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EC2 Instance Recovery and Resilience

1. Introduction

Amazon EC2 (Elastic Compute Cloud) enables users to run applications on a cloud infrastructure. This lesson focuses on the recovery and resilience of EC2 instances, which are critical for maintaining uptime and availability in cloud environments.

2. Key Concepts

Definitions

  • Resilience: The ability of an EC2 instance to recover from failures and continue operating.
  • Recovery: The process of restoring an EC2 instance to a functional state after a failure.
  • Availability Zone (AZ): A distinct location within a region that is engineered to be isolated from failures in other AZs.

3. EC2 Recovery Options

There are several strategies to recover EC2 instances:

  1. **Stop and Start**: Stopping and starting an instance can help reset its state.
  2. **Reboot**: A simple reboot can resolve many temporary issues.
  3. **Instance Recovery**: Automatically recover instances when a system impairment is detected.
  4. **Elastic Load Balancing (ELB)**: Distributes incoming traffic and redirects to healthy instances.
  5. **Auto Scaling Groups**: Automatically replace unhealthy instances to maintain application availability.
Note: Each recovery option has different implications for data loss and application state. Always assess the best option based on your architecture.

Example: Using AWS CLI to Reboot an EC2 Instance


aws ec2 reboot-instances --instance-ids i-1234567890abcdef0

4. Best Practices

  • Regularly back up your instances using Amazon EBS snapshots or AMIs.
  • Implement health checks and monitoring using Amazon CloudWatch.
  • Use multiple Availability Zones to increase fault tolerance.
  • Regularly test your recovery processes to ensure they work effectively.
  • Document recovery procedures and maintain an updated runbook.

5. FAQ

What is the difference between stopping and terminating an EC2 instance?

Stopping an instance saves the instance's configuration and data on the EBS volume, while terminating an instance deletes the instance and is irreversible.

How can I automate EC2 instance recovery?

Use CloudWatch Alarms to monitor the instance health and trigger AWS Lambda functions to automate recovery actions.

What is the role of Auto Scaling in resilience?

Auto Scaling automatically adjusts the number of EC2 instances in response to demand, ensuring that applications remain available and resilient against failures.