Alert notification and action capabilities (for example, CloudWatch alarms to Amazon SNS, Lambda, EC2 automatic recovery)

Can you explain what Amazon CloudWatch is and how it integrates with Amazon SNS for alert notifications?

Amazon CloudWatch is a monitoring and observability service that provides data and actionable insights for AWS resources. It can collect and track metrics, collect and monitor log files, and set alarms. When integrated with Amazon SNS (Simple Notification Service), CloudWatch can send notifications or automatically make changes to the resources when certain thresholds are breached or alarms are triggered. CloudWatch alarms can publish messages to SNS topics, which can then trigger notifications to subscribers or other supported AWS services like Lambda for automated responses.

How do you set up a CloudWatch alarm to trigger an automatic EC2 instance recovery action?

In CloudWatch, you create an alarm that monitors the health of a specific EC2 instance. You can specify the action to recover the instance when the alarm is in the ‘ALARM’ state. To do this, you choose the “Take the recovery action” option as the alarm action and select “Recover this instance” for an EC2 status check alarm.

What is AWS Lambda, and how can it be used in response to CloudWatch alarms?

AWS Lambda is a compute service that lets you run code without provisioning or managing servers. In response to CloudWatch alarms, Lambda functions can be triggered to perform automated tasks or remediations, such as resizing an EC2 instance, clearing disk space, or restarting services. This is done by associating a CloudWatch alarm with an SNS topic that triggers the Lambda function.

Can you describe the difference between Amazon CloudWatch logs and events, and how each might trigger a different automated action?

CloudWatch Logs are used to monitor, store, and access log files from EC2 instances, AWS CloudTrail, and other sources. Logs can be analyzed and filtered, and metric filters can trigger alarms. CloudWatch Events, now part of Amazon EventBridge, deliver a stream of system events that describe changes in AWS resources. Both logs and events can trigger automated actions, but the use depends on the context; logs are typically used for deeper analysis requiring log data, while events are used for real-time monitoring of resource changes.

What is the difference between standard and FIFO queues in Amazon SNS, and how could this impact alarm notifications?

Amazon SNS has two types of queues: Standard and FIFO (First-In-First-Out). Standard queues offer maximum throughput, best-effort ordering, and at-least-once delivery. FIFO queues ensure messages are processed exactly once and in the exact order they are sent. This distinction can impact alarm notifications because standard queues may result in out-of-order alarm messages or duplicates, which might complicate the downstream processing or automation logic. FIFO queues provide a more strict sequence, making them suitable for applications where the order and accuracy of the notifications are critical.

Describe an appropriate use-case for an Amazon SNS dead-letter queue when dealing with notification failure.

A dead-letter queue is used to collect messages that could not be successfully delivered to subscribers of an SNS topic. An appropriate use-case for an SNS dead-letter queue is when critical notifications such as alerts or alarms must not be lost due to delivery failures. It allows you to perform post-failure analysis and reprocessing to ensure that not a single important notification is missed.

How do you ensure that a specific AWS Lambda function is triggered only by a particular CloudWatch alarm?

To ensure a specific Lambda function is triggered only by a particular CloudWatch alarm, you can create an SNS topic dedicated to that alarm and a subscription that invokes the Lambda function. Restrict the Lambda function’s execution role to allow invocations only from that SNS topic. Finally, configure the CloudWatch alarm to publish to the dedicated SNS topic upon alarm state changes.

How can you temporarily disable a CloudWatch alarm without deleting it?

You can temporarily disable a CloudWatch alarm by modifying the alarm state to ‘Disable Actions’. This way, even if the alarm’s conditions are met, it will not perform any actions. Alternatively, you can disable specific actions associated with the alarm individually if the alarm has multiple actions configured.

Explain a scenario where you would configure AWS CloudWatch to take snapshots of an EBS volume on an alarm trigger.

You might configure CloudWatch to take snapshots of an EBS volume when monitoring for a specific event that suggests potential data corruption, unexpected application crash, or other critical issues. When an alarm triggers on low disk space or high-latency I/O, a snapshot can be taken as a precautionary backup before any automated scaling or recovery actions are performed. This could be done by using SNS to trigger a Lambda function which then initiates the EBS snapshot creation.

How can you set up a CloudWatch alarm that notifies you when your estimated AWS charges exceed a certain threshold?

To set up an alarm for estimated AWS charges, first, you must enable monitoring of estimated AWS charges by activating the relevant setting in the Billing and Cost Management Console. Then, you create a CloudWatch alarm that watches the metric “EstimatedCharges” and specifies the threshold amount. Once the estimated charges exceed your defined limit, CloudWatch will trigger the alarm, and a notification can be issued through an SNS topic.