DevOps

EC2

Elastic Compute Cloud

FAQs |

Overview

  • A virutal server

  • Can scale up and down within minutes

  • SLA = 99.99%

Instance type

  • T2, G is a general purpose instance type.

  • X1e, R is memory optimized.

  • H1 is storage optimized.

  • P3 is for advanced computing and can include special hardware for graphics processing.

EBS Volume

EBS is a network disk that is attached to EC2.

EC2 Instance store

When you need very high IOPS storage for EC2, refer to EC2 Instance store.

Provision EC2

Steps to provision an EC2 instance

  • Remember to create & download keypair.

  • Capacity reservation (reserve capacity for EC2 instance in a specific AZ): None. Turn this to None to save cost.

Connect to EC2

Session Manager (easiest)

  • Session are secured using AWS Key Management service key.

  • Can log session commands in S3 bucket or CloudWatch Logs log group.

  • No SSH, no Bastion host, No need to open inbound ports.

  • 1-click access.

SSM trouble shooting

# check system agent is enabled?
sudo systemctl status amazon-ssm-agent

# when creating EC2 instance, you should configure the IAM profile to use SSM. 
# if not, after attaching the IAM profile, you need to restart the SSM agent
sudo systemctl restart amazon-ssm-agent

Session manager URL

https://us-east-1.console.aws.amazon.com/systems-manager/session-manager/i-08d8812972af11492

EC2 instance connect

  • Using IAM policies to control SSH access.

  • No need of SSH Keys, but actually using SSH access to your instance.

SSH to EC2

ssh -i MyKeyPair.pem ec2-user@Public-ipaddress

Features

ASG: Auto Scaling Group

  • Ensure that you have correct number of EC2 instances available to handle the load on your application.

  • Automatically instance replacement -> If the health check fail, it will trigger the lauching of new healthy instance.

  • Instance rebalancing -> When an AZ failed, it will shift the instances from that failed AZ to the remaining healthy AZ.

  • Provision new resources take minutes. Slow if compare to Lambda scaling ability.

EC2 Hibernate

  • Hibernation saves the contents from the instance memory (RAM) to your EBS root volume.

  • Allows applications to pick up exactly where they left off.

  • Use cases

    • Services that take time to initialize

    • Saving RAM state

    • Long-running processing

    • eg: 2-weeks company shutdown

  • To use hibernate

    • Root volume: must be encrypted EBS volume.

    • AMI: Linux or Windows

    • RAM size: must less than 150GB.

    • NOT hibernated > 60 days.

-> It is not possible to enable or disable hibernation for an instance after it has been launched.

Placement group

There are 3 types of Placement group

Cluster
Partition
Spread

high-performance low-latency

large distributed, replicated workloads

high-availability reduce failures

placing EC2 instnaces next to each other

Hadoop, Cassandra, Kafka

placing EC2 instances in different hardware cross-AZs.

Detailed monitoring

Send metric to Cloud Watch every 1-minute (instead of 5-minute period).

Troubleshooting

  • Check inbound of Security group if it already allow the right protocol/port.

  • Check NACLs associated with the subnets, to ensure they allow inbound and outbound traffic.

  • ALB listener if the traffic is being directed to the correct protocol:port of the Target Group

  • Check if the Target group includes the EC2 instances as registered targets.

  • EC2 instance:

    • Check health status, and Status check 2/2?

    • Connect to the EC2 instance to check if the httpd server is running.

  • Check logs

    • Check EC2 instance's system logs.

    • CloudWatch log: CPU, network traffic, disk I/O...

    • CloudTrail log.

Trivia

  • Termination protection will not prevent an Autoscaling Group from terminating instances, instance scale-in protection will. Termination protection protect from manually termination.

  • DefaultInstanceWarmup : determines how long your instances need to finish initializing to be InService state.

  • The only way to retrieve instance metadata is to use the link-local address, which is 169.254.169.254.

  • When you stop an instance, AWS may move the virtualized EC2 instance to another host computer; the instance may get a new public IP address, and the data in your attached instance store volumes will be deleted.

  • When you provision an IAM to use with SSM, refer pre-installed ssm agent AMI list.

  • You can combine Spot + On-Demand instance only. You cannot combine Spot and Reserved instances.

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