Auto-Restart EC2 Instances on Status Check Failure: Quick Setup Guide

Introduction

In this comprehensive guide, we’ll take you through the process of setting up an automated system to restart an EC2 instance when its status check fails using AWS CloudFormation. By creating a CloudWatch Alarm that specifically monitors “Status Check Failure” metrics and integrating it with Simple Notification Service (SNS), we can receive notifications and trigger an automatic restart. This ensures the health and availability of your EC2 instances, especially in scenarios where status check failures may impact performance and reliability.

Prerequisites

• AWS Account
• Basic knowledge of AWS CloudFormation

CloudFormation Template Overview

The CloudFormation template includes parameters, resources, and outputs. Key components:

• Parameters: Customize with the existing EC2 instance ID.
• Resources: Define CloudWatch Alarm, SNS Topic, and SNS Subscription.
• Outputs: Display the EC2 instance ID.

Launch the CloudFormation Stack

1. Access AWS CloudFormation.
2. Choose “Create Stack” > “With new resources.”
3. Upload the provided template.

AWSTemplateFormatVersion: '2010-09-09'
Description: Template to Create a CloudWatch alarm for EC2 instance status check failure

Parameters:
  ExistingInstanceId:
    Type: String
    Description: ID of the existing EC2 instance

Resources:
  SnsTopic:
    Type: AWS::SNS::Topic
    Properties:
      DisplayName: "EC2StatusCheckFailureTopic"
      
  SnsSubscription:
    Type: AWS::SNS::Subscription
    Properties:
      Protocol: email
      TopicArn: !Ref SnsTopic
      Endpoint: [email protected]  # Replace with your email address

  InstanceStatusAlarm:
    Type: AWS::CloudWatch::Alarm
    Properties:
      AlarmName: InstanceStatusAlarm
      Namespace: AWS/EC2
      MetricName: StatusCheckFailed
      Dimensions:
        - Name: InstanceId
          Value: !Ref ExistingInstanceId
      Statistic: Maximum
      Period: 300
      EvaluationPeriods: 1
      Threshold: 0.99
      ComparisonOperator: GreaterThanOrEqualToThreshold
      AlarmActions:
        - Ref: 'SnsTopic'
        - !Sub 'arn:aws:automate:${AWS::Region}:ec2:reboot'
      Dimensions:
        - Name: 'InstanceId'
          Value: !Ref ExistingInstanceId

    DependsOn: SnsSubscription

1. Fill in parameters, including the ExistingInstanceId.
2. Click through and “Create stack.”
   
   
    

CloudWatch Alarm for Status Check Failure

The InstanceStatusAlarm is set to monitor the "StatusCheckFailed" metric. If it exceeds 0.99 for 300 seconds, the alarm triggers.

Simple Notification Service (SNS)

The template creates SnsTopic and SnsSubscription to your email. Replace the placeholder with your email for notifications.

Triggering Auto-Restart on Status Check Failure

1. Wait for stack creation.
2. Intentionally stop the EC2 instance or let it fail a status check.
3. CloudWatch Alarm detects failure, triggers SNS notification.
4. Check email for SNS notification.

Conclusion:

With this CloudFormation template, you’ve set up a quick and efficient system to automatically restart EC2 instances on status check failures. By integrating CloudWatch Alarms and SNS, you ensure prompt responses to keep your instances running smoothly.

Take charge of your AWS instance health! Deploy our CloudFormation template for automated EC2 restarts on status check failures. Swiftly monitor, get alerts, and enhance reliability. Elevate your AWS game — deploy now!