HA and Elasticity

Question 1

EC2 virtualization types

Answer 1

hardware virtual machine HVM (new and better way)

para virtualization PV

Question 2

Change Instance Type

Answer 2

• stop instance
• change instance type
• only works for EBS backed root volume
• cannot be used for machines which use instance store to store root volume
• new instance type should be compatible with the existing instance virtualization type i.e. HVM or PV

Question 3

Setting up ELB and Autoscaling group

Answer 3

1. Create hosted zone in Route 53, copy NS records provided by AWS into godaddy
2. Create new certificate from AWS to be applied to ELB
3. Go to ELB setup and click on classic ELB, select AZ and all other parameters. Add the registered cert since we have to use port 443. Don’t set any EC2 instances as yet
4. Create new DNS record in Route 53 with ELB url and CNAME
5. Goto autoscaling group - 2 steps - launch configuration and setup auto scaling group

Launch Configuration
1. Select AMI, name, Role, etc

Autoscaling Group

1. select VPC
2. select group size
3. select subnet
4. select ELB
5. select scaling policies - CPU/Memory etc
6. Setup notification SNS

Question 4

Classic ELB v/s Application ELB

Answer 4

Classic ELB

• makes routing decisions at application or transport layer (layer 4)
• it can only inspect only IP and port

application ELB

• makes decisions at application level (layer 7)
• it can inspect not only port and IP but also application level content,
• it can have more complex rules i.e. looking at url parameters and making a routing decision
• It has path based routing

Question 5

Scaling ELB

Answer 5

1. auto scaling based on cloudwatch metrics or on demand
2. scaling based on schedule

scaling policies

1. step based - don’t have to wait for cool down period, you can go on responding to scaling needs when triggered
2. simple - need to wait for cool down period once scaling starts to restart again

Actual metric is aggregate of all the instances in the autoscaling group.

Question 6

Using spot instances for autoscaling

Answer 6

1. need to setup launch configuration to use sport instances. Need to add max bid price
2. . Create new autoscaling group with this new launch configuration

Note: cannot use t2.micro as spot instance

Question 7

Lifecycle Hooks

Answer 7

Allows us to execute scripts on the new instances before they are provisioned after a scaling event. Also can provides a handle before scaling down.

Provides ability to execute cleanup logic etc.

Question 8

Architecting of new Application

Answer 8

TODO