Amazon Web Services- Elastic Load balancer

In this Topic we will discuss Amazon Web services ELB or Elastic Load Balancers

So first question is : What does Load balancers Do?  The answer is:

•  Send Traffic to many Back-end Servers
• Attempt to evenly distribute load
• Allows yours service to be elastic
• It allows for Horizontal Scaling
• Grow and shrink on demand

However,

Horizontal Scaling by the ELB in the cloud gives us:

• Near Infinite Scaling
• Huge cost savings
• High Availability
• Scaling By Tier

So what is Scaling by Tier? 

We can scale up or down web tier independent of APP Tier. This sis called scaling by tier

ELB Auto-scales ( Adds more IPs with increased traffic to the DNS)

ELB can also Terminate SSL, encrypt SSL to the back-end Machines

ELB also supports X-Forwarded-FOR

ELB has deep Integration with Auto Scaling and Cloud watch

Integration with Auto Scaling and Cloud watch

ELB can detect unhealthy Instances

• Unhealthy by TCP or HTTP check
• It automaticvally removes them dfrom scaling

However, Cloudwatch can add more instances behind ELB

• Based on ELB metrics ( RequestCount, Latency and More)
• Based on Instance Metrics (CPU. I/O, etc)

Remember,

• Load balanced is first by Availability Zone
• Then across instance in availability zone
• ELB cost is static
• ELB scaling is always reactive