC2_INSTANCE_TERMINATE

Successful instance termination

autoscaling:EC2_INSTANCE_TERMINATE_ERROR

Failed instance termination

The message includes the following information:

  • Event — The event.

  • AccountId — The Amazon Web Services account ID.

  • AutoScalingGroupName — The name of the Auto Scaling group.

  • AutoScalingGroupARN — The ARN of the Auto Scaling group.

  • EC2InstanceId — The ID of the EC2 instance.

For example:

Service: AWS Auto Scaling
Time: 2016-09-30T19:00:36.414Z
RequestId: 4e6156f4-a9e2-4bda-a7fd-33f2ae528958
Event: autoscaling:EC2_INSTANCE_LAUNCH
AccountId: 123456789012
AutoScalingGroupName: my-asg
AutoScalingGroupARN: arn:aws:autoscaling:region:123456789012:autoScalingGroup...
ActivityId: 4e6156f4-a9e2-4bda-a7fd-33f2ae528958
Description: Launching a new EC2 instance: i-0598c7d356eba48d7
Cause: At 2016-09-30T18:59:38Z a user request update of AutoScalingGroup constraints to ...
StartTime: 2016-09-30T19:00:04.445Z
EndTime: 2016-09-30T19:00:36.414Z
StatusCode: InProgress
StatusMessage: 
Progress: 50
EC2InstanceId: i-0598c7d356eba48d7
Details: {"Subnet ID":"subnet-id","Availability Zone":"zone"}
Origin: AutoScalingGroup
Destination: EC2

Configure Amazon SNS notifications for Amazon EC2 Auto Scaling

To use Amazon SNS to send email notifications, you must first create a topic and then subscribe your email addresses to the topic.

Create an Amazon SNS topic

An SNS topic is a logical access point, a communication channel your Auto Scaling group uses to send the notifications. You create a topic by specifying a name for your topic.

When you create a topic name, the name must meet the following requirements:

  • Between 1 and 256 characters long

  • Contain uppercase and lowercase ASCII letters, numbers, underscores, or hyphens

For more information, see Creating an Amazon SNS topic in the Amazon Simple Notification Service Developer Guide.

Subscribe to the Amazon SNS topic

To receive the notifications that your Auto Scaling group sends to the topic, you must subscribe an endpoint to the topic. In this procedure, for Endpoint, specify the email address where you want to receive the notifications from Amazon EC2 Auto Scaling.

For more information, see Subscribing to an Amazon SNS topic in the Amazon Simple Notification Service Developer Guide.

Confirm your Amazon SNS subscription

Amazon SNS sends a confirmation email to the email address you specified in the previous step.

Make sure that you open the email from AWS Notifications and choose the link to confirm the subscription before you continue with the next step.

You will receive an acknowledgment message from AWS. Amazon SNS is now configured to receive notifications and send the notification as an email to the email address that you specified.

Configure your Auto Scaling group to send notifications

You can configure your Auto Scaling group to send notifications to Amazon SNS when a scaling event, such as launching instances or terminating instances, takes place. Amazon SNS sends a notification with information about the instances to the email address that you specified.

To configure Amazon SNS notifications for your Auto Scaling group (console)

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/, and choose Auto Scaling Groups from the navigation pane.

  2. Select the check box next to your Auto Scaling group.

    A split pane opens up in the bottom part of the page, showing information about the group that's selected.

  3. On the Activity tab, choose Activity notifications, Create notification.

  4. On the Create notifications pane, do the following:

    1. For SNS Topic, select your SNS topic.

    2. For Event types, select the events to send the notifications.

    3. Choose Create.

To configure Amazon SNS notifications for your Auto Scaling group (AWS CLI)

Use the following put-notification-configuration command.

aws autoscaling put-notification-configuration --auto-scaling-group-name my-asg --topic-arn arn --notification-types "autoscaling:EC2_INSTANCE_LAUNCH" "autoscaling:EC2_INSTANCE_TERMINATE"

Test the notification

To generate a notification for a launch event, update the Auto Scaling group by increasing the desired capacity of the Auto Scaling group by 1. You receive a notification within a few minutes after instance launch.

To change the desired capacity (console)

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/, and choose Auto Scaling Groups from the navigation pane.

  2. Select the check box next to your Auto Scaling group.

    A split pane opens up in the bottom part of the Auto Scaling groups page, showing information about the group that's selected.

  3. On the Details tab, choose Group details, Edit.

  4. For Desired capacity, increase the current value by 1. If this value exceeds Maximum capacity, you must also increase the value of Maximum capacity by 1.

  5. Choose Update.

  6. After a few minutes, you'll receive notification for the event. If you do not need the additional instance that you launched for this test, you can decrease Desired capacity by 1. After a few minutes, you'll receive notification for the event.

Delete the notification configuration

You can delete your Amazon EC2 Auto Scaling notification configuration if it is no longer being used.

To delete Amazon EC2 Auto Scaling notification configuration (console)

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/, and choose Auto Scaling Groups from the navigation pane.

  2. Select your Auto Scaling group.

  3. On the Activity tab, select the check box next to the notification you want to delete and then choose Actions, Delete.

To delete Amazon EC2 Auto Scaling notification configuration (AWS CLI)

Use the following delete-notification-configuration command.

aws autoscaling delete-notification-configuration --auto-scaling-group-name my-asg --topic-arn arn

For information about deleting the Amazon SNS topic and all subscriptions associated with your Auto Scaling group, see Deleting an Amazon SNS subscription and topic in the Amazon Simple Notification Service Developer Guide.

Key policy for an encrypted Amazon SNS topic

The Amazon SNS topic you specify might be encrypted with a customer managed key created with the AWS Key Management Service. To give Amazon EC2 Auto Scaling permission to publish to encrypted topics, you must first create your KMS key and then add the following statement to the policy of the KMS key. Replace the example ARN with the ARN of the appropriate service-linked role that is allowed access to the key. For more information, see Configuring AWS KMS permissions in the Amazon Simple Notification Service Developer Guide.

In this example, the policy statement gives the service-linked role named AWSServiceRoleForAutoScaling permissions to use the customer managed key. To learn more about the Amazon EC2 Auto Scaling service-linked role, see Service-linked roles for Amazon EC2 Auto Scaling.

{
  "Sid": "Allow service-linked role use of the customer managed key",
  "Effect": "Allow",
  "Principal": {
    "AWS": "arn:aws:iam::123456789012:role/aws-service-role/autoscaling.amazonaws.com/AWSServiceRoleForAutoScaling"
  },
  "Action": [
    "kms:GenerateDataKey*",
    "kms:Decrypt"
  ],
  "Resource": "*"
}

The aws:SourceArn and aws:SourceAccount condition keys are not supported in key policies that allow Amazon EC2 Auto Scaling to publish to encrypted topics.