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Elastic Load Balancer

  • Managed Load Balancer.

  • Costs less to setup your own load balancer; but is more efforts.

  • Integrated with many AWS services / offerings.

  • AWS has four managed load balancers:

    • Classic Load Balancer
    • Application Load Balancer
    • Network Load Balancer
    • Gateway Load Balancer

Load Balancer Security Groups​

lb-security-groups

Application Load Balancer​

  • Layer 7 (Application layer)
  • Multiple HTTP applications across machines (target goups)
  • Multiple applications on the same machine (containers)
  • Supports for HTTP/2 and WebSocket.
  • Support redirects (eg., from HTTP to HTTPS)
  • Routing to different target groups based on URL path, hostname, query string and headers.
  • Great for micro services and container based applications (Docker and Amazon ECS)

Target Groups​

  • EC2 instances, ECS tasks, Lambda Functions, IP Addresses
  • Health checks are at the target group level.

Network Load Balancer​

  • Allow forward TCP & UDP traffic to instances
  • Handle millions of requests per seconds.
  • Ultra-low latency.
  • One static IP / AZ.
  • Supports assigning Elastic IP

Target Groups​

  • EC2 instances, IP Addresses, Application Load Balancer
  • Health checks support the TCP, HTTP and HTTPS Protocols.

Gateway Load Balancer​

  • Operates at level 3 (Network Layer)

gateway-load-balancer

Target Groups​

  • EC2 Instances
  • IP Addresses

Sticky Sessions​

  • Client is always redirected to the same instance.
  • "Cookie" is used for stickiness and it has an expiration date.
  • May bring imbalance to the load.

Application-based Cookies​

  • Generated by the application
  • Name must be specified for each target group.
  • Generated by load balancer

Duration-based Cookies​

  • Generated by load balancer.

Cross-Zone Load Balancing​

cross-zone-load-balancing

  • For Application Load Balancer: Enabled be default; can be disabled at Target Group Leve; no charges.
  • For Network Load Balancer and Gateway Load Balancer: Disabled be default; extra charges.

SSL Certificates​

ssl-certificates

  • Manage certificates using AWS Certificate Manager.
  • Alternatively, upload your own certificate.

Server Name Indication (SNI)​

  • Solves the issue of loading multiple SSL certificates to serve multiple websites.
  • Requires client to indicate the hostname of the target server in the initial SSL handshake.

server-name-indication

Deregistration Delay​

  • Time to complete in-flight requests while the instance is unhealthy.
  • Stops sending the request to that instance.
  • Default to 300 seconds (1 to 3600 seconds); can be disabled (set to 0).