Auto Scaling Solutions

• Monitors your applications and adjusts capacity to fit your needs.
• Adjusts capacity, manage costs.
• Free to use, results of use may cost: more instances, CloudWatch, Elastic Load Balancers…

Auto Scaling Groups:

• Collection of instances with similar characteristics.
• Can be scaled based on criteria.
• Unhealthy instances can be auto-replaced (only non-running services)
• Takes time to launch and configure a server, consider this!

Termination Policies (Scaling In)

Custom Termination Policies:

• OldestInstance (Oldest First)
• NewestInstance (Newest First)
• OldestLaunchConfiguration
• ClosestToNextInstanceHour
• Default (AZ Zones -> oldestLaunch -> nextClosestBillingHour -> Random)

Launching Auto Scaling Groups

• You must create a Launch Configuration to create an auto-scaling group.
• The Launch configuration contains the instance type, key pair & security groups.

Launch Methods:

• Launch template must include ALL parameters required to launch an EC2 instance, such as an AMI Id and instance type.
• Role or user using a Launch template must have permission to use the Ec2:RunInstances.
• You can create a custom AMI then launch it through an auto-scaling group.
• Role or user using a Launch template must have permission to use EC2:RunInstances.
• You can create a custom AMI then launch it through an auto-scaling group.

Load Balancer Concepts

Load Balancing Categories:

1. Sender Initiated: Sender locates best target.
2. Receiver Initiated: Receiver selects best target (ie load balancer).

Static Load Balancing:

• Multi-Tier applications.
  • Specific actions are assigned to specific servers/resources.
  • Actions always processed on assigned target.
  • No scalability.

Dynamic Load Balancing:

• True load balancing.
  • Actions dynamically assigned.
  • Scalability is provided.
  • Used by AWS Elastic Loading Balancing (ELB)

Load Balancing Algorithms:

1. Round Robin (RR)
2. Randomized
3. Centrally Managed
4. Threshold-Based

Elastic Load Balancing (ELB):

• Highly available, secure, flexible, monitoring and auditing included.

3 Types on AWS:

1. Classic Load Balancer: Intended to work with the legacy EC2-Classic network.
2. Network Load Balancer: Layer 4 (Network), suited for TCP traffic among Amazon VPC.
3. Application Load Balancer: Layer 7 (Individual requests), best suited for http and https requests

Supported Services: EC2, ECS, Auto-Scaling, CloudWatch, Route 53