Chapter 11 - Elastic Load Balancing

Question 1

Application Load Balancers

Answer 1

Which is Layer 7

• It only support HTTP and HTTPS.
• And to use an HTTPS listener, you must deploy at least one SSL or TLS server certificate on your load balancer.
• And the load balancer uses the server certificate
• to terminate the frontend connection
• to decrypt the requests from your clients before sending them to the targets.
• also have sticky sessions
• you can enable sticky sessions for your Application Load Balancer,
• but it’s going to be sent to the target group level, not to to the individual EC2 instances.

Question 2

Network Load Balancers

Answer 2

which are Layer 4

• You’re going to use them when you need extreme performance.
• Other use cases are where you need protocols that are not supported by Application Load Balancers.
• And Network Load Balancers can also decrypt your traffic, but you’re going to need to install the certificate on the load balancer.

Question 3

Classic Load Balancers

Answer 3

which operate between Layer 4 and Layer 7

• Remember what a 504 error means.
• It just means that the gateway has timed out.
• And this means your application is not responding within the idle timeout period.
• And to basically solve this, you just need to troubleshoot the application.

Question 4

health check

Answer 4

You can use health checks to route your traffic to instances or targets that are healthy.

Question 5

Application Load Balancers - listener

Answer 5

• A listener checks for connection requests from clients using the protocol and the port that you configure.
• So, it’s either going to be port 80 or port 443.

Question 6

rules

Answer 6

These determine how the load balancer routes your request to its registered target.

And each rule consists of:

• a priority
• one or more actions
• and one or more conditions

Question 7

target groups

Answer 7

basically each target group routes requests to one or more registered targets

• Such as our EC2 instances
• Using the protocol and port numbers that you specify.

Question 8

X-Forwarded-For header

Answer 8

if you need the IPv4 address of your end user

Question 9

sticky sessions

Answer 9

They enable your users to stick to the same EC2 instance.

• And this can be useful if you’re storing information locally to that instance.
• And you may see scenario based questions where you remove an EC2 instance from a pool that the load balancer continues to direct traffic to that EC2 instance.
• In a scenario like that, you just need to disable sticky sessions.

Question 10

deregistration delay or connection draining

Answer 10

Depending on if it’s an Application Load Balancer or a Classic Load Balancer, they’re exactly the same thing.

• So, you basically want to enable deregistration delay and this will keep existing connections open if the EC2 instance becomes unhealthy.
• Or you could choose to disable deregistration delay or connection draining
• You do this if you want your load balancer to immediately close connections to the instances that deregistered or that have become unhealthy.