How to send email notification alerts using CloudWatch metrics when EC2 instance down

Configuring AWS CloudWatch to send alerts using Amazon SNS if an EC2 instance goes down involves several steps. Here’s a step-by-step guide to achieve this:

Step 1: Create an SNS Topic

1. Navigate to the Amazon SNS Console:
   • Go to the Amazon SNS console.
2. Create a Topic:
   • Click on Create topic.
   • Choose the Standard type.
   • Enter a name for the topic (e.g., EC2-Instance-Down-Alerts).
   • Click Create topic.
3. Create a Subscription:
   • After creating the topic, click on Create subscription.
   • Select the newly created topic.
   • Choose a protocol (e.g., Email, SMS, HTTP/S).
   • Enter the endpoint (e.g., your email address if you chose Email).
   • Click Create subscription.
4. Confirm Subscription:
   • If you chose Email as the protocol, check your email and confirm the subscription.

Step 2: Create a CloudWatch Alarm

1. Navigate to the CloudWatch Console:
   • Go to the Amazon CloudWatch console.
2. Create an Alarm:
   • Click on Alarms in the left navigation pane.
   • Click Create alarm.
3. Select a Metric:
   • Click on Select metric.
   • Choose EC2 metrics.
   • Navigate to Per-Instance Metrics.
   • Select the StatusCheckFailed_Instance metric for your desired EC2 instance. This metric indicates a failure of the instance status check.
4. Configure Alarm:
   • Specify the threshold type (Static).
   • Set the condition:
     • Whenever StatusCheckFailed_Instance is >= 1 for 1 consecutive period(s) of 5 minutes.
   • Click Next.
5. Add Notification:
   • Under the Notification section, click on Add notification.
   • For Send a notification to, select your SNS topic (e.g., EC2-Instance-Down-Alerts).
   • Click Next.
6. Name and Description:
   • Enter a name and description for the alarm (e.g., EC2_Instance_Down_Alarm).
   • Click Next.
7. Review and Create:
   • Review the settings and click Create alarm.

Step 3: Verify the Alarm and Notification

1. Test the Setup:
   • You can stop the EC2 instance temporarily to test if the alarm triggers and sends a notification.
   • Go to the EC2 console, select your instance, and click Instance state > Stop instance.
2. Check Notifications:
   • Once the instance is stopped and fails the status check, CloudWatch should trigger the alarm.
   • You should receive an alert via your configured SNS subscription (e.g., an email if you set up email notifications).

Step 4: Automate Recovery (Optional)

If you want to automatically recover the instance when it goes down, you can create an additional CloudWatch alarm that triggers the recovery action.

1. Create a Recovery Alarm:
   • Follow the steps to create another CloudWatch alarm.
   • Select the same StatusCheckFailed_Instance metric.
   • Set the threshold condition.
   • Under Actions, choose Recover this instance.