Elastic Load Balancers

• AWS Managed load balancer
• Integrates with many AWS services
• Health check feature
• Types of load balancers - Classic load balancer (deprecated), Application Load balancer, Network Load balancer, Gateway Load balancer
• Security with Security Groups
• SSL/TLS Termination for offloading application with certificate management

Application Load Balancer

• Works are layer 7 (http)
• Load balancing to multiple services called target groups
• Load balancing to multiple applications in a same machine (container)
• Support for http/2 and websocket
• Support for redirects, https to http
• Routing Table to multiple target groups
  • based on path in url
  • based on hostname in url
  • based on query string in url
• ALB is great fit for micro-services and container-based application
• Has a port mapping feature to redirect to dynamic port of ECS
• Has a fixed hostname
• Target group gets the client ip in header in x-forwarded-for, x-forwarded-proto

What can be target groups in ALB

• EC2 instances, can be managed by ASG
• ECS tasks
• Lambda functions
• IP Addresses, must be private address

Hands-On

• ELB is listed under feature of EC2
• Select type of load balancer - ALB
• Load balancer Name
• Scheme - Cannot be changed after creation - Internet-facing or Internal (Require private IPs)
• IP address Type - IPV4
• Mappings - Atleast two AZ, for obvious reason, as traffic will be directed to the respective AZ
• Security Group - Add firewall rules
• Listeners and routing - Based on listener rules, traffic is routed to the target group added to the listener
• Create Target Groups - Give tg name, protocol, health check, then register the targets with a port.
• Select the created target group
• Create Load balancer
• Can add rules in listeners, like header, protocol, query string, etc and percentage of traffic routed to the tg group

Network Load Balancer

• Works at layer 4
• Forward the TCP and UDP traffic
• High performance, handled millions of request per sec, and less latency

• NLB has one static IP per AZ and supports assigning Elastic IP

• Since operates at layer, can be routed directly on IP address.

Hands-On

• Everything is same as ALB, except listener protocol will be TCP, UDP, etc
• Also, option to select Elastic IP address, and in case of Internal, can specify private IP address within the CIDR

Gateway Load Balancers

• This works in layer 3, which is at the Network layer. Somewhat where the home router works at, the home router have IP address, when a traffic comes in, router decides to forward it to which computer connected.
• For Example, gateway load balancer is like a cop, who stops a car (data packet) and directs it to the checkpoint, and to be noted, it is the cop who directs and not checkpoint.
• Now the checkpoint can be like a 3rd party network appliance running on a EC2 instance.
• When it passes through the EC2, the data packet comes back to the GLB and then directed to the application.

SSL Certificates

• Load balancers can listen to HTTPs traffic uses SSL/TLS which can be uploaded to ACM
• ALB and NLB can supports SNI, which is newer protocol to support multiple certificates

Connection Draining

• If a target is set for draining or de-registering in ALB, new connections are stopped, and existing connections given time to finish the process

ASG - Auto Scaling Group

• Helps us to manage variable loads on the application, as EC2 servers can be quickly scaled.
• Ensures the min, max, and desired counts, healthy-unhealthy servers, auto registering and de-registering in Load balancers.
• No cost for ASG, only the underlying EC2 instances and resources will cost

ASG Launch Template

• Its template for the EC2, plus the scaling configs, and scaling policies
• EC2 Attributes
  • AMI + Instance Type
  • EC2 user data
  • EBS Volumes
  • Security Groups
  • SSH Key pair
  • IAM Roles for EC2 instance
  • Network + Subnets information
  • Load Balancer Information

ASG Hands On

• Go to ASG in EC2 Page

• Create ASG

• Step 1 :

  • Give ASG Name
  • Select or Create Launch Template
    • Create Launch Template, Give Template Name
    • Select AMI, instance type, ssh key pair, subnets, volume, user data, etc (basically its same EC2 form)

• Step 2: Instance Launch Option